Chemicals, the Environment,

and You: Explorations in

Science and Human Health

developed under a contract from the

National Institutes of Health

National Institute of Environmental Health Sciences

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Ann C. Lanari, Research Assistant

Education Officer

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Karen Bertollini, Project Assistant

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Carrie Hamm, Project Assistant

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National Institutes of Health

Diane Gionfriddo, Photo Research

Allen Dearry, National Institute of Environmental Health

Lisa Chilberg, Graphic Designer

Sciences (NIEHS)

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Videodiscovery, Inc. Development Team

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Field-test Teachers

Lucy Flynn Zuccotti, Photo Research

Bernard Bastick, Beckley-Stratton Junior High School, Beckley, WV

Michele Moore, Assistant to Project Director

Joey Beckett, Beckley-Stratton Junior High School, Beckley, WV

Jennifer Hunt, Costumes and Makeup

Louisa Bliss, Gilman Middle School, Gilman, VT

Mike Commins, Gaffer (Lighting)

Alice Cook, Moundsville Junior High School, Moundsville, WV

Chet McKnight, Sound

Cassie Cox, Moundsville Junior High School, Moundsville, WV

Lee Strucker, Script Writer

Rose DiCenso, Sabin Middle School, Colorado Springs, CO

Anthony DiSipio, Jr., Octorara Middle School, Atglen, PA

Advisory Committee

Claireen Espinoza, Taos Day School, Taos, NM

Allen Dearry, National Institute of Environmental Health Sciences,

Anna Kong, Stone Academy, Chicago, IL

Research Triangle Park, NC

Susan Long, Frankfort Middle School, Ridgeley, WV

David Eaton, University of Washington, Seattle, WA

Greg Nichols, New Options Middle School, Seattle, WA

Juliane Hill, University of Washington, Seattle, WA

Josina Romero O’Connell, Challenger Middle School,

Larry Johnson, Texas A & M University, College Station, TX

Colorado Springs, CO

Greg Nichols, New Options Middle School, Seattle, WA

Barrington Ross, Shepard Magnet Middle School, Durham, NC

Josina Romero O’Connell, Challenger Middle School,

Jan Ryan, Brandeis Hillel Day School, San Francisco, CA

Colorado Springs, CO

Mehar Safvi, Shepard Magnet Middle School, Durham, NC

Jan Ryan, Brandeis Hillel Day School, San Francisco, CA

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Karen Steinmetz, SUGEN, Inc., South San Francisco, CA

Susan Wooley, American School Health Association, Kent, OH

Special Thanks to:

W. Richard Ulmer of InVitro International, Irving, CA, for

Writing Team

providing the photograph of the Corrositex® assay (page 45).

Juliane Hill, University of Washington, Seattle, WA

Deputy Chief Vickery of the Seattle Fire Department and the

Charlene A. McQueen, University of Arizona, Tucson, AZ

Seattle Fire Department Hazmat Team for their participation in

Josina Romero O’Connell, Challenger Middle School,

and staging of the Ride Along with HAZMAT mini-documentary.

Colorado Springs, CO

Shaun Taylor, Videodiscovery, Seattle, WA

This material is based on work supported by the National Institutes

Mike Trush, Johns Hopkins University Bloomberg School of

of Health under Contract No. 263-98-C-0056. Any opinions,

Public Health, Baltimore, MD

find ings, conclusions, or recommendations expressed in this

publication are those of the authors and do not necessarily

Artists

reflect the view of the funding agency.

Susan Bartel

Lisa Chilberg

Copyright ©2000 by BSCS and Videodiscovery, Inc. All rights

reserved. You have the permission of BSCS and Videodiscovery,

Cover Design

Inc. to reproduce items in this module (including the software)

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for your classroom use. The copyright on this module, however,

National Institutes of Health

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For permissions and other rights under this copyright, please

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contact BSCS, 5415 Mark Dabling Blvd., Colorado Springs, CO

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Revised December 2012

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Please contact NIH with questions

about this supplement at

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Contents

Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

About the National Institutes of Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

About the National Institute of Environmental Health Sciences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

About Biological Sciences Curriculum Study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

Introduction to Chemicals, the Environment, and You . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

What Are the Objectives of the Module? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Why Teach the Module? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

What’s in It for the Teacher? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Implementing the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

What Are the Goals of the Module? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

What Are the Science Concepts and How Are They Connected? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

How Does the Module Correlate with the National Science Education Standards? . . . . . . . . . . . . . . . . .3

How Does the 5E Instructional Model Promote Active, Collaborative, Inquiry-Based Learning? . . . .6

What’s the Evidence for the Effectiveness of the BSCS 5E Instructional Model? . . . . . . . . . . . . . . . . .8

How Does the Module Support Ongoing Assessment? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

How Can Teachers Promote Safety

in the Science Classroom? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

How Can Controversial Topics Be Handled in the Classroom? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Using the Student Lessons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Format of the Lessons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Timeline for Teaching the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Master List of Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Using the Web Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Hardware and Software Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Getting the Most out of the Web Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Collaborative Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Web Activities for People with Disabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Lesson 1. Chemicals, Chemicals, Everywhere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Lesson 2. The Dose Makes the Poison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Lesson 3. Dose-Response Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Lesson 4. Individual Responses Can Be Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Lesson 5. What Is the Risk? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Lesson 6. Environmental Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Additional Resources for Teachers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Masters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

iii

Foreword

This curriculum supplement, from The NIH

active and collaborative learning and are inquiry-

Curriculum Supplement Series, brings cutting-edge

based to help students develop problem-solving

medical science and basic research discoveries

strategies and critical-thinking skills.

from the laboratories of the National Institutes

of Health (NIH) into classrooms. As the largest

Each of our curriculum supplements comes

medical research institution in the United

with a complete set of materials for teachers

States, NIH plays a vital role in the health of

and students, including extensive background

all Americans and seeks to foster interest in

and resource information, detailed lesson plans,

research, science, and medicine-related careers

masters for student worksheets, and a Web site

for future generations. NIH’s Office of Science

with videos, interactive activities, updates, and

Education (OSE) is dedicated to promoting

corrections (as needed). The supplements are

scientific literacy and the knowledge and skills

distributed at no cost to educators across the

we need to secure a healthy future for all.

United States upon request. They may be copied

for classroom use but may not be sold.

We designed this curriculum supplement to

complement existing life science curricula at both

We welcome your comments. For a complete

the state and local levels and to be consistent

list of curriculum supplements and ordering

with the National Science Education Standards

information, or to submit feedback, please visit

(released by the National Academy of Sciences

http://science.education.nih.gov.

in 1996). It was developed and tested by a team

of teachers, scientists, medical experts, and

We appreciate the valuable contributions of

other professionals with relevant subject-area

the talented staff at BSCS and Videodiscovery,

expertise from institutes and medical schools

Inc. We are also grateful to the NIH scientists,

across the country, representatives from the

advisors, and all other participating professionals

National Institute of Environmental Health

for their work and dedication. Finally, we thank

Sciences, and curriculum design experts from

the teachers and students who participated in

Biological Sciences Curriculum Study (BSCS) and

focus groups and field tests to ensure that these

Videodiscovery, Inc. The authors incorporated

materials are both engaging and effective.

real scientific data and actual case studies into

classroom activities. A three-year development

I hope you find our series a valuable addition to your

process included geographically dispersed

classroom and wish you a productive school year.

field tests by teachers and students. For the

2012 edition, key sections of the supplement

Bruce A. Fuchs, Ph.D.

were updated, but the Student Lessons remain

National Institutes of Health

basically the same.

supplements@science.education.nih.gov

The curriculum supplements enable teachers

to facilitate learning and stimulate student

interest by applying scientific concepts to

real-life scenarios. Design elements include a

conceptual flow of lessons based on the BSCS 5E

Instructional Model, cutting-edge science content,

and built-in assessment tools. Activities promote

v

About the National Institutes of Health

Founded in 1887, NIH is the federal focal point

research and clinical investigators, as well as the

for health research in the United States. Today,

myriad professionals in the many allied disciplines

NIH is one of the agencies within the Department

who support the research enterprise. These efforts

of Health and Human Services. Its mission is

also help educate people about scientific results so

science in pursuit of fundamental knowledge

that they can make informed decisions about their

about the nature and behavior of living systems

own—and the public’s—health.

and the application of that knowledge to extend

healthy life and reduce the burdens of illness and

This curriculum supplement was one such

disability. NIH works toward meeting the mission

education effort. It is a collaboration among

by providing leadership, direction, and grant

the National Institute of Environmental Health

support to programs designed to improve the

Sciences, the NIH Office of Science Education,

health of the nation through research.

Biological Sciences Curriculum Study, and

Videodiscovery, Inc.

NIH’s education programs contribute to ensuring

the continued supply of well-trained basic

For more about NIH, visit http://www.nih.gov.

vi

About the National Institute

of Environmental Health Sciences

The National Institute of Environmental Health

the conditions that allow it to occur. NIEHS

Sciences (NIEHS) is one of 27 institutes and

takes a holistic approach to health, viewing it

centers of the National Institutes of Health (NIH).

as an integrated response of all organ systems

The mission of NIEHS is to reduce the burden of

of the body to the environment. A key strategy

human illness and disability by understanding

for preventing many diseases or minimizing

how the environment influences the development

their effects is to eliminate or reduce exposures

and progression of human disease. Headquartered

to chemicals and other toxic agents in our

in Research Triangle Park, North Carolina,

environment, especially our food, water, and air.

NIEHS supports environmental health research at

To help reduce exposure to these agents, NIEHS

universities, independent laboratories, and centers

supports environmental public health activities

throughout the United States.

that increase public awareness about the nature

of the chemicals and how they may affect our

NIEHS is unique within NIH because its

health and that empower communities to take

primary focus is on the public health impact of

action to manage environmental health issues.

environmental exposures, rather than on one

or two specific organs such as the heart or liver

Environmental public health is defined as the

and finding ways to treat illnesses people already

science of conducting and translating research

have. Promoting public health and preventing

into action to address environmental exposures

disease is one of the most important services the

and health risks of concern to the public.

government can provide to its citizens. Protecting

NIEHS recognizes the importance of working in

people from avoidable illness and death spares

partnership with community groups to address

suffering, saves money, and improves the quality

their environmental health concerns. The institute

of life for society as a whole.

supports programs that build the capacity of

community groups and researchers to work

NIEHS provides the sound scientific foundation

together, advance environmental health literacy,

for defining the health effects of a broad array of

increase awareness of environmental health

environmental agents. Translating these findings

concepts, and engage community residents as

into effective public health and prevention

partners in the research process.

strategies requires that NIEHS communicate its

discoveries to federal regulatory agencies such as

NIEHS supports environmental public health

the Environmental Protection Agency (EPA) and

activities through

the Food and Drug Administration (FDA), as well

• Grants to support university-community

as to public health agencies such as the Centers

partnerships that address local environmental

for Disease Control and Prevention (CDC). These

health issues.

organizations, in turn, use this information to

• Outreach activities NIEHS requires of academic

calculate new standards to protect health and

research institutes it supports.

communicate public health messages to the

• Communication tools such as the science

public. This information is also the scientific basis

journal Environmental Health Perspectives.

for many laws passed by Congress to protect the

nation’s health.

Research areas of special interest to NIEHS are

environmentally related diseases and disorders

The most effective way to promote public

such as cancer, asthma, Alzheimer’s disease,

health and prevent disease and disability is to

autism, and the potential effects on human

understand the cause of an illness and change

health of endocrine disruptors, metals, pesticides,

vii

nanotechnology, and climate change. To fully

For more information see

understand these diseases and conditions,

environmental health research must examine

NIEHS Science Education:

the interface of exposure, genetic susceptibility,

http://www.niehs.nih.gov/health/scied/index.cfm

and time and duration of exposure.

Environmental Health Perspectives

NIEHS has a vested interest in developing

Science Education:

and training the next generation of diverse

http://ehp03.niehs.nih.gov/static/scied.action

environmental health scientists who will be

needed to solve the complex problems mentioned

Summers of Discovery:

above. The Chemicals, the Environment, and

http://www.niehs.nih.gov/careers/research/summers/

You curriculum is just one example of NIEHS’s

index.cfm

efforts to improve science education and literacy,

increase the nation’s understanding of the role of

NIEHS Web site:

the environment in disease, empower teachers

http:// www.niehs.gov

and other communicators to translate science,

and provide the most current and credible

information on environmental health science.

viii

About Biological Sciences

Curriculum Study

Headquartered in Colorado Springs, Colorado,

Instructional Model and inquiry are hallmarks

BSCS was founded in 1958 as a curriculum study

of its materials, placing students at the center of

committed to an evidence- and inquiry-based

their learning.

approach to science education. BSCS instructional

materials and professional development services

The BSCS mission is to transform science teaching

are based on current research about teaching and

and learning through research and development

learning for all science classrooms, kindergarten

that strengthens learning environments and

through college.

inspires a global community of scientifically

literate citizens. BSCS is a 501(c)3 nonprofit

BSCS’s materials are extensively field-tested

organization. For more information, please visit

in diverse settings across the country and

http://www.bscs.org.

evaluated for proven effectiveness. The BSCS 5E

ix

Introduction to Chemicals,

the Environment, and You

What Are the Objectives of the Module?

Knowledge (what is known and not known)

Chemicals, the Environment, and You has several

+ Choice = Power

objectives. The first is to help students understand

Power + Behavior = Enhanced Human Health

major concepts that describe the relationship

(that is, personal and public health)

between chemicals in the environment and

human health. By focusing on the science

An additional objective of this module is to

of toxicology, the module seeks to introduce

encourage students to think in terms of these

students to the ways scientists learn about and

relationships now and as they grow older.

measure how chemicals can both help and harm

human health.

Why Teach the Module?

The second objective is to convey to students the

Middle school science classes offer the perfect

ever-changing nature of our understanding of

opportunity to integrate many areas of student

the influence of chemicals on the health of living

interest. In this module, students participate

organisms. For example, with each introduction

in activities that integrate inquiry science,

of a new synthetic chemical, researchers

environmental studies, human health, history,

must learn at what dose and by what route of

decision-making concepts, and mathematics.

exposure the chemical might be hazardous to

The real-life context of the module’s lessons is

human health. New data have informed people

engaging for students, and the knowledge gained

of the dangers of lead in paint and the disease

by participating in the module can be applied

implications of breathing secondhand smoke. Our

immediately to students’ lives.

increasing knowledge about the effects chemicals

can have on the human body enables us to make

“The activities provided actual real-life occurrences

choices to limit our exposure to some chemicals

that students could relate to.”

while using other chemicals in ways that improve

—Field-test Teacher

the quality of our lives.

“The lab made me think about medicines and what

Science plays an important role in assisting

dose I should take.”

individuals as they make choices about enhancing

—Field-test Student

personal and public welfare. In this module,

students see that science provides evidence that

What’s in It for the Teacher?

can be used to support ways of understanding

Chemicals, the Environment, and You meets

and treating human disease. Because the mission

many of the criteria used to assess teachers and

of the National Institute of Environmental

their programs.

Health Sciences is to reduce human illness from

• The module is standards based and meets

environmental causes, the institute believes

science content, teaching, and assessment

that education provides one context in which

standards as expressed in the National Science

it can fulfill its mission. The lessons in this

Education Standards. It pays particular attention

module encourage students to think about the

to the standards that describe what students

relationships among knowledge, choice, behavior,

and enhanced human health in this way:

1

Chemicals, the Environment, and You

should know and be able to do with respect to

Horsley et al. write that replacement modules

scientific inquiry.

such as Chemicals, the Environment, and You can

• As described above, it is an integrated module,

“offer a window through which teachers can get a

drawing most heavily from the subjects of

glimpse of what new teaching strategies look like

science, history, mathematics, and health.

in action.” By experiencing a short-term unit like

• The module has an online technology

this one, teachers can “change how they think

component that includes mini-documentaries,

about teaching and embrace new approaches

laboratory information and data tables, and

that stimulate students to problem solve, reason,

interactive activities.

investigate, and construct their own meaning for

• Finally, the module includes built-in

the content.” The use of a replacement unit like

assessment tools indicated by an assessment

this one can encourage reflection and discussion

icon in each lesson.

and stimulate teachers to improve their practices

by focusing on student learning through inquiry.

In addition, the module provides a means for

professional development. Teachers can engage

Table 1 correlates topics often included in the

in new and different teaching practices like those

middle school curriculum with the lessons in this

described in this module without completely

module. This information is presented to help

overhauling their entire yearlong program. In

teachers make decisions about incorporating this

Designing Professional Development for Teachers

material into the curriculum.

of Science and Mathematics (1), Susan Loucks-

Table 1. Correlation of Chemicals, the Environment, and You to middle school topics.

Topics

Lesson 1 Lesson 2 Lesson 3 Lesson 4 Lesson 5 Lesson 6

Chemical composition of all matter

•

Chemicals in the environment

•

•

•

•

Human health and medicine

•

•

•

•

Individual variation/susceptibility

•

•

•

•

Risk assessment and management

•

•

•

Scientific methods

•

•

•

2

Implementing the Module

The six lessons in this module are designed to

Table 2 summarizes the sequence of major

be taught either in sequence for two or more

concepts addressed by the six lessons.

weeks (as a replacement for a part of the standard

curriculum) or as individual lessons that support

How Does the Module Correlate

or enhance your treatment of specific concepts in

with the National Science Education

middle school science. The following pages offer

Standards?

general suggestions about using these materials in

Chemicals, the Environment, and You supports

the classroom; you will find specific suggestions

teachers in their efforts to reform science

in the procedures provided for each lesson.

education in the spirit of the National Research

Council’s 1996 National Science Education

What Are the Goals of the Module?

Standards (NSES). The content of the module is

Chemicals, the Environment, and You is designed to

explicitly standards based: Each time a standard

help students develop the following major goals

is addressed in a lesson, an icon appears in the

associated with scientific literacy:

margin and the applicable standard is identified.

• to understand a set of basic scientific principles

Table 3 lists the specific content standards this

related to chemicals, human health, and the

module addresses (page 5).

study of toxicology;

• to experience the process of scientific inquiry

Teaching Standards

and develop an enhanced understanding of the

The suggested teaching strategies in all the

nature and methods of science; and

lessons support teachers as they work to meet

• to recognize the role of science in society and

the teaching standards outlined in the National

the relationship between basic science and

Science Education Standards. The module helps

human health.

teachers of science plan an inquiry-based science

program by providing short-term objectives for

What Are the Science Concepts and

students. It also includes planning tools such as

How Are They Connected?

the Conceptual Flow of the Lessons ( Table 2) and

We have organized the lessons to form a

the Suggested Timeline (Table 8) for teaching the

conceptual whole that moves students from

module. Teachers can use this module to update

an introduction to chemicals and toxicology

their curriculum in response to their students’

( Chemicals, Chemicals, Everywhere), to an

interest in this topic. The focus on active,

investigation of the effect of various doses of

collaborative, and inquiry-based learning in the

chemicals on seed germination ( The Dose Makes

lessons helps teachers support the development of

the Poison), to a discussion of the relationship

student understanding and nurture a community

between dose and response that can be

of science learners.

represented by a dose-response curve ( Dose-

Response Relationships). Once students have

The structure of the lessons in this module

experienced the process of toxicology testing,

enables teachers to guide and facilitate learning.

they discuss how individual responses to

All the activities encourage and support student

chemicals can vary ( Individual Responses Can Be

inquiry, promote discourse among students,

Different), and how knowledge about chemicals

and challenge students to accept and share

can be used to assess and manage risk from

responsibility for their learning. The use of

chemical exposure ( What Is the Risk? ). Finally,

the 5E Instructional Model combined with

students consider how their understanding of

active, collaborative learning allows teachers to

how chemicals can affect human health can help

respond effectively to the diversity of student

them make decisions related to personal and

backgrounds and learning styles. The module is

public health ( Environmental Hazards).

fully annotated, with suggestions for how teachers

3

Chemicals, the Environment, and You

Table 2. Conceptual flow of the lessons.

Lesson

Learning Focus

Major Concept

Lesson 1

Engage: Students express Everything in the environment is made of chemicals.

Chemicals,

prior knowledge and

Both naturally occurring and synthetic substances are

Chemicals,

become engaged in the

chemical in nature. People are exposed to chemicals

Everywhere

study of toxicology.

by eating or swallowing them, breathing them, or

absorbing them through the skin or mucosa, and they

can protect themselves from harmful chemicals by

blocking these routes of exposure.

Lesson 2

Explore: Students

The total amount of chemical that is administered

The Dose

explore the response

to, or taken by, an organism is called a dose, and

Makes the

seeds have to different

the effect a chemical has on a living organism is

Poison

doses of chemicals. The

called the response. The effect a chemical has on a

Explore phase gives

living organism is related to dose and the resultant

students a common

concentration of the chemical in the organism. Toxicity

set of experiences

tests enable toxicologists to learn about responses of

upon which to begin

living organisms to doses of chemicals.

building conceptual

understanding.

Lesson 3

Explain: Students

Dose and response are related and can be represented

Dose-Response

express their conceptual

by a dose-response curve. Data from toxicology testing

Relationships

understanding of the

can be represented by a dose-response curve, from

laboratory investigation

which scientists can describe the threshold and potency

in their own words and

of chemicals.

using graphs.

Lesson 4

Explain/Elaborate:

The variety of responses among organisms that get the

Individual

Students broaden

same dose of chemical is due to individual susceptibility.

Responses

their conceptual

Dose and individual susceptibility play roles in all

Can Be

understanding and apply situations involving chemicals, including those involving Different

what they have learned

medicines and caffeine.

in a new context.

Lesson 5

Elaborate: Students

People can make some choices about chemical

What Is

extend the module’s

exposure; however, some exposure is controlled at a

the Risk?

concepts in a different

level other than an individual one. Collective groups

activity to help them

of people, such as communities and governments,

apply scientific terms

seek to control chemical exposure on a community

and concepts in

or global level.

appropriate ways.

Lesson 6

Evaluate: Students

People can use their understanding of the science of

Environmental

demonstrate their

toxicology to identify potential sources of harm to

Hazards

understanding

human health from chemicals in the environment.

of concepts and

They can use their knowledge to propose possible

performance of skills.

means to eliminate or reduce exposure to

environmental toxic agents.

4

Table 3. Content Standards: Grades 5−8.

Standard A: As a result of activities in grades 5–8, all students should Correlation to Chemicals,

develop abilities necessary to do scientific inquiry and understandings

the Environment, and You

about scientific inquiry.

• Design and conduct a scientific investigation.

Lessons 2, 4

• Use appropriate tools and techniques to gather, analyze, and

Lessons 2, 3, 4

interpret data.

• Develop descriptions, explanations, predictions, and models using

Lessons 2, 3, 4, 6

evidence.

• Think critically and logically to make the relationships between

Lessons 3, 4, 6

evidence and explanations.

• Communicate scientific procedures and explanations.

Lesson 3

• Use mathematics in all aspects of scientific inquiry.

Lessons 2, 3, 4

• Develop understandings about scientific inquiry.

Lessons 2, 4, 6

Standard B: As a result of their activities in grades 5–8, all students Correlation to module

should develop an understanding of properties of matter.

• There are more than 100 known elements that combine in a

Lesson 1

multitude of ways to produce compounds, which account for the

living and nonliving substances we encounter.

Standard E: As a result of their activities in grades 5–8, all students Correlation to module

should develop understandings about science and technology.

• Perfectly designed solutions do not exist. All technological solutions

Lessons 1, 5

have trade-offs, such as safety, cost, efficiency, and appearance.

• Technological solutions have intended benefits and unintended

Lessons 1, 4, 5

consequences. Some consequences can be predicted, others cannot.

Standard F: As a result of their activities in grades 5–8, all students Correlation to module

should develop an understanding of

• personal health

Lessons 4, 5, 6

• natural hazards

Lessons 1, 5, 6

• risks and benefits

Lessons 1, 5, 6

Standard G: As a result of their activities in grades 5–8, all students Correlation to module

should develop an understanding of the history and nature of science.

• Understand science as a human endeavor.

All lessons

• Understand the nature of science.

All lessons

• Understand the history of science.

Lesson 5

5

Implementing the Module

Chemicals, the Environment, and You

can encourage and model the skills of scientific

constructivism. A constructivist view of learning

inquiry, as well as the curiosity, openness

recognizes that students need time to

to new ideas and data, and skepticism that

• express their current thinking;

characterize science.

• interact with objects, organisms, substances,

and equipment to develop a range of

Assessment Standards

experiences on which to base their thinking;

• reflect on their thinking by writing and

Teachers can engage in ongoing assessment of

expressing themselves and comparing what

their teaching and of student learning using the

they think with what others think; and

variety of assessment components embedded

• make connections between their learning

within the module’s structure. The assessment

experiences and the real world.

tasks are authentic: They are similar in form

to tasks in which students will engage in their

This module provides a built-in structure for

lives outside the classroom or in which scientists

creating a constructivist classroom: The 5E

participate. Annotations guide teachers to these

Instructional Model. The model sequences the

opportunities for assessment and provide answers

learning experiences so that students have the

to questions that can help teachers analyze

opportunity to construct their understanding of

student feedback.

a concept over time. The model takes students

through five phases of learning that are easily

How Does the 5E Instructional Model

described using five words that begin with the

Promote Active, Collaborative, Inquiry-

letter “E”: Engage, Explore, Explain, Elaborate,

Based Learning?

and Evaluate. The following paragraphs illustrate

Because learning does not occur through a

how the 5Es are implemented across the lessons

process of passive absorption, the lessons in

in this module.

this module promote active learning: Students

are involved in more than listening and

Engage

reading. They are developing skills, analyzing

Students come to learning situations with prior

and evaluating evidence, experiencing and

knowledge. This knowledge may or may not

discussing, and talking to their peers about

be congruent with the concepts presented in

their own understandings. Students work

this module. The Engage lesson provides the

collaboratively with others to solve problems

opportunity for teachers to find out what students

and plan investigations. Many students find that

already know or what they think they know

they learn better when they work with others in

about the topic and concepts to be developed.

a collaborative environment than they can when

they work alone in a competitive environment.

The Engage lesson in this module, Lesson 1:

When all this active, collaborative learning

Chemicals, Chemicals, Everywhere, is designed to

is directed toward inquiry science, students

• pique students’ curiosity and generate interest,

succeed in making their own discoveries. They

• determine students’ current understanding

ask questions, observe, analyze, explain, draw

of the concepts of chemicals and routes

conclusions, and ask new questions. These

of exposure,

inquiry experiences include both those that

• invite students to raise their own questions

involve students in direct experimentation and

about chemicals and human health,

those in which students develop explanations

• encourage students to compare their ideas with

through critical and logical thinking.

the ideas of others, and

• allow teachers to assess what students do or do

This view of students as active thinkers who

not understand about the stated outcomes of

construct their own understanding out of

the lesson.

interactions with phenomena, the environment,

and other individuals is based on the theory of

6

Explore

• compare their ideas with what scientists

know and understand about toxicology

In the Explore phase of the module, Lesson 2:

testing and the application of the results to

The Dose Make the Poison, students explore the

human systems.

effect different doses of chemicals have on seed

germination. This lesson provides a common

Elaborate

set of experiences within which students can

compare what they think about what they are

In Elaborate lessons, students apply or extend

observing and experiencing.

the concepts in new situations and relate their

previous experiences to new ones.

During the Explore lesson, students

• interact with materials and ideas during the

In the Elaborate lessons in this module, part of

seed investigation;

Lesson 4: Individual Responses Can Be Different

• consider different ways to solve a problem or

and Lesson 5: What Is the Risk? , students

answer a question;

• make conceptual connections between new

• acquire a common set of experiences with

and former experiences, particularly with

their classmates so they can compare results

respect to the dose of medicine they take and

and ideas;

the effect of the caffeine they drink;

• observe, describe, record, compare, and share

• use what they have learned to explain the

their ideas and experiences; and

acetaminophen mystery and the tragedy that

• express their developing understanding of the

happened in Minamata, Japan;

effects of chemicals on seed germination orally

• connect ideas, solve problems, and apply their

and by making graphs.

understanding in these new situations;

• use scientific terms and descriptions;

Explain

• draw reasonable conclusions from evidence

and data;

The Explain lesson provides opportunities for

• add depth to their understanding of concepts

students to connect their previous experiences

and processes; and

and to begin to make conceptual sense of the

• communicate their understanding to others.

main ideas of the module. This stage also allows

for the introduction of formal language, scientific

Evaluate

terms, and content information that might make

students’ previous experiences easier to describe

The Evaluate lesson is the final stage of the

and explain.

instructional model, but it only provides a

“snapshot” of what the students understand

In the Explain lessons in this module, Lesson

and how far they have come from where they

3: Dose-Response Relationships and Lesson 4:

began. In reality, the evaluation of students’

Individual Responses Can Be Different, students

conceptual understanding and ability to use skills

• explain concepts and ideas about their seed

begins with the Engage lesson and continues

investigations in their own words;

throughout each stage of the model, as described

• listen to and compare others’ explanations of

in the following section. Combined with the

their results with their own;

students’ written work and performance of tasks

• become involved in student-to-student

throughout the module, however, the Evaluate

discourse in which they explain their thinking

lesson can serve as a summative assessment of

to others and debate their ideas;

what students know and can do.

• revise their ideas;

• record their ideas and current understanding;

The Evaluate lesson in this module, Lesson 6:

• use labels, terminology, and formal language to

Environmental Hazards, provides opportunities for

describe dose-response relationships;

students to

• compare their current thinking with what they

• demonstrate what they understand about the

previously thought; and

concepts of toxicology and how well they can

7

Implementing the Module

Chemicals, the Environment, and You

implement the skills of assessing risk and

aligned with the most commonplace instructional

deciding on risk management;

strategies found in U.S. science classrooms (as

• share their current thinking with others;

documented by Weiss et al., 2003). Both groups

• apply their understanding and knowledge of

had the same master teacher.

the relationship between chemicals in the

environment and human health in a unique,

Students taught with the BSCS 5Es and

but related, situation;

an inquiry-based approach demonstrated

• assess their own progress by comparing

significantly higher achievement for a range of

their current understanding with their prior

important learning goals, especially when the

knowledge; and

results were adjusted for variance in pretest

• ask new questions that take them deeper into a

scores. The results were also consistent across

concept or topic area.

time (both immediately after instruction and four

weeks later). Improvements in student learning

To review the relationship of the 5E Instructional

were particularly strong for measures of student

Model to the concepts presented in the module,

reasoning and argumentation. The following

see Table 2.

chart (Table 4) highlights some of the study’s key

findings. The results of the experiment strongly

When a teacher uses the 5E Instructional Model,

support the effectiveness of teaching with the

he or she engages in practices that are very

BSCS 5Es.

different from those of a traditional teacher.

In response, students also participate in their

Evidence also suggests that the BSCS 5Es are

learning in ways that are different from those

effective in changing students’ attitudes on

seen in a traditional classroom. Tables 5 and 6

important issues. In a research study conducted

outline these differences.

during the field test for the NIH curriculum

supplement The Science of Mental Illness (2005),

What’s the Evidence for the

BSCS partnered with researchers at the University

Effectiveness of the BSCS 5E

of Chicago and the National Institute of Mental

Instructional Model?

Health. The study investigated whether a short-

Support from educational research studies for

term educational experience would change

teaching science as inquiry is growing (for

students’ attitudes about mental illness. The results

example, Geier et al., 2008; Hickey et al., 1999;

showed that after completing the curriculum

Lynch et al., 2005; and Minner et al., 2009). A

supplement, students stigmatized mental illness

2007 study, published in the Journal of Research

less than they had beforehand. The decrease in

in Science Teaching (Wilson et al., 2010), is also

stigmatizing attitudes was statistically significant

relevant here.

(Corrigan et al., 2007; Watson et al., 2004).

In 2007, with funding from NIH, BSCS conducted

How Does the Module Support

a randomized, controlled trial to assess the

Ongoing Assessment?

effectiveness of the BSCS 5Es. The study used an

Because teachers will use this module in a

adaptation of the NIH supplement Sleep, Sleep

variety of ways and at a variety of points in their

Disorders, and Biological Rhythms, developed by

curriculum, the most appropriate mechanism

BSCS in 2003. Sixty high school students and

for assessing student learning is one that occurs

one teacher participated. The students were

informally at various points within the six

randomly assigned to the experimental or the

lessons, rather than something that happens

control group. In the experimental group, the

more formally just once at the end of the module.

teacher used a version of the sleep supplement

Accordingly, integrated within the six lessons in

that was very closely aligned with the theoretical

the module are specific assessment components.

underpinnings of the BSCS 5Es. For the control

These embedded assessment opportunities

group, the teacher used a set of lessons based on

include one or more of the following strategies:

the science content of the sleep supplement but

8

Table 4. Differences in performance of students receiving inquiry-based and commonplace instructional approaches.

Mean for

Mean for

Students

Students

Measure

Receiving

Receiving

Effect Size

Commonplace

Inquiry-Based

Teaching

Teaching

Total test score pretest (out of 74)

31.11

29.23

Not applicable

Total test score posttest

42.87

47.12

0.47

Reasoning pretest (fraction of responses at

0.04

0.03

Not applicable

the highest level)

Reasoning posttest

0.14

0.27

0.68

Score for articulating a claim (out of 3)

1.58

1.84

0.58

Score for using evidence in an explanation

1.67

2.01

0.74

(out of 3)

Score for using reasoning in an explanation

1.57

1.89

0.59

(out of 3)

Source: Wilson, C.D., et al. 2010. The relative effects and equity of inquiry-based and commonplace science teaching on students’

knowledge, reasoning, and argumentation. Journal of Research in Science Teaching, 47(3), 276−301.

Note: Effect size is a convenient way of quantifying the amount of difference between two treatments. This study used the standardized mean difference (the difference in the means divided by the standard deviation, also known as Cohen’s d ). The posttest scores controlled for the variance in students’ pretest scores. The reasoning posttest scores controlled for variance in students’ reasoning pretest scores at the highest level.

• performance-based activities (for example,

How Can Teachers Promote Safety

developing graphs or participating in a

in the Science Classroom?

discussion of risk assessment);

Even simple science demonstrations and

• oral presentations to the class (for example,

investigations can be hazardous unless teachers

presenting experimental results); and

and students know and follow safety precautions.

• written assignments (for example, answering

Teachers are responsible for providing students

questions or writing about demonstrations).

with active instruction concerning their conduct

and safety in the classroom: Posting rules in

These strategies allow the teacher to assess

a classroom is not enough. They also need to

a variety of aspects of the learning process,

provide adequate supervision and advance

such as students’ prior knowledge and current

warning if there are dangers involved in the

understanding, problem-solving and critical-

science investigation. By maintaining equipment

thinking skills, level of understanding of new

in proper working order, teachers ensure a safe

information, communication skills, and ability

environment for students.

to synthesize ideas and apply understanding to a

new situation.

The following are important ways to implement

and maintain a safety program.

An assessment icon and an annotation that

• Provide eye protection for students,

describes the aspect of learning teachers can

teachers, and visitors. Require that everyone

assess appear in the margin beside the step in

participating wear regulation goggles in any

which each embedded assessment occurs.

9

Implementing the Module

Chemicals, the Environment, and You

Table 5. The key components of the BSCS 5E Model: What the teacher does.

What the teacher does that is

What the teacher does that is

Phase

consistent with the 5E Model

inconsistent with the 5E Model

Engage

• Piques students’ curiosity and generates interest

• Introduces vocabulary

• Determines students’ current understanding (prior • Explains concepts knowledge) of a concept or idea

• Provides definitions and

• Invites students to express what they think

answers

• Invites students to raise their own questions

• Provides closure

• Discourages students’ ideas

and questions

Explore

• Encourages student-to-student interaction

• Provides answers

• Observes and listens to the students as they

• Proceeds too rapidly for

interact

students to make sense of

• Asks probing questions to redirect the students’

their experiences

investigations when necessary

• Provides closure

• Asks questions to help students make sense of

• Tells the students that they

their experiences

are wrong

• Provides time for students to puzzle through

• Gives information and facts

problems

that solve the problem

• Leads the students step-by-

step to a solution

Explain

• Encourages students to use their common

• Neglects to solicit students’

experiences and data from the Engage and

explanations

Explore lessons to develop explanations

• Ignores data and information

• Asks questions that help students express

students gathered from

understanding and explanations

previous lessons

• Requests justification (evidence) for

• Dismisses students’ ideas

students’explanations

• Accepts explanations that are

• Provides time for students to compare their

not supported by evidence

ideas with those of others and perhaps to revise

• Introduces unrelated concepts

their thinking

or skills

• Introduces terminology and alternative

explanations after students express their ideas

Elaborate

• Focuses students’ attention on conceptual

• Neglects to help students

connections between new and former experiences

connect new and former

• Encourages students to use what they have

experiences

learned to explain a new event or idea

• Provides definitive answers

• Reinforces students’ use of scientific terms and

• Tells the students that they

descriptions previously introduced

are wrong

• Asks questions that help students draw reasonable • Leads students step-by-step to conclusions from evidence and data

a solution

Evaluate

• Observes and records as students demonstrate

• Tests vocabulary words, terms,

their understanding of concept(s) and

and isolated facts

performance of skills

• Introduces new ideas or

• Provides time for students to compare their

concepts

ideas with those of others and perhaps to revise

• Creates ambiguity

their thinking

• Promotes open-ended

• Interviews students as a means of assessing their

discussion unrelated to the

developing understanding

concept or skill

• Encourages students to assess their own progress

10

Table 6. The key components of the BSCS 5E Model: What the students do.

What the students do that is

What the students do that is

Phase

consistent with the 5E Model

inconsistent with the 5E Model

Engage

• Become interested in and curious about the

• Ask for the “right” answer

concept/topic

• Offer the “right” answer

• Express current understanding of a concept

• Insist on answers or explanations

or idea

• Seek closure

• Raise questions such as, What do I already

know about this? What do I want to know

about this? How could I find out?

Explore

• “Mess around” with materials and ideas

• Let others do the thinking and

• Conduct investigations in which they

exploring (passive involvement)

observe, describe, and record data

• Work quietly with little or no

• Try different ways to solve a problem or

interaction with others (only

answer a question

appropriate when exploring ideas

• Acquire a common set of experiences so they

or feelings)

can compare results and ideas

• Stop with one solution

• Compare their ideas with those of others

• Demand or seek closure

Explain

• Explain concepts and ideas in their own

• Propose explanations from “thin

words

air” with no relationship to

• Base their explanations on evidence acquired

previous experiences

during previous investigations

• Bring up irrelevant experiences

• Become involved in student-to-student

and examples

conversations in which they debate their

• Accept explanations without

ideas

justification

• Record their ideas and current understanding • Ignore or dismiss other plausible

• Reflect on and perhaps revise their ideas

explanations

• Express their ideas using appropriate

• Propose explanations without

scientific language

evidence to support their ideas

• Compare their ideas with what scientists

know and understand

Elaborate

• Make conceptual connections between new

• Ignore previous information or

and former experiences

evidence

• Use what they have learned to explain a new • Draw conclusions from “thin air”

object, event, organism, or idea

• Use terminology inappropriately

• Use scientific terms and descriptions

and without understanding

• Draw reasonable conclusions from evidence

and data

• Communicate their understanding to others

Evaluate

• Demonstrate what they understand about

• Disregard evidence or previously

the concept(s) and how well they can

accepted explanations in drawing

implement a skill

conclusions

• Compare their current thinking with that of

• Offer only yes-or-no answers

others and perhaps revise their ideas

or memorized definitions or

• Assess their own progress by comparing

explanations as answers

their current understanding with their prior

• Fail to express satisfactory

knowledge

explanations in their own words

• Ask new questions that take them deeper

• Introduce new, irrelevant topics

into a concept or topic area

11

Implementing the Module

Chemicals, the Environment, and You

situation where there might be splashes, spills,

technology, and society. Society expects all citizens

or spattering. Teachers should always wear

to participate in the democratic process, and our

goggles in such situations.

educational system must provide opportunities for

• Know and follow the state and district safety

students to learn to deal with contentious issues

rules and policies. Be sure to fully explain to

with civility, objectivity, and fairness. Likewise,

the students the safety rules they should use in

students need to learn that science intersects with

the classroom.

life in many ways.

• At the beginning of the school year, establish

consequences for students who behave in an

In this module, students have a variety of

unsafe manner. Make these consequences clear

opportunities to discuss, interpret, and evaluate

to students.

basic science and health issues in the light

• Do not overlook any violation of a safety

of values and ethics. As students encounter

practice, no matter how minor. If a rule is

issues about which they feel strongly, some

broken, take steps to ensure that the infraction

discussions might become controversial. How

will not occur a second time.

much controversy develops will depend on many

• Set a good example by observing all safety

factors, such as how similar the students are with

practices. This includes wearing eye protection

respect to socioeconomic status, perspectives,

when it is required for students.

value systems, and religious preferences. It will

• Know and follow waste disposal regulations.

also depend on how you handle your role as

• Be aware of students who have allergies or

facilitator. Your language and attitude factor into

other medical conditions that might limit their

the flow of ideas and the quality of exchange

ability to participate in activities. Consult with

among the students.

the school nurse or school administrator.

• Anticipate potential problems. When planning

The following guidelines may help you think

teacher demonstrations or student investigations,

about how to guide your students in discussions

identify potential hazards and safety concerns. Be

that balance factual information with feelings.

aware of what might go wrong and what can be

• Remain neutral. Neutrality may be the single

done to prevent the worst-case scenario. Before

most important characteristic of a successful

each activity, alert the students to the potential

discussion facilitator.

hazards verbally and distribute specific safety

• Encourage your students to discover as much

instructions as well.

information about the issue as possible.

• Supervise students at all times during a

• Keep the discussion relevant and moving

hands-on activity.

forward by questioning or posing appropriate

• Provide sufficient time for students to set up

problems or hypothetical situations. Encourage

the equipment, perform the investigation, and

everyone to contribute, but do not force

properly clean up and store the materials after use.

reluctant students into the discussion.

• Never assume that students know or remember

• Emphasize that everyone must be open to

safety rules or practices from their previ ous

hearing and considering diverse views.

science classes.

• Use unbiased questioning to help students

critically examine all views presented.

How Can Controversial Topics Be

• Allow for the discussion of all feelings

Handled in the Classroom?

and opinions.

Teachers sometimes feel that the discussion of

• Avoid seeking consensus on all issues.

values is inappropriate in the science classroom or

The multifaceted issues that the students

that it detracts from the learning of “real” science.

discuss result in the presentation of divergent

The lessons in this module, however, are based on

views, and students should learn that this

the conviction that there is much to be gained by

is acceptable.

involving students in analyzing issues of science,

• Keep your own views out of the discussion.

If your students ask what you think, you may

12

wish to respond with a statement such as, “My

• Insist on a nonhostile environment in the

personal opinion is not important here. We

classroom. Help your students learn to

want to consider your views.”

respond to ideas instead of to the individuals

• Acknowledge all contributions in the same

presenting those ideas.

evenhanded manner. If a student seems

• Respect silence. Reflective discussions are

to be saying something for its shock

often slow. If you break the silence, your

value, see whether other students recognize

students may allow you to dominate the

the inappropriate comment and invite them

discussion.

to respond.

• Finally, at the end of the discussion, ask your

• Create a sense of freedom in the classroom.

students to summarize the points they and

Remind students, however, that freedom

their classmates have made. Let students know

implies the responsibility to exercise that

that your respect for them does not depend on

freedom in ways that generate positive results

their opinion about any controversial issue.

for all.

13

Implementing the Module

Using the Student Lessons

The heart of this module is the set of six lessons,

• Photocopies or transparencies lists the copies

which we hope will carry important concepts

that need to be made from masters, which

related to human health and chemicals in

follow the student lessons.

the environment to your students. To review

• Materials lists all the materials needed for

the concepts in detail, refer to Table 2 in

each of the activities in the lesson. A complete

“Implementing the Module” (page 4).

materials list for the entire module can be

found on pages 18 and 19.

Format of the Lessons

• Preparation outlines the things you need to

As you scan the lessons, you will find that each

do to be ready to teach each of the activities in

contains several major features.

the lesson.

At a Glance gives you a convenient summary of

Procedure outlines the steps for each activity

the lesson.

in the lesson. It provides implementation

• The Overview provides a short summary of

suggestions and answers to questions. Lessons

what students do.

1–5 each include an Extension Activity that

• Major Concepts states the central idea(s) the

describes ways to extend or enrich the lesson.

lesson is designed to convey.

• Objectives lists two to six specific

Within the procedures, annotations provide

understandings or abilities students should

additional commentary.

have after completing the lesson.

• Tip from the Field Test includes actual

field-test teachers’ suggestions for teaching

Background Information gives you the science

strategies, class management, and module

content that underlies the key concepts of

implementation.

the lessons. The information provided here is

• Assessment provides strategies for assessing

not intended to form the basis of lectures to

student progress throughout the module and is

students. Instead, it is designed to enhance

identified by an assessment icon (see below).

your understanding of the content so that you

• Icons identify specific annotations:

can more accurately facilitate class discussions,

answer student questions, and provide

identifies teaching strategies that

additional examples.

address specific science content

standards as defined by the National

Notes about the Lessons places each lesson

Science Education Standards.

in the context of the concepts presented in

the Background Information. It provides a short

identifies when to use the Web site

commentary about the practical application of the

as part of the teaching strategies.

concepts to the activities in the lesson.

A print-based alternative (with "-p"

after step numbers) is provided in

In Advance provides instructions for collecting

each lesson for all Web-based activities in case

and preparing the materials required to complete

access to the Web site is not available.

the activities in the lesson.

• Web-Based Activities tells you which of the

identifies when assessment is

lesson’s activities make use of segments on the

embedded in the module’s structure.

Web site.

An annotation suggests strategies

for assessment.

15

Chemicals, the Environment, and You

The Masters required to teach the lessons are in a

activities on consecutive days. It is important that

separate section at the end of the module.

Activities 3 and 4 from Lesson 2 and Activity

1 from Lesson 3 follow each other on three

Timeline for Teaching the Module

consecutive days. If your class requires more time

There are several ways to complete the six

for laboratory procedures, discussion of issues

lessons in this module. The first timeline

raised in this module, or completing the Web-

(Table 7) outlines the optimal plan for completing

based activities, adjust your timeline accordingly.

the lessons. The plan assumes you will teach the

Table 7. Suggested optimal timeline.

Cross-Curricular

Timeline

Activity

Opportunities

3 weeks ahead

Reserve computers and bookmark the Web site.

None

1 week ahead

Copy masters.

None

Make transparencies.

Gather materials.

Day 1

Lesson 1

None

Wednesday

Activity 1: What Is a Chemical?

Activity 2: Protect the Toxicologist

Day 2

Activity 3: Case Studies of Routes of Exposure

Language Arts

Thursday

Day 3

Lesson 2

Friday

Activity 1: Dose and Concentration

Mathematics

Activity 2: Planning the Seed Investigation

Day 4

Activity 3: Setting Up the Seed Investigation

None

Monday

Day 5

Activity 4: Gathering Data

Mathematics

Tuesday

Day 6

Lesson 3

Wednesday

Activity 1: Graphing the Response to Chemical Dose

Mathematics

Day 7

Lesson 4

None

Thursday

Activity 1: Different Doses for Different People

Day 8

Activity 2: A Poisonous Dose?

Mathematics/Health

Friday

Day 9

Activity 3: The Chemical Caffeine: How Do You

Mathematics/Health

Monday

Respond?

Day 10

Lesson 5

Social Studies

Tuesday

Activity 1: People at Risk

Language Arts

Activity 2: What Is Your Risk?

Day 11

Lesson 6

None

Wednesday

Activity 1: The Field Trip

Activity 2: What Can I Do?

16

The second timeline (Table 8) outlines an

Master List of Supplies

abbreviated schedule for completing the lessons

Table 9 is the master list of supplies for the

in the curriculum supplement by assigning some

supplement based on a class of 30 students.

activities as homework, using the Web site in

place of the laboratory experience, and deleting

one activity.

Table 8. Abbreviated timeline.

Timeline

Activity

3 weeks ahead

Reserve computers and bookmark the Web site.

1 week ahead

Copy masters.

Make transparencies.

Gather materials.

Day 1

Lesson 1

Wednesday

Activity 1: What Is a Chemical? Activity 2: Protect the Toxicologist

Activity 3 (assigned as homework): Case Studies of Routes of Exposure

Day 2

Lesson 2

Thursday

Activity 1: Dose and Concentration

Activity 2: Planning the Seed Investigation

Day 3

Use the Web site to gather data for the seed investigation.

Friday

Lesson 3

Activity 1 (assigned as homework): Graphing the Response to Chemical Dose

Day 4

Discuss the homework and Web version of investigation

Monday

Day 5

Lesson 4

Tuesday

Activity 1: Different Doses for Different People

Activity 2: omit

Day 6

Activity 3: The Chemical Caffeine: How Do You Respond?

Wednesday

Day 7

Lesson 5

Thursday

Activity 1: People at Risk

Activity 2: What Is Your Risk?

Day 8

Lesson 6

Friday

Activity 1: The Field Trip

Activity 2: What Can I Do?

17

Using the Student Lessons

Chemicals, the Environment, and You

Table 9. Master list of supplies for Chemicals, the Environment, and You, based on a class of 30 students, by lesson (L) and activity number (E, extension activity).

L1 L1 L1 L1 L2 L2 L2 L2 L2 L3 L3 L4 L4 L4 L4 L5 L5 L5 L6 L6

Lesson (L)

-1

-2 -3 -E -1 -2

-3

-4 -E -1 -E -1 -2

-3

-E -1 -2 -E

-1

-2

Beaker (50-mL)

1

60

1

Beaker (100-mL)

10

1

Beaker (1000-mL)

3

4

or large jars

Caffeinated soft

30

drink (12 oz.)

Chemicals

(variety)

P

P

Clear containers

3

(different sizes)

Clock with

second hand

P

Clothing

(variety)

P

Coin (only for

30

print version)

Computer with

Web access

P

P P

P

P

P

P

P

Current events

stories

P

P

Eyedropper

P

10

P

Food coloring

(blue)

P

Graduated

cylinder

P

10

(50-mL)

Graduated

cylinder

10

(10-mL)

Index cards

(4 x 6)

P

Jar with lid

(50 mL or larger)

1

18

L1 L1 L1 L1 L2 L2 L2 L2 L2 L3 L3 L4 L4 L4 L4 L5 L5 L5 L6 L6

Lesson (L)

-1

-2 -3 -E -1 -2

-3

-4 -E -1 -E -1 -2

-3

-E -1 -2 -E

-1

-2

Latex gloves,

pair

P

30

P

P

Masking tape

P

Overhead

markers

P

P

Overhead

projector

P

P

P

P

P P

P P P

Paper napkin

(one-ply,

120

12 x 115/8 in.)

Permanent

10

marker

Plain paper

P P

Plastic resealable

1

60

sandwich bag

Poster board,

1

white

Purified water

P

P

Radish seeds

P

600

Red marker (only

1

for print version)

Safety glasses

P

30

Science

30

notebook

P

P P

P

P

P

Shoe box (large

1

with cover)

Transparency

P

P

P P

Tray

10

19

Using the Student Lessons

Using the Web Site

The Web component of Chemicals, the

they do not allow all students to experience the

Environment, and You is a wonderful tool that

in-depth discovery and analysis that the Web site

you can use to help organize your use of the

was designed to stimulate.

module, engage student interest in learning, and

help orchestrate and individualize instruction.

If you are teaching all six lessons as a unit, we

The site features simulations, animations, and

recommend that you keep your students in the

videos that articulate with the lessons. To access

same collaborative groups for all of the activities.

the curriculum’s home page, go to http://science.

This will allow each group to develop a shared

education.nih.gov/supplements/chemicals. (If your experience with the software and with the ideas

classes don’t have access to the Internet, you

and issues that the activities present. A shared

can use the print alternatives included with

experience also will enhance your students’

the lessons.)

perceptions of the lessons as a conceptual whole.

Hardware and Software Requirements

If your student-to-computer ratio is greater than

The Web site can be accessed with any computer

six students to one computer, you will need to

browser. Adobe Flash Player should be installed

change the way you teach the module from the

on the hard drive of each computer that will

instructions in the lessons. For example, if you

access the site. It’s freely available at http://get.

have only one computer available, you may want

adobe.com/flashplayer/.

students to complete the Web-based work over

an extended time period. You can do this in

Getting the Most out of the Web Site

several ways. The most practical one is to use

The ideal use of the Web site requires one

your computer as a center along with several other

computer for each student group. However, if you

centers at which students complete other activities.

have only one computer available, you can still

In this approach, students rotate through the

use the site. You can, for example, project the

computer center, eventually completing the Web-

monitor image for the whole class. If you do not

based work you have assigned.

have access to the Web site, you can use the print-

based alternative provided for each Web activity.

A second way to structure the lessons if you have

only one computer available is to project the

Collaborative Groups

monitor image for the whole class to see. Giving

We designed many of the activities in this

selected students in the class the opportunity

module to be completed by groups of students

to manipulate the Web activities in response to

working together. Although individual students

suggestions and requests from the class can give

working alone can complete many of the specific

students some of the same autonomy in their

steps, this strategy will not stimulate the types

learning they would have gained from working in

of student-student interactions that are one of

small groups.

the goals of active, collaborative, inquiry-based

Web Activities for People with Disabilities

learning. Therefore, we recommend that you

organize collaborative groups of between two and

The Office of Science Education provides access

six students each, depending on the number of

to the Curriculum Supplement Series for people

computers available. Students in groups larger

with disabilities. The online versions of this series

than this will have difficulty organizing the

comply with Section 508 of the Rehabilitation Act.

student-computer interactions equitably, which

If you use assistive technology (such as a Braille

can lead to one or two students’ assuming the

or screen reader) and have trouble accessing

primary responsibility for the computer-based

any materials on our Web site, please let us

work. Although large groups can be efficient,

know. We’ll need a description of the problem,

21

Chemicals, the Environment, and You

the format in which you would like to receive

Contact us at

the material, the Web address of the requested

supplements@science.education.nih.gov

material, and your contact information.

or

(301) 402-2469

22

L E S S O N 1

Chemicals,

Engage

Chemicals,

Everywhere

Overview

At a Glance

Students divide substances into categories: made of chemicals/not made

of chemicals, synthetic/naturally occurring, and toxic/nontoxic. When

the teacher reveals that all the substances are made of chemicals, students discuss how their concept of what a chemical is might differ from the

scientific definition. Students observe a mystery chemical and determine

what precautions they might need to take when handling an unknown

substance. Then, students read case studies of real exposures to chemicals.

Major Concepts

Everything in the environment is made of chemicals. Both naturally

occurring and synthetic substances are chemical in nature. People are

exposed to chemicals by eating or swallowing them, breathing them,

or absorbing them through the skin or mucosa, and they can protect

themselves from harmful chemicals by blocking these routes of exposure.

Objectives

After completing this lesson, students will

• understand that everything in their environment is made of chemicals;

• indicate that both naturally occurring and synthetic substances are

chemical in nature;

• recognize that their view of a chemical as “bad” or “good” relates to

their perception of a chemical’s potential toxicity to humans or other

living organisms;

• realize that toxicologists study chemicals to find out if they are harmful to living organisms;

• understand that people are exposed to chemicals by eating or

swallowing them, breathing them, or absorbing them through the skin

or mucosa; and

• demonstrate that people can protect themselves from harmful chemicals

by blocking these routes of exposure.

23

Chemicals, the Environment, and You

What Is a Chemical?

Background

Simply stated, a chemical is any substance that has a defined molecular Information

composition. Molecules, which are the smallest units into which a

compound can be divided and still be that compound, can be made up of

one or more elements. Sometimes, the elements are the same, such as in

oxygen: Two oxygen atoms are chemically bonded together to form the

gas oxygen, or O . Sometimes, the elements that form molecules are of

2

different types, such as those in water: Two hydrogen atoms combine with

one oxygen atom to form a molecule of water, or H O. All forms of matter

2

are made of one or more of the more than 100 elements combined in many

different molecular combinations. This means that all forms of matter are

made of chemicals.

2

The Science of Toxicology

Long ago, humans observed that some chemicals derived from nature were

poisonous. Poisonous chemicals produced naturally by living organisms

Paracelsus.

(such as plants, animals, and fungi) are called toxins. Historically, (Reproduced with the permission

knowledge of toxins was a powerful tool to use against enemies: Many

of the Albertina Wien (Vienna).)

24

murderers in ancient Greece and later throughout Europe used toxins

(Klassen, 2008). A significant contribution to the field of toxicology was made by the scientist Paracelsus (1493–1541). He recognized that the same

chemical could have both therapeutic (medicinal) and toxic (poisonous)

properties depending on how much of it was used. His work paved the way

for the concept of the dose-response relationship (see Lesson 3 for more

information about dose and response) (Klassen, 2008; Gilbert, 2004).

With the onset of the industrial revolution and the emergence of the science of synthetic chemistry, a variety of new chemicals was made by humans.

It is estimated that more than 65,000 chemicals have been manufactured

for commercial use in industrialized countries (Eaton and Gallagher, 1997). Whether on purpose or not, humans come into contact with these

chemicals during manufacturing, handling, or consumption. Exposure to a

vast array of synthetic chemicals can occur when a person ingests food or

drink, works in an agricultural setting with pesticides, or lives in a home among solvents, paints, plastics, and fuels. Although many of the chemicals greatly benefit us, some can have a toxic effect on human systems. These

substances are called toxicants, a broad category that includes naturally occurring toxins.

How do people know if a chemical is toxic? The science of toxicology

informs them of the nature of poisons. A toxicologist is a scientist who is trained to study the harmful effects of chemicals on living organisms. These harmful effects can include death, but not all toxicants are lethal. Some

other harmful effects that toxicologists study are disease, tissue damage, genetic alterations, and cancer. Because there are so many ways that

toxicants can affect living things and there are so many different kinds of chemicals in the environment, toxicology is a very broad science and there are many different kinds of toxicologists (Klassen, 2008).

Routes of Exposure

Toxicants can harm an organism only if they are absorbed by the organism

and reach the organs that are the target of their toxicity. This can happen through three routes:

• ingestion,

• inhalation, and

• absorption through the skin (Gilbert, 2004).

In humans and other animals, toxicants usually affect one or more target

organs such as the lungs, skin, or gastrointestinal tract. For example, if a person inhales asbestos fibers, the fibers get stuck in the airways of the lungs and irritate the lung lining, causing lung impairment over time.

Dermatitis can result if the asbestos fibers irritate skin cells.

Sometimes the toxicant crosses from the external environment of the lung,

skin, or gastrointestinal tract into the bloodstream (Klassen, 2008). Many parts of the human body are designed to absorb chemicals quickly and

effectively. The stomach, intestines, and colon absorb nutrients from our

diet. These organs easily absorb nutrients and other chemicals because of

25

Student Lesson 1

Chemicals, the Environment, and You

What Do Toxicologists Do?

Descriptive toxicologists evaluate the toxicity of drugs, food additives, and other products.

They ask the question, What happens if …? about the amount of a toxicant and the response that a living system has to the toxicant. The descriptive toxicologist might work in a pharmaceutical laboratory or in an academic setting doing data analysis, animal testing, and/or human clinical trials (Society of Toxicology, 2012).

Mechanistic toxicologists study how a chemical

causes toxic effects on living organisms. They

study biomedical research, biochemistry, and

physiology to understand how a chemical is

absorbed, distributed, and excreted. In order

to develop antidotes, a mechanistic toxicologist

uses information about how a chemical harms an

organism. This kind of toxicological work is often

done in an academic setting or in private industry

(Society of Toxicology, 2012).

Photo: Corel

Clinical toxicologists are usually physicians interested in the prevention, diagnosis, and treatment of poisoning cases. Clinical toxicologists specialize in toxicology issues concerning drugs used for treatment, such as side effects and overdoses; drugs of abuse, such as alcohol and cocaine; and accidental poisonings. These toxicologists have specialized training in emergency medicine and poison management. Veterinarians can be clinical toxicologists who study poisons in animals (Society of Toxicology, 2012)

Forensic toxicologists study the application of toxicology

to the law. They work with pathologists and law

enforcement officers at a crime scene. The forensic

toxicologist uses chemical analysis to help establish the

cause of death and determine the circumstances of death

in a postmortem investigation (Klassen, 2008)

Environmental toxicologists study the effects of pollutants

on organisms, populations, ecosystems, and the biosphere.

Toxicologists concerned with the effects of environmental

Photo: Cameron Davidson

pollutants on human health fit into this group. Most

commonly, however, environmental toxicologists study

the impacts of chemicals on nonhuman organisms such as fish, birds, terrestrial animals, and plants (Klassen, 2008).

Regulatory toxicologists use scientific data to decide how to protect humans and animals from excessive risk. Regulatory toxicologists aim to protect the public from chemical exposure by establishing regulatory standards for food, drugs, water, air, and insecticides, to name only a few. Government bureaus such as the U.S. Food and Drug Administration (FDA) and the U.S. Environmental Protection Agency (EPA) employ regulatory toxicologists (Klassen, 2008; Society of Toxicology, 2012).

26

their large surface area, thin diffusion distance, and high blood flow. The lungs are also designed for rapid absorption. Chemicals that are inhaled

are quickly absorbed into the bloodstream through the thin walls of the air sacs in the lungs. The skin protects the body from harmful agents in the

environment. However, the skin is in direct contact with the environment.

While the dense outer layer of skin cells is a good barrier to chemical

absorption, it is not perfect, even when intact. When the skin is cut or

abraded, it absorbs chemicals very rapidly (Project Greenskate, 2000).

Students’ Misconceptions about Chemicals

Students often harbor misconceptions about chemicals. When asked what

a chemical is, rather than define the word, students tend to give examples of synthetic, toxic chemicals like pesticides. When asked to name some

things made of chemicals, students list items such as shampoo, window

cleaner, processed foods, and “fake sugar” (aspartame). Students believe

that chemicals pollute rivers and air. Students often do not realize that

natural substances in the world around them also are made of chemicals.

When asked if it would be better if there were fewer chemicals in the world, one student replied that fewer human-made chemicals would mean less

pollution. When pressed, students will agree that some synthetic chemicals, like a pain reliever, can be good; however, students also recognize that even

“good” chemicals like pain relievers can be toxic if a person takes too much.

Notes about Lesson 1

The purpose of this lesson is to help move students from the view that

chemicals are toxic, synthetic substances that are bad for human health

and the environment to the more inclusive view that all things in the

environment, including their bodies, are made of chemicals. Some of both

naturally occurring and synthetic chemicals can have a detrimental effect

on human health and the environment, but many do not. Those that have

a harmful effect on human health do so because they get into the body

through inhalation, ingestion, and absorption.

27

Student Lesson 1

Chemicals, the Environment, and You

In Advance

Web-Based Activities

Activities 1, 2, and 3 have Web components.

Materials and Preparation

Photocopies and Transparencies

Equipment and Materials

1 copy of Master 1.1 for

• computers, overhead projector

the class

• 12 samples of things made

1 transparency of Master 1.2

of chemicals

(optional)

• 1 set of item cards from

1 transparency of Masters 1.3

Master 1.1

and 1.4

• 8 4-by-6-inch index cards

1 copy of Master 1.5, Case

• blue food coloring

Study #1, for each student;

• 50-mL graduated cylinder

for number of copies of

• 50 mL of purified water

Case Studies #2–5, see

• 50-mL or larger glass jar

Preparation for Activity 3

with a lid

• 1 large shoe box with a lid

• variety of clothing in a large

basket or box

• science notebook for

each student

Notes: Because everything in the environment is made of chemicals, any item will work for the 12 samples. Use the chemicals students test in Lesson 2, Activity 3, plus others that do and do not fit students’ concept of chemicals.

The Master 1.1 item cards depict objects that are too big for the materials table or are potentially dangerous. The jar should fit into the shoebox. The clothing could include, for example, elbow pads, shorts, different kinds of hats, boots, sunglasses, earplugs, mittens, and latex gloves.

Preparation

Activity 1

Arrange for students to have access to computers.

Collect samples of things made of chemicals. Place them on a

materials table.

Tip from the field test: To make gathering the materials easier, ask students to bring in one item they think is made of chemicals and one they think is not made of chemicals.

Duplicate and cut out the Item Cards from Master 1.1, Item Cards. Fold them in half to make tent cards. Place the Item Cards on the materials table with the things made of chemicals.

Fold the index cards in half to make tent cards and label them with one of the following titles:

• made of chemicals

28

• not made of chemicals

• synthetic

• naturally occurring

• toxic

• nontoxic

• good

• bad

Make a transparency of Master 1.2, Periodic Table of Elements (optional).

Make a transparency of Master 1.3, Elemental Composition of the

Human Body.

Activity 2

Arrange for students to have access to computers.

Make 50 mL of a mystery chemical:

• Measure 5 mL of blue food coloring into a 50-mL graduated cylinder.

• Add purified water to the graduated cylinder until you have 50 mL of

blue solution.

• Pour the mystery chemical into a 50-mL or larger glass jar and screw on the lid tightly. Place it inside the shoe box. Place the shoe box behind

your desk.

• Ask students to bring in articles of clothing. Place them and any you have gathered in a basket or box behind your desk.

Activity 3

Arrange for students to have access to computers.

Make a transparency of Master 1.4, Questions for Case Studies. Duplicate Case Study #1 from the Master 1.5, Case Studies of Routes of Exposure, 1 for each student. Decide whether each student or teams will complete Case

Studies #2–5 and duplicate the appropriate number.

ACTIVITY 1: What Is a Chemical?

Procedure

1. Place the samples of things made of chemicals and the Item Cards on the materials table.

29

Student Lesson 1

Chemicals, the Environment, and You

2. Ask the students to look at the materials table and select one thing that they think is made of chemicals and one thing they think is not

made of chemicals. Direct students not to remove the items, but to

record the name of the items in their science notebooks.

Tip from the field test: In large classes where it might be difficult for students to see the materials, prepare a list of the names of all the materials and make a copy for each student. Instruct students to circle those materials on the list that are made of chemicals.

You might find that students want more information. They might want

to know what you mean by “made of chemicals.” They might want you

to be more specific about whether they should consider only synthetic

items or those that may be toxic. Acknowledge that you have given

them limited information, but ask them to do their best to make their

choices. Do not provide any assistance at this time.

3. Once all the students have recorded the items in their notebooks (or circled the items on their list), ask each student to name one item that is made of chemicals and one that is not. As students tell you their

choices, stand by the materials table and separate the items according

This activity provides you

to student choices into two categories: made of chemicals and not

with a good assessment

made of chemicals. Continue until all students have shared their

of students’ prior

ideas. Use two of the tent cards to label the two categories: “made of

chemicals” and “not made of chemicals.”

knowledge of the

concept of chemicals.

4. Direct students to look at the groups of substances they think are and aren’t made of chemicals. Conduct a discussion by asking questions

similar to these:

• Why do you think these are (or are not) chemicals?

• Can you redivide these items into several different categories, such

as synthetic (made by people) or naturally occurring? Good for

humans or the environment or bad for humans or the environment?

Toxic (harmful) or nontoxic (not harmful)?

• Can a natural substance be made of chemicals?

• Can a synthetic substance not be made of chemicals?

• Is a natural substance always nontoxic, or a synthetic substance

always toxic?

30

As you conduct this discussion, rearrange the items on the table several

times and use new tent cards to label the new categories: “synthetic” or

“naturally occurring”; “toxic” or “nontoxic”; and “bad” or “good.”

5. As you progress through the discussion in Step 4, students may

realize that they do not know a useful definition for “chemical.”

Have this definition ready for them:

chemical: any substance that is made of specific elements combined

Content Standard B:

into molecules

…There are more than

100 known elements

6. As a class, view the segment on the Web site titled Everything Is Made

that combine in a

of Chemicals.

multitude of ways to

produce com-pounds,

To view the segment, go to http://science.education.nih.gov/

which account for the

supplements/chemicals/student. Click on Chemicals, Chemicals,

living and nonliving

Everywhere and select the segment titled Everything Is Made of Chemicals.

substances we encounter.

Note: If you do not have access to the Web site, set up a computer center where students can view the segment on their own or in small groups

at a later time. At this time, display the transparency of Master 1.2,

Periodic Table of Elements, and discuss the following:

Water

• Ask students to consider one substance, water, in

light of the definition. Is water made of elements

combined into molecules?

Students are familiar with the molecular

composition of water: H O. Point out the elements

2

hydrogen and oxygen on the periodic table.

Table sugar

• Help students recognize that sugar and salt

also are made of a combination of elements

that form molecules.

Table sugar is a crystalline carbohydrate,

C H O . Salt is sodium chloride, NaCl.

12 22 11

31

Student Lesson 1

Chemicals, the Environment, and You

7. After viewing the Web site segment or discussing the periodic table, continue by helping students recognize that all of the substances on

the materials table are made up of specific molecules, even if the

students don’t know exactly what they are. Once they recognize this,

students will begin to realize that all things are made of chemicals.

Ask students to tell you, based on their new understanding, some

other things around them that are made of chemicals. Let students

continue until you see that they understand that everything around

them, or everything in their environment, is made of chemicals.

8. To make sure that the students understand that they, too, are

made of chemicals, display a transparency of Master 1.3, Elemental

Composition of the Human Body. Let your students know that these elements are combined in many different ways to form thousands

of different chemicals that make up the human body.

9. Discuss with students how their original idea about what a chemical is, which led them to their choices in Step 2, is different from the

scientific definition of a chemical. Why do they think this is so?

Students will recognize that they hear most about the chemicals that

are toxic to humans or the environment. Because of this, students

often think of chemicals as only those synthetic substances that

are introduced to the environment and cause harm. Help students

recognize that they also know a lot about synthetic chemicals that

are beneficial to humans, such as pain relievers and other medicines.

They also know about naturally occurring chemicals that are toxic to

humans, such as hydrogen sulfide (sewer gas) and carbon monoxide, to

name two. By the end of the discussion, help students recognize that

chemicals can be synthetic or naturally occurring and make up every

substance on Earth, even our bodies.

Bridge to Activity 2 by helping students understand that many

chemicals, both synthetic and naturally occurring, can be beneficial to

humans and the environment. Those chemicals that are not beneficial

are the ones we want to know more about so that we can protect

ourselves and the environment from harm.

ACTIVITY 2: Protect the Toxicologist

1. Bring out the shoe box from behind your desk. Tell the students that inside the shoe box is a mystery chemical. Discuss with the students

some things they might want to know about the contents of the shoe box

before they open it. Ask why it would be important to know these things.

Be sure that students recognize that they would want to know what

the chemical is (for example, name; naturally occurring or synthetic;

solid, liquid, or gas; how much of the chemical is in the container).

Most importantly, they would want to know if it is toxic to the humans

in the classroom because they would not want to accidentally expose

themselves to a harmful substance.

32

2. Tell the students that they are asking a lot of the same questions that a toxicologist might ask. Write the word toxicologist on the board. Ask students to identify the root of the word toxic. Underline it on the board. Tell students that toxicologists are scientists who are specially trained to examine the nature of the harmful effects of chemicals

Content Standard G:

on living organisms. They try to understand which chemicals are

Students should develop

toxic to living organisms and in what amounts those chemicals are

an understanding of science

toxic. While they want to know which chemicals might cause death,

as a human endeavor.

they also are interested in other toxic effects, such as disease, tissue damage, genetic alterations, and cancer.

3. Select a student (or ask for a volunteer) and tell the student that he or she is a toxicologist. Tell students that you want the student

toxicologist to open the shoe box and look at the mystery chemical,

but you do not know anything about the chemical. The student

toxicologist needs to protect himself or herself in case the chemical

is harmful to humans.

Present to the class the large basket or box of clothing. Ask the class

to work together to think of items that the toxicologist should wear for

protection from exposure to the chemical. Find items in the basket as

students suggest them and give the items to the student toxicologist to

put on until he or she is dressed in a protective manner that satisfies

the class.

Tip from the field test: You may not have access to a wide variety of true protective gear. Use regular clothing, but ask students what problems there might be with certain items. For example, if students suggest that the

toxicologist’s hands need to be covered, you could pull out a pair of mittens.

This activity is engaging

Direct the toxicologist to put on the mittens, but ask the class if the mittens and fun for the students,

are the best choice and why or why not.

but it also helps you

As students select an item, question why a toxicologist needs to wear it.

assess students’

Probe for understanding that a toxicologist is concerned about exposure

knowledge of an

to a chemical by eating or drinking it, by breathing it, and by absorbing

important concept of

it through the skin. Look to see whether the student toxicologist’s skin,

toxicology: routes of

eyes, mouth, and nose are covered.

exposure.

4. Once the student toxicologist is dressed protectively, explain that real toxicologists know that chemicals can enter the body in three

ways, called routes of exposure: through the mouth by ingestion,

through the nose and mouth by inhalation, and through the skin by

absorption. Write the list of the three routes of exposure on the board: Routes of Exposure

✓ ingestion

✓ inhalation

✓ absorption through the skin

33

Student Lesson 1

Chemicals, the Environment, and You

Use the list as a checklist and ask students if they think the student

toxicologist is adequately protected from all routes of exposure. If not,

have them adjust the protective clothing or suggest useful clothing that

is not in the basket.

Point out that the mystery chemical could be a solid, a liquid, or a gas.

Discuss each form of a chemical and how the form can help determine

which routes of exposure are most likely. For example, a gas might

be easily inhaled as soon as the container is opened, while a solid

might only be harmful if a person touches it or ingests it. In addition,

chemicals can change form. For example, dry ice is solid carbon dioxide

that quickly becomes a gas. Liquid mercury can evaporate into a gas,

causing exposure by inhalation.

Thank the student toxicologist and ask him or her to return the

protective clothing to the basket.

5. Tell students that people who work around toxic chemicals protect

themselves in ways similar to those the students suggested for the

student toxicologist. Provide time for students to view the segment

Ride Along with HAZMAT on the Web site.

To find the segment, go to http://science.education.nih.gov/

supplements/chemicals/student and choose Lesson 1, then

Ride Along with HAZMAT.

Photo: Corel

6. Tell the students that you will dress protectively and remove the

mystery chemical from the container when they are not in the room

(because they are not protected). Let them know that they will be able

to examine the chemical during the next class if you decide it is safe

to do so.

34

ACTIVITY 3: Case Studies of Routes of Exposure

1. Set up the class so that each team of students has access to a

computer, such as in a computer lab. Instruct teams to do the activity

titled What’s Wrong Here? on the Web site. Circulate around the room Content Standard E:

and listen as groups work through each situation.

Students should develop

understandings about

To view the activity, go to http://science.education.nih.gov/

science and technology.

supplements/chemicals/student and choose Lesson 1, then

Content Standard F:

What’s Wrong Here?

Students should develop

understanding of

2. Tell students that now they will consider some true chemical

natural hazards, and

exposures. Display a transparency of Master 1.4, Questions for Case

Studies. Then, distribute a copy of Case Study #1 from Master 1.5, risks and benefits.

Case Studies of Routes of Exposure, to each student.

Content Standard G:

Students should develop

3. Ask students to work in teams and to read Case Study #1.

understanding of science

Instruct them to answer the questions on the transparency in

as a human endeavor.

their science notebooks.

4. Once teams have read and answered the questions about Case Study

#1, conduct a class discussion about the case study by answering the

ques tions on the transparency.

Sample Answers to Questions for Case Study #1 on Master 1.4

Question 1. What happened? Where did it happen? When did it happen?

A Dartmouth College scientist died of mercury poisoning in 1997 in

New Hampshire after being exposed to the chemical in 1996.

Question 2. What chemical was involved?

The chemical was dimethylmercury (die-METH-ul-MER-kyoo-ree).

Question 3. What was the route of exposure?

The route of exposure was absorption through the skin.

Question 4. What were the symptoms of toxicity?

The symptoms of toxicity were permanent nervous system damage,

numbness of fingers, unsteady walking, difficulty speaking, blurred

vision, hearing problems, coma, and death.

Question 5. How could a person have prevented his or her exposure to

the chemical?

Answers will vary. The researcher used precautions thought to be

adequate at the time.

35

Student Lesson 1

Chemicals, the Environment, and You

Question 6. Have any changes occurred since the incident? Describe them.

Researchers now know that dimethylmercury can seep through latex

gloves. They now use neoprene gloves with long cuffs or wear two pairs

of gloves, one of them laminated and one of them heavy duty.

5. There are four more case studies, two describing chemical exposure

through inhalation and two describing chemical exposure through

ingestion. Continue to have students read, discuss, and answer the

questions about each case study.

This is a good time to

Tip from the field test:

assess your students’

Give a different study to each team and ask the

teams to read their study. Then, instruct teams to present their case study understanding of the

to the class. Teams can explain their case study and answer the questions

three ways chemicals

from the transparency so that everyone in the class learns about the case

can enter the human

and discusses the route of chemical exposure. The case studies vary in

body and cause harm:

length, allowing you to individualize the reading assignment for students

ingestion, inhalation,

of varying reading abilities.

and absorption.

Sample Answers to Questions for Case Studies #2–5 on Master 1.4:

Case Study #2

Question 1. What happened? Where did it happen? When did it happen?

Gas leaked from a chemical plant in 1984 in India.

Question 2. What chemical was involved?

The chemical involved was methylisocyanate (METH-ul-EI-soh-

SIE-uh-nate).

Question 3. What was the route of exposure?

The routes of exposure were inhalation and absorption through the

eyes and the nose.

Question 4. What were the symptoms of toxicity?

The symptoms of toxicity were eyes and lungs burning, vomiting, lung

impairment, loss of motor control, neurological disorders, and damaged

immune system.

36

©Bettmann/CORBIS

Question 5. How could a person have prevented his or her exposure to

the chemical?

Answers will vary. Students should recognize that people who lived in

Bhopal had little choice over their exposure. People could have made

the choice not to live near a chemical plant.

Question 6. Have any changes occurred since the incident?

Describe them.

The chemical plant was sold to a company in Calcutta. Proceeds from

the sale supported hospitals and clinics in Bhopal.

Case Study #3

Question 1. What happened? Where did it happen? When did it happen?

Jane had lead poisoning; it happened in her home during her first two

years of life.

Question 2. What chemical was involved?

The chemical involved was lead.

Question 3. What was the route of exposure?

The route of exposure was ingestion.

Question 4. What were the symptoms of toxicity?

The symptoms of toxicity were abdominal pain, constipation, vomiting,

and lethargy; in severe cases, learning disabilities, decreased growth,

hyperactivity, impaired hearing, and even brain damage can occur.

37

Student Lesson 1

Chemicals, the Environment, and You

Question 5. How could a person have prevented his or her exposure to

the chemical?

Prevention for children includes annual blood tests to check lead levels;

clean play areas, floors, windowsills, and hands; professional paint

removal; and drinking milk.

Question 6. Have any changes occurred since the incident?

Describe them.

Students can assume that Jane’s mother acted on the doctor’s

suggestions for minimizing the family’s exposure to lead.

Case Study #4

Question 1. What happened? Where did it happen? When did it happen?

Jimmy Green died from sniffing gasoline in the spring of 1999.

Question 2. What chemical was involved?

The chemical was gasoline.

Question 3. What was the route of exposure?

The route of exposure was inhalation.

Question 4. What were the symptoms of toxicity?

The symptoms of toxicity were short-term memory loss, hearing loss,

arm and leg spasms, permanent brain damage, liver and kidney damage,

and death.

Question 5. How could this person have prevented his or her exposure to

the chemical?

Jimmy Green voluntarily exposed himself to gasoline fumes. He could

have prevented his exposure by choosing not to sniff gasoline.

Question 6. Have any changes occurred since the incident?

Describe them.

Parents and students are now informed of the dangers of inhalants.

38

Case Study #5

Question 1. What happened? Where did it happen? When did it happen?

In 1971, more than 6,500 people were poisoned in Iraq.

Question 2. What chemical was involved?

The chemical was methylmercury (METH-ul-MER-kyoo-ree).

Question 3. What was the route of exposure?

The route of exposure was ingestion.

Question 4. What were the symptoms of toxicity?

The symptoms of toxicity were nervous system disorders.

Question 5. How could a person have prevented his or her exposure to

the chemical?

If people had been better informed, they would have planted the seed

instead of eating it.

Question 6. Have any changes occurred since the incident?

Describe them.

No changes were mentioned in the case study, but students might

discuss the need for better warning labels and instructions for grain

shipped between countries.

©Bettmann/CORBIS

39

Student Lesson 1

Chemicals, the Environment, and You

Extension

Ask students to find current event stories in newspapers, magazines, or Activity

television programs that talk about chemical exposure. Challenge students to find one event that involves a chemical exposure that harms humans

or other living things and one that involves a chemical exposure that

benefits humans or other living things.

You will be able to use a chemical exposure described in these articles in the extension activity in Lesson 5.

Tip from the field test: If students in your school are required to bring in current event articles for several other classes, coordinate with teachers making similar assignments so that students are not duplicating efforts.

Alternatively, collect articles yourself and display them in the classroom.

40

L E S S O N 2

Explore

The Dose

Makes the Poison

Overview

At a Glance

Students observe beakers of water that contain different amounts of a

mystery chemical. They discuss how each amount of the chemical might

affect them if the chemical was beneficial or harmful to their bodies.

Then, students set up investigations to test the effects of different doses of chemicals on seed germination and collect data for two consecutive days.

Their investigations model the kinds of investigations toxicologists do to determine dose-response relationships in living systems.

Major Concepts

The total amount of chemical administered to, or taken by, an organism is

called a dose, and the effect a chemical has on a living organism is called the response. The effect a chemical has on a living organism is related to its dose and the resultant concentration of chemical in the organism. Toxicity tests enable toxicologists to learn about responses of living organisms to doses of chemicals.

Objectives

After completing this lesson, students will

• recognize that the total amount of a chemical administered to, or taken by, the organism is called a dose,

• understand that the effect a chemical has on a living organism is called the response,

• recognize that the effect a chemical has on a living organism is related to its dose and the resultant concentration of chemical in the organism, and

• demonstrate how toxicity tests enable toxicologists to learn about

responses of living organisms to doses of chemicals.

41

Chemicals, the Environment, and You

Background

Dose, Concentration, and Threshold

The beneficial and harmful effects that a chemical has on an organism

Information

depend, in part, on the amount of the chemical that gets into the organism.

The total amount of a chemical that is administered to, or taken by, the

organism is called the dose. The effect of a chemical depends not only on the amount of the chemical that gets into the organism but also on

the resulting concentration of the chemical in the body (the amount of chemical compared with the body size), the length of exposure to the

chemical, and the route of exposure.

The measure of dose in toxicology is important; a large dose of a beneficial chemical can have a harmful effect, and a small dose of a harmful chemical can have no adverse effect. In the words of the 16th-century physician

Paracelsus, “All substances are poisons; there is none which is not a poison.

The right dose differentiates a poison from a remedy” (Klassen, 2008).

Approximate Lethal Doses of Common Chemicals

(calculated for a 160-lb. human from data on rats)

Chemical

Lethal Dose

Sugar (sucrose)

3 quarts

Alcohol (ethyl alcohol)

3 quarts

Salt (sodium chloride)

1 quart

Herbicide (2,4-D)

1/2 cup

Arsenic (arsenic acid)

1–2 teaspoons

Nicotine

1/2 teaspoon

Food poison (botulism)

microscopic

Source: Marczewski, A.E., and Kamrin, M. Toxicology for the citizen. Retrieved August 17, 2000, from http://www.iet.msu.edu/Tox_for_Public/citizen.htm.

• A chemical is considered toxic if it produces adverse effects in a living organism at levels of exposure that are likely to occur. These adverse

effects can range from slight symptoms, such as headache, nausea, or

rashes, to severe symptoms, such as coma, convulsions, and death.

Toxicologists recognize that for most types of toxic responses to a

chemical, there exists a dose threshold below which no toxicity is

evident. As the dose increases, more severe toxic responses occur.

Toxicity Testing

How does a toxicologist know when a chemical is toxic to humans? When

available, toxicologists study data from human populations that have been

exposed to specific chemicals. The data usually come from studies of

workplace exposure or incidents such as the Union Carbide chemical plant

accident in India. In this way, toxicologists further their understanding

of the effects of chemicals on humans. In the absence of human data,

toxicologists test the toxicity of different doses of chemicals on cell and 42

tissue cultures, plants, and other animals, such as rats and mice. These

studies guide toxicologists in their understanding of which chemicals might be harmful to humans and in what amounts.

The use of animals in toxicology research is not taken lightly. Following

is the Society of Toxicology’s Animals in Research Policy Statement on the Society of Toxicology’s Web site ( http://www.toxicology.org):

• Research involving laboratory animals is necessary to ensure and

enhance human and animal health and protection of the environment.

• In the absence of human data, research with experimental animals is the most reliable means of detecting important toxic properties of chemical

substances and for estimating risks to human and environmental health.

• Research animals must be used in a responsible manner.

• Scientifically valid research designed to reduce, refine, or replace the need for laboratory animals is encouraged.

Toxicologists know that the kinds of questions they want to answer cannot

always be answered by observing and describing humans exposed to

chemicals. They need to devise experiments that involve a system that

resembles the human system. By studying a model of the human system,

rats or mice, for example, toxicologists hope to apply the knowledge

they gain to understanding the harmful effects of chemicals on humans.

Although the basic tenet of toxicological studies is that “experimental

results in animals, when properly qualified, are applicable to humans,”

toxicologists recognize that different species can respond to doses of toxic substances differently (Klassen, 2008). For example, on the basis of dose

per unit of body surface, toxic effects in humans are usually about the same as for experimental animals; on a body-weight basis, though, humans are

about 10 times more vulnerable than small experimental animals, such as

mice (Klassen, 2008).

Because of both practicality and ethics, scientists who use animals in

research carefully select the species and design experiments to achieve

scientifically valid results. They obey strict regulations about the use of animals in experiments (Society of Toxicology, 2012). Typically in these

experiments, toxicologists expose experimental animals to high doses of

toxic agents so that they minimize the number of animals they use. This

experimental design assumes that the results of tests at high doses on a

small number of animals can be extrapolated to estimate the risk of low

doses to a large population of humans.

Toxicity testing is not designed to demonstrate that a chemical is safe

for humans, but is used to identify the types of toxic effects a chemical

can produce. One early test performed on a chemical is the Ames test,

named after Bruce Ames of the University of California–Berkeley. In

this test, specially engineered bacteria are exposed to a chemical. If the bacteria mutate, the chemical reacted with DNA and is a potential mutagen

or carcinogen. Scientists use the Ames test to economically weed out

mutagenic chemicals because it avoids testing on higher animals.

43

Student Lesson 2

Chemicals, the Environment, and You

Often, scientists use cell cultures in toxicology testing. Scientists expose isolated cells to a chemical and observe the response. If the cells die during the experiment, the chemical may be too toxic for use by humans. As

with the Ames test, tests on cell cultures help scientists narrow the list of chemicals they need to test further on animals by eliminating those that are clearly too toxic.

If these preliminary tests suggest a chemical might be used safely with

humans, scientists consider testing with animals. One of the first animal

tests that scientists perform on a new chemical determines its acute

toxicity. Toxicologists determine what dose of the chemical, under the

intended route of exposure, causes 50 percent of the animals (mice or rats) to die (lethal dose, or LD ). Toxicologists also determine the effective

50

concentration at which 50 percent of the animals exhibit a measurable

response (EC ).

50

Scientists perform subacute toxicity tests to learn about the toxicity of a chemical after repeated doses. To test a chemical that is likely to enter the body through ingestion, scientists add doses of a chemical (high, low, and intermediate) to the feed for the experimental animals, usually rats or mice.

Each animal receives a specified dose over the course of 90 days. Scientists observe the animals once or twice daily for signs of toxicity, including

changes in body weight, diet consumption, changes in fur color or texture, respiratory or cardiovascular distress, motor and behavioral abnormalities, or palpable masses. They record premature death and collect blood and

tissue samples from all animals for further study. If the chemical is likely to pose a risk to humans through skin contact or inhalation, scientists perform tests that incorporate those routes of exposure. They conduct long-term

or chronic exposure studies in a similar manner, but the exposure time is

increased to a time period that can range from six months to two years.

Efforts are under way by at least two groups to reduce the use of animals

in some kinds of toxicity testing (NIEHS, 2012 and 2009). For example,

researchers have developed a collagen matrix barrier that serves as a kind of artificial skin. If a chemical or chemical mixture penetrates the artificial skin, it is likely to irritate, corrode, or burn human skin.

For example, in the illustration on page 45, the drawing shows how a

chemical is tested using the collagen matrix barrier. A sample of the

test chemical is dropped onto the matrix. If no chemical penetrates the

matrix, the solution in the bottle below the matrix remains clear. If the

chemical penetrates the matrix, it will cause a color change in the solution in the bottle below. The photo on the right shows the indicator solution

changing color after the test chemical has penetrated the matrix. This

method, using artificial skin, can replace the current practice of using three animals to test every new chemical. Because more than 2,000 chemicals are

introduced each year and many are tested before they are introduced on the market, this replacement means a significant reduction in the number of

experimental animals used in toxicity testing (NIEHS, 2012).

44

Photo: Courtesy InVitro International

Researchers are also developing techniques that are more accurate than

the traditional methods. In the past, when researchers wanted to know if a blood pressure medicine was working in an animal, they inserted a catheter into an artery in the animal’s leg. The animal then needed to be restrained so that scientists could take readings over a four- to five-hour period. Today, a sensor implanted in the animal’s abdominal cavity allows researchers to

continually measure results while the animal can move freely and remain

with its family. Its heart rate is more relaxed and normal, so the results do not mirror the compounding effect of stress.

The rate at which new technology is being used to help researchers

reduce their reliance on laboratory animals is accelerating. People who are concerned about animal welfare are working with researchers to encourage

better experimental design and more humane techniques. Together, they

are working to replace laboratory animals with scientifically valid

alternatives, reduce their numbers, and refine techniques to minimize

pain and suffering.

Even as progress is made in the name of animal welfare, however,

conflicting pressures arise from the public’s interest in knowing more

about the health and safety data on major industrial chemicals. For

example, in October 1998, Vice President Al Gore announced his plan

to collect data on 2,800 high-production-volume chemicals. Animal

rights groups recognized that such testing would require the destruction

of more than 1 million animals. For a year, to minimize the number of

animals and avoid needless testing, animal welfare activists lobbied to

halt or modify the plan. One year later, the U.S. Environmental Protection Agency (EPA) made new recommendations for high-production-volume

chemical testing that should reduce animal use. They now will consider

previous results from chemical safety databases to ensure that testing is

not redundant and will postpone the testing of some chemicals in the

hope that nonanimal tests will become available.

45

Student Lesson 2

Chemicals, the Environment, and You

Notes about Lesson 2

In this lesson, students perform toxicity tests on seeds, paying careful

attention to the dose and concentration of chemicals. Students might not be aware that plants differ from animals in many ways: They have no nervous

system or efficient circulatory system, and they have a photosynthetic

mechanism and cell walls that animals do not. Therefore, the students’

results from toxicity tests on seeds cannot be extrapolated to suggest a

chemical’s risk or safety to humans without further testing on animal

systems, which is inappropriate for the classroom. However, students

can understand the importance of using model systems in science when

human subjects cannot be used because of the potential risk. Students can

understand that many questions in science suggest a variety of investigation methods and that their use of models in scientific inquiry can help them

establish relationships based on evidence from their own observations.

In Advance

Web-Based Activities

Activities 2 and 4 have optional Web components.

Materials and Preparation

Photocopies and Transparencies

1 transparency of Master 2.1

1 copy of Master 2.2 for each team

1 copy of Master 2.3 for each student (print version only)

Note: If you want students to calculate percent concentration on their own, in Master 2.2, mask the numbers in the concentration column before copying.

Materials

Activity 1

For the class:

• overhead projector

• shoe box from Lesson 1

• 1 small jar containing the mystery chemical from Lesson 1

• 1 eyedropper

• 1 pair of safety glasses

• 1 pair of latex gloves

• 3 1,000-mL beakers or 3 large jars of the same size, each containing 500

mL of water

• 1 piece of white poster board to use as a backdrop for the demonstration

• 1 resealable plastic sandwich bag containing radish seeds

• 1 beaker containing 250 mL of water (optional)

For each student:

• science notebook

46

Activity 2

For the class:

• computer

• chemicals from Lesson 1

• mystery chemical from Lesson 1

• 1 resealable plastic sandwich bag containing radish seeds

For each student:

• science notebook

Activity 3

For each team of 3 students (print version):

• 3 pairs of safety glasses

• 3 pairs of latex gloves

• 1 100-mL beaker filled with 50 mL of a chemical; see Preparation for Activity 3

• 1 permanent marker

• length of masking tape

• 6 50-mL beakers

• 1 50-mL graduated cylinder

• 1 10-mL graduated cylinder

• 100 mL of purified water in a beaker

• 1 eyedropper

• 6 resealable plastic sandwich bags

• 12 paper napkins

• 60 radish seeds in a resealable plastic sandwich bag

• 1 tray

For each student:

• science notebook

Activity 4

For each team of 3 students:

• bags of seeds treated with chemicals from Activity 3 (print version only)

• 1 copy of Master 2.3 from Activity 3 (print version only)

• Web version of data for Day 2 (optional; see Preparation for Activity 4) For each student:

• science notebook

Extension Activity

For the class:

• computers with Web access

• materials for designing a bulletin board display

47

Student Lesson 2

Chemicals, the Environment, and You

Notes on Materials:

1. The mystery chemical is the solution of blue food coloring and water used in Lesson 1.

2. Check that no students are allergic to latex. If any are, assign their team a chemical that you know will not irritate the skin, such as

sugar water or cola. The team members with the latex allergy then

can work safely without gloves. Alternatively, they can use vinyl

gloves, if available.

3. Instead of 50-mL beakers, you could use 6 clean baby food jars or

6 test tubes set up in a rack made out of a shoe box.

4. For the paper napkins, use regular, white, one-ply napkins

(12 x 115/8 inches, unfolded) that you can buy in bulk at the

grocery store. If you use something different, test your setup to

make sure that the napkins or paper towels you use can absorb

20 mL of liquid in a plastic bag.

Preparation

Activity 1

Pour 500 mL of water into each of the 3 1,000-mL beakers. Label the

beakers #1, #2, and #3.

Put a handful of radish seeds in a resealable plastic sandwich bag. Gather the materials you need for the demonstration.

Make a transparency of Master 2.1, Opening Questions.

Activity 2

Gather the materials you will need for this activity.

Copy Master 2.2, Making Solutions for Toxicity Testing, 1 copy for each team. Set up a computer center at which students can view the Chemicals Web site.

Activity 3

Decide whether you will use the print or Web version of the laboratory

investigation. It is tempting to avoid the preparation and materials that

a laboratory investigation requires, but students benefit from conducting

a scientific investigation, using tools to gather data, and developing a

hands-on understanding of the use of models in scientific inquiry. The

simulation presented on the Web site enables teachers and students

without access to laboratory equipment to gather data to use in Lesson 3,

48

but it should not replace actual laboratory experience. In addition,

Lesson 2’s laboratory investigation provides students with an opportunity

to meet Content Standard A of the National Science Education Standards: All students should develop abilities necessary to do scientific inquiry and understandings about scientific inquiry (NRC, 1996).

For the print version (preferred) of the laboratory investigation:

Prepare the chemicals, 1 chemical for each team of 3 students:

1-p. Choose a wide variety of chemicals for testing:

• water-soluble plant food

• liquid detergent

• soft drink

• instant coffee

• nontoxic environmental cleaner

• tempera paints

• all-purpose disinfectant cleaner (Lysol)

• artificial sweetener

• shampoo

• window cleaner

• salt

• sugar

• fruit and vegetable rinse

Tip from the field test: During the field test, the following chemicals yielded data that made the most interesting dose-response curves for

students to graph in Lesson 3: salt, Miracle Gro, fruit punch soft drinks, window cleaner, and Lysol. The results from other chemicals were also

of interest to students, so be sure to include a wide variety of familiar

chemicals, such as shampoo, soft drinks, coffee, and sweetener, even if their dose-response curves are less exciting. One of the reasons to use a variety of chemicals is to demonstrate the range of responses that are possible.

2-p. Measure 50 mL of each liquid chemical into a 100-mL beaker.

Label the beaker with the name of the chemical (for example,

window cleaner).

3-p. Make solutions of nonliquid chemicals by mixing them with water.

Then, measure 50 mL of each liquid solution into a 100-mL beaker.

Label the beaker with the name of the chemical.

When available, follow directions on the container to make solutions

of nonliquid chemicals, such as plant food or instant coffee. When no

directions are available, make as saturated a solution as possible: Heat

the water and slowly stir in a small amount of the chemical until it no

longer dissolves easily in the water. In pilot testing this activity, we

made a sugar solution with 40 g of sugar in 100 mL of water and a salt

solution with 24 g of salt in 100 mL of water. Be sure to make enough

solution for all your classes.

49

Student Lesson 2

Chemicals, the Environment, and You

4-p. Place each chemical on a tray, 1 tray and chemical per team.

Purchase radish seeds. Put 60 radish seeds into a resealable

plastic sandwich bag. Continue until you have a bag for each team

of 3 students.

Radish seeds found in a local garden store work well for this investigation.

They will germinate in 1 to 3 days. If you prefer faster germination

(6–24 hours), you can purchase Wisconsin Fast Plants™, Brassica rapa seeds (which are close relatives of the radish) from Carolina Biological Supply. Be aware that the Brassica rapa seeds are quite a bit smaller than radish seeds, so consider your students’ dexterity when deciding which seeds to use.

Tip from the field test: Counting the 60 seeds can be time consuming.

Estimate the number of seeds by measuring approximately ¼ teaspoon of

regular radish seeds (less if you use Brassica rapa seeds) for each bag. There will be a little more than 60 seeds in each bag. Students tend to lose a few as they set up the investigation, so it doesn’t hurt to have a few extra seeds in the bag or on hand at the materials table.

Activity 4

If your students conducted the Web version of Activity 3, arrange for them to have access to computers for this activity.

Extension Activity

Arrange for students to have access to the Web. Gather materials needed to design a bulletin board display or ask students to provide them.

Procedure

ACTIVITY 1: Dose and Concentration

1. Place the shoe box with the mystery chemical from Lesson 1 in it

and the three beakers of water on a table in the front of the room.

2. Display a transparency of Master 2.1, Opening Questions.

3. Allow the students a few minutes to puzzle through the questions on the transparency. Assure them that it is perfectly acceptable not to

know the answers to all the questions right now. Remind students that

toxicologists study chemicals and perform toxicity tests because they

don’t know the answers to questions like these about every chemical.

4. Once students have answered the opening questions, draw their

attention to the shoe box that holds the mystery chemical from

Lesson 1. Announce to the students that a toxicologist partially

analyzed the mystery chemical and informed you that the chemical

50

would not enter your body through inhalation or contact with the

skin, so it is safe to handle the chemical as long as you don’t ingest it.

5. Demonstrate appropriate laboratory safety measures by putting on

safety glasses and a pair of latex gloves. Open the shoe box and

remove the jar of mystery chemical.

6. Direct students’ attention to the three large beakers of water. Let students know that each beaker holds exactly the same amount of

water as the other two. As the students watch, use the eyedropper

to add

• 1 drop of mystery chemical into Beaker #1,

• 4 drops into Beaker #2, and

• 16 drops into Beaker #3.

Gently swirl or stir each beaker until the drops of mystery chemical

are totally distributed in the water. Use the white poster board as a

backdrop and ask students to tell you what they can observe.

Students will observe that the water in the three beakers has turned a

shade of blue. In Beaker #1, the color of the water is a very pale blue.

In Beaker #2, the water is a darker blue. In Beaker #3, the water is the

deepest blue.

7. Suggest that the beakers of water represent human bodies. Ask

students to tell you what they know about the relative sizes of the

three “bodies.” Once they recognize that all the bodies are the same

size, discuss the added chemicals using questions such as these:

• If we found out that the mystery chemical is harmful to people,

which of these beakers would you rather be right now and why?

Students probably will say that they would rather be Beaker #1 because

it contains the smallest amount of the harmful chemical.

• Are you sure that the amount of chemical in Beaker #2 is enough

to cause harm? Is there enough in Beaker #3 to cause harm?

Students may realize that they do not know how much of the chemical

must be present to cause harm, but they would want to err on the safe

side and choose Beaker #1. Some students may wonder if even the small

amount in Beaker #1 is harmful.

• What if we learned that the chemical is good for you? Which

beaker would you choose to be and why?

Students probably will choose Beaker #3 because it has more of the

beneficial chemical in it. Some students may recognize that they don’t

know enough about the chemical to know how much of it is good for a

person. They may wonder if it is possible for too much of even a good

chemical to be harmful.

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Student Lesson 2

Chemicals, the Environment, and You

• Some chemicals are good for you in small doses but bad for you

in large doses. If that were the case here, which beaker would you

want to be?

Some students may opt for Beaker #1 because the amount of chemical

is small. Others may choose the middle road, Beaker #2, so that there

is enough of the chemical to be beneficial but not enough to do harm.

Others may say that they cannot choose because they do not know

enough about the amount of chemical that is beneficial or the amount of

chemical that is harmful.

8. Point out to students that the questions they have about how much of a chemical is harmful and how much is beneficial are the same kinds

of questions that toxicologists study. Help students understand some

basic vocabulary of toxicology by asking them these questions and

writing the terms on the board.

• When toxicologists look at the total amount of chemical that is

given to, or taken by, an organism, they talk about dose. In which

beaker did the body receive the largest dose of chemical?

Beaker #3 received the largest dose: 16 drops of the chemical.

• Toxicologists study the concentration of a chemical in an

organism by comparing the dose of chemical to the size of the

organism. In which of these three beakers is the concentration

of chemical highest?

Beaker #3 has the highest concentration of all the beakers because it

has the largest dose of chemical compared with the constant volume of

water. For the same-size person, ingesting more of a chemical results

in a higher concentration of the chemical in that person’s body. It

follows that if several people of various sizes take the same amount of a

chemical, the final concentration to which each person is exposed can

vary, depending on the size of the person.

To help clarify the difference between dose and concentration, you can

use a fourth beaker. This time, fill it with only 250 mL of water, half

the amount of the other three beakers. Ask students to describe to you

the relative size of this new “body” compared with the other beakers.

Tell students that you are going to give this new body the same dose as

you gave Beaker #2: 4 drops. Add that dose to the beaker. Ask students

to observe the color and compare the concentration of chemical in the

fourth beaker with the concentrations in the other three beakers. Is this

concentration more or less than the others? Students should see that the

water in the fourth beaker does not look like the water in Beaker #2, even though the dose was the same. The color is deeper, showing that the

concentration of chemical in the smaller body is greater for the same

dose than it is in the larger body.

52

9. Ask students to come up with ways to find out if the mystery chemical at different doses (1, 4, and 16 drops) is harmful or beneficial to living things.

Students might suggest that someone could drink the three solutions

of chemical and see what happens. If you ask for volunteers, however,

you probably will not get any; you can discuss with students why this

method may provide information but would not be a responsible way to

test the toxicity of a particular dose of chemical. Ask students to think

of other living things that they could use for testing. Use the Background Information in this lesson to discuss how animals are used in research.

Be sure to discuss the Society of Toxicology’s policies and guidelines for animals in research (2012).

10. Help students recognize that they are not equipped to safely and

ethically handle toxicology tests on animals. Tell them that there are

many animal welfare laws, regulations, guidelines, and policies that

govern the use of animals in research. Let students know that there

are other living organisms that they can use for testing the mystery

chemical in the classroom. Hold up a bag of seeds and ask students to

tell you if they think the seeds are living organisms.

Seeds are living organisms that grow into plants. As living organisms,

plants respond to chemicals in their environment, particularly in water.

Plants are not the same as humans or other animals in structure, however,

so results from tests that determine toxicity to plants might not be

applicable to humans. Students will discuss this problem with the model

Photo courtesy of American Association for

system of plants when they analyze their data in Lesson 3.

Laboratory Animal Science

11. Tell the students that they are going to perform toxicology tests on seeds, but first they need to formulate a question and design

an investigation.

ACTIVITY 2: Planning the Seed Investigation

1. Put on your desk some of the chemicals from Lesson 1. Show the

students the mystery chemical. Show the students the seeds in the

bag. Ask the students what they want to know about the chemicals

and the seeds.

Conduct this discussion as a brainstorming session, perhaps writing on

the board all of the questions the students formulate. Help the students

arrive at a general question, such as this one:

• What effect does the chemical have on the seeds?

2. Ask the students to refine their question by considering what they

learned in the beaker demonstration about dose.

The students’ question should address both effect and dose. If students

do not provide such a question on their own, suggest one like this:

• What effect does the chemical have on seeds, and how is the effect

different if the seeds receive different doses of the chemical?

53

Student Lesson 2

Chemicals, the Environment, and You

3. Refresh students’ memories about the function of seeds in the life

cycle of a plant. In doing so, discuss with students what they would

expect a seed to do if it is exposed to moisture.

Seeds have three parts: the protective outer seed coat, the embryo that

becomes the new plant, and the endosperm that provides the food to

nourish the embryo. Most students have looked at the germination

of a bean seed in elementary school. Remind them that before a seed

germinates, it absorbs moisture and it swells and bursts its seed coat.

At this time, the embryo starts to grow and the root tip, or radicle,

pushes through the eye of the seed. This “sprouting” is the first

evidence of growth that students can observe with the naked eye.

Several days later, seed leaves emerge and the embryonic stem begins

to extend upward. At this time, chlorophyll pigment is visible. If

planted in favorable conditions with the right moisture, temperature,

and light, the plant will develop leaves, lengthen its stem, flower,

produce fruit, and develop mature seeds. Once the seeds dry, the cycle

is complete and the seeds are ready to produce new plants.

4. Ask students to further refine their question from Step 2 based on the discussion of what seeds do under normal conditions.

Guide students to a question like this one:

• How does the chemical affect the germination of the seeds, and how

is the effect different if the seeds receive different doses of

the chemical?

5. Distribute copies of Master 2.2, Making Solutions for Toxicity Testing.

Ask students to interpret the information presented in the handout by

asking questions similar to these:

• In which beaker is the dose of chemical going to be the highest?

• In which beaker is the concentration of chemical going to be the highest?

In both cases, the highest dose and highest concentration is in

Beaker #6. Beaker #6 contains the greatest volume of chemical. Because

the total amount of solution remains the same in each beaker, the

highest concentration will be in the beaker that has the largest amount

of chemical in it, Beaker #6.

54

• How do you calculate the percent concentration of chemical in

the solution?

The percent concentration refers to the amount of chemical compared

with the total volume in the beaker. For example, students put 2.50 mL

Content Standard A:

of chemical and 17.50 mL of water in Beaker #3. The total amount

Students use mathematics

of liquid in the beaker is 20 mL. Therefore, the amount of chemical

in all aspects of scientific

divided by the total amount of liquid is

inquiry.

2.50 mL of chemical = 0.125, or 12.5% concentration

20.00 mL of liquid

If you choose to do so, have students calculate the percent concentration

for each beaker.

Tip from the field test: Some students may need a review of the conversion of decimals into percentages.

• Why do you think you need a beaker that is just water

(0% concentration)?

Remind students that they need to have a control for their experiment.

In this way, students can see what happens to seeds under normal

conditions and compare that with what they observe in the seeds

treated with various concentrations of chemicals.

• Suppose you expose seeds to the different concentrations

of chemical suggested in the chart on this worksheet. What

predictions can you make about how they will respond?

Give students time to make some general predictions about what

they think could happen to seeds exposed to high, medium, and low

concentrations of different chemicals. Students will have a chance to

write specific predictions about their own chemical once it is assigned

or chosen, so make this discussion brief.

6. Instruct teams to put their copies of Master 2.2 in their science

notebooks so that they can use them during the next class period.

7. Make the Web site available at a computer center for students who

want more practice determining concentrations of chemicals.

Go to the Web site and choose Lesson 2 ( http://science.education.nih.

gov/supplements/chemicals/student). This brings up the page on which students can manipulate chemical concentrations. Instruct the students

not to click Do Experiment at this time.

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Student Lesson 2

Chemicals, the Environment, and You

ACTIVITY 3: Setting Up the Seed Investigation

The following procedures describe how to conduct a hands-on laboratory

investigation, which is the preferred method of instruction for this activity.

Important note to teachers: Activity 3 requires at least three consecutive school days (without interruption by a weekend or holiday). Usually,

that means you need to start no later than the Wednesday of a full week

of school.

For those classes not equipped to conduct a laboratory

investigation, the Web site includes a simulation of the

results students can expect from the Dose-Response Seed

Germination Experiment using three different chemicals.

Go to http://science.education.nih.gov/supplements/chemicals/student and choose The Dose Makes the Poison: Dose-Response Relationships. This brings up the page on which students can manipulate chemical concentrations.

Click on Do Experiment to access the simulation of the experiment. After completing that, continue with Activity 4, Step 3.

Print Version

1-p. Direct students’ attention to the beakers of chemicals you prepared.

Distribute chemicals on the trays, one chemical to each team.

Prepare at least one chemical per team and perhaps more if you want

to give teams a variety of choices for testing. Alternatively, you can

assign chemicals to teams. Ask one team to test the mystery chemical,

or you can test it for the class.

2-p. Ask teams to get out their copy of Master 2.2, Making Solutions for

Toxic ity Testing, from the previous class period. Ask students, How are you going to label your beakers of solutions so that you know

what is in each one?

Answers will vary, but impress upon students that it is important to

keep accurate records in toxicology testing. At a minimum, students

should number the beakers 1 to 6 to correspond with the beaker

numbers on the chart on Master 2.2.

3-p. Direct students to gather their materials, put on their gloves

and safety glasses, and follow the chart on Master 2.2 to make

their solutions.

If necessary, review proper measuring techniques for fluids in

a graduated cylinder before the students attempt to make their

solutions. Make sure they know how to measure at eye level so that

56

they can see when the meniscus is right on the line that demarcates

the target volume. Demonstrate to students how they can use the

eyedropper to add or subtract small amounts of volume.

Tip from the field test: If students have not measured liquid volume before, they might need to practice before completing this step of the activity.

Refer to measurements from Master 2.2, Making Solutions for Toxicity

Testing, and, using clear and colored water, set up a practice lab for inexperienced students.

4-p. Once teams have completed their solutions and have six small

beakers of chemical solutions on their work tables, ask students to

discuss how they might test the toxicity of these solutions on seeds.

This discussion can be brief, but it helps students design their own

investigation rather than simply following directions without giving

a thought to their purpose. Students will recognize that they want

to put the seeds in contact with the chemical solutions in some way.

Many will remember seed germination activities from previous years

and will suggest moist paper towels in petri dishes or plastic bags.

Show students the assembly they will use in this investigation.

Content Standard A:

Ask students how they will know if a chemical was toxic to seeds.

Students design and

conduct a scientific

Ask students what they predict should happen to healthy seeds in

investigation.

a nontoxic environment (the seeds will germinate). Help students

recognize that they will want to look at nongermination as an

indicator of toxicity in their investigation.

Ask students how they will know it was the chemical or a particular

dose of the chemical that caused the observed effect and not some

other factor.

Take this opportunity to discuss experimental design:

• Emphasize careful measuring and cleanliness (making sure not to

contaminate the beakers or graduated cylinders with solutions of

chemicals that are different from the intended solution).

• Discuss the experimental control. Remind students that a control

is a group of experimental subjects that are not exposed to the

chemical being investigated so they can be used as a comparison

against tested subjects. The control will be the seeds they do

not expose to any chemical other than water (the 0% chemical

solution in Bag #1). They will compare the germination of seeds in

this control with the germination of the seeds in Bags #2–6. Then

they will determine whether the addition of the chemical affects

the germination of seeds.

• Discuss the importance of controlling variables. Ask students

to think of some variables they will want to control. Some

possibilities might be

• number of seeds tested for each solution

• volume of chemical solution put on each group of seeds

57

Student Lesson 2

Chemicals, the Environment, and You

• amount of light

• temperature

• kinds of containers in which the seeds are placed

• number of paper napkins used for each group of seeds

When students return to

• type of water source

class with their work-

5-p. Distribute copies of Master 2.3, Toxicity Testing on Seeds, one to each sheets complete, review

student. Direct teams to work together to set up the investigation.

their answers to assess

their understanding of

Tip from the field test: During the field test, some students and teachers the investigation and

tried to short-cut the solution preparation and set-up steps by adding water underlying toxicological

and then chemical directly to the bag in which they already had placed

principles. Do they know

the paper napkins and seeds. This resulted in an unequal distribution of

the primary route of

chemical; some areas on the napkins had a high concentration of chemical

exposure of a human

and others had a low concentration. In addition, the seeds flowed to the

to their chemical?

bottom of the bag and got lost under the layers of napkin. The seeds should Can they describe

be added to the bag only after the napkins are saturated with completely

how concentration is

mixed solutions of chemicals. Encourage your students to work carefully

determined in a beaker?

and methodically through the preparation of the chemical solutions (see

Are they able to make a

Step 3-p above) and then the preparation of the seed bags as outlined on

Master 2.3, Toxicity Testing on Seeds.

reasonable prediction

about the outcome of

the investigation based on

an understanding

of dose, concentration,

and response?

6-p. Provide space for the trays of seeds from each team. Tell the

students that they will check on their seeds during the next class.

Tip from the field test: Storing multiple sets of seeds for multiple science classes can be a challenge. Remember that germinating seeds do not need

light, so the seed bags for each team can be stacked. One field-test teacher gave each team a dissecting tray and told the teams to stack their seed bags in the tray. She then stacked the trays for each class. In this way, she was able to fit the ongoing investigations for four science classes on one shelf in her classroom.

7-p. Students might need to complete the rest of the work on Master

2.3 at home. Remind students to construct a data table in their

science notebooks (or to put the data table from Master 2.3 in

their notebooks). Ask them to fill out Day 1 on the data table with

observations of their seeds at the start. Instruct them to answer the

questions at the end of the worksheet.

58

ACTIVITY 4: Gathering Data

1-p. As students come into the room, ask them to get their team’s seed investigation from Activity 3 and bring it to their team’s table.

Content Standard A:

2-p. Ask students to observe their seeds and share with the class what is Students use appropriate

hap pening with their seeds.

tools and techniques to

gather, analyze, and

Ask students to make observations that are qualitative (descriptive) interpret data.

and quantitative (measurable). An example of a qualitative

observation might be that the seeds seem to be “puffed up” and are

turning the paper napkin yellow underneath them. An example of a

quantitative observation might be that 6 out of the 10 seeds in Bag

#2 have germinated.

3. Direct the students to the question that guided the seed investigation:

• How does the chemical affect the germination of the seeds, and

how is the effect different if the seeds receive different doses of

the chemical?

Note to teachers: The term dose is used rather loosely here because it is difficult to know how much chemical penetrates each seed. It is reasonable to assume, however, that seeds exposed to a higher concentration of

chemical receive a higher dose. Getting students accustomed to thinking

about the term dose will prepare them for activities later in the unit.

Help students see that they can begin to answer this question based on

their observations by asking them the following questions:

• How do you know that a chemical is having an effect?

Content Standard A:

Students develop

You can look at the control and see what a population of seeds does

descriptions, explanations,

under normal conditions and compare control seeds with seeds exposed

predictions, and models

to the chemical.

using evidence.

59

Student Lesson 2

Chemicals, the Environment, and You

Tip from the field test: Begin to talk about the seeds in each bag as a

“population” of individuals. This reference will help students understand

how to translate their data into a dose-response curve in Lesson 3.

• What is happening to the population of seeds in the control?

Seeds are germinating.

• What is happening to the populations of seeds in the other

five bags? Is the same thing happening in all the bags to which

chemicals were added?

Answers will vary: Some seeds might be germinating, some might not.

Students might notice differences in seed germination between the

seeds in the bag with the lowest dose of chemical and those in the bag

with the highest dose of chemical.

• What is the reaction that your populations of seeds have to your

chemical? This reaction is called the response.

Answers will vary, but students should begin to describe what is

happening with their populations of seeds in terms of a response.

The response to the chemical might be that seeds do not germinate as

quickly as they do in the control bag. Students might be able to see that

more seeds are responding to the chemical (not germinating) in the

bags with the highest dose of chemical.

• Why might the whole population in each bag (all 10 seeds) not

respond in the same way?

By asking this question, you will help students begin to think about

individual susceptibility, a concept students will explore further in Lesson 3. Just as there are individual differences among people, there

are individual differences among seeds that affect how each seed

responds to the chemical. In addition, students can begin to critique

their experimental procedure and decide if they think they had enough

liquid in each bag, spaced the seeds evenly, or in some way influenced

the results through experimental error.

• How do you measure the response your populations of seeds has

to the chemical?

Since the seeds’ response to the chemical is a variation in germination,

the measurement would be to count the number of seeds in each bag

that germinated and those that did not germinate. By focusing students

on measurable observations rather than only qualitative ones, you will

make it easier for students to graph the results of their investigation in Lesson 3.

60

4-p. Instruct students to fill in Day 2 of their data table on Master 2.3, which they placed in their science notebooks (see Activity 3, Step 7-p).

Remind students that they will observe the seeds again on the next

day to see if there are further changes.

5-p. Direct students to place their trays of seeds in the same spot as the day before.

The hazard of chemicals in the environment is one that is often exaggerated.

Extension

Activity

Because we are exposed to many chemicals, both naturally occurring and

synthetically produced, it makes sense to understand when to worry and

when not to worry. The problem arises when people do not know the dose

of a chemical required to cause an adverse effect. In many cases, people

assume that any exposure to a chemical that can cause harm is harmful.

To illustrate the flaw in this reasoning, the American Council on Science

and Health publishes a Holiday Dinner Menu each year. In this menu,

scientists from the council analyze the foods we eat at Thanksgiving to

determine our exposure to natural chemicals known to cause adverse

effects in rats. For example, people consume natural chemicals such as ethyl benzene in their coffee, hydrogen peroxide in their tomatoes, and furan

in their sweet potatoes. How are humans not being poisoned by their own

food supply?

1. Invite students to log on to the American Council on Science and

Health Web site to learn more about the importance of dose with

respect to the dangers of chemicals in our food source: www.acsh.org/

publications/booklets/menu98.html.

2. Ask those students who choose to explore this extension to share their findings with the class.

3. Encourage students to design a bulletin board that illustrates how

much of a food containing a harmful chemical a human would have

to consume to get a toxic dose of the chemical. Such calculations

are presented on the council’s Web site. Past years’ examples have

included the amount of turkey a person would have to eat to get a

toxic dose of malonaldehyde and the amount of bread a person would

have to eat to get a toxic dose of furfural. The calculations for the

bread example are shown in the box on the next page.

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Student Lesson 2

Chemicals, the Environment, and You

Calculating a toxic dose of furfural

The bread in Thanksgiving stuffing contains furfural, a chemical that can cause cancer in rats when they are fed high doses of it. But, before you start to worry about your Thanksgiving dinner, take into account the difference in body weight between a human and a rodent. How much bread would you have to eat to consume an amount of furfural equal to the amount that increased the risk of cancer in rodents?

Here are the facts:

• One slice of white bread contains 167 micrograms of furfural.

• The carcinogenic dose of furfural for a rodent is 197 milligrams per kilogram of body weight per day, fed every day of its life. (This is the same as 197,000 micrograms/

kilogram/day because there are 1,000 micrograms in a milligram.)

• The weight in kilograms of a middle school student who weighs 110 pounds is 50 kilograms because there are 2.2 pounds in every kilogram.

Here is the solution:

197,000 micrograms x 50 kilograms = 9,850,000 micrograms per day, a carcinogenic 1 kilogram person dose for an average middle school student 9,850,000 micrograms = 58,982 slices of bread

167 micrograms/slice

What does this mean?

The average middle school student would have to

eat 58,982 slices of bread a day to get a carcinogenic

dose of furfural, assuming he or she responded

the same way experimental animals do. When

looking at this example, remember the conditions

of animal studies: Doses are fed every day of the

rodent’s life (usually two years). To get an equivalent

carcinogenic dose, a human would have to consume

those 58,982 slices every day for years.

62

L E S S O N 3

Explain

Dose-Response

Relationships

Overview

At a Glance

Students complete their observations of the germinating seeds on the

third consecutive day. They express their data on a graph and develop a

dose-response curve for their chemical. Students then compare the data

from their investigation of a chemical with those of other teams and other chemicals. Students learn to analyze dose-response curves to determine

threshold and potency.

Major Concepts

Dose and response are related and can be represented by a dose-response

curve. Data from toxicology testing can be represented by a dose-response

curve, from which scientists can describe the threshold and potency

of chemicals.

Objectives

After completing this lesson, students will

• be able to describe the response of seeds to certain doses of chemicals,

• recognize that dose and response are related and be able to represent that relationship on a graph,

• compare the threshold and potency of chemicals, and

• be able, based on their seed investigation, to draw conclusions that relate to chemicals in the environment.

Dose-Response Curves

Background

The characteristics of exposure to a chemical and the spectrum of effects

Information

caused by the chemical come together in a correlative relationship that

toxicologists call the dose-response relationship. This relationship is the most fundamental and pervasive concept in toxicology (Klassen, 2008;

Gilbert, 2004). To understand the potential hazard of a specific chemical, toxicologists must know both the type of effect it produces and the amount, or dose, required to produce that effect.

63

Chemicals, the Environment, and You

The relationship of dose to response can be illustrated as a graph called

a dose-response curve. There are two types of dose-response curves: one

that describes the graded responses of an individual to varying doses of the chemical and one that describes the distribution of responses to different doses in a population of individuals. The dose is represented on the x-axis.

The response is represented on the y-axis.

The following graph shows a simple example of a dose-response curve

for an individual with a single exposure to the chemical ethanol (alcohol), with graded responses between no effect and death (Marczewski and

Kamrin, 2000).

Individual Dose-Response Curve

From: Marczewski, A.E., and Kamrin, M. Toxicology for the citizen (Figure 6).

Institute for Environmental Toxicology, Michigan State University, reprinted with permission.

A simple example of a dose-response curve for a population of mice in a

study of a carcinogenic chemical might look like the following graph:

Population Dose-Response Curve

Adapted from: Eaton, D.L., and Klaassen, C.D. 1996. Principles of toxicology. In Casarett & Doul s’

Toxicology: The Basic Science of Poisons (5th ed.). New York: McGraw-Hil .

64

An important aspect of dose-response relationships is the concept of

threshold. For most types of toxic responses, there is a dose, called a threshold, below which there are no adverse effects from exposure to the

chemical. The human body has defenses against many toxic agents. Cells in

human organs, especially in the liver and kidneys, break down chemicals

into nontoxic substances that can be eliminated from the body in urine and feces. In this way, the human body can take some toxic insult (at a dose

that is below the threshold) and still remain healthy.

The identification of the threshold beyond which the human body cannot

remain healthy depends on the type of response that is measured and can

vary depending on the individual being tested. Thresholds based on acute

responses, such as death, are more easily determined, while thresholds

for chemicals that cause cancer or other chronic responses are harder

to determine. Even so, it is important for toxicologists to identify a level of exposure to a chemical at which there is no effect and to determine

thresholds when possible.

Hypothetical Dose-Response Curve Showing Threshold

When a threshold is difficult to determine, toxicologists look at the slope of the dose-response curve to give them information about the toxicity

of a chemical. A sharp increase in the slope of the curve can suggest

increasingly higher risks of toxic responses as the dose increases, as

illustrated by line A on the next graph. A relatively flat slope suggests that the effect of an increase in dose is minimal (line B).

Two Hypothetical Dose-Response Curves with Different Slopes

65

Student Lesson 3

Chemicals, the Environment, and You

A comparison of dose-response curves among chemicals can offer

information about the chemicals as well. A steep curve that begins to climb even at a small dose suggests a chemical of high potency. The potency of a chemical is a measure of its strength as a poison compared with other

chemicals. The more potent the chemical, the less it takes to kill (Klassen, 2008). In the previous dose-response graph, line A describes a chemical that is more potent than the chemical described by line B, as can be seen by the relative positions of the lines along the dose axis and their slopes.

Although some dose-response tests use lethality as an index, toxicologists also make observations of responses that do not include death. Other

symptoms of toxic response to a chemical include fever, hair loss, headache, nausea, rash, urine abnormalities, and numbness in arms and legs.

Regardless of the response that is used for measurement with respect to

dose, toxicologists find that the form of the dose-response curve is similar.

Notes about Lesson 3

In this lesson, students will use the data they collected on the germination of their seeds in the presence of a chemical to create a dose-response curve for their chemical. In doing so, students will be able to compare visually the slope of their chemical’s curve with those of other students. Students also can compare the potency of the chemicals by measuring germination

of seeds. It is important for students to remember that they cannot make

inferences about the potency of the chemicals with respect to human

health; they can only use their data to inform them of the chemicals’

potential toxicity to humans. In this way, students must think critically

and logically to make the relationships between evidence and explanations.

66

Web-Based Activities

In Advance

Activity 1 has an optional Web-based component.

Materials and Preparation

Photocopies and Transparencies

Extension Activity

1 transparency of Master 3.1

• overhead projector

1 copy of Master 3.2 for each team

• blank transparency

• overhead markers

For each team of 3 students:

• bags of seeds treated with

chemical from Lesson 2

(print version)

• materials for laboratory

investigation from Lesson 2,

Activity 2

For each student:

• Master 2.3, Toxicity Testing

on Seeds, from Lesson 2

• data from the Web site

(optional)

• 1 copy of Master 3.2

• pencil

Preparation

Activity 1

If your students conducted the Web version of Lesson 2, arrange for them to have access to computers.

Make a transparency of Master 3.1, Dose-Response Curves. Make copies of Master 3.2, Graph Paper, one for each team.

Extension Activity

Gather the materials needed for students to conduct their investigation.

67

Student Lesson 3

Chemicals, the Environment, and You

Procedure

ACTIVITY 1: Graphing the Response to Chemical Dose

If students are investigating seed germination using the Web

site, direct them to access the data on the site and proceed to

Step 3 of this activity (see Lesson 2, Activity 4).

1-p. As the students enter the room, ask them to get their bags of seeds treated with chemicals from Lesson 2 and bring them to their

team’s table.

2-p. Direct students to observe each of their six bags of seeds. Ask them to record in the Day 3 column of their data table the number of

seeds in each population that have germinated and the number of

seeds that have not germinated.

Students might see more than just germination: Some plants now

might be developing leaves. Encourage students to note any growth in

the margin of their data table.

3. Once students have completed their data table, tell them that

scientists graph data like theirs to help them understand the

relationship between dose and response and make judgments

about the safety of particular chemicals. Be sure to point out that

Content Standard A:

students can assume that the dose the seeds receive is related to the

Students use appropriate

concentration of the chemicals in each bag. Display the sample graphs

tools and techniques to

of dose-response relationships on the transparency of Master 3.1,

gather, analyze, and

Dose-Response Curves.

interpret data.

Point out to students that, in the top graph, the dose of alcohol is along the x-axis and the response is graded along the y-axis, from no effect to death. On the second graph, the dose of chemical in milligrams is

along the x-axis. The response, the incidence of tumors in a population of mice, is along the y-axis. Use the Background Information to provide information for students about the two types of dose-response curves:

for individuals and for a collection of subjects.

68

It might be of interest to your students to think about a word that

often describes a person who has had too much to drink: intoxicated.

Using their knowledge of toxicology, students should recognize that

the base of the word toxic accurately describes what happens when

a person is drinking. A person who is drinking alcohol is exposing

himself or herself to a toxic substance that, at a high enough dose,

can cause death. Impress upon students that the dose-response

curve on the overhead provides evidence that binge drinking (which

provides a high dose of alcohol in a very short time) can be very

dangerous, and even deadly.

4. Tell students that you would like them to graph the data they

recorded for Day 3 of their seed investigation. Using a blank

transparency, work with students to design a graph that shows

the relationship between dose and response. To do that, students

will need to help you decide the following:

Content Standard A:

Students use mathematics

• Which of the two types of dose-response graphs will

in all aspects of scientific

they use?

inquiry.

Students will want to use the dose-response graph that represents

data from a population of individuals.

• What is the response that you want to graph?

This is sometimes counterintuitive for students. The response that

they want to graph is the one caused by the chemical (the response

that was different from the response of the control group). In most

cases, the response is the lack of germination, so students would

graph the number of seeds in the population that did not germinate.

• What measurement should be on the x-axis?

The dose is recorded along the x-axis, in increasing concentrations from 0% to 100%. Help students recognize that they need to space

their measurements accurately along the x-axis, but not at even

intervals since their concentrations are 0%, 6.25%, 12.5%, 25%, 50%,

and 100%.

• What measurement should be on the y-axis?

The response is recorded along the y-axis, as the number of seeds in the population that did not germinate, from 0 to 10.

69

Student Lesson 3

Chemicals, the Environment, and You

When you are finished making a sample of the graph, it should look like the following graph:

Dose-Reponse Curve for Seed Germination Investigation

Chemical:

d 10

9

8

7

6

NOT germinate 5

4

Response: seeds 3

of 2

1

0

Number

0 6.25 12.5

25

50

100

Dose (% Concentration)

5. Distribute copies of Master 3.2, Graph Paper, one to each team. Direct teams to make a dose-response graph for their chemical on Graph A.

Remind students to label their graph with the name of their chemical.

6. Once teams have made a graph of their chemical, instruct them to get data from two other teams that tested different chemicals. Tell teams

to graph the data on Graphs B and C, remembering to label each

graph with the name of the chemical.

Tip from the field test: Included here are several dose-response graphs for chemicals tested by students who participated in the field test.

70

Chemical: Pine-Scented Cleaner

Chemical: Coffee

71

Student Lesson 3

Chemicals, the Environment, and You

Chemical: Insect Repellent

Chemical: Fruit Punch Soda

72

Chemical: Salt

Chemical: Window Cleaner

73

Student Lesson 3

Chemicals, the Environment, and You

Chemical: Water-Soluble Plant Fertilizer

7. Circulate around the room and, as they work, ask the teams to study the team graphs to decide which chemical had the highest potency or

which chemicals have a clear threshold.

Of the chemicals graphed above, Lysol (pine-scented cleaner) is the

Listen to students’

most potent and coffee is the least potent. Field-test students found

descriptions of the

that it was difficult to determine threshold. They knew only that they

dose-response

exceeded the threshold below which there was no effect when they

curves to see if they

used Lysol, salt, window cleaner, bug repellent, fruit punch soda, and

understand the

plant fertilizer. To pinpoint the exact threshold, students would need

concepts of threshold

to repeat their investigation using additional concentrations between

0% and 6.25%. When they tested coffee, students found no threshold:

and potency.

Coffee had no effect on seed germination, even at 100% concentration.

8. Discuss with students what conclusions they can make, if any, about the safety or potential harm of the chemicals tested for humans.

Ask students to evaluate the use of plants as a model system for

toxicology testing.

Students should recognize that plants do not have the same structure

Content Standard A:

as humans or other animals, so results from tests that determine

Students develop

toxicity to plants may not apply to humans. In fact, there are

descriptions, explanations,

chemicals that are toxic to plants that do not harm humans and,

predictions, and models

conversely, there are chemicals that do not harm plants but are

using evidence.

capable of harming animals like humans. For this reason, it is best to

Content Standard A:

test chemicals on systems that most closely resemble the human system

Students think critically

if knowledge about effects on humans is the goal. Even so, students may

and logically to make

recognize that data from toxicity tests on seeds could help inform them

the relationships between

of possible toxicants to humans.

evidence and explanations.

74

Toxicologists use to their advantage their understanding that it is

possible for some chemicals to cause injury to one kind of living matter

without harming another kind of living matter. By understanding

this biological phenomenon, scientists can, for example, help farmers

develop pesticides that are lethal to fungi or insects but do not harm

crops, or antibiotics that kill infectious bacteria (also living organisms) but have low toxicity in humans.

Ask students to describe other questions they would like to answer about Extension

the effects of their chemical on plants. Allow space and time for students Activity

to investigate their questions.

For example, students might want to know if their chemical has an

effect on the growth of plants. They can sprout seeds and then water the

seedlings with varying concentrations of chemical solutions. By setting up an investigation that can last a longer time, students can experiment with the concept of exposure over time. They can administer a small dose of

chemical repeatedly for many days and compare the responses to those in

plants that receive only one large dose of chemical.

75

Student Lesson 3

L E S S O N 4

Explain/Elaborate

Individual

Responses Can

Be Different

Overview

At a Glance

Students are aware after Lesson 3 that not all chemicals have the same effect on seed germination. In this lesson, students look at the variation among

responses of seeds to the same dose of the same chemical. In reviewing

their seed investigation, students note that sometimes not all seeds in the same bag responded in the same way. Students then use information about

acetaminophen to learn more about dose and individual susceptibility. They learn that individual variability accounts for the different responses in the same types of organisms exposed to the same dose of a chemical. Students

conduct an investigation into their own susceptibility to caffeine and

compare individual responses.

Major Concepts

The variety of responses among organisms exposed to the same dose

of chemical is due to individual susceptibility. Dose and individual

susceptibility play roles in all situations involving chemicals, including those involving medicines and caffeine.

Objectives

After completing this lesson, students will

• understand that the variety of responses among seeds exposed to the

same dose of chemical is due to individual susceptibility and

• recognize that dose and individual susceptibility play roles in human

exposure to chemicals, such as drugs and caffeine.

77

Chemicals, the Environment, and You

Toxic Effects of Chemicals

Background

The human body is a complex organism. It responds to both external and

Information

internal conditions. For example, when the body gets too hot, it begins to cool itself by turning on its cooling system: sweat. When sensors in the

brain detect that the body has cooled enough, the brain turns off the

sweat glands.

Sometimes the body’s balance is upset by chemical agents that put stress

on different body functions. Some chemicals increase heart rate or

sweating. Others decrease the rate of breathing. A chemical can have a

wide-ranging effect, or it can cause a very limited change in a particular organ of the body. A chemical is toxic if the body’s response to it is an

adverse one, such as headaches, nausea, rashes, convulsions, or death.

Chemicals vary widely in their toxic potential. The variation among chemicals is due to their chemical structure. A chemical’s structure determines

• how the chemical is metabolized,

• the rate at which it is absorbed, and

• how it is excreted.

Small differences in structure can cause big differences in toxicity

(Marczewski and Kamrin, 2000).

Individual Susceptibility

The effect of a chemical also depends on another set of variables.

Organisms will have various responses to chemical exposures because each

organism is unique. For example, if a population of people was exposed to

the same amount of the same chemical, some people might have very severe

reactions to the chemical while others might have no reaction at all. Those with a severe reaction are considered more “susceptible” to the chemical.

Individual susceptibility varies but is influenced by age, gender, health

status, genetics, and lifestyle.

Photos: Corel

78

Photos: Corel

Children and elderly people often have an increased susceptibility to

chemicals. For example, children have higher rates of respiration and

consume more calories per unit of body weight than adults do. This can

result in a greater exposure to and dose of a chemical for children compared with adults. The metabolism of chemicals also can vary because children’s

metabolic systems are still developing. In contrast, changes in physiologic functions, such as diminished kidney function, can impair the ability to

excrete chemicals in an elderly person.

Some people’s susceptibility is related to their overall health. People with asthma may be more susceptible to air pollution. Lifestyle factors such as smoking, drinking, and drug use may affect a person’s susceptibility to

toxicants. On the other hand, people with good nutrition and health are

more resilient, so they can metabolize and excrete toxic substances faster.

Chemicals sometimes affect males and females differently. For example,

women absorb and metabolize alcohol differently from men. Women will

generally have a higher blood alcohol concentration after ingesting the same amount of alcohol as men. While some of the difference in blood alcohol

concentration can be attributed to the difference in size between men and

women, scientists have also found that women have less-active enzymes

that metabolize alcohol, causing a larger proportion of the ingested alcohol to reach the blood (NIAAA, 1997). When drinking heavily, women are

more susceptible to alcoholic liver disease, heart muscle damage, and brain damage. In addition, pregnant women can share an exposure to a chemical

with the fetus through the placenta, and women who are nursing may

expose their babies to the chemical through breast milk.

Inherited differences among people account for some of the different ways

people respond to chemicals. For example, some people are genetically more susceptible to poisoning from the insecticide parathion. Most commonly,

people are exposed to parathion by eating foods grown with the use of the

insecticide. Differences in individual reactions to the chemical depend on which of the two variants, or alleles, of a particular gene the individual carries. One variant results in low activity of the enzyme paraoxanase,

and one variant results in high activity of the enzyme. Scientists have

79

Student Lesson 4

Chemicals, the Environment, and You

determined that the

enzyme paraoxanase

breaks down parathion

into inactive, nontoxic

products that are

excreted in the urine.

Those people who

have the highly active

enzyme and are exposed

to parathion have mild

symptoms such as

abdominal discomfort,

vomiting, and diarrhea,

followed by headache and

weakness, because their

bodies are able to break

down the parathion

into nontoxic products

at a higher rate. Those

people with the gene that

results in low activity

of the enzyme can

have much more severe

symptoms when exposed

Courtesy of the Bayer Corporation

to the same amount of

parathion. These people may experience sudden collapse, coma, sweating,

and difficulty breathing because their bodies cannot break down parathion

quickly and the chemical remains in the body for a longer time.

Understanding the variety of responses that different individuals

can have to different doses of a chemical is important to the study of

pharmaceuticals. Written on the label of any drug are indications describing who can use the drug and how much to take. In addition, warning

statements describe who should not use the drug. Such information is the

result of the knowledge scientists have gained about the way the chemical

affects a diverse population over time.

The Chemical Caffeine

Caffeine is a chemical that most people ingest at some time in their

lives, and many people ingest caffeine daily. People consume caffeine in

coffee, tea, cocoa, chocolate, soft drinks, and some drugs. It is a naturally occurring chemical that comes from the coffee bean, tea leaf, kola nut, and cacao pod.

As a central nervous system stimulant, caffeine in moderate doses can

increase alertness, reduce fine motor coordination, alter sleep patterns, and cause headache, nervousness, and dizziness. In massive doses, caffeine is

lethal. However, it is hard to get a lethal dose of caffeine just by ingesting it in food and drink: A lethal dose of caffeine is 170 milligrams of caffeine 80

Photos: Corel

for every kilogram of body weight, or about 10 grams for an average-sized

adult. One would have to drink 80–100 cups of coffee in rapid succession to reach that threshold (Chudler, 2010).

Caffeine is absorbed rapidly into the bloodstream from the gastrointestinal tract. It can exert its effects within 15 minutes after it is consumed and reaches maximum concentration in the bloodstream within about one hour.

The blood distributes caffeine throughout the body, where the caffeine

increases metabolic rate by about 10 percent. Once in the body, caffeine will stay around for hours: It takes about six hours for one-half of the caffeine to be eliminated. Gender affects a person’s response to caffeine: Females

metabolize caffeine 20–30 percent more quickly than do males (ABC, 1997).

Because caffeine constricts the cerebral blood vessels, blood pressure rises and heart rate increases in the presence of caffeine. When people who

regularly ingest caffeine stop ingesting it, they can suffer severe headaches because the blood vessels in their brain are dilating.

Research into the detrimental effects of caffeine has not uncovered any

connections between ingestion of caffeine and heart disease, stroke, or

cancer. There are some studies that show that large doses of caffeine, such as five to seven cups of coffee a day, can delay fertility (ITIS, 2010).

Compared with other drinks popular with adults, the caffeine content in

soft drinks is lower. Coffee can contain between 80 and 175 milligrams

of caffeine (per 7 ounces) depending on how it is brewed; espresso has

100 milligrams in just 1.5 to 2.0 ounces. Tea can contain 40–60 milligrams of caffeine (per 7 ounces). Ice tea contains 70 milligrams of caffeine in

12 ounces.

Many soft drinks popular among youth contain caffeine. The following

table lists some soft drinks (12-ounce size) and the amounts of caffeine

they contain.

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Student Lesson 4

Chemicals, the Environment, and You

Amount of Caffeine in Soft Drinks

Soft Drink

Milligrams in 12 ounces

Jolt Cola

71 mg

Josta

58 mg

Mountain Dew

55 mg

Surge

51 mg

Diet Coke

45 mg

Coca-Cola

45 mg

Dr Pepper

41 mg

Sunkist Orange Soda

40 mg

Pepsi Cola

37 mg

Barqs Root Beer

23 mg

7-Up

0 mg

Minute Maid Orange Soda

0 mg

Mug Root Beer

0 mg

Source: Center for Science in the Public Interest. Soft drinks and health: Caffeine content of foods and drugs. Retrieved August 17, 2000, from www.cspinet.org/new/cafchart.htm.

Notes about Lesson 4

In this lesson, students can use information from their seed investigation to help them understand some of their own voluntary exposures to

chemicals. When they take a medicine, they are exposing themselves to

a chemical. When they follow the correct dosage for that medicine, they

are taking advantage of what scientists know about how much exposure

to the chemical results in the desired response. In addition, although they might not think of it in these terms, students are exposing themselves to

the chemical caffeine each time they drink a caffeinated soft drink or eat a piece of chocolate. Students intuitively know that caffeine, a stimulant, affects some people more than others: It may keep some people awake

at night, while others can drink a caffeinated drink right before bedtime

and still sleep. In this lesson, students measure their own heart rates after drinking a soft drink containing caffeine to see if they can quantify some of those individual differences.

In Advance

Web-Based Activities

Activity 2 has a Web-based component.

Photocopies and Transparencies

1 transparency of Masters 4.1 and of 4.2 (optional)

1 copy of Masters 4.3 (print version only), 4.4, and 4.5 for

each student

82

Materials

Activity 1

For the class:

• overhead projector

• overhead markers

• 3 large beakers filled with equal amounts of water and drops of mystery chemical from Lesson 2, Activity 1

• 3 clear containers of distinctly different sizes, each filled with distinctly different amounts of water, labeled #1, #2, #3

• jar of mystery chemical from Lessons 1 and 2

• eyedropper

For each student:

• science notebook with seed investigation data table

• pencil

Activity 2

For the class:

• computers

• overhead projector

Activity 3

For the class:

• clock with a second hand

For each student:

• 1 12-ounce can of caffeinated soft drink, or equivalent amount of water

• pencil

Extension Activity

• none

Preparation

Activity 1

If necessary, fill the three beakers from Lesson 2 with equal amounts of

water. Add 1 drop of the mystery chemical to Beaker #1, 4 drops to

Beaker #2, and 16 drops to Beaker #3.

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Student Lesson 4

Chemicals, the Environment, and You

Collect three clear containers of different sizes and label them #1, #2, and

#3. Fill each container with water, making sure that each container holds

obviously different amounts of water, with #1 having the least and #3

having the most.

Make a transparency of Master 4.1, Acetaminophen Dosage Chart.

Activity 2

Decide whether you will use the Web or print version of this activity. If you choose the Web version, arrange for students to have access to computers.

If you use the print version, conduct the activity with the whole class. Later, let students review the problem online on their own.

Activity 3

At least one week before conducting Activity 3, send home personalized

parent letters (Master 4.4, Parent Letter) to inform parents of the investigation and to get permission for the students to consume a

caffeinated soft drink during science class. You can use the letter to ask each student to bring in his or her own can of the designated caffeinated

soft drink.

Arrange to have enough cans of the same kind of caffeinated soft drink for each student who participates in the investigation. There are several ways to do this:

• purchase all the soft drinks yourself through your school budget,

• ask for parent or business donations to cover the cost, or

• request that each student bring in one can of the same kind of soft drink, labeled with his or her name, for his or her consumption only.

Before the day of Activity 3, have students practice taking a resting heart rate so they are used to finding their pulse, counting the beats for 15

seconds, and multiplying the number they count by four to get a resting

heart rate for one minute (see Activity 3).

Procedure

ACTIVITY 1: Different Doses for Different People

1. Ask students why they think toxicologists look at both whether a

chemical has an effect on living things and what happens at different

doses. Why do students think it matters to look at doses?

Students may bring up the term overdose, which refers to a situation in which a person receives too much of a particular chemical, usually

a drug. Students should realize that the proper dose of a chemical is

what makes it beneficial to people and that knowing the dose is useful

in determining the appropriate human consumption of that chemical.

Some chemicals, such as vitamins and minerals, are beneficial at a

84

particular dose, but human health suffers if the chemicals are present in

high or very low doses (you can have too much or not enough). Other

chemicals, such as drugs and pesticides, are usually more harmful as

the dose increases.

2. Tell students that you are going to demonstrate one reason why paying attention to dose is important in the study of toxicology.

• First, on one side of a desk at the front of the room, place the three

large beakers filled with equal amounts of water and different

amounts of mystery chemical from the demonstration in Lesson 2.

Remind students that this is the demonstration they saw before they

began their seed investigation.

• Then, place three different-size clear containers on the desk. Fill

each container with water, making sure that it is obvious that each

container holds a different amount of water (#1 holds the least and

#3 holds the most).

• Using the eyedropper from Lesson 1, place two drops of mystery

chemical in each of the containers. Swirl the containers to mix the

chemical and the water.

3. Ask students to observe the three new containers and compare them

with the setup of the demonstration from Lesson 2. Discuss their

observations by asking questions like these:

• Is this new demonstration the same as the one I did for you before

you began your seed investigation? Why or why not?

Students will recognize that the demonstration is different. Today, you

are using different-size containers (and different amounts of water) and

Content Standard A:

the same amount of chemical; earlier you used the same-size containers

Students think critically

and different amounts of chemical.

and logically to make the

relationships between

• What was the variable in the earlier demonstration?

evidence and explanations.

The variable was the amount of chemical you added to each beaker of

water. The dose was the variable. The amount of water was the constant.

• What is the variable I am using today?

Today, the variable is the amount of liquid in each container. The dose

of chemical is a constant.

• How would you describe the concentrations of chemicals in each

of the containers in today’s demonstration?

The concentration of chemical in each container is different in

today’s demonstration because the amount of water in each container

is different although the amount of chemical is the same. Because

concentration is a measurement of the amount of chemical compared

with the volume of water, the concentration of chemical in Container #1

is higher than the concentration in #2 or #3.

85

Student Lesson 4

Chemicals, the Environment, and You

• What do you think the containers in today’s demonstration are

illustrating? Why do you think it matters that the containers are

different sizes?

The different-size containers represent the different variations in

size of people who might be exposed to the mystery chemical. In

smaller people (Container #1), 2 drops of chemical result in a higher

concentration of chemical in their bodies than do 2 drops in either of

the larger people (Containers #2 and #3). This higher concentration

could be beneficial (if it approaches the threshold that creates beneficial results) or it could be harmful (if the higher concentration exceeds the

threshold for safe use of the chemical).

• When might understanding this relationship of dose to size matter?

When people use drugs to treat illness, they are exposing themselves

to chemicals. To understand how much of a chemical is needed to get

the desired effect, such as lowering fever or reducing pain, you need to

understand that the same dose of chemical will have different effects

on different-size people because it results in different concentrations in their bodies.

Tip from the field test: This is a simple demonstration that, when coupled with students’ understanding of the earlier demonstration, moves students

to use the language of toxicology: dose, response, concentration.

Ask students to

4. Keep the containers of water on the desk while you display the

write about the two

transparency of Master 4.1 Acetaminophen Dosage Chart. Ask demonstrations

questions such as these to discuss the concept of dose with respect to

and clearly discuss

body size:

what is different

about the two.

• What is acetaminophen?

Students might need you to tell them that acetaminophen is the active

ingredient in Tylenol products. It is a chemical that, when taken into

the human body, elevates the pain threshold and reduces fever.

• For all people, what is the response they want to get from

exposure to a dose of acetaminophen?

They want to reduce their fever or pain.

• What does the dosage chart tell you about the relationship

between dose and body size?

The dose increases as the body size of the individual increases.

Students can see from the chart that each tablet of Children’s Chewable

Acetaminophen provides a dose of 80 milligrams of acetaminophen. As

a child grows, the amount of acetaminophen needed to reduce fever and

86

pain increases. For example, a child weighing 40 pounds needs a dose

of three tablets at 80 milligrams of acetaminophen per tablet, or 240

milligrams of medicine. A child weighing 80 pounds needs six tablets

at 80 milligrams each, or a dose of 480 milligrams of acetaminophen.

Tip from the field test: Use this time to teach students how to read a dosage chart. Show them where to find information about the number of

milligrams of acetaminophen each measurement contains (for example, one

tablet contains 80 milligrams of acetaminophen). Impress upon them the

importance of knowing a person’s size (weight) to determine correct dosage.

Familiarity with dosage charts makes it easier for students to work the

problem in Activity 2.

Dosage Chart for Children’s Chewable Acetaminophen

(80 mg/tablet)

Weight (lb)

Weight (kg)

Age (yr)

Dose

under 24

under 11

under 2

consult doctor

24–35

11–16

2–3

2 tablets

36–47

17–21

4–5

3 tablets

48–59

22–27

6–8

4 tablets

60–71

28–32

9–10

5 tablets

72–95

33–43

11

6 tablets

Warning: Take no more than five doses per day.

Dosage is determined by body weight. Age is not an accurate measure

for dose but is included on many charts in case weight is unknown.

Dose is expressed in number of tablets (or capsules, teaspoons, or

droppers). Dosage charts always include information about milligrams

per unit of measure.

• Look again at today’s demonstration. Which size child from the

chart might each container in today’s demonstration represent?

Container #1 represents the smallest child, #2 a medium-size child, and

#3 the largest child.

• If the 2-drop dose the smallest child received in Container #1 was

correct for the child’s size, what can you say about the dose the

other two children received?

The concentration of chemical in the larger children’s bodies would be

lower and might not be enough to provide the desired effect.

• If the 2-drop dose in Container #3 resulted in a toxic response

for the largest child, what can you say about the dose for the two

smaller children?

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Student Lesson 4

Chemicals, the Environment, and You

The dose for the two smaller children would almost certainly be toxic

because the concentration of chemical in their bodies is higher.

5. Tell the students that size is one difference in people that can affect how susceptible they are to chemicals. Ask students what other

factors about an individual might make the individual more or less

susceptible to chemicals such as acetaminophen. List the factors on

Content Standard F:

the board.

Students should

Start the list with size (weight). Other factors that can affect

develop understanding

susceptibility to chemicals are age, lifestyle or behavior (such as being

of personal health.

an alcoholic), gender, genetics, and general health.

6. Tell students that toxicologists know that these variable factors

determine an individual’s susceptibility to the effects of environmental toxicants. Write individual susceptibility as the title of the list you made on the board in Step 5. Tell students that, because of their

understanding of individual susceptibility, toxicologists expect that

individuals may respond differently to the same dose of a chemical.

7. Ask students to apply the concept of individual susceptibility to their observations of the seeds in their investigation. If students need help, prompt them with questions such as these:

• Did all of the seeds in each of your bags respond to their dose of

chemical in the same way?

Answers will vary, but most likely students will have had bags in which

not all of the seeds reached the same stage of germination by Day 3.

• What factors in the seeds might account for the differences in

germination among them?

Seeds are processed from many different plants, so the genetic makeup

might not be exactly the same among 10 seeds. Age might be a factor

because some seeds might be older than other seeds. General health of

the seeds could be a factor because some seeds might be less healthy

than other seeds.

Photos: Corel

88

• Why did you use 10 seeds to test each of the concentrations

of chemical?

By using 10 seeds, you can compensate for possible responses due only

to individual susceptibility by observing the response in the majority

of the seeds. If you tested only one seed, you wouldn’t know if the

response you observed was due only to the dose of the chemical or was

a reflection of the seed’s individual susceptibility to the chemical.

ACTIVITY 2: A Poisonous Dose?

The following procedures describe how to conduct the Web version of this activity, which is the preferred method of instruction. Instructions for the print version follow.

Use a computer lab where you can set up multiple computers.

Go to http://science.education.nih.gov/supplements/chemicals/

student. Select Lesson 4— Individual Responses Can Be

Different. Start the activ ity by watching the video. Encourage

students to work in pairs to solve the problem. Then go to Activity 3.

Print Version

If your students do not have access to the Web site or you would like an opportunity to assess students individually on their understanding of a toxicology problem involving humans, use the following print version of Activity 2.

1-p. Display the first page of the transparency you made from Master 4.2, A

Poisonous Dose? The Case History. Read the transparency with the students.

2-p. Distribute copies of the first page of Master 4.3, A Poisonous Dose?

The Problem. Ask students to work in teams of three to complete Part I. Circulate around the room to help students read the dosage

chart, understand the math, and draw some conclusions.

Students should select letter e: Both b and d are correct. Andy received 1 teaspoon four times a day, or 4 teaspoons in all. Because there

are 6.25 dropperfuls of acetaminophen in each teaspoon and

80 milligrams of acetaminophen in each dropper, the calculation of the

amount of acetaminophen Andy received from his aunt should read:

4 teaspoons x 6.25 dropperfuls x 80 milligrams = 2000

1 teaspoon

1 dropperful milligrams of

acetaminophen

The calculation of the maximum number of milligrams a child Andy’s

size should receive should read:

5 doses = 10 dropperfuls x 80 milligrams = 800 milligrams of 1 dropperful

acetaminophen

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Student Lesson 4

Chemicals, the Environment, and You

As students work through the math, they see that the dose of

acetaminophen the aunt gave Andy is much higher than the

recommended maximum dose. Students can hypothesize, based on

their understanding of dose and concentration and its relationship to

size, that Andy was sick from too much acetaminophen.

3-p. Distribute copies of the second page of Master 4.3, A Poisonous Dose?

The Problem. Instruct students to continue to work in their teams of three to complete Part II up to the conclusion. Then ask students to

work individually on the conclusion by writing about how they think

the accidental overdose of acetaminophen happened.

The calculation of the amount of acetaminophen in four doses of

Children’s Suspension Liquid should read:

4 doses = 4 teaspoons x 160 milligrams = 640 milligrams of

Content Standard A:

1 teaspoon

acetaminophen

Use mathematics in all

aspects of scientific inquiry.

Andy’s mother uses a teaspoon to measure a dose of Children’s

Suspension Liquid. Andy’s aunt used a teaspoon to measure Infants’

Content Standard E:

Concentrated Suspension Drops. The dosage chart says to use a

Students should develop

dropper to measure infants’ drops.

understandings about

science and technology.

Students can conclude that incorrect amounts of acetaminophen

Technological solutions

were given to Andy because his aunt did not understand that the

have intended benefits

acetaminophen in infants’ formula is concentrated: It cannot be

and unintended

measured using the same units (teaspoons) as the children’s formula.

consequences.

In fact, a teaspoon of infants’ formula is more than three times

Some consequences

stronger than a teaspoon of children’s formula. Instead of teaspoons,

can be predicted,

infants’ formula should be measured in droppers, which is indicated

others cannot.

on the dosage chart. Unfortunately, the similarity in the appearance of

the two liquids leads parents, care givers, and even doctors to believe

that the two medicines are interchangeable.

Students may ask why the infants’ formula is stronger, when

medicine formulas usually get stronger for people only as their

body size gets bigger. Because it is so difficult to give medicine to

a baby, it is important to pack as much acetaminophen as possible

Collect students’ written

into the smallest volume of liquid. The higher concentration of

conclusions of what

the acetaminophen in infants’ formula ensures that parents can

happened to Andy. Assess

administer the appropriate amount of medicine with the least amount

students’ writing for

of trouble.

understanding of the roles

4-p. Display the second page of the transparency you made from Master

dose and concentration

4.2, A Poisonous Dose? The Case History. Review with students the played in Andy’s overdose

diagnosis and treatment.

and how the confusion

over the two kinds of

The doctor handling Andy’s case had seen severe liver damage and

acetaminophen led to

even death from liver failure among children who experienced

the problem.

accidental acetaminophen poisoning. She knew that an overdose

90

Courtesy of Children’s TYLENOL a product of McNeil Consumer Healthcare

of acetaminophen is 150 milligrams for each kilogram of body

weight. For Andy, who weighs 12 kilograms, an overdose would be

1,800 milligrams. In Part I, students calculated that Andy received

2,000 milligrams of acetaminophen, clearly an overdose. The doctor

administered an antidote ( N-acetylcysteine) within 8 to 12 hours of the poisoning, and the boy recovered.

5-p. Ask students how they think a mistake like the one that poisoned

Andy could be avoided.

Because of situations like Andy’s, changes in the labels and inserted

instructions for acetaminophen products now inform people of the

potential dangers of taking too much acetaminophen and more clearly

describe appropriate dosage. Adults are reminded to use the dropper

for the infants’ formula acetaminophen, which is the appropriate unit

of measure.

ACTIVITY 3: The Chemical Caffeine: How Do You Respond?

Note: Before beginning this investigation, be sure to have a signed permission letter from parents or guardians for the students to ingest a

caffeinated soft drink (use Master 4.4, Parent Letter). Those students for whom you do not have permission can participate in the investigation by

drinking water; they will provide a control for the activity.

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Student Lesson 4

Chemicals, the Environment, and You

1. Because their heart rates might be elevated from their walk to class, spend several minutes allowing students to rest and talk quietly. Find

out what students know about the chemical caffeine. Use material

from the Background Information to discuss caffeine briefly. Then, if you have not already done so, teach students how to find their pulse,

count their heartbeats, and calculate their resting heart rate.

You can find your pulse most easily by pressing two fingers against the

artery in your neck or on the inside of your wrist. It is easiest to count beats for only 15 seconds and then multiply the number you count by

four to find your resting heart rate for one minute. Repeat the counting

several times until most students have calculated a resting heart rate

that is close to the same number several times in a row. Alternatively,

you can have partners verify each other’s heart rate.

2. Distribute Master 4.5, The Chemical Caffeine: How Do You Respond? , one to each student. On your signal, ask students to measure their

heartbeats one more time for 15 seconds, stopping when you call time.

Instruct students to calculate

their resting heart rate for

one minute by multiplying the

number they counted by four.

Direct them to record it on the

data table on the master.

3. Ask students to work in pairs.

Distribute the cans of the same

kind of caffeinated soft drink,

one to each student. Instruct

students to follow the directions

on the master. Remind them to

continue to sit at rest. They can talk to their partner but should

keep their bodies still so that they do not elevate their heart rate

with activity.

92

Tip from the field test: Assign some reading to students from which they can take a break periodically to measure their heart rate. Planning ahead for quiet activity helps keep the students focused on the task.

4. When all the students have filled in their data tables and calculated the difference between their resting heart rate and the highest heart

rate after ingesting a caffeinated soft drink, discuss their findings by asking questions such as these:

Content Standard A:

• Did your heart rate go up, down, or stay the same after you drank

Students should develop

a caffeinated soft drink?

abilities necessary to do

scientific inquiry and

On average, most students should have seen their heart rate go up after

understandings about

drinking the caffeinated soft drink. Some sample data from a field-test

scientific inquiry.

class looked like this:

Measurements of Heart Rate at Rest

and After Caffeine for a Field-Test Class

Highest Post-

Male or Female

Resting Heart Rate

Caffeine Heart Rate

F

80

88

M

88

100

M

76

116

M

68

76

M

72

92

M

80

92

F

76

92

F

68

84

F

68

92

F

72

80

M

80

74

M

64

84

F

68

88

F

84

84

M

80

96

M

72

104

• On the basis of your observations, what generalization can you

make about the effect of caffeine on the human body?

Caffeine appears to increase heart rate.

• Why was it important that all students drank the same kind and

amount of soft drink?

Students will recognize that the variable they are interested in testing

is individual susceptibility to caffeine. They need to keep as many other

factors in the investigation constant, such as amount and kind of soft

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Student Lesson 4

Chemicals, the Environment, and You

drink (because different soft drinks have different amounts of caffeine),

time of day for the investigation, and temperature of the classroom.

• Did all the members of the class have exactly the same results

when they drank a caffeinated soft drink?

While most members of the class will see their heart rate increase, the

amount of increase will vary significantly.

• Compare your results with those of other members of the class.

What is your individual susceptibility to caffeine?

Ask students to compare how much their heart rates increased after

exposure to caffeine. Those whose heart rates increased significantly

can draw the conclusion that they are very susceptible to caffeine.

Those whose heart rates did not increase very much, or went down,

can draw the conclusion that they are less susceptible to caffeine.

• Why might some people be more individually susceptible to the

effects of caffeine than others?

Students vary from one another in gender, size, frequency of caffeine

consumption, metabolic rates, and so on. This variability makes each

student react differently to exposure to caffeine.

• What do the results of your investigation tell you about the

possible risks to some people of ingesting the chemical caffeine?

Although research has shown that caffeine is safe to consume in

moderate amounts, doctors suggest that people who have high blood

pressure or trouble with irregular heartbeats avoid caffeine.

Extension

Ask students to examine the labels from some product packages for

Activity

directions for use and warnings. Suggest that students look at a variety

of products, such as household cleaners, cold medicines, and vitamins.

Instruct students to summarize information about the following for

each product:

• route of exposure

• dose

• individual susceptibility

Students’ summaries will vary depending on the products they choose.

Encourage them to examine at least one product that is meant for

human ingestion, such as a medication, because the product label should

contain information about dose and individual susceptibility. Remind

them that labels from some products, such as household cleaners, will

have information about routes of exposure but probably will not include

information about dose or individual susceptibility.

94

L E S S O N 5

Elaborate

What Is

the Risk?

Overview

At a Glance

Students apply their growing understanding of the concepts of toxicology

(dose, response, individual susceptibility, potency, and threshold) to their discussion of the 1950s tragedy in Minamata, Japan. They learn how to

assess the risk to people of specific chemical hazards and make decisions

about how to manage that risk.

Major Concepts

People can make some choices about chemical exposure; however, some

exposure is controlled at a level other than an individual one. Collective groups of people, such as communities and governments, seek to control

chemical exposure on a community or global level.

Objectives

After completing this lesson, students will

• use their knowledge about dose, response, individual susceptibility,

and route and frequency of exposure to understand a historical

situation involving hazardous chemical exposure;

• assess the risk to people in Minamata of mercury poisoning using a

risk-assessment flow chart;

• compare their own risk of mercury poisoning with that of the people

of Minamata; and

• understand the kinds of critical choices people make about chemical

exposure and that some exposure is controlled at a level other than

an individual one, such as the community or global level.

95

Chemicals, the Environment, and You

Background

The Minamata Case Study

Information

When people living in Minamata, Japan, in the 1950s began slurring their

speech occasionally or dropping their chopsticks at a meal, no one thought much of it. Some people

cruelly laughed, claiming their

clumsy friends were acting like

the cats that were “dancing”

strangely in the street and

falling to their death in the

sea. When it seemed like more

and more people were suffering

from the mysterious lack of

coordination, the community

began to realize that something

was seriously wrong. But,

people did not know that they

were seeing the first signs of a

debilitating nervous condition

caused by ingesting mercury

(Japanese Environmental

Health Department, 2002).

We now know the tragic story of Minamata. The Minamata Bay was

polluted with the industrial waste from the Chisso Corporation, which

manufactured acetaldehyde used to make plastics. The mercury the

company used in the production process was discharged into the bay,

incorporated into bacteria, and passed through the food chain to people

living in the area. The people in the town were slowly being poisoned by

their most important food source: fish.

The consequences of such blatant polluting seem obvious to people today.

But at the time, science had not yet documented the hazards of mercury,

and environmental awareness was not pervasive. In fact, the Minamata

case has become a classic lesson in the tragedy of industrial pollution

and the need to anticipate the unexpected consequences of introducing

chemicals into the environment. Although the story is now half a century

old (and “ancient history” for today’s middle school students), it has a well-documented cause and effect, as well as a resolution. In this way, it provides a good model for teaching about risk assessment and management that

students can apply to their analysis of current exposures to chemicals.

Risk Assessment

Today, when toxicologists study the extent and type of negative effects

associated with a particular level of chemical exposure, they can use what they learn to assess the threat of that chemical to people’s health. To do this, toxicologists measure a person’s risk of exposure to the chemical.

For example, even though dioxin is considered the most toxic synthetic

chemical known, it does not pose the greatest risk to humans because the

Minamata photographs by W. Eugene Smith

potential for significant dioxin exposure is quite small. In addition, while and Aileen M. Smith.

96

the lethal dose of a chemical is an important measurement to make, it is

quite possible that a chemical will produce a very undesirable toxic effect at doses that cause no deaths at all. These lower doses may be the amount to

which people are regularly exposed.

How a person is exposed to a chemical also determines the factor of risk.

In the case of a single exposure, the amount of chemical and way the body

is known to respond to the chemical determine the severity of the toxic

response. In the case of repeated exposures to a chemical, it is not only the amount of chemical that counts, but also the frequency of exposure. If the body is able to rid itself entirely of the chemical before the next exposure, it is possible that each exposure is akin to a single exposure to the chemical.

If, however, the body still retains some of the chemical from the previous exposure, accumulation of the chemical can occur and eventually can reach

toxic levels, even if each exposure is small.

Many of the measurements that guide toxicologists in their assessment

of human risk are based on studies of animals other than humans. This

fact, coupled with the individual susceptibility of different members of

the human population, makes it difficult to know with absolute certainty

the level of risk to which each individual is exposed. With adequate

information, however, toxicologists can predict the health risks associated with specific chemical exposures and help the human population make

informed decisions about how to limit those exposures.

Managing Risk

The built-in uncertainty of risk assessment makes it essential for people to possess enough knowledge to make decisions about their own exposures

to chemicals. With adequate knowledge, individuals can make decisions

concerning their exposure to tobacco smoke, pollutants in water, and

chemicals in food. By modifying their individual behavior, people can have some control over the chemicals they absorb into their body.

Not all decisions about chemical exposure and control can be made at

an individual level, however. Local, national, and global communities of

people are exposed to chemicals over which they have very little individual control. People are exposed to air pollution from factories and cars or

chemicals used by farmers on crops without any individual consent.

To manage a community’s risk from chemicals in the environment,

organizations and agencies set standards to protect human health.

There are choices about chemical exposure over which individuals

have control (represented by the inner circle in the adjacent diagram).

Individuals are also affected by their immediate environment (their friends and family, as well as the air, soil, and water around their homes and

workplaces); the middle circle of the diagram describes influences on an

individual over which he or she has less control. Finally, the outer circle describes the world that surrounds individuals over which they have little control but that can have an impact on them. The arrows between each

concentric circle indicate that individuals, their environment, and the world at large all affect each other.

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Student Lesson 5

Chemicals, the Environment, and You

One step in community risk management is to determine how much risk is

acceptable to people. If the chance that exposure to a particular chemical causes cancer is only 1 in 1 million, people are often less concerned than if the chance is 1 in 10. The picture becomes more complicated when societal

issues weigh in (Marczewski and Kamrin, 2000). Is the exposure voluntary

(as in smoking cigarettes) or involuntary (as in pollution from a factory)?

Does it occur in the workplace or at home? Are there acceptable alternatives to the use of the toxic chemical? How would use of a safer chemical change the economic picture?

To establish some individual control over community management of

chemical exposure, people can choose to be involved with organizations

and agencies that are concerned with the prevention of toxic chemical

exposure on a community level.

Notes about Lesson 5

In this lesson, students have the opportunity to apply many of the concepts of toxicology to a scenario that involved toxic chemicals in Minamata,

Japan. By looking at a situation from the 1950s, students can recognize how far scientists and the general public have come in their understanding of

chemical hazards and their knowledge of how to minimize risk from these

hazards. Students can begin to identify situations in their own lives in

which they make conscious decisions to limit their chemical exposure and

those over which they have little control.

In Advance

Web-Based Activities

Activity 1 has a Web-based component.

Photocopies and Transparencies

Materials

1 transparency of Master 5.1

• computer

1 copy of Master 5.2 for each

• overhead projector

student

• plain paper

• current event stories

students began collecting in

Lesson 1, Extension Activity

(optional)

98

Preparation

Activity 1

Arrange for students to have access to computers.

Make a transparency of Master 5.1, Risk Assessment and Management.

Duplicate Master 5.2, Minamata Disease, one for each student. To allow students to read only small amounts of the information at a time, fold along the dashed lines.

Activity 2

Gather the same materials used in Activity 1.

Extension Activity

Remind students to bring in the current event stories they began collecting in Lesson 1.

Be sure to have a transparency of Master 5.1, Risk Assessment

and Management.

ACTIVITY 1: People At Risk

Procedure

1. Remind students that there are chemicals in the environment that

cause health problems for humans. Tell students that toxicologists

study the extent and type of health problems associated with a

particular level of chemical exposure. Then, they use what they

learn to assess the threat of that chemical to the health of people in

particular situations. This kind of analysis is called a risk assessment.

Display the top half of a transparency of Master 5.1, Risk Assessment

and Management.

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Student Lesson 5

Chemicals, the Environment, and You

2. Distribute the folded sheets made from Master 5.2, Minamata Disease.

Tell students that they are going to practice the steps to making a

risk assessment by using a well-known case from Japan in the 1950s.

Instruct students to read Part I of Master 5.2. Then, discuss the

answers to the questions in Step 1 on the Master 5.1 transparency.

• Is a new health problem present?

Yes. Fish, cats, and birds were sick and dying. Also, people were

Minamata photographs by W. Eugene Smith

and Aileen M. Smith.

acting strangely.

• What are the symptoms?

People were stumbling, unable to write, fumbling with their buttons,

having difficulty balancing, falling from boats, suffering from

Content Standard F:

convulsions, and dying.

Students should develop

understanding of personal

• What do the affected individuals have in common?

health, natural hazards,

and risks and benefits.

Many work as fishermen or were in the families of fishermen.

Once students have answered the questions on the transparency, ask

them to offer ideas about what they think was contaminating the fish.

3. Instruct students to unfold the first fold, revealing Part II. Ask them to read the paragraphs and then answer the questions in Step 2 of

Master 5.1.

• What is causing the problem?

Pollution was contaminating the fish with mercury, and people were

getting sick when they ate the fish.

• What is the source of the problem?

The Chisso Corporation was dumping the mercury, so the company

was the source of the problem. It might be interesting to discuss the

role the community had in allowing the pollution of the bay to continue

by accepting compensation for poor fishing conditions. Could the

townspeople have demanded cleaner water instead of being satisfied

with a monetary solution to the problem of fewer fish for harvest?

Once students have answered the questions on the transparency, ask

them to suggest answers to the question at the end of Part II: What

made this contamination of the fish so dangerous to humans?

100

4. Instruct students to unfold the next fold, revealing Part III. Ask

students to read the paragraph and then answer the questions in

Step 3 of the risk assessment (Master 5.1).

•

What are the sources of exposure to the chemical?

Content Standard E:

Students should develop

People were exposed to mercury by eating contaminated fish. The

understandings about

contamination of the fish was serious because it was a primary food

science and technology.

source for the community.

Perfectly designed

solutions do not exist.

• How much exposure are people in the area receiving?

All technological solutions

have tradeoffs, such as

People in Minamata, especially fishermen and their families, ate fish

often. They were getting a small amount of mercury often over a period

safety, cost, efficiency,

of time. Any amount of contaminated fish over 30 pounds per year is

and appearance….

likely to provide a harmful exposure to mercury.

Technological solutions

have intended benefits

• Is the exposure acute or chronic? (Is it likely to happen only once

and unintended

or often over the course of time?)

consequences. Some

consequences can be

The exposure to mercury happened in Minamata over a long period of

predicted, others cannot.

time: It was a chronic chemical exposure.

5. Ask students not to unfold the last fold until directed to do so during the next activity. Discuss the information from the reading and

answer the concluding question on the risk assessment (Master 5.1):

How great is the risk to people?

Photo: Corel

Because of their dependence on fish as a primary source of food, the

potential risk of mercury poisoning from contaminated fish for people

living in Minamata was very high.

6. Play the video segment on the Web site that describes the Minamata story.

Go to the Web Portion of Student Activities page

and choose Lesson 5 ( http://science.education.nih.

gov/supplements/chemicals/student). Play the video

documentary for the students.

Because the time period and geographic location of the Minamata

tragedy are so far removed from students’ experiences, the visual

representation of the story on the Web site helps it come alive

for students.

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Student Lesson 5

Chemicals, the Environment, and You

ACTIVITY 2: What Is Your Risk?

1. Remind students that mercury is used today in thermometers and

batteries. (Although newer thermometers now use red alcohol, many

old ones contain mercury.) Tell students that although they do not live in Minamata in the 1950s, inappropriate disposal of items containing

mercury poses a threat to their environment, even today. Since

garbage is either incinerated or covered up in landfills, mercury can

make its way into the environment through emission of burning

gases into the air or groundwater contamination. Fish contaminated

with mercury can make their way into the food supply.

2. Ask students how they think they can avoid mercury poisoning from

contaminated fish.

Most students will say that they could stop eating fish, thereby

eliminating their risk just by avoiding exposure to the mercury-

contaminated fish. Some students may indicate that the risk of

mercury poisoning provides a great excuse to avoid a less-than-

favorite food: fish.

Ask students if it is possible always to avoid a chemical in order to

eliminate possible exposure. What about a chemical in the air?

Photo: Corel

Could students choose not to breathe in order to avoid exposure to

an air pollutant?

This question brings up the issue of control. If your food supply is

varied enough, you can choose not to eat fish and still remain healthy.

(This might not be an option for an island population that depends on

fish for protein.) You cannot, however, choose not to breathe as a way

to avoid exposure to an air pollutant. You would need to find other

ways to limit your exposure to the air pollutant, like staying inside, not exercising outside, or wearing a mask that filters the air.

3. Tell students that one of the reasons for understanding the role of toxicology in human health is to empower the students to make

choices that decrease their risk of becoming ill due to exposure

to harmful chemicals. Once they know the risk from a chemical

exposure, they can manage their risk by deciding how to deal with

the risk. Walk the students through the steps of Risk Management

on the bottom half of the transparency of Master 5.1. Contrast the

situation in Minamata, Japan, in the 1950s with the life of a today’s

typical U.S. middle school student.

First, ask the students to think about risk assessment:

• What is a person’s risk of mercury poisoning?

Because of their dependence on fish as a primary source of food, the

potential risk for a person living in Minamata in the 1950s was high.

For today’s middle school students, the risk is relatively low. The

102

average middle school student does not consume enough fish to pose

a problem, and most of the fish is commercially caught in regulated

waters. Only a middle school student who lived near contaminated

water and regularly ate the fish from the contaminated water would

be at a higher risk.

Then, continue answering the questions in the Risk Management

section of Master 5.1:

• How do the people involved perceive the risk? Are their perceptions

accurate?

Possible answers: At first, Minamata residents did not know of the

risk or worry about it. Once they began to see the effects of mercury

poisoning, the Minamata residents perceived the risk as very serious.

Their perceptions were accurate: Their primary food source was

contaminated by industrial pollution, and that pollution was having

a direct effect on the health of the community.

Middle school students should perceive their risk as minimal. If a

student perceives his or her risk as high, that perception would not

be accurate according to the risk assessment above.

• Who is responsible for the harmful substance and its presence

in the environment? What role does the responsible party have

in any cleanup?

Allow time for students to discuss who they think was responsible

for the situation in Minamata and what they think the responsible

party should have done. Then, instruct them to unfold the last fold

on Master 5.2 and read Part IV.

The Chisso Corporation was responsible for discharging polluted

effluent into the bay. The corporation ultimately was held liable for

its negligence in the 1970s. More complicated, however, are the social

and economic pressures that influenced the placement of the plant in

Minamata: People in the fishing village were interested in progress

and enjoyed the prosperity that the industry brought to the town.

Middle school students could be indirectly responsible for some of

the mercury contamination in their local area because of the way

they dispose of batteries. Students and family members can take

responsibility for disposing of potentially harmful materials in a

safe way and using safer alternatives, such as rechargeable batteries.

• What are the benefits and trade-offs that a person must weigh

when making a decision about the risk?

Fish provide many health benefits to the cardiovascular system and

to brain development. The dietary proteins that fish provided to the

residents of Minamata were very important to good health. However,

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Student Lesson 5

Chemicals, the Environment, and You

Photos courtesy of the City of Minamata, Japan.

we now know that mercury poisoning from eating contaminated fish

results in serious brain damage. The U.S. Environmental Protection

Agency has advised that there are health benefits to eating fish and that

consumption of fish should continue, but at a rate not to exceed

30 pounds per year. Because middle school students rarely reach an

annual level of consumption of 30 pounds of fish, they can enjoy all

the health benefits of eating fish without being concerned about any

negative trade-offs.

• What action should people take to minimize their risk? Can the risk

be managed by individuals, the community, and/or governments?

In Minamata, industrial manufacture of acetaldehyde needed to stop.

The corporation still operates in Minamata but produces liquid crystals,

preservatives, fertilizers, and other chemicals. Over several years,

1.5 million cubic meters of contaminated sludge was dredged from the

bay. Over the main dumping site there now are museums, memorial

sites, parks, and a study center. In 1997, the water in the bay was

declared safe again for fishing and swimming. People have chosen to

move away from Minamata to make their living elsewhere: The town

has only 70 percent of the number of people it once had.

Middle school students can eat fish sensibly, dispose of mercury-

containing products safely, and support organizations that provide

hazardous waste cleanup in their communities. Regulatory agencies

can measure mercury contamination in fish and regulate fishing

or sales of fish from contaminated waters.

104

Review a local or current situation in which people are being exposed to a Extension

hazardous chemical. Use the Master 5.1, Risk Assessment and Management, Activity

transparency to discuss students’ ideas about the level of risk for the community and ways to manage that risk.

Tip from the field test: This is a good time to go back to the current event articles the students have been collecting since Lesson 1. Choose one or

two of the most interesting situations and assess risk for the population and decide how to manage the risk.

Before discussing the

current event with

Because a current situation most likely will be unresolved, you will need to the class, ask students

lead an open-ended discussion and help students recognize that there might not be answers for some of their questions at this time. This process of

to do a risk assessment

asking questions and not knowing the “right” answers is representative of

individually. Collect

the nature of science and scientific inquiry.

students’ written

summaries and evaluate

them for understanding

of the process of

assessing risk. Then

discuss the students’

ideas for managing

the risk.

Content Standard G:

Students should develop

understanding of the

nature of science and

the history of science.

105

Student Lesson 5

L E S S O N 6

Evaluate

Environmental

Hazards

Overview

At a Glance

Students use the knowledge they have gained from previous lessons to

solve a problem depicted in a fictional scenario. In the scenario, students participate in a field trip to a natural history museum. Upon returning to the school, many participants complain of headache and nausea. Students

consider the potential chemical exposures experienced by the field-trip

participants and analyze who was exposed, how they were exposed, and

how much exposure they experienced. Using fact sheets to learn about

the specific hazards and health reactions attributable to certain chemicals, students solve the problem and recommend ways that the participants

could have minimized or eliminated their exposure.

Major Concepts

People can use their understanding of the science of toxicology to

identify potential sources of harm to human health from chemicals in

the environment. They can use their knowledge to propose possible

means to eliminate or reduce exposure to environmental toxic agents.

Objectives

After completing this lesson, students will

• be able to identify potential sources of harm to human health from

chemicals in the environment;

• be able to apply their knowledge about dose, response, route of

exposure, and individual susceptibility to situations involving

potentially hazardous chemical exposures; and

• propose possible means to eliminate or reduce exposure to

environmental toxic agents.

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Chemicals, the Environment, and You

Background

Protecting Human Health

Information

Decisions about chemical exposures occur at different levels. For example, a person can choose whether he or she wants to consume caffeine. In other

cases, an individual is not able to control a chemical exposure simply by

making a personal decision. For example, while a person might choose not

to smoke in order to avoid exposure to the chemicals in tobacco smoke, he

or she sometimes is unable to avoid secondhand smoke.

Sometimes there are larger social, economic, and political forces involved in hazardous exposure at a community level. As a result, organizations and agencies, including different levels of government, often become involved

in prevention of chemical exposure and intervention when people suspect

chemical exposure. For example, regulations made at a community level

can minimize the exposure of members of the community to secondhand

smoke in public places.

On a national level, many organizations are concerned with protecting

and improving human health. The Department of Health and Human

Services is the U.S. government’s principal agency for protecting the health of all Americans. Within the Department of Health and Human Services

operate many different divisions. The National Institutes of Health (NIH) is the world’s premier medical research organization. Among its many

institutes and centers is the National Institute of Environmental Health Sciences (NIEHS), whose mission is to reduce the burden of human

illness and dysfunction from environmental causes by understanding

how environmental factors, individual susceptibility, and age interrelate.

The NIEHS achieves its mission through multidisciplinary biomedical

research programs, prevention and intervention efforts, and communication

strategies that encompass training, education, technology transfer, and

community outreach.

The mission of the Agency for Toxic Substances and Disease Registry

(ATSDR) is to prevent adverse effects on human health and diminished

quality of life associated with exposure to hazardous substances from

waste sites, unplanned releases, and other sources of pollution present

in the environment. The ATSDR is directed by congressional mandate

to perform specific functions concerning the effect on public health of

hazardous substances in the environment. These functions include public

health assessments of waste sites, health consultation concerning specific hazardous substances, health surveillance and registries, response to

emergency releases of hazardous substances, applied research in support

of public health assessments, information development and dissemination,

and education and training concerning hazardous substances.

The Food and Drug Administration (FDA) ensures that the food we eat is safe and wholesome, the cosmetics we use don’t hurt us, the medicines

and medical devices we use are safe and effective, and radiation-emitting

products such as microwave ovens won’t harm us. Feed and drugs for pets

108

and farm animals also come under FDA scrutiny. The FDA also sees that

all of these products are labeled truthfully with the information that people need to use them properly. First and foremost, the FDA is a public health

agency, charged with protecting American consumers by enforcing the

Federal Food, Drug, and Cosmetic Act and several related public health

laws. Investigators and inspectors visit more than 15,000 facilities a year, checking that products are made correctly and labeled truthfully. On

average, 3,000 products a year are determined to be unfit for consumers

and are withdrawn from the marketplace. In addition, about 30,000 import

shipments a year are detained at the port of entry because the goods appear to be unsafe.

In addition to divisions of the Department of Health and Human Services,

there are other government agencies for the communal protection of health.

The mission of the U.S. Environmental Protection Agency (EPA) is to protect human health and to safeguard the natural environment—air, water,

and land—upon which life depends. The EPA’s purpose is to ensure that

• all Americans are protected from significant risks to human health and

the environment where they live, learn, and work;

• national efforts to reduce environmental risk are based on the best

available scientific information;

• federal laws protecting human health and the environment are enforced

fairly and effectively;

• environmental protection is an integral consideration in U.S. policies

concerning natural resources, human health, economic growth, energy,

transportation, agriculture, industry, and international trade, and these

factors are similarly considered in establishing environmental policy;

• all parts of society (communities, individuals, business, state and local governments, tribal governments) have access to accurate information

sufficient to participate effectively in managing human health and

environmental risks;

• environmental protection contributes to making our communities and

ecosystems diverse, sustainable, and economically productive; and

• the United States plays a leadership role in working with other nations to protect the global environment.

Part of the U.S. Department of Labor is the Occupational Safety and Health Administration (OSHA). The mission of OSHA is to save lives, prevent injuries, and protect the health of America’s workers. To accomplish this, federal and state governments work in partnership with the more than

100 million working men and women and their employers to comply with

the Occupational Safety and Health Act of 1970. OSHA currently regulates

exposure to approximately 400 substances present in the workplace that

are capable of causing harm. Together with the National Institute for

Occupational Safety and Health (NIOSH), which is part of the Centers for Disease Control and Prevention (CDC), OSHA provides guidelines

about chemicals, including chemical and physical properties, health

effects, exposure limits, and recommendations for medical monitoring.

These guidelines summarize pertinent information about chemicals for

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Student Lesson 6

Chemicals, the Environment, and You

workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such

information to conduct effective occupational safety and health programs.

The U.S. Department of Agriculture (USDA) has agricultural toxicology regulatory authority, and the Food and Nutrition Service (FNS) participates with the CDC on food safety issues.

Notes about Lesson 6

In Lesson 6, students analyze a fictional situation in which members

of a class are exposed to a chemical that makes them sick. While they

investigate several scenarios in which individual behavior increased the

risk of chemical exposure, students recognize that the actual cause of the sickness in the scenario is carbon monoxide poisoning caused by a faulty

exhaust system in a school bus. Because the maintenance of the bus is a

school district responsibility, and not an individual one, the exposure of students to carbon monoxide is not one over which the exposed students

had control. Students see that there are various regulations, agencies, and organizations in place to protect them as citizens from chemical exposure

over which they have little control. It is important, however, for students to recognize that they have the right, as citizens of their school, community, nation, and the world, to seek direct input into how to reduce the extent

of chemical exposure on a communal level.

As the Evaluate lesson for the curriculum supplement, Lesson 6 offers

students the opportunity to express their understanding of the concepts in the supplement in a new context. As students share and compare their ideas with those of others, they can refine and revise them. As you listen to them reasoning out loud, you can assess their individual understanding of human health and the environment.

This lesson is not the only opportunity you have had to assess your

students’ progress. As noted in each of the previous lessons, assessments

have gone hand in hand with instruction throughout the supplement.

Whenever individual students expressed themselves by talking, writing,

or performing tasks, you have had an opportunity to assess their thinking

and thus their learning. The assessment tasks are embedded within the

lessons and offer you the opportunity to

• determine students’ initial understanding of concepts to be learned,

• determine students’ initial familiarity with processes and their ability to use them,

• monitor students’ conceptual development and ability to use certain

processes and skills, and

• collect information about students’ achievement of the outcomes of each lesson and of the supplement as a whole.

(continued)

110

The approach to assessment in this supplement is congruent with the

following recommendations in the National Science Education Standards

( National Research Council, 1996).

• Assessment tasks are deliberately designed.

• Assessment tasks have explicitly stated purposes.

• Assessment data focus on the science content that is most important for students to learn.

• Assessment tasks are valid and authentic.

• Students have adequate opportunities to demonstrate their achievements.

• Assessment tasks are set in a variety of contexts.

• Assessment tasks include opportunities for students’ self-assessment

and reflection.

Web-Based Activities

In Advance

Activity 1 has a Web-based component.

Photocopies and Transparencies

Materials

1 copy of Master 6.1 for each student • computers

(print version only)

• 1 red marker

1 Choice Card from Master 6.2 for

(print version only)

each student (print version only)

• 1 coin for each student

5 copies (at least) of Master 6.3

(print version only)

(print version only)

PREPARATION

Activity 1

Decide whether you will use the Web or print version of this activity. If you choose to use the Web version, which is preferred, arrange for students to have access to computers.

If you use the print version, gather the materials needed to conduct the

activity. Duplicate Master 6.1, Heads or Tails? , 1 for each student. Copy Master 6.2, Choice Cards, and cut apart the cards, making enough for each student to have one card. Make at least five sets of the six fact sheets in Master 6.3, Fact Sheets on Chemicals. Fold each fact sheet in half. Label the outside of each sheet with the location from the scenario. Place the sets of fact sheets on a desk in the front of the room.

Activity 2

If you used the print version of Activity 1, students need their completed copy of Master 6.1, Heads or Tails?

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Student Lesson 6

Chemicals, the Environment, and You

Procedure

ACTIVITY 1: The Field Trip

Web Version

The following procedures describe how to conduct the Web version of this activity. Instructions for the print version follow after Step 4-w.

1-w. Gather students in the computer lab and direct them to work with a partner for this Web-based activity.

Have students go to the Web Portion of Student Activities

Content Standard A:

page and choose Lesson 6 ( http://science.education.nih.gov/

Students should develop

supplements/chemicals/student). Then, have them click on

abilities necessary to do

The Field Trip and watch the video.

scientific inquiry.

2-w. Instruct students to work through the problem posed in the video

using the available resources, records, and data.

3-w. Once all teams have reached a conclusion about the cause of the

illness on the field trip, conduct a class discussion during which

teams present their conclusions and their supporting evidence.

Circulate around the room,

listening to students

Because most students should reach the same conclusion (that a

as they solve the problem

faulty exhaust system in the old yellow bus created carbon monoxide

presented on the Web site.

in high enough concentrations to poison some of the students),

Listen to see if students are

encourage teams to share one piece of evidence they used to come to

using the language of

their conclusion. Then, let other teams add to the picture of carbon

toxicology: chemical, dose,

monoxide poisoning, or share evidence for why another chemical

exposure probably did not contribute to the illness of the students. In

response, individual

this way, all students have an opportunity to share new ideas.

susceptibility, and route of

exposure.

4-w. To complete the discussion of the field trip, go to Activity 2.

Print Version

If you do not have access to the Web site, use the following print version of Activity 1.

1-p. Tell students that today they are going to participate in a recreation of a field trip to a natural history museum. To let them know what

the field trip was like, read to them the journal entry from one of the participants on the field trip (see page 113).

Content Standard A:

2-p. Distribute to each student one copy of Master 6.1, Heads or Tails?

Students should develop

Tell students that they are going to determine their actions on the

abilities necessary to do

field trip based on a coin toss. For each action, if they get heads,

scientific inquiry.

they will check the box for the action on the left-hand side of the

page. If they get tails, they will check the box for the action on the

right-hand side of the page.

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113

Student Lesson 6

Chemicals, the Environment, and You

3-p. Next, distribute one Choice Card (from Master 6.2) to each student.

Tell students that they can use the Choice Card to overrule one of

their coin flips if they would rather choose the opposite action.

4-p. Give each student one coin. Proceed as a class through the Heads

or Tails? worksheet, one action at a time. Ask students to record the results of their coin toss by checking the appropriate box on the

sheet. Remind students that they can use their Choice Card for one

turn to choose the opposite action.

5-p. After all the students have completed the worksheet, announce that some of the members of the class got sick after the field trip and

ended up going to the emergency room with their parents because

they had severe headaches and nausea. Circulate around the room

looking at all the students’ sheets. With a red marker, write the

words “Sick” or “Not Sick” on the top of each sheet.

Mark “Sick” on the worksheets if the student marked “you sat in

the back of the yellow bus” (got heads in the coin toss for the last

action). If the student marked “you sat in the front of the yellow bus”

(got tails for the last action), then the student is not sick. Do not let

the students know that you are looking only at the last action: Make

it look like you are studying all the actions for the trip to decide if

the student is sick.

Tip from the field test: To make the discussion more interesting and the problem harder and less obvious to solve, mark one or two students sick

who did not sit at the back of the yellow bus. These students represent individuals who have higher susceptibility to carbon monoxide even though

they did not sit in the back of the bus nearest to the faulty exhaust system.

More-susceptible individuals would be affected by a lower concentration of carbon monoxide.

6-p. Discuss the problem of some students getting sick by asking

these questions:

• Why do you think some of the students got sick?

114

Answers will vary, but try to get students to recognize that some

students might have been exposed to chemicals during the field trip.

• To what chemicals could students have been exposed during each

of the parts of the field trip?

Conduct a brainstorming session with students of possible

chemical exposures:

• Ride in new van: “new car smell” from new carpet and seat

fabrics, exhaust fumes

• Gas station: gasoline fumes

• Paleontology lab: fiber glass dust, plywood fumes

• Lunch: caffeine in soda, food poisoning from sack lunches

• Painting activity: paint on the skin, cleanup solvents

• Bus ride in the old bus: gasoline fumes, exhaust fumes

• Why didn’t all of the students get sick?

Answers will vary. Some students might not have been exposed to

chemicals because their actions were different. Some might not be

susceptible to the chemicals that made other students sick.

• How would you figure out what made some students sick while

others remained healthy?

Answers will vary. Accept possible strategies before moving to

Step 7-p. Students might suggest comparing sick students’ actions

to the actions of students who did not get sick. Propose this strategy

if students do not mention it.

7-p. Ask each student who is sick to pair up with a student who

is not sick.

Statistically, you should end up with nearly an equal amount of sick

and healthy students. If the numbers are not even, make a few groups

of three students.

Tell students that you want them to figure out what made one

student sick in each pair. Ask students to work with their partners

to determine what actions and chemicals could have caused the

sickness in their pair.

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Student Lesson 6

Chemicals, the Environment, and You

Students will realize that they can compare the actions each took on

the field trip. If there are actions that the sick student did that the other student did not do, students might hypothesize that those actions put

the sick student more at risk of exposure to certain chemicals.

8-p. Ask the students what information they need to solve the problem of what caused the sickness in some students.

Help students realize that they need more information about the

kinds of chemicals to which students were exposed and the symptoms

caused by each.

Show students the sets of fact sheets (Master 6.3) at the front of the

room. Tell the students that each fact sheet contains information

about chemicals to which some students were exposed at specific

locations during the field trip. Instruct students to go to the front of the room and select one fact sheet the pair would like to study based

on their determination from Step 7-p of what actions and chemical

exposures might have caused the sickness. They can return that fact

sheet and select another if time allows.

Direct students to read the information on the fact sheet, discuss it

with their partner, and decide whether the chemical in the location

could have caused the sickness.

Students should consider the chemical, the route of exposure, the

dose, and the symptoms that a person exposed to the chemical

exhibits. When they read the fact sheet, they may determine that

the chemicals to which they were exposed in a certain location

could not have caused the illness because there was not enough

chemical there, the dose they might have received was too little, or

the symptoms of the sick people do not match those produced by

exposure to the chemicals.

Students will probably have more than one possible location of

chemical exposure to check. They will need to study all the possible

locations and chemicals to determine which one might have caused

the sickness. It is possible that they may not be able to decide between

two possibilities until the class meets together and compares notes.

9-p. Once students have come to some conclusions about the possible

cause of sickness, discuss their solutions with the whole class.

There are two ways to figure out why some students became sick.

The first is by the process of elimination. Help students narrow the

possible chemicals that caused illness by determining how many

of the sick stu dents were exposed to chemicals at each location.

Compare the total number of sick students with those sick students

who were involved in actions at the various locations. For example,

if the total number of sick students was 15, but only 6 sick students

drank caffeine, what conclusions can students draw?

116

From the discussion, students can see that all the students who sat

at the back of the yellow bus became sick, while students who took

part in each of the other actions were not universally sick. Ask the

sick students how many were not sitting at the back of the yellow bus.

Only those few students you purposely marked sick (if you chose

To assess your students’

to) should reply. Explain their illness in the context of individual

understanding of

susceptibility to chemical exposure.

individual susceptibility,

ask them to explain what

The second way to figure out what made the students sick is to study

could have happened to

the fact sheets. In all cases except carbon monoxide, the exposure the

those few students who

students received to the chemicals in each location is insignificant.

did not sit at the back

Students can see that, even though there might be chemicals present

of the bus but were

in various locations or associated with various activities, their health

is not at risk when they are exposed at the levels that were present on

sick anyway.

the field trip. Being able to recognize that an exposure to a chemical is

not at a level that causes harm is an important part of the risk-

assessment process.

Students will make the correlation between sitting in the back of the

yellow bus and carbon monoxide poisoning by referring to the fact

sheets. They will reach the conclusion that the sick students were

suffering from carbon monoxide poisoning, which was caused by a

faulty exhaust system in the old yellow bus. Those in the back of the

bus were exposed to more carbon monoxide than those in the front

of the bus. Those who got sick who were sitting in places other than

the back of the bus must be more sensitive to carbon monoxide

than average.

10-p. To complete the discussion of the field trip, go to Activity 2.

ACTIVITY 2: What Can I Do?

1. Ask students whether some of the students on the field trip made

choices that either limited or increased their exposure to chemicals on the museum field trip. Discuss how the choices the students on

Content Standard F:

the field trip made are similar to decisions that they make in their

Students should develop

own lives.

understanding of personal

health, natural hazards,

Students who did the Web version of the activity can refer to the

and risks and benefits.

records online to find out how exposure to the chemicals present at the

field trip locations can be avoided.

If students did the print version of Activity 1, ask them how their use of the Choice Cards simulated decisions they make in their own lives

that influence their exposure to chemicals.

Informed citizens can make decisions to limit or eliminate their exposure

to environmental hazards. They can alter their lifestyles, their work, their use of materials that are made of hazardous chemicals, and so on.

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Student Lesson 6

Chemicals, the Environment, and You

2. Discuss with students that the cause of the sickness in some of the field-trip students was related to a situation over which the students

had no control. Ask students what they think they would be able to do

about the faulty exhaust system in the bus. Go one step further and

ask students what they think they can do about chemical exposure on

a community level.

Some choices are not left to the individual because the decisions are

made at a community or national level. For example, people could be

at risk of exposure to radiation when they live near a nuclear power

plant even if they do not support the decision to use nuclear energy to

produce power. In the scenario in this activity, students did not know

that the yellow bus had a faulty exhaust system, so they were unable

to decide to limit their exposure to carbon monoxide. In response

to the situation with the bus, students could write letters to their

superintendent, petition the school for stricter safety standards, or raise money to support a better maintenance program. Share with students

information about the various organizations and agencies whose

mission it is to protect human health (see Background Information).

Encourage students to investigate the organizations by logging onto the

following Web sites:

• U.S. Department of Health and Human Services

http://www.hhs.gov

• National Institutes of Health

http://www.nih.gov

• National Institute of Environmental Health Sciences

http://www.niehs.nih.gov

• Agency for Toxic Substances and Disease Registry

http://www.atsdr.cdc.gov

• U.S. Food and Drug Administration

http://www.fda.gov

• U.S. Environmental Protection Agency

http://www.epa.gov

• U.S. Occupational Safety and Health Administration

http://www.osha.gov

• National Institute for Occupational Safety and Health

http://www.cdc.gov/niosh

• Centers for Disease Control and Prevention

http://www.cdc.gov

• U.S. Department of Agriculture and Food and Nutrition Service

http://www.usda.gov

118

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Farrar, Straus and Giroux.

Supplement Series. Colorado Springs: BSCS.

Available from http://science.education.nih.gov/

Public Health Institute/Children’s Environmental

supplements/nih1/cancer.

Health Network. 1997. Resource Guide on

Children’s Environmental Health. .

Marczewski, A.E., and Kamrin, M. Toxicology

for the Citizen. East Lansing, MI: Michigan

Sipes, I.G., McQueen, C.A., and Gandolfi, A.J.

State University, Institute for Environmental

1997. Comprehensive Toxicology, Vol. 1. New

Toxicology. Retrieved May 2012 from http://

York: Elsevier Science Ltd.

web.archive.org/web/20041221161515/http://

Sullivan, T.F.P. 1993. Environmental Regulatory

www.iet.msu.edu/Tox_for_Public/citizen.htm.

Glossary (6th ed.). Rockville, MD:

McQueen, Charleen. 1999. Personal

Government Institutes, Inc.

communication.

121

References

Additional Resources

for Teachers

The following resources may provide additional

health information to teach students about the

background information for you and your

interconnection between their health and the

students about chemicals in the environment

world around them.

and human health.

International Food Information Council

Agency for Toxic Substances

http://www.foodinsight.org

and Disease Registry

Read the article titled “Caffeine and health:

http://www.atsdr.cdc.gov

Clarifying the controversies.” The site includes

This site includes ToxFAQs™, summaries about

information for educators on food and food risks.

hazardous substances with easy-to-understand

information about exposure to hazardous

National Environmental Education

substances and effects on human health

Foundation

( http//:www.atsdr.cdc.gov/toxfaq.html). The site

http://www.neefusa.org

also includes a kids’ page ( http://www.cdc.gov/

NEEF provides credible resources to solve

family/kidsites/index.htm) with facts about toxic

everyday environmental problems.

chemicals and the environment.

National Institute of Environmental

Centers for Disease Control

Health Sciences

and Prevention

http://www.niehs.nih.gov

http://www.cdc.gov/

This site provides current and authoritative

Offers information on a range of topics including

information about the work of the National

diseases and conditions ( http://www.cdc.gov/

Institute of Environmental Health Sciences and

DiseasesConditions/) like ADHD, autism, cancer,

about the institute’s latest research projects. The

HIV/AIDS; environmental health ( http://www.

site includes links to NIEHS curricula, resources

cdc.gov/Environmental/) issues like air quality,

for science teachers, and fact sheets about

asthma, climate change, natural disasters; life

environmental health topics ( http://www.niehs.gov/

stages and populations ( http://www.cdc.gov/

health/scied/index.cfm).

LifeStages/) covering pregnancy, children, women,

older adults; healthy living ( http://www.cdc.gov/

National Toxicology Program

HealthyLiving/) covering topics like aging, mental

http://ntp-server.niehs.nih.gov

health, genetics and genomics, and obesity.

Headquartered at the National Institute of

Environmental Health Sciences, the National

Environmental Health Perspectives

Toxicology Program coordinates toxicology

http://www.ehponline.org

research and testing activities within the

A monthly journal of peer-reviewed research

Department of Health and Human Services. This

and news published by the NIEHS. The

site includes factsheets on chemicals, reports

EHP Science Education Program promotes

on carcinogens, and links to other sites, such as

environmental health science as an integrative

the Interagency Coordinating Committee on the

context for learning to promote students’ use

Validation of Alternative Methods (ICCVAM)

and understanding of scientific literature. We do

regarding toxicology testing ( http://iccvam.niehs.

this by using current, credible environmental

nih.gov/).

123

Chemicals, the Environment, and You

Resource Guide on Children’s

Other Helpful Sites

Environmental Health

AAAS Educational Resources on ScienceNetLinks

http://www.cehn.org/cehn/resources/resource_guide

• Toxicology: http://www.sciencenetlinks.com/

This site, provided by the Children’s

lessons.php?DocID=429

Environmental Health Network, includes a

• Endocrine Disruptors: http://www.

keyword index so students can search specific

sciencenetlinks.com/lessons.php?DocID=407

toxicants ( http://www.cehn.org/resources/resource_

guide_keyword_index).

A Small Dose of Toxicology

• Learn about the effects of common chemicals:

Society of Toxicology (SOT)

http://www.asmalldoseof.org/toxicology/index.php

http://www.toxicology.org

A professional and scholarly organization of

Baylor College of Medicine Teacher Resources

scientists who practice toxicology in the U.S. and

• BioEd Online: http://www.bioedonline.org/

abroad. SOT provides teachers with extensive

• K8 Science: http://www.k8science.org/

resources to teach toxicology-related topics in

the classroom and to familiarize students with

Canadian Network of Toxicology Centers

the study of toxicology ( http://www.toxicology.org/

• Toxicology: http://www.uoguelph.ca/cntc/educat/

teachers/curriculum.asp).

guide/guide_index.shtml

Toxlearn

EPA Teaching Center

http://toxlearn.nlm.nih.gov/

• Teaching Resources: http://www.epa.gov/teachers/

A joint project of NLM and SOT is another

teachresources.htm

extensive selection of databases and other

toxicology related information resources.

LessonPlanet

• Toxicology: http://www.lessonplanet.com/search?

U.S. Environmental Protection Agency

media=lesson&keywords=toxicology&grade=All+

http://www.epa.gov/kids

Grades&rating=3

This site has teacher and student resources

for learning about the environment and the

Maryland Public Television: Thinkport

connection between the environment and human

• EnviroHealth Connections: http://www.

health.

thinkport.org/classroom/connections/default.tp

U.S. National Library of Medicine (NLM)

Minimata Disease Resources

http://www.nlm.nih.gov

• Minimata Disease History: http://www.env.go.jp/

The U.S. National Library of Medicine is the

en/chemi/hs/minamata2002/index.html

world’s largest medical library. This site includes

• National Institute for Minimata Disease:

the Toxicology and Environmental Health

http://www.nimd.go.jp/english/index.html

Information Program, which provides information

on toxicology, hazardous chemicals, and

NIEHS Science Mentor Idea

toxicological effects of drugs, among other topics

• For toxicologists: http://www.toxexpo.com/AI/FA/

( http://sis.nlm.nih.gov/enviro.html). For a listing of

Tipsheet1Toxic_eMay%202303.pdf

educational resources, go to http://sis.nlm.nih.gov/

• Oregon State University Environmental Health

enviro/edcotox.html#a4. ToxTown for Teachers is at

Sciences Center Educational Resources:

http://toxtown.nlm.nih.gov/text_version/teachers.php,

http://www.ehsc.orst.edu/teachers

and ToxMap Resources for Teachers are at http://

• Podcasts: http://ehsc.science.oregonstate.edu/

toxmap.nlm.nih.gov/toxmap/home/forTeachers.jsp.

podcasts

124

Southwest Environmental Health Sciences Center

PTCL Safety Glossary – Structure Activity

COEP

Relationship. 2008. Oxford, England: Physical

• Basic Toxicology Lab Stations: http://coep.

and Theoretical Chemistry Laboratory, Oxford

pharmacy.arizona.edu/curriculum/basictoxlab/

University. Retrieved February 17, 2010, at http://

index.html

msds.chem.ox.ac.uk/glossary/structure_activity_

• Chemicals and Human Health: http://coep.

relationship.html.

pharmacy.arizona.edu/curriculum/chh/index.html

Toxic Chemicals. San Marcos, Texas: Texas State

WGBH Boston Public Television

University. Retrieved February 17, 2010, at http://

• PBS Teachers Domain: http://www.

www.fss.txstate.edu/ehsrm/safetymanual/chemical/

teachersdomain.org/

toxchems.html.

• Environmental Public Health Collection:

http://www.teachersdomain.org/special/enh/

Chemical Hygiene Plan: 5.0 Toxic Chemicals.

Radford, VA: Radford University. Retrieved

February 17, 2010, at http://www.radford.edu/fpc/

Safety/ChemHyg/chp5.htm.

125

Additional Resources for Teachers

Glossary

Definitions for the following terms were gathered

carbon monoxide: A colorless, odorless poison

from a variety of sources, which are listed in the

gas produced by incomplete combustion of

Reference section.

organic matter. Carbon monoxide may be

produced in lethal quantities in automobile

absorption: The process of taking in, as when

exhaust, faulty home heating systems, improperly

a sponge takes up water. Chemicals can be

used portable gas stoves and heaters, improperly

absorbed through the skin into the blood stream

vented wood stoves and fireplaces, and in many

and then transported to other organs. Chemicals

industrial situations.

also can be absorbed into the blood after they are

breathed in or swallowed.

carcinogenic: Any substance that may produce

cancer.

acetaminophen: A synthetic chemical used as an

analgesic and as an antipyretic.

chemical: Any substance having a defined

molecular composition.

acute exposure: A single exposure to a toxic

substance that results in a severe response or

chronic exposure: Exposure to toxic chemicals

death. Acute exposures are characterized as

occurring over a long period of time (months to

lasting no longer than a day, as compared to

over one year).

longer, continuing chronic exposure over a

period of time.

collagen matrix barrier: An artificial “skin” used

to test whether a chemical is likely to irritate,

Ames test: Mutagenic assay (a measure of

corrode, or burn human skin.

mutagenic ability) that involves specially

engineered strains of bacteria. Because of

concentration: The amount of one substance

the relationship between mutagenicity and

dissolved or contained in a given amount of

carcinogenicity, the test is used as a rapid and

another. For example, sea water contains a higher

relatively inexpensive first screening of untested

concentration of salt than an equal amount of

chemicals that are suspected of being carcinogens.

fresh water does.

benzene: A clear, colorless liquid with a sweet

dimethylmercury: The same as methylmercury,

odor that burns readily. Benzene is obtained

but containing two methyl radicals, (CH ) .

3 2

from crude petroleum. Small amounts may

be found in products such as paints, glues,

dosage: The amount of a toxicant, drug, or

pesticides, and gasoline.

other chemical administered to, or taken by, an

organism and expressed as some function of the

caffeine: A bitter crystalline alkaloid found in

organism and of time (mg/kg body weight/day).

coffee, tea, kola nuts, and cacao pods; it is a heart

and central nervous system stimulant.

dose: The total amount of a toxicant, drug, or

other chemical that is administered to, or taken

by, an organism.

127

Chemicals, the Environment, and You

dose response: How an organism’s response to a

hazardous waste: Byproducts of society that can

toxic substance quantitatively shifts as its overall

pose a substantial or potential hazard to human

exposure to the substance increases (e.g., a small

health or the environment when improperly

dose of carbon monoxide may cause drowsiness; a

managed. Possesses at least one of four

large dose can be fatal).

characteristics (ignitability, corrosivity, reactivity,

or toxicity), or appears on special EPA lists.

EC : Effective concentration; the dosage at which

50

the desired response is present for 50 percent of

heart rate: The number of pulses of the heart in

the population.

one minute.

element: A form of matter that cannot be broken

herbicide: Chemicals developed to kill plants or

down into simpler substances. Elements exist in

regulate plant growth.

nature as solids, liquids, or gases.

individual susceptibility: Differences in

environment: The interdependent system of

reactions between people after exposure to the

living and nonliving things.

same amount of a hazardous substance. A person’s

body size, age, gender, genetics, and health status

experimental control: A group of experimental

can affect individual susceptibility.

subjects that is not exposed to a chemical or

treatment being investigated so that it can be

ingestion: Swallowing (such as eating or

compared with experimental groups that are

drinking). One route of exposure to chemicals.

exposed to the chemical or treatment.

After ingestion, chemicals can be absorbed into

the blood and distributed throughout the body.

exposure: Contact with a chemical by

swallowing, breathing, or touching (such as with

inhalation: Breathing. One route of exposure

the skin or eyes). Exposure may be short term

to chemicals. During inhalation, chemicals can

(acute) or long term (chronic).

be deposited in the lungs, taken into the blood,

or both.

fiber glass: Fine-spun filaments of glass. Fiber

glass is often made into yarn that is woven into

insecticide: A chemical specifically used to kill or

textiles, used in woolly masses as insulation, or

prevent the growth of insects.

pressed and molded as plastic material.

irritant: A substance that can cause irritation of

formaldehyde: A colorless, pungent gas used

the skin, eyes, or respiratory system.

in solution as a strong disinfectant and

preservative, and in the manufacture of synthetic

kilogram: A basic unit of mass; abbreviated kg.

resins and dyes.

LD : The dosage of chemicals needed to produce

50

genetic: Inherited; having to do with information

death in 50 percent of treated organisms.

that is passed from parents to children through

LD s are usually expressed as the weight of

50

DNA in the genes.

the chemical per unit of body weight (mg/kg).

Chemicals may be fed (oral LD ), applied to the

50

germinate: To sprout from a seed.

skin (der mal LD ), or administered in the form of

50

vapors (inhalation LD ).

50

hazard: A source of risk. A hazard produces

risk only if organisms are exposed to it and if

lead: A heavy metal that is hazardous to human

exposure creates the possibility of harm.

health if it is breathed or swallowed.

128

meniscus: Curved surface of a liquid in a

nervous system: Includes the brain and all

graduated cylinder.

the nerves.

mercury: A heavy metal that can accumulate in

neurotoxin: Any substance that is capable of

tissue of organisms in the environment and is

destroying or adversely affecting nerve tissue.

highly toxic if breathed or swallowed.

National Institute of Environmental Health

metabolism: All the chemical reactions that

Sciences (NIEHS): One of the National Institutes

enable the body to function. For example, food is

of Health (NIH) research institutes. The mission

metabolized (chemically changed) to supply the

of NIEHS is to reduce the burden of human illness

body with energy. Chemicals can be metabolized

and dysfunction from environmental causes

by the body and made either more or less harmful.

by understanding how environmental factors,

individual susceptibility, and age interrelate.

methylisocyanate: A toxic chemical used in

pesticide production.

National Institutes of Health (NIH): One of

eight health agencies of the Public Health Service

methylmercury: A human-made molecule,

(the Public Health Service is part of the U.S.

synthesized for commercial purposes (to kill

Department of Health and Human Services).

mold), and a naturally occurring compound made

Composed of 24 separate institutes, centers, and

by certain bacteria. Methylmercury penetrates the

divisions, NIH is the largest biomedical research

brain and is a potent neurotoxin. Methylmercury

facility in the world.

also crosses the placenta and, as a result, a large

number of women who were exposed during

nontoxic: Not harmful or poisonous.

pregnancy in past methylmercury epidemics gave

birth to severely brain-damaged children.

organism: The highest level of cell organization.

All organisms carry out life processes.

mg/kg: Milligrams per kilogram.

overdose: Too large a dose; a dose to excess.

microgram (µg): One millionth of a gram.

Paracelsus: A 16th-century physician (1493−1541)

milligram (mg): One thousandth of a gram.

who saw the need for scientific experimentation

in toxicology and thus gave toxicology a scientific

Minamata disease: A neurological disease first

basis. He recognized that chemicals often have

identified in Minamata, Japan, as a result of

both therapeutic and toxic properties based on

mercury poisoning.

dose. His observations laid the foundation for the

concept of the dose-response relationship.

molecule: The smallest part of a compound that

has all the properties of the compound; made up

parathion: An organophosphate that is used as

of two or more atoms chemically bonded.

an insecticide; it is absorbed through the skin,

eaten, or inhaled; it is toxic because it acts on the

mutagen: An agent that causes a permanent

nervous system.

genetic change in a cell other than what

occurs during normal genetic recombination.

pesticide: Chemicals developed to control a

Mutagenicity is the capacity of a chemical or

wide variety of pests in primarily agricultural and

physical agent to cause such permanent alteration.

forest environments.

natural: Produced or existing in nature; not

pollution: The undesirable presence of matter

artificial or manufactured.

or energy that can cause harmful environmental

effects.

129

Glossary

Chemicals, the Environment, and You

population: A group of individuals of the same

threshold: The lowest dose of a chemical at which

species living in a particular area.

a certain measurable effect is observed and below

which it is not observed.

potency: The measure of a chemical’s

effectiveness as a medicine or a poison. The

toxic: Harmful; poisonous.

more potent the chemical, the less it takes to

exert its effect.

toxicant: Any chemical or mixture of chemicals

that presents a risk of death, disease, injury, or

response: The variety of reactions to exposure to

birth defects in organisms that ingest or absorb it.

chemicals that might occur in an organism.

toxicity: The capacity or property of a substance

risk assessment: Qualitative and quantitative

to cause adverse effects.

evaluation of the risk posed to human health and/

or the environment by exposure to a chemical.

toxicologist: A scientist trained to examine the

nature of the adverse effects of chemicals on

risk management: The process by which

liv ing organisms and assess the probability of

risk is reduced or controlled. Risk assessment

their occurrence.

information is used, along with other information,

such as values, cost, and feasibility, to arrive at a

toxicology: The multidisciplinary science

risk management decision.

that examines the adverse effects of chemicals

on organisms.

route of exposure: The way in which a person

may contact a chemical substance. For example, a

toxin: A naturally occurring substance or agent

person may ingest a chemical, inhale a chemical,

that may injure an organism exposed to it.

or absorb a chemical through the skin.

solvent: A substance (usually a liquid) capable

of dissolving or dispersing one or more

other substances. Water is a solvent. Organic

solvents include alcohols, aldehydes, benzene,

toluene, glycol ethers, trichloroethylene (TCE),

formaldehyde, and carbon tetrachloride. Drinking

water is an important source of solvent exposure;

solvents also pass rapidly through the skin and

produce high levels in the bloodstream within

minutes after skin exposure. Nearly all solvents

(other than water) can cause acute and chronic

injury to the central nervous system. Many

solvents are associated with development of

kidney failure and chronic kidney disease, and

others can cause acute toxic damage to the liver.

subacute exposure: Repeated exposure to a

chemical for one month or less.

synthetic: Made by forming a compound by

combining two or more simpler compounds,

elements, or radicals; human-made, not

from nature.

130

Masters

Lesson 1, Chemicals, Chemicals, Everywhere

Activity 1: What Is a Chemical?

Master 1.1, Item Cards ................................................................................................ classroom set Master 1.2, Periodic Table of Elements .........................................................................transparency Master 1.3, Elemental Composition of the Human Body ...............................................transparency Activity 3: Case Studies of Routes of Exposure

Master 1.4, Questions for Case Studies .........................................................................transparency Master 1.5, Case Studies of Routes of Exposure .........................................................student copies Lesson 2, The Dose Makes the Poison

Activity 1: Dose and Concentration

Master 2.1, Opening Questions .....................................................................................transparency Activity 2: Planning the Seed Investigation

Master 2.2, Making Solutions for Toxicity Testing ..........................................................team copies Activity 3: Setting Up the Seed Investigation

Master 2.3, Toxicity Testing on Seeds ........................................ student copies ( print version only) Lesson 3, Dose-Response Relationships

Activity 1: Graphing the Response to Chemical Dose

Master 3.1, Dose-Response Curves ................................................................................transparency Master 3.2, Graph Paper ................................................................................................team copies Lesson 4, Individual Responses Can Be Different

Activity 1: Different Doses for Different People

Master 4.1, Acetaminophen Dosage Chart ....................................................................transparency Activity 2: A Poisonous Dose?

Master 4.2, A Poisonous Dose? The Case History .........................................................transparency Master 4.3, A Poisonous Dose? The Problem .............................. student copies ( print version only) Activity 3: The Chemical Caffeine: How Do You React?

Master 4.4, Parent Letter ............................................................................................student copies Master 4.5, The Chemical Caffeine: How Do You Respond? ........................................student copies 131

Chemicals, the Environment, and You

Lesson 5, What Is the Risk?

Activity 1: People at Risk

Master 5.1, Risk Assessment and Management .............................................................transparency Master 5.2, Minamata Disease ...................................................................................student copies Lesson 6, Environmental Hazards

Activity 1: The Field Trip

Master 6.1, Heads or Tails? ....................................................... student copies ( print version only) Master 6.2, Choice Cards ............................................................classroom set ( print version only) Master 6.3, Fact Sheets on Chemicals ........................................ classroom sets ( print version only) 132

Item Cards

Master 1.1a (page 1 of 4)

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Master 1.1b (page 2 of 4)

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Master 1.1c (page 3 of 4)

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Master 1.1d (page 4 of 4)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Periodic Table of Elements

m

8

o tiu

11

Uu Ununoc

6

h um

11

Uu Ununhexi

4

q diuma

11

Uu nunquU

2

b

11

Uu Ununbium

u m

111

Uu Unununiu

0

n um

11

Uu Ununnili

Master 1.2

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Elemental Composition of the Human Body

Element

% of Human Body

oxygen

65.00

carbon

18.00

hydrogen

10.00

nitrogen

3.00

calcium

2.00

phosphorus

1.10

potassium

0.35

sulfur

0.25

chlorine

0.15

sodium

0.15

iodine

0.10

trace elements

under 0.10

Source: DiSpezio, M., et al. 1996. Science insights: Exploring living things. (Teacher’s Edition) Menlo Park, CA: Addison-Wesley Publishing Company, p. 57.`

Master 1.3

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Questions for Case Studies

1. What happened? Where did it happen? When did it happen?

2. What chemical was involved?

3. What was the route of exposure?

4. What were the symptoms of toxicity?

5. How could a person have prevented his or her exposure to the chemical?

6. Have any changes occurred since the incident? Describe them.

Master 1.4

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Case Studies of Routes of Exposure

CASE STUDY #1

Dr. Karen Wetterhahn, a Dartmouth College scientist and leading researcher on the impact of toxic metals on living organisms, died in June of 1997 of a lethal dose of dimethylmercury (die-METH-ul-MER-kyoo-ree). She was studying how mercury prevents cells from repairing themselves, a characteristic commonly seen in cancer cells.

Ten months earlier, Dr. Wetterhahn had an accident in her laboratory. A drop of the toxic compound spilled and seeped through her latex gloves. Dr. Wetterhahn followed all the known safety procedures when working with a toxic chemical: She used a hood to protect her from fumes and wore a face shield and gloves. Tests in an independent laboratory after the accident, however, showed that dimethlymercury can pass through latex gloves in 15 seconds or less, usually without damage to the gloves. It came as a surprise to the chemistry department at Dartmouth and to the doctor’s research colleagues that the gloves she was wearing at the time of the spill were not sufficient protection. Since the accident, researchers working with dimethylmercury are urged to wear neoprene gloves with long cuffs or two pairs of gloves, one of them laminated and one of them heavy duty.

Dimethylmercury is a thick, colorless liquid with a sweet odor. It is not the same kind of mercury found in thermometers. Instead, it looks like water but is three times as dense. It is attracted to the oil in human skin and is readily absorbed by the body. It can cause permanent nervous system damage or death. Dr.

Wetterhahn sought medical attention when she felt numbness in her fingers, was unsteady while walking, had difficulty speaking, had blurred vision, and had problems hearing. Within three weeks of diagnosis of mercury poisoning, she went into a coma that lasted until her death four months later.

Poisoning from dimethylmercury is a rare event. According to Dartmouth officials, only one other researcher has died of dimethylmercury poisoning in this century: a Czechoslovakian scientist in 1971.

Before that, two people died from exposure to the chemical when it was first made in the laboratory in the mid-1800s.

Sources: Associated Press. 1997, March 28. Hanover, NH; Associated Press. 1997, June 11. Hanover, NH; Haworth, K. 1997, April 1. Mercury poisoning from lab work puts Dartmouth chemist in hospital. The Chronicle of Higher Education; Holden, C.

(Ed.). 1997, June 20. Random samples: Death from lab poisoning. Science 276, 1797.

Master 1.5a (page 1 of 6)

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CASE STUDY #2

Early in the morning of December 3, 1984, a young autorickshaw (taxi) driver finally finished his day of work in Bhopal (boh-PAWL), India. As he drove home to his family, he began to notice that the air felt hot even though it was a winter’s night. There was smoke in the air that made his eyes burn.

He arrived at his house and went in, calling to his wife and two children.

“What is going on?” he said.

“We don’t know,” replied his wife, coughing. “But, we have noticed the smell, too. It is making us feel very sick.”

Just then, the young man noticed thick smoke coming in under the door. Outside he heard screaming and shouting. Suddenly, there was a knock on the door. The next-door neighbor shouted through the door, “Run, run away from here. Gas has leaked from the Union Carbide plant and people are collapsing in the streets!”

The man and his wife looked at each other, frightened. “Why was there no siren or warning?” they asked each other.

It was then that the children started crying. They coughed as if they were choking and then vomited, over and over again. The young man covered his mouth with a wet muffler and picked up his children.

He and his wife got into the taxi to begin to drive away from the cloud of gas.

Everywhere in the streets were people running, vomiting, wearing only pajamas. Many people tried stopping the taxi and begged for space, but there was no room for more people. The gas cloud was so thick that the streetlights looked like dim candles burning. Corpses lay in the streets, some bloated to twice their usual size. Police vans were roaming the city, blaring through their loudspeakers,

“Evacuation!” The young man drove on, leaving the city and the terror behind.

The next day, news came that the pesticide plant in Bhopal had leaked the chemical methylisocyanate (METH-ul-IE-soh-SIE-uh-nate). The workers and people living around the plant were exposed to a deadly gas. By the end of the week, at least 6,000 people were dead. When the young man and his family returned to the city, it was like a graveyard.

During the next two months, the man and his family suffered, too. Unable to find medical care, one of the children died a slow, painful death. The man’s wife was no longer able to do her chores because she felt so weak and her lungs always burned. The man worked from dawn to dusk to bring in money for the family and to take care of his wife and child.

Today, thousands of people in Bhopal, India, are still seriously ill. Many people who were exposed to the cloud of gas continue to suffer from diseases related to their exposure to the chemical. They have problems with their lungs, less control over their limb movements, nervous system diseases, and damaged immune systems.

(continued)

Master 1.5b (page 2 of 6)

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When an investigation into the disaster in Bhopal was completed, Union Carbide was accused of having poor safety and maintenance standards. Defects in the methylisocyanate unit were found in various places: the gauges measuring temperature and pressure were unreliable and ignored; the refrigeration unit had been shut off; the gas scrubber, designed to neutralize any escaping chemical, had been shut off for maintenance; the flare tower, designed to burn off any escaping chemical, was undersized and turned off; the water curtain, designed to neutralize any remaining gas, was too short to reach the tower where the gas was billowing; the alarm on the storage tank did not signal the increase in temperature; and there were inadequate storage tanks for excess chemical. Officials from Union Carbide believed that the leak was the result of sabotage by a disgruntled employee, but the company has never brought charges against anyone.

In February 1989, the Supreme Court of India ordered Union Carbide Corporation (United States) and Union Carbide India Limited, the owner and operator of the chemical plant, to pay $470 million in settlement of all claims arising out of the chemical leak. In addition, the companies were ordered to build a hospital in Bhopal and set up a charitable trust in England to support it. In 1994, Union Carbide Corporation completed the sale of its interest in Union Carbide India Limited to a company in Calcutta.

Part of the proceeds from the sale went to the hospital and clinics in Bhopal.

Source: Testimony of Bhopal Gas Victims. Retrieved August 9, 2000, from http://www.bhopal.org/testimony/jewan_shinde.html.

Master 1.5c (page 3 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

CASE STUDY #3

A two-year-old girl named Jane ended up in the emergency room after her mother began to worry about her illness. Jane complained of abdominal pain, she had lost her appetite, she was vomiting, she was constipated and, lately, she seemed very tired.

The doctor in the emergency room asked Jane’s mother where the family lived. He recognized the area as an inner-city neighborhood of old homes, many in poor repair, with peeling and chipping paint. He asked that a blood sample be taken and tested for the level of lead in it. He discovered that Jane’s blood lead level was 100 micrograms of lead per deciliter (1 deciliter = 100 mL) of blood. Because any amount of lead above 10 micrograms per deciliter of blood is dangerous, Jane was at risk of major seizures and cardiac arrest. The doctor told Jane’s mother that Jane was suffering from lead poisoning, but that she would feel better within a short time if she began drug therapy immediately. The drug was easy for Jane to take by mouth, and she could continue her treatment at home.

The cause of Jane’s illness was the lead in the dust, paint, or soil around her home. The doctor told Jane’s mother that the long-term effects of lead in a child can be severe. They include learning disabilities, decreased growth, hyperactivity, impaired hearing, and even brain damage. If caught early, however, these effects can be limited by medical treatment and by reducing exposure to lead.

Jane’s mother wondered why she and her husband were not sick. The doctor explained it this way.

Children swallow lead or breathe lead-contaminated dust when they play in dust or dirt and then put their fingers or toys in their mouths. Often, children eat without washing their hands first. They tend to chew on window ledges and cribs and get lead paint in their mouths. All of these behaviors would be unusual for an adult, so adults are not at as high a risk of exposure. In addition, adults’ organ systems are not affected by lead the way children’s organs are.

When Jane’s mother asked the doctor what she should do to minimize the family’s exposure to lead, the doctor had several suggestions. First, test children living in older homes once a year for high lead levels in their blood. Second, keep areas where children play as clean as possible. Wash things that have fallen on the floor, like bottles and pacifiers. Mop floors and windowsills twice a week. Third, make sure children wash their hands before meals, naptime, and bedtime because these are times when they tend to put their hands in their mouths. Fourth, get professional help to remove lead paint that is peeling or chipping.

Paint over lead paint in good condition to seal it in. Fifth, give children milk with their diet. The calcium in the milk will be absorbed by the body instead of the lead. Children with poor nutrition are more likely to have elevated blood lead levels. Finally, the doctor told Jane to check with her local health department and housing authority for help with her task of minimizing lead exposure. Many government programs and agencies can help educate people about lead poisoning and prevention.

Master 1.5d (page 4 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

CASE STUDY #4

The news spread through the school like a wildfire in the spring of 1999. A boy in the eighth grade, Jimmy Green, had died. He had tried for the first time sniffing gasoline from a plastic bag in his garage.

He had a heart attack within minutes of breathing the fumes.

Mr. Cobb, the biology teacher, gathered students and their parents for a meeting. He told them that Jimmy Green died because he inhaled a deadly chemical. He told them that inhaling chemicals, especially ones like gasoline that are made up of so many different chemicals, can be very damaging to the body. Mr.

Cobb reminded students that the lungs can deliver the toxic chemicals that students sniff directly to vital tissues in the body in high concentrations. The results can be short-term memory loss, hearing loss, arm and leg spasms, permanent brain damage, liver and kidney damage, and death.

Mr. Cobb let the families know that Jimmy Green died of “sudden sniffing death syndrome.” In some people, breathing toxic fumes from gasoline can interrupt the normal rhythm of the heart and result in a heart attack. It is impossible to know who might die from sniffing, but 3 out of 10 people who die from sniffing do so during their first use, as Jimmy did. Besides dying from sudden sniffing death syndrome, people who inhale toxic chemicals also die of asphyxia, or suffocation, because of the plastic bags they use; from choking on vomit; and from accidents, fires, and suicides that result from poor decisions made while intoxicated.

Mr. Cobb told the parents that the commercial products that students sniff are easy to get because many people have these products in their homes. In this way, starting a habit of abuse with these chemicals is less expensive than with other substances, such as marijuana or cocaine.

Treatment for people who abuse inhalants is similar to that for people who abuse drugs. It is very difficult to stop using inhalants. Many people who go through rehabilitation to help them stop sniffing need to repeat the program after relapsing back into inhalant use.

Parents and students left the meeting knowing that they did not want to intentionally expose themselves to the dangers of sniffing toxic chemicals. Losing Jimmy Green was enough.

Master 1.5e (page 5 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

CASE STUDY #5

In December of 1971, an epidemic occurred in Iraq. More than 6,500 people in many parts of the country became ill with nervous system disorders. They had numbness and tingling around their mouths, lips, fingers, and toes. They had a clumsy, stumbling walk and a feeling of weakness. Some had difficulty swallowing and pronouncing words. Many had vision and hearing loss. In all, 459 people fell into a coma and died.

It took considerable detective work to determine the source of the widespread illness. Finally, it became apparent that a shipment of seed grain from Mexico, which was intended only for planting, was used to make bread instead. The seed had been treated before shipment with a fungicide containing methylmercury (METH-ul-MER-kyoo-ree). The warning about the fungicide and instructions for the seed use were not written in Iraqi, so the people at the southern port of Basra, in Iraq, did not realize the seed should not be eaten. The seed was distributed to households around the country. The women in the country ground the seed to make flour and used it in their baking. The result was mass mercury poisoning from a very unusual source: homemade bread.

Master 1.5f (page 6 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Opening Questions

As a team, think of a chemical that you would like to be exposed to because it makes you healthier. Think of a chemical that you would try to avoid because it harms you in some way. Record these two chemicals in your science notebook.

Use complete sentences to answer the following questions about each of the chemicals:

• Where do you find the chemical?

• How does the chemical enter your body?

• How does it make you healthier or harm you?

• How much chemical do you need to be exposed to for it to help you or harm you?

Master 2.1

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Making Solutions for Toxicity Testing

Materials for Each Team

6 50-mL beakers, clean and empty

eyedropper

1 50-mL graduated cylinder

masking tape

1 10-mL graduated cylinder

permanent marker

1 100-mL beaker with 50 mL of chemical

safety glasses

100 mL of water in a beaker

latex gloves

1 tray

Procedure

1. Put on the latex gloves and safety glasses.

2. Use the masking tape and marker to label each of the six empty 50-mL beakers with information from the following table.

Beaker #

Amount of

Amount of

Total Volume

% Concentration

Water

Chemical

of Liquid

of Chemical

1

20.00 mL

0.00 mL

20 mL

0%

2

18.75 mL

1.25 mL

20 mL

6.25%

3

17.50 mL

2.50 mL

20 mL

12.5%

4

15.00 mL

5.00 mL

20 mL

25%

5

10.00 mL

10.00 mL

20 mL

50%

6

0.00 mL

20.00 mL

20mL

100%

3. Use the 50-mL and the 10-mL graduated cylinders to measure the correct amount of water. Pour the water into each of the labeled beakers according to the above table. Use the eyedropper for small corrections.

4. Use the 50-mL and the 10-mL graduated cylinders to measure the correct amount of chemical.

Pour the chemical into each of the labeled beakers of water according to the above table. Use the eyedropper for small corrections.

5. When you have finished, check that all the beakers contain 20 mL of chemical solution. If a beaker contains more or less than 20 mL, consult the above table and repeat the procedure for that beaker.

Place the beakers in order on the tray, with 0 percent concentration on the left and 100 percent concentration on the right.

6. Return any unused chemical to your teacher. Wash all other containers and put them away.

Master 2.2

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Toxicity Testing on Seeds

Materials for Each Team

6 resealable plastic sandwich bags

12 paper napkins

6 beakers of chemical solution, ranging from 0% to 100% concentration

1 bag of seeds (approximately 60 seeds in a bag)

1 permanent marker

latex gloves

safety glasses

1 tray

Procedure

1. Label all six bags with your team members’ initials and a number and a percent concentration of chemical, like this:

Step 1

#1

0% (control)

#2 6.25%

#3 12.5%

#4 25%

#5 50%

#6 100%

2. Put two napkins together and fold them in half so that they fit into the plastic bag. Fill each bag with two folded paper napkins.

Step 2

Step 3

Step 4

3. Put on the safety glasses and latex gloves. Carefully pour the chemical solutions into the bags, making sure to match the numbers and concentration percentages of the bag and the chemical. Each bag now will contain 20 mL of chemical solution that is absorbed by the paper napkins.

Master 2.3a (page 1 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

4. Count out 10 seeds. Carefully place the seeds on the moist paper napkins in the control bag (#1), making sure to space them evenly (do not clump them in one spot). Seal the plastic bag, pushing out the air as you go.

5. Repeat Step 4 for the remaining bags.

6. Observe the seeds and fill in the following data table with information you know at this time.

Data table for toxicity testing.

Bag #, Dose

Day 1:

Day 1:

Day 2:

Day 2:

Day 3:

Day 3:

(% concentration)

# of seeds

# of

# of seeds

# of

# of seeds

# of

germinated

seeds not germinated

seeds not germinated

seeds not

germinated

germinated

germinated

1 (control), 0%

2, 6.25%

3, 12.5%

4, 25%

5, 50%

6, 100%

7. Place the seed bags in a stack, lying flat with the seeds up, on the tray. Put the tray of seeds in the spot designated by your teacher. Put this worksheet in your science notebook.

Questions

1. What is your chemical? Describe what you know about the chemical. (Do you consider it harmful, beneficial, or neither? What is it used for? How would a human be exposed to this chemical?) 2. In which bag is the dose of chemical the highest? In which bag is the concentration of chemical in the solution the highest? Describe how you know.

3. Do you think you will see a difference in the effect on seeds of a small dose of chemical compared with the effect of a larger dose? Predict what you think will happen to the seeds in each bag.

Master 2.3b (page 2 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Dose-Response Curves

Response

e

Respons

Dose

Dose

Tumor

incidence

(%)

Dose (mg)

Master 3.1

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Graph Paper

Name _________________________________________

Date __________________________________________

Class _________________________________________

Directions: Plot dose-response data for your chemical on graph A and for two other teams’ chemicals on graphs B and C.

Chemical A ____________________________________

Master 3.2a (page 1 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Chemical B ____________________________________

Chemical C ____________________________________

Master 3.2b (page 2 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Acetaminophen Dosage Chart

Children’s Chewable Acetaminophen Dosage (80 mg/tablet)

Weight (lb)

Weight (kg)

Age (yr)

Dose

under 24

under 11

under 2

consult doctor

24–35

11–16

2–3

2 tablets

36–47

17–21

4–5

3 tablets

48–59

22–27

6–8

4 tablets

60–71

28–32

9–10

5 tablets

72–95

33–43

11

6 tablets

Warning: Take no more than five doses per day.

Master 4.1

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

A Poisonous Dose? The Case History

Master 4.2a (page 1 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Master 4.2b (page 2 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

A Poisonous Dose? The Problem

Your teacher will display a transparency of a doctor’s chart. Read the first page of the doctor’s chart that describes Andy Brown’s case. Then use information provided on the transparency and on this worksheet to answer the following questions.

Part I

How much Infants’ Concentrated Suspension Drops did Andy receive from his aunt?

a. 1 teaspoon

b. 1 teaspoon 4 times in 1 day

c. 3 teaspoons

d. 4 teaspoons

e. b and d

f. none of the above

Use the dosage chart below to calculate how much acetaminophen, in milligrams (mg), Andy’s aunt gave him in one day. Remember, Andy’s aunt gave Andy his medicine in a teaspoon. To use the dosage chart, you need to know that each teaspoon contains 6.25 dropperfuls of medicine.

4 teaspoons x 6.25 dropperfuls x

milligrams = milligrams of acetaminophen

1 teaspoon

1 dropperful

Infants Concentrated Suspension Drops (80 mg/dropper)

Weight (lb)

Weight (kg)

Age (yr)

Dose

under 24

under 11

under 2

consult doctor

24–35

11–16

2–3

2 dropperfuls

Warning: Take no more than five doses per day.

The warning on the dosage chart says that a child should take no more than five doses of Infants’

Concentrated Suspension Drops in one day. How many milligrams of acetaminophen would there be in five doses for a child Andy’s size?

5 doses = 10 dropperfuls x

milligrams = milligrams of acetaminophen

1 dropperful

Conclusion to Part I

What do you think is making Andy sick?

Master 4.3a (page 1 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Part II

When Andy’s mother gives him a pain reliever, she usually gives him Children’s Suspension Liquid. Use the chart below to calculate how many milligrams of acetaminophen a boy Andy’s size would get in four doses of Children’s Suspension Liquid.

4 doses = 4 teaspoons x

milligrams = milligrams of acetaminophen

1 teaspoon

Children’s Suspension Liquid (160 mg/teaspoon)

Weight (lb)

Weight (kg)

Age (yr)

Dose

under 24

under 11

under 2

consult doctor

24–35

11–16

2–3

1 tsp.

36–47

17–21

4–5

1 1/2 tsp.

48–59

22–27

6–8

2 tsp.

60–71

28–32

9–10

2 1/2 tsp.

72–95

33–43

11

3 tsp.

Warning: Take no more than five doses per day.

What did Andy’s mother use to measure a dose of Children’s Suspension Liquid? (Circle one.) a teaspoon

a dropper

What did Andy’s aunt use to measure Andy’s doses of Infants’ Concentrated Suspension Drops?

a teaspoon

a dropper

What does the dosage chart for infants’ drops say should be used to measure the medicine?

a teaspoon

a dropper

Conclusion to Part II

Andy received an accidental overdose of acetaminophen. On a separate piece of paper, describe how you think the mistake happened.

Master 4.3b (page 2 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Parent Letter

Dear Parents,

Next week in science class we will be investigating individual responses to caffeine. Each student will need to bring in a 12-ounce can of

. Please provide a can and

label it with your child’s name and class period.

During the investigation, students will consume 12 ounces of the caffeinated soft drink and measure what effect it has, if any, on their heart rates.

Students are not to bring in any soft drink other than the one specified. Students who do not bring in a drink, or those without permission to drink a soft drink during science class, will be the “control” in the investigation and will drink 12 ounces of water. In this way, everyone can take part in the investigation.

Thank you for your continued support.

Teacher’s Signature

My child,

, has permission to participate in the caffeine

investigation in science class and will bring in a 12-ounce can of

to consume as part of the activity.

My child,

, will not participate by consuming a 12-ounce soft

drink, but will participate in the activity as a control by drinking the same amount of water.

Parent’s or Guardian’s Signature

Date

Master 4.4

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

The Chemical Caffeine:

How Do You Respond?

Materials for Each Team

M 2

at cans

erial of

s fcaf

o feinated

r Each T soft

eam drink (1 for each student)

2 c 1

a watch

ns of c or

aff classr

einateoom

d sofclock

t dri with

nk ( a

1 f second

or eac hand

h stude nt)

data

1 watc table

h or cl (pr

assovided

room c with

loc these

k wit

instructions)

h a second hand

datpencils

a table (provided with these instructions)

pencils

Procedure

Pr Do

oce Steps

dure 1–3 with your teacher.

Do S1.

te When

ps 1– your

3 wit teacher

h your tedi

a re

ch cts

er. you to do so, find your pulse. You can find it

most easily by pressing two fingers against the artery in your neck or on

1. W the

he inside

n your t of

ea your

che wrist.

r direct Practice

s yo

counting

u to do so, fin the

d y beats.

our p ulse. You can find it

most easily by pressing two fingers against the artery in your neck or on

t2.

h When

e insid your

e of y teacher

our wri di

st rects

. Pra you

ctic to

e costart,

untincount

g th the

e bea number

ts.

of beats you feel

in 15 seconds. Your teacher will tell you when to stop. Record the number

2. W in

he the

n yofirst

ur t column

eacher d of

irethe

ct data

s yo

table

u to sta on

rt the

, cou next

nt th page.

e number of beats you

feel in 15 seconds. Your teacher will tell you when to stop. Record the

3.

nu Multiply

mber in tthe

h number

e first col of

um beats

n of t you

he d counted

ata tabl in

e o 15

n t seconds

he nex by

t pag four

e.

to calcu-

late the number of beats you would have counted in one minute. This

3. M number

ultiply t is

h your

e num re

be sting

r of b heart

eats yrate.

ou c Recor

ounte d your

d in 1 re

5 s sting

econdheart

s by frate

ou on

r to the

caldata

culattable.

e the number of beats you would have counted in one minute.

This number is your resting heart rate. Record your resting heart rate on

Wtith

he your

data t partne

able. r, complete the rest of this investigation.

Wit 4.

h yWhat

our p do

art you

ner think

, complmight

ete th happen

e rest o to

f th your

is in heart

vesti rate

gationafter

.

you drink a caffeinated soft drink? Write

your prediction here:

4. W __________________________________________________________________________________________

hat do you think might happen to your heart rate after you drink a caffeinated soft drink? Write your prediction here:

__________________________________________________________________________________________

5. Together, at the same time, drink the cans of soft drink. For best results, try to drink them quickly, taking no more than 10 minutes to finish the can. Write the name of the soft drink at the top of your 5. To data

gethetable.

r, at the same time, drink the cans of soft drink. For best results, try to drink them quickly, taking no more than 10 minutes to finish the can. Write the name of the soft drink above your 6.

da Sit

ta t at

a re

ble.st for about 5 minutes. You can talk to your partner, but keep your body still so that you do not elevate your heart rate with activity. If your teacher instructs you to do so, read quietly at your 6. Si seat

t at r .est for about 5 minutes. You can talk to your partner, but keep your body still so that you do not elevate your heart rate with activity. If your teacher instructs you to do so, read quietly at 7. One

your se partner

at.

at a time, measure your heart rate for 15 seconds. To do this, have one partner be the counter and find his or her pulse. Have the other partner be the timer and watch the second hand on 7. O a

n watch

e partn or

e on

r a

the

t a ti classr

me, m oom

easur clock.

e you Have

r hear the

t rat timer

e fo say

r 15 s “Start”

econds and

. T “Stop”

o do this at

, h the

av beginning

e one partn and

er b end

e th

e

co of

un 15

te seconds

r and fin while

d his othe

r h counter

er pulse counts

. Have this

h or

e ot her

he beats.

r partne Recor

r be t d

h the

e ti number

mer an

of

d wa beats

tch thin your

e secon data

d ha nd

o table

n a wa in

tc the

h o first

r on t column

he class of

ro ro

o w

m c 1.

lo Repeat

ck. Hav the

e thprocedur

e timer se

a so

y “ that

Startthe

” a other

nd “S partner

top” at t can

he b count

eginn his

in or

g an her

d

en heartbeats

d of 15 sec in

on 15

d seconds.

s while th e counter counts his or her beats. Record the number of beats in your data table in the first column of row 1. Repeat the procedure so that the other partner can count his or her heartbeats in 15 seconds.

Master 4.5a (page 1 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

8. Once every two minutes, repeat Step 7, until you have measured the number of heartbeats in 15

seconds at least 10 times. Record each measurement in the first column in your data table.

9. From each of your measurements, calculate your heart rate after drinking caffeine by multiplying the number of beats you counted by four. Record your heart rate for each measurement in the final column of your data table.

10. Using the highest number you calculated for heart rate after drinking a soft drink, determine the difference between your resting heart rate and your heart rate after drinking a caffeinated soda.

Record that number below the data table. Then, calculate the number of minutes it took after finishing the drink for your heart rate to reach its peak. Record the number below the data table.

Name of soft drink:

Data table for caffeine experiment.

Heartbeats counted in 15 seconds

Multiply by 4

Heart rate per minute

Resting:

x 4

1

x 4

2

x 4

3

x 4

4

x 4

5

x 4

6

x 4

7

x 4

8

x 4

9

x 4

10

x 4

Difference between resting heart rate and highest heart rate after caffeine: Number of minutes after finishing the drink for the heart rate to reach its peak: 11. How accurate was your prediction? Did your heart rate go up, down, or stay the same after you drank a caffeinated soft drink?

Extension Question

Could sugar have been the ingredient in soda that affected your heart rate, rather than caffeine? How could you find out?

Master 4.5b (page 2 of 2)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Risk Assessment and Management

Risk Assessment

Step 1

• Is a new health problem present?

• What are the symptoms?

• What do the affected individuals have in common?

Step 2

• What is causing the problem?

• What is the source of the problem?

Step 3

• What are the sources of exposure to the chemical?

• How much exposure are people in the area receiving?

• Is the exposure acute or chronic? (Is it likely to happen only once or often over the course of time?)

Conclusion: How great is the risk to people?

Risk Management

• How do the people involved perceive the risk? Are their perceptions accurate?

• Who is responsible for the harmful substance and its presence in the environment?

What role does the responsible party have in any cleanup?

• What are the benefits and tradeoffs that a person must weigh when making a decision about

the risk?

Conclusion: What action should people take to minimize their risk? Can the risk be managed by individuals, the community, and/or governments?

Master 5.1

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Minamata Disease

Part I

In the city of Minamata, along the western coast of Japan, unusual things began to happen in the 1950s.

First, dead fish began to float in the bay. Then, cats began to fall into the sea and die in what people in the town called “cat suicide.” At the same time, birds began to drop dead from the sky.

Soon, people began to act strangely, too. They stumbled while walking, were unable to write, and had trouble buttoning their buttons. In only a few years, the illness seemed to be an epidemic. Fishermen seemed the most severely afflicted. Men who were once strong suddenly had trouble keeping their balance. They could not stay afloat if they fell into the sea from their fishing boats. They had convulsions and had to be tied to their beds, where many of them died. Sadly, other members of their families also had the strange disease, which came to be known as Minamata disease.

Doctors believed that the mysterious symptoms were caused by poisoning. They tried to find a food source that birds, cats, fish, and people had in common. Finally, they realized that it was the fish that were contaminated, and the birds, cats, and people were eating the fish. What was contaminating the fish?

Part II

Although Minamata used to be a poor fishing village, it prospered when the Chisso Corporation built a manufacturing plant in the city. For 20 years, the plant had been making a chemical called acetaldehyde (a-seh-TAL-deh-hide), which is used to make plastics, drugs, and perfume. As part of its normal operations, the Chisso Corporation dumped waste products into Minamata Bay. Fishermen complained that the dumping was killing the fish. The company paid the fishermen money to help them since there were fewer fish to catch and sell. This arrangement seemed to work well for everyone until people started getting sick.

Mercury is one ingredient that is used to manufacture acetaldehyde. When mercury is dumped into water, the bacteria in the water convert it into organic mercury. When the bacteria are eaten by small fish, which are in turn eaten by larger fish, the mercury becomes concentrated in the tissue of the fish. What made this contamination of the fish so dangerous to humans?

Part III

Mercury is a strong toxin that causes damage to the brain. Most people are exposed to mercury by eating contaminated fish. The U.S. Environmental Protection Agency has estimated that people who eat more than 30 pounds of fish in a year are at higher risk of experiencing toxic effects from mercury. In Minamata, fishermen and their families often ate contaminated fish for every meal. It was this exposure to small amounts of mercury over long periods of time that caused the Minamata disease. In all, more than 12,000 people have suffered from the disease.

Part IV

Many people, devastated by the disease, moved away from Minamata to make their living elsewhere: The city now has only 70 percent of the number of people it once had. The Chisso Corporation no longer uses mercury in its manufacturing or dumps waste into the bay. It has paid more than $2 billion to victims of Minamata disease. The bay was dredged, and 1.5 million cubic meters of contaminated sludge was removed from it. Finally, 40 years later, the water in the bay is safe for swimming and fishing.

Master 5.2

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Heads or Tails?

If you get heads

If you get tails

_____ you sat in the front of the blue van

____ you sat in the back of the blue van

_____ you leaned out the window

____ you stayed inside the van

_____ you watched from outside the lab

____ you sneaked inside the lab

_____ you drank soda with caffeine

____ you drank soda without caffeine

_____ you got paint on your skin

____ you painted neatly

_____ you sat in the back of the yellow

____ you sat in the front of the yellow bus bus

Master 6.1

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Choice Cards

CHOICE

CHOICE

CARD

CARD

CHOICE

CHOICE

CARD

CARD

CHOICE

CHOICE

CARD

CARD

CHOICE

CHOICE

CARD

CARD

CHOICE

CHOICE

CARD

CARD

Master 6.2

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheets on Chemicals

Fact Sheet #1

Chemicals in the Blue Passenger Van

Sometimes, when people are exposed to new products such as carpet or furniture in their homes or new automobiles, they experience a variety of symptoms such as headaches, itchy eyes, and difficulty breathing. Scientists are not always able to determine whether the chemicals emitted by the new products are responsible, but they are aware that chemicals used in building materials can harm humans. When these products are inside small areas, such as rooms in houses, in mobile homes, or in vehicles, the gases they emit can produce an odor.

Formaldehyde

Formaldehyde is a chemical used in the manufacturing of pressed wood products, as a component of glues and adhesives, and for adding permanent-press qualities to fabrics. Formaldehyde is released as gas into the air from new products that are made with it, such as carpet, carpet adhesives, fabrics, and plywood. This “outgassing” is greatest when the product is new and gradually decreases as the product ages until it no longer occurs. High heat and humidity increase the rate at which formaldehyde is released and shorten the time during which the odor of formaldehyde gas is noticeable.

A person exposed to high levels of formaldehyde in the air can have watery eyes, burning sensations in the eyes and throat, nausea, and difficulty breathing. High concentrations sometimes trigger attacks in people with asthma. New products made for homes, autos, and buses do not release high levels of formaldehyde.

To minimize exposure to formaldehyde, people can ventilate areas that contain new products that emit formaldehyde. They can choose to use wood products that are not pressed wood but should weigh their worry about formaldehyde against the fact that the use of pressed wood conserves more natural resources. They can request low-emitting adhesives for carpets.

The blue van, although new to the students, was built four years ago with materials containing chemicals including formaldehyde. The van previously was owned by a touring company in Florida and was bought by the school district in August of the current year.

Master 6.3a (page 1 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheet #2

Chemicals at the Gas Station

Benzene in Gasoline

Gasoline is a mixture of chemicals, including benzene. Benzene is a colorless liquid with a sweet odor.

It evaporates into the air very quickly when you pump gas into your car or when gasoline is accidentally spilled onto surfaces at a gas station. The concentration of benzene in gasoline is low.

Outdoor air contains low levels of benzene from tobacco smoke, gas stations, exhaust from motor vehicles, and industrial emissions. The air around gas stations contains slightly higher levels of benzene than air in other places.

Breathing benzene vapor in small amounts occasionally causes headache, euphoria (a “high”), a light-headed feeling, dizziness, drowsiness, or nausea. Higher levels of benzene exposure can result in drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Fifteen to 20 breaths of concentrated gasoline vapor can produce a response for five to six hours, ranging from dizziness and confusion to restlessness and hallucinations. Very high doses of benzene can result in death.

Benzene vapors are mildly irritating to the skin, eyes, and lungs. If liquid benzene splashes into the eyes or onto the skin, it can cause burning pain and damage the cornea of the eyes.

No long-term effects are likely from a single, small exposure to benzene. Repeated small exposures (for more than 365 days) can cause blood disorders and cancer of blood-forming cells. Benzene can cause harmful effects in bone marrow and a decrease in red blood cells, leading to anemia. It also can cause excessive bleeding and affect the immune system, increasing the chance for infection.

Many states require gas stations to install vapor-return barriers that cover gas pump nozzles. These barriers help prevent air pollution from gasoline fumes and protect people who are pumping gas from gasoline fumes. In addition, overflow shut-off valves help keep people from accidentally spilling gasoline onto the ground.

The Environmental Protection Agency’s annual inspection of the gas station where the school van stopped for gas indicated that the overflow shut-off valve on the gas pump needed adjusting and people using it often spilled a small amount of gasoline.

Master 6.3b (page 2 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheet #3

Chemicals in the Paleontology Lab

In the paleontology lab, scientists, artists, and technicians work to create models of dinosaurs and their environments out of plaster, fiber glass, plywood, and fiberboard.

Fiber Glass

Fine particles in the air can cause health problems. In areas where materials are cut, ground, or sanded, the particulate matter that becomes airborne is a source of air pollution. The health effects of breathing in the particles can include eye, nose, and throat irritation; respiratory infections and bronchitis; and lung cancer.

The use of fiber glass in building materials creates fiber glass dust, fine glass fibers that can be breathed into the lungs. Manufacturers of materials made with fiber glass suggest that people working with the material, like those in the paleontology lab, use a mask over their nose and mouth to protect themselves from airborne glass fibers. The Occupational Safety and Health Administration’s report on the paleontology lab states that the work place complies with regulations; the level of particles in the air requires that scientists in the lab wear respirators, which they do.

Formaldehyde

Pressed-wood board is made with adhesives that contain urea-formaldehyde resins. Some examples of pressed board that are commonly used as building materials are particle board, plywood, and fiberboard.

The higher the resin-to-wood ratio, the more formaldehyde there is in the product.

Pressed-wood products emit formaldehyde gas, and the air in rooms where pressed-wood products are used can have elevated levels of formaldehyde. If the heat and humidity are high in a room, the emission of formaldehyde can increase. As the product made with formaldehyde ages, the emissions of formaldehyde decrease until they are no longer measurable.

Most people will notice the pungent odor of formaldehyde if they are exposed to it. They will experience a burning sensation in their eyes, nose, and throat when they breathe the gas, even in small amounts for short periods of time. Breathing in the gas over a longer time or at higher doses can cause coughing or choking. Very high exposures can cause death from throat swelling or from chemical burns to the lungs.

People working for long periods of time in areas with formaldehyde gas wear respirators or work in a room with good ventilation.

People are surrounded by pressed-wood products in their everyday life. The use of pressed-wood products in the paleontology lab does not pose an increased health hazard to the workers. Because they use respirators, the workers’ exposure to formaldehyde is minimal.

Master 6.3c (page 3 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheet #4

Chemicals at Lunch

Caffeine

Caffeine is a naturally occurring substance found in the leaves, seeds, or fruits of more than 60 plants.

Coffee and cocoa beans, kola nuts, and tea leaves contain caffeine and are used to make beverages such as coffee, tea, cola drinks, and chocolate.

The U.S. Food and Drug Administration and the American Medical Association have conducted extensive research into the health aspects of caffeine. They agree that moderate consumption of tea, coffee, and other caffeinated drinks does not cause health problems. Moderate caffeine consumption is defined as about 300 milligrams a day, which is equal to three cups of coffee or between four and eight cans of a caffeinated soft drink.

People differ greatly in their sensitivity to caffeine. Some people can drink many cups of coffee, tea, or soft drinks a day and feel no effect, while others feel stimulating effects after one cup. When trying to lessen their intake of caffeine, some sensitive individuals might experience mild, temporary symptoms of withdrawal, including headaches, restlessness, and irritability.

Caffeine can increase alertness in tired individuals and help people stay alert when they work or study.

There is no difference in the way children and adults handle caffeine, and caffeinated beverages do not affect hyperactivity or the attention span of children.

Caffeine can cause a temporary rise in blood pressure, less than that normally experienced when climbing stairs and not lasting more than several hours. However, individuals with high blood pressure should consult their physicians about caffeine consumption.

The students on the field trip each brought their own lunch. As a treat, the teachers brought soft drinks for the students. Some of the soft drinks contained caffeine, some did not.

Master 6.3d (page 4 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheet #5

Chemicals in the Art Room

Solvents

Solvents are substances that dissolve other substances. Water is one example of a solvent. Some solvents smell like kerosene and are used as paint thinner and cleaner. The chemicals that make up some solvents can be harmful to human health.

Exposure to the harmful chemicals occurs when people use products such as paint thinner and breathe the vapors or get the vapors in their eyes. Exposure to these substances can affect the nervous system and cause dizziness, headache, or a prolonged reaction time. Exposure also can cause eye, skin, or throat irritation.

Children attending school and participating in arts and crafts might use art supplies that contain small amounts of solvents, such as rubber cement, permanent felt tip markers, pottery glazes, enamels, and spray fixatives.

The use of glue-containing solvents in a small room with no fresh air can cause headaches, which can signal central nervous system problems. Large doses, such as those experienced during intentional glue sniffing, can cause loss of coordination, nausea, and even death.

Chronic exposure in poorly ventilated areas to hobby materials containing solvents can result in chronic health effects that are hard to trace to their cause. These include skin disease, liver damage, and nervous system damage.

Most schools use only nonhazardous art materials. The selection of materials is based on fulfilling the following conditions:

• no dust or powders;

• no harmful solvents or solvent-containing products;

• no aerosol spray cans or air brushes;

• nothing that stains the skin or cannot be washed out of clothing;

• no acids, alkalis, bleaches, or other corrosive chemicals;

• no lead, cadmium, or other metal products (these can be found in glazes, metal work, and stained-glass products)

• no donated or found materials, unless ingredients are known;

• no old materials purchased before 1990 (when the new labeling standard of the American Society of Testing and Materials (ASTM) became effective);

• only use products that meet the ASTM standard and are labeled “conforms to ASTM D-4236.”

[Source: Environmental and Occupational Health Sciences Institute. 1997. Infosheet: Children’s Art Supplies. ]

The dinosaur model painting the students did used tempera paint, which is a brilliant, opaque, nontoxic watercolor. Its solvent is water; it can be thinned with water and cleans up with water. The coloring agents in the paint are nontoxic.

Master 6.3e (page 5 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

Fact Sheet #6

Chemicals in the Yellow Bus

Carbon Monoxide

Carbon monoxide is an odorless, colorless, poisonous gas released from the incomplete burning of fossil fuels, such as gasoline, propane, natural gas, oil, wood, and coal. Burning tobacco also produces carbon monoxide, one of the gases in cigarette smoke.

When people breathe in carbon monoxide, the carbon monoxide molecules compete with oxygen molecules for the same binding sites on hemoglobin. The hemoglobin molecule cannot tell the difference between carbon monoxide and oxygen, so it carries carbon monoxide in the blood instead of oxygen.

When tissues become starved of oxygen, people begin to experience fatigue. As the concentration of carbon monoxide increases, people experience headaches, weakness, nausea, dizziness, dim vision, and changes in heart rhythm. If carbon monoxide is present at very high concentrations, it can lead to unconsciousness, coma, convulsions, and death. According to the Mayo Clinic, approximately 10,000

people are poisoned by carbon monoxide in the United States each year. Fetuses, infants, elderly people, and people with anemia or a history of heart or respiratory disease are especially sensitive to carbon monoxide exposures.

About two-thirds of all deaths from carbon monoxide poisoning occur in cars. Automobile exhaust contains up to 9 percent carbon monoxide, although catalytic converters substantially reduce carbon monoxide levels to below 1 percent. Because of lack of ventilation, automobile exhaust can leak into the car and slowly overcome the passengers.

People can reduce their exposure to carbon monoxide. They can use carbon monoxide detectors to warn them of any carbon monoxide in their home or workplace. They can keep gas appliances in their homes properly adjusted. They can install and use vents and exhaust fans for their gas stoves, space heaters, and fireplaces. They can make sure that their furnaces are working properly and are not leaking. They can make sure they never idle their car in the garage or breathe the fumes from other idling vehicles. Finally, they can keep their automobile in good condition, paying particular attention to the exhaust system. A state vehicle emissions report made the day after the field trip indicated that the yellow bus the students rode home in from the field trip had a faulty exhaust system.

Master 6.3f (page 6 of 6)

Copyright © 2000 by BSCS and Videodiscovery, Inc. Permission granted. Updated 2012.

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Table of Contents

Part I

Part II

Part I

Part II

Part III

Part IV