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General InstructionsTopics: (1) Environmental Health and Toxicology; (2) Geology, Minerals, and Mining.NOTE: Question #3 for Unit 3 is eliminated from the pool and you are not required to answer the question. This does not alter the required 1000 word count and 3 scholarly sources for the unit. Question #1Question #2Question #3Question #4Question #5Question #6Question #7Question #8Question #9Question #10 SaveAssignment Submitted1.What is BPA? How might you get exposed to BPA? 2.Name and describe each of the four major types of environmental hazards.3.Describe three reasons contagious diseases often claim more lives in developing nations than non-contagious disease. 4.Differentiate between an LD50 and an ED50 response to toxicity. Explain why there is a response threshold to some toxins.5.Explain how scientists identify and assess risks.6.Thoroughly describe the “Precautionary Principle” policy. Do you agree with this policy? Explain.7.Using your own words, describe the three types of possible tectonic plate boundaries. Why do so many earthquakes and volcanos occur along the “ring of fire” circum-pacific belt?8.Thoroughly describe the rock cycle. 9.What is a mineral? Why is it important that items that use minerals be recycled?10.Describe two types of mining. What are the effects of each on the environment? FontSize
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10
Environmental Health
and Toxicology
Upon completing this chapter, you will be able to:
➤ Identify major environmental health hazards and explain the goals of environmental health
➤ Describe the types of toxic substances in the environment, the factors that affect their toxicity,
and the defenses that organisms possess against them
➤ Explain the movements of toxic substances and how they affect organisms and ecosystems
S
A
and dose-response analysis
➤ Compare and contrast risk assessment
Nand risk management
➤ Compare philosophical approaches to
Frisk and how they relate to regulatory policy
O
R
D
,
➤ Discuss the study of chemical hazards, including wildlife toxicology, epidemiology, animal testing,
B
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Is this baby ingesting toxic
substances?
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M10_WITH2901_04_SE_C10.indd 205
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CENTR AL C A SE S TUDY
Poison in the Bottle: Is Bisphenol A Safe?
“Babies in the U.S. are born pre-polluted with BPA. What more evidence do we need to act?”
—Dr. Janet Gray, Director of the Environmental Risks and Breast Cancer Project, Vassar College
“There is no basis for human health concerns from exposure to BPA.”
—The American Chemistry Council
H
ow is it that a chemical found to alter reproductive development in animals gets
S
A
tate cancer, and heart disease is routinely used in food and drink containers? The
N
chemical bisphenol A (BPA for short) has been associated
with everything from neurological
F
effects to miscarriages. Yet it’s in hundreds of products
we use every day, and there’s a 90%
O
chance that it is coursing through your body right
Rnow.
D
To understand how
What, if anything, is BPA do,
chemicals that may pose
ing to us? Over 200 studies with
used in baby bottles? How can it be that a substance linked to breast cancer, pros-
health risks come to be
rats, mice, and other animals
widespread in our society,
have shown many apparent efB
we need to explore how
fects of BPA, including a wide
E
scientists and policymakers
range of reproductive abnorstudy toxic substances and
malities, and a few recent studBisphenol A: Worldwide
T
other environmental health
ies suggest human health imH
risks—and
the
vexing
pacts (see THE SCIENCE BEHIND
A
challenges these pursuits
THE STORY, pp. 214–215). Many
of these effects are seen at exentail.
N
tremely low concentrations. SciBisphenol A is a synY
entists say this is because BPA
thetic organic compound
mimics the female sex hormone
(C15H16O2) used in the
resins that line metal food
estrogen and can induce some
1
cans and drink cans and water supply pipes, and in
of estrogen’s effects in animals. Hormones such as
3
dental sealants for our teeth. It’s also found in the
estrogen function at very low concentrations in the
5
hard, clear polycarbonate plastic in some water botbody, so a synthetic chemical in the body at simitles, food containers, eating utensils, eyeglass lenses,
larly low concentrations can fool the body into re3
CDs and DVDs, electronics, baby bottles, and chilsponding as it would to estrogen.
T In reaction to the burgeoning research, a growdren’s toys.
Unfortunately, bisphenol A leaches out of these
ing number of researchers, doctors, and consumer
S
products into our food, air, and bodies. The Centers
advocates are calling on governments to regulate bifor Disease Control and Prevention (CDC) reports that
sphenol A and for manufacturers to stop using it. The
93% of Americans carry detectable concentrations
chemical industry insists that BPA is safe, pointing
in their urine. Because most of the chemical passes
to industry-sponsored research that finds no health
through the body within hours of exposure, its wideimpacts. Expert panels convened to assess the fastspread presence in urine suggests that most Amerigrowing body of scientific studies on BPA have strugcans receive continuous exposure to BPA. Babies and
gled with the fact that traditional research methods
children accumulate the most BPA, because they eat
are not geared to test hormone-mimicking substances
more for their body weight and metabolize the chemthat exert effects at low doses. These panels have ofical less effectively.
ten arrived at divergent conclusions. For instance, the
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M10_WITH2901_04_SE_C10.indd 206
8/7/11 11:17 PM
the environment over which we have little or no control, as
well as anthropogenic (human-caused) factors. Practitioners
of environmental health seek to prevent adverse effects on
human health and on the ecological systems that are essential
to our well-being.
We face four types of environmental
hazards
ENVIRONMENTAL HEALTH
Examining the impacts of human-made chemicals such as bisphenol A is just one aspect of the broad field of environmental health. The study and practice of environmental health
assesses environmental factors that influence our health and
quality of life. These factors include wholly natural aspects of
S
Physical hazards Physical hazards arise from processes
A that occur naturally in our environment and pose risks to
N human life or health. Some are ongoing natural phenomena, such as excessive exposure to ultraviolet (UV) radiation
F from sunlight, which damages DNA and has been tied to skin
O cancer, cataracts, and immune suppression (FIGURE 10.2A).
We can reduce these risks by shielding our skin from intense
R sunlight with clothing and sunscreen.
D
,
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CHAPTER 10
U.S. Food and Drug Administration (FDA) insisted in
2008 that it saw no reason to regulate BPA, but its own
science advisory committee disagreed, and in 2009
the FDA decided to start a testing program.
In 2008, the Canadian government was the first to
declare bisphenol A toxic, banning its sale and importation. As of 2011, the use of BPA in certain products
for children was banned in China, Malaysia, and in nine
U.S. states. Despite the lack of federal regulation of BPA
in the United States, grassroots lobbying efforts have
led many companies to voluntarily remove BPA from
their products, especially those made for children and
infants. The six major U.S. manufacturers of plastic baby
bottles promised in 2008 to stop using BPA, and the
manufacturer Sunoco stopped selling BPA to companies that use it in children’s products. Nalgene phased
out its BPA-containing polycarbonate water bottles.
The retailers Walmart and Toys “R” Us decided to stop
carrying children’s products with BPA. As a result, concerned parents can now more easily find BPA-free products for their children, but the rest of us remain exposed
through thousands of products (FIGURE 10.1).
Bisphenol A is by no means one of our greatest
environmental health threats. However, it provides a
timely example of how we as a society assess health
risks and decide how to manage them. As scientists
and government regulators assess BPA’s potential
risks, their efforts give us a window on how hormonedisrupting chemicals are challenging the way we
appraise and control the environmental health risks
we face. ■
Environmental Health and Toxicology
We can categorize environmental health hazards into four
main types: physical, chemical, biological, and cultural. Although some amount of risk is unavoidable, much of environmental health focuses on taking steps to minimize the
risks of encountering hazards and to mitigate the impacts of
the hazards we do encounter.
FIGURE 10.1 ▲ Researchers for Consumer Reports magazine
tested these (and more) common packaged foods in 2009; they
found that nearly all of them contained bisphenol A that had
leached from the linings of their containers.
207
(a) Physical hazard
1
3
5
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S (c) Biological hazard
(b) Chemical hazard
(d) Cultural hazard
FIGURE 10.2 ▲ Environmental health hazards come in four types.
The sun’s ultraviolet radiation is an example of a physical hazard (a).
Excessive exposure increases the risk of skin cancer. Chemical hazards (b) include both synthetic and natural chemicals. Much of our
exposure comes from pesticides and household chemical products.
Biological hazards (c) include diseases and the organisms that transmit them. Some mosquitoes, for example, are vectors for pathogenic
microbes, including those that cause malaria. Cultural or lifestyle
hazards (d) include the behavioral decisions we make, as well as the
socioeconomic constraints forced on us. Smoking is a lifestyle choice
that raises one’s risk of lung cancer and other diseases.
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M10_WITH2901_04_SE_C10.indd 207
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Other physical hazards include discrete events such as
earthquakes, volcanic eruptions, fires, floods, landslides,
hurricanes, and droughts. We cannot prevent many of
these hazards, but we can minimize risk by preparing ourselves with emergency plans and avoiding common practices that make us vulnerable to certain physical hazards.
For example, clearing vegetation from hillsides increases
the chance of landslides, and channelizing rivers promotes flooding in some areas while preventing it in others
(p. 261).
Chemical hazards Chemical hazards include many of the
synthetic chemicals that our society manufactures, such as
pharmaceuticals, disinfectants, and pesticides (FIGURE 10.2B).
Some natural substances that we process for our use (such as
hydrocarbons, lead, and asbestos) are also harmful to human
health. Following our overview of environmental health,
much of this chapter will focus on chemical health hazards
and the ways we study and regulate them.
Biological hazards Biological hazards result from ecological interactions among organisms (FIGURE 10.2C). When
we become sick from a virus, bacterial infection, or other
pathogen, we are suffering parasitism (pp. 66–67). This is
what we call infectious disease. Infectious diseases such as
malaria, cholera, tuberculosis, and influenza (flu) are major
environmental health hazards, especially in developing nations with widespread poverty and few resources for health
care. As with physical and chemical hazards, it is impossible for us to avoid risk from biological agents completely, but
through monitoring, sanitation, and medical treatment we
can reduce the likelihood and impacts of infection.
4.5
Respiratory and
digestive diseases
Maternal
and
perinatal
conditions
8.6%
10.3%
6.3%
Injuries
9.8%
12.6%
4.0
Infectious
diseases
14.9 million
23.4%
Cardiovascular
diseases
29.0%
Cancers
Annual deaths (millions)
208
Other
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Cultural hazards Hazards that result from our place of
residence, our socioeconomic status, our occupation, or our
behavioral choices can be thought of as cultural hazards or
lifestyle hazards. We can minimize or prevent some of these
cultural or lifestyle hazards, but others may be beyond our
control. For instance, individuals can choose whether or not
to smoke cigarettes ( FIGURE 10.2D), but exposure to secondhand smoke in the home or workplace may be beyond one’s
control. Much the same might be said for other cultural
hazards such as drug use, diet and nutrition, crime, and
mode of transportation. Environmental justice advocates
(pp. 14–15) argue that “forced” risks from cultural hazards,
such as living near a hazardous waste site, are often higher for
people with fewer economic resources or less political clout.
SThe biological hazard of disease
Ais a focus of environmental health
NDespite all our technological advances, we still find ourselves
battling disease, which causes the vast majority of human
Fdeaths worldwide (FIGURE 10.3A). Over half the world’s
Odeaths result from noninfectious diseases, such as cancer and
disease. These diseases are not spread from one person
Rheart
to another, but rather are influenced by genetics, environDmental factors, and lifestyle choices. For instance, whether a
develops heart disease depends not only on his or her
, person
genes, but also on lifestyle choices such as diet and exercise.
Infectious diseases account for almost one of every
four
B deaths that occur each year—nearly 14 million people
worldwide (FIGURE 10.3B). Some pathogenic viruses, bacteria,
Eand protists attack us directly; others cause infection through
Ta vector, an organism that transfers the pathogen to the host.
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0
Respiratory Diarrheal
infections diseases
(influenza,
pneumonia, etc.)
(a) Leading causes of death across the world
AIDS
TB
Malaria Childhood
diseases
(measles,
pertussis,
tetanus, etc.)
(b) Leading causes of death by infectious disease
FIGURE 10.3 ▲ Infectious disease is the second-leading cause of death worldwide (a), accounting for nearly
one-quarter of all deaths. Six types of diseases (b) —respiratory infections, diarrhea, AIDS, tuberculosis (TB),
malaria, and childhood diseases—account for 80% of all deaths from infectious disease. Data from World Health
Organization, 2009. World health statistics 2009. WHO, Geneva, Switzerland.
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M10_WITH2901_04_SE_C10.indd 208
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Toxicology is the study
of chemical hazards
Although most indicators of human health are improving as
the world’s wealth increases, our modern society is exposing
us to more and more synthetic chemicals. Some of these substances pose threats to human health, but figuring out which
of them do—and how, and to what degree—is a complicated
scientific endeavor. Toxicology is the science that examines
the effects of poisonous chemicals on humans and other
organisms. Toxicologists assess and compare substances
to determine their toxicity, the degree of harm a chemical
substance can inflict. A toxic substance, or poison, is called
a toxicant, but any chemical substance may exert negative
impacts if we ingest or expose ourselves to enough of it. Conversely, a toxicant in a small enough quantity may pose no
health risk at all. These facts are often summarized in the
catchphrase, “The dose makes the poison.” In other words, a
substance’s toxicity depends not only on its chemical identity,
but also on its quantity.
In recent decades, our ability to produce new chemicals
has expanded, concentrations of chemical contaminants in the
environment have increased, and public concern for health
and the environment has grown. These trends have driven the
rise of environmental toxicology, which deals specifically
with toxic substances that come from or are discharged into
the environment. Toxicologists generally focus on human
health, using other organisms as models and test subjects. Environmental toxicologists study animals and plants to determine the ecological impacts of toxic substances, and to see if
other organisms can serve as indicators of health threats that
could soon affect people.
Modern Americans spend roughly 90% of their lives indoors.
Unfortunately, our homes and workplaces, just like the outdoors, can be rife with physical, biological, chemical, and
cultural hazards (TABLE 10.1; also see Figure 13.21, p. 295).
S Cigarette smoke and radon are leading indoor hazards
294–296) and are the top two causes of lung cancer in
A (pp.
developed nations. Homes and offices can have problems with
N toxic compounds produced by mold, which can flourish in
F wall spaces when moisture levels are high. Asbestos, used in
the past as insulation in walls and other products, can be danO gerous when it is inhaled. Lead poisoning from water pipes
R or old paint can cause damage to the brain, liver, kidney, and
stomach; learning problems and behavioral abnormalities;
D anemia; hearing loss; and even death. Lead poisoning among
, U.S. children has greatly declined in recent years as a result of
education campaigns and the phaseout of lead-based paints
and leaded gasoline (p. 5), which was prompted by governB ment regulation to protect public health.
There are also indoor chemical hazards that we have yet
E to discover. One recently recognized hazard is polybrominated
T diphenyl ethers (PBDEs). These compounds are used as fire
retardants in computers, televisions, plastics, and furniture,
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TABLE 10.1 Selected Environmental Hazards










Outdoor Air
Chemicals from automotive exhaust
Chemicals from industrial pollution
Photochemical smog (pp. 288–289)
Pesticide drift
Dust and particulate matter
Environmental Health and Toxicology
People face environmental health
hazards indoors
CHAPTER 10
Infectious disease is a greater problem in developing countries, where it accounts for close to half of all deaths. Infectious disease causes many fewer deaths in developed nations
because their wealth allows their citizens better nutrition,
sanitation, hygiene, and access to medical care.
Decades of public health efforts have lessened the impacts
of infectious disease and even have eradicated some diseases—yet other diseases are posing new challenges. Some, such
as acquired immunodeficiency syndrome (AIDS), continue to
spread globally despite concerted efforts to stop them. Others,
such as tuberculosis and strains of malaria, are evolving resistance to our antibiotics, in the same way that pests evolve resistance to our pesticides (p. 147). Additionally, human-induced
global warming of the climate (Chapter 14) is enabling tropical
diseases (such as malaria, dengue, and cholera) to gain footholds in temperate regions.
In our world of global mobility and dense human populations, novel infectious diseases (or new strains of old diseases)
that emerge in one location are more likely to spread quickly
to other locations. Recent examples include severe acute respiratory syndrome (SARS) in 2003, the H5N1 avian flu starting in 2004, and the H1N1 swine flu that spread across the
globe in 2009–2010. Diseases like influenza, whose pathogens
evolve rapidly, give rise to a variety of strains, making it more
likely that one may turn exceedingly dangerous and cause a
global pandemic (a widespread outbreak of a disease).
Thousands of dedicated people—from doctors and nurses to policymakers to philanthropists—are dedicating their
lives to reducing the incidence of disease and improving human health. They use a diversity of approaches to better the
living conditions of those most affected by infectious disease
by improving access to clean drinking water, sanitation, medical care, and nutritious foods.
209
Water
Pesticide and herbicide runoff
Nitrates and fertilizer runoff
Mercury, arsenic, and other heavy metals in groundwater
and surface water
Food
Natural toxins
Pesticide and herbicide residues
Indoors
Smoking and secondhand smoke
Radon
Lead in paint and pipes
Asbestos
Toxicants (e.g., PBDEs, phthalates, bisphenol A) in plastics
and consumer products
▶ Dust and particulate matter





Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M10_WITH2901_04_SE_C10.indd 209
8/7/11 11:17 PM
and they may evaporate at very slow rates throughout the lifetime of the product. Like bisphenol A, PBDEs appear to act as
hormone disruptors. The European Union decided in 2003 to
ban PBDEs, but in the United States there has so far been little
movement to address the issue.
Risks must be balanced against rewards
As we review the impacts of toxic substances t …
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