Chapter 7
Human Health and Environmental Toxicology
Lecture Outline:
I. Human Health
A. Two indicators of human health in a given country are life expectancy (how long
people are expected to live) and infant mortality (how many infants die before the age
of one)
B. Health issues in highly developed countries
i.
Average life expectancy for American women is 80 and 75 for American men
ii. A significant fraction of premature deaths in the United States is caused in
part by individual lifestyle habits (poor diet, lack of exercise, smoking)
iii. Healthcare professionals use the body mass index (BMI) to determine whether
a person is overweight and/or obese
C. Health issues in developing nations
i.
Malnutrition, unsafe water, poor sanitation, and air pollution still prevail in
many less developed countries despite gradual improvements in sanitation and
drinking water
ii. Average overall life expectancy for developing countries is 65
iii. Average overall life expectancy for the very poorest developing countries is
<45
iv.
18% of the 57 million deaths that occur worldwide each year are children less
than 5 years of age
D. Emerging and reemerging diseases
i.
Emerging diseases are infectious diseases that were not previously found in
humans; they typically jump from an animal host to the human species (i.e.,
HIV/AIDS, Lyme disease, West Nile virus, influenza (new strains), SARS,
Ebola)
ii. Reemerging diseases are infectious diseases that existed in the past but for a
variety of reasons are increasing in incidence or in geographic range (i.e.,
tuberculosis, yellow fever, malaria, dengue fever)
iii. The main factors involved in the emergence or reemergence of infectious
diseases include
1. Evolution of the infectious organisms
2. Evolution of antibiotic resistance
3. Urbanization (overcrowding, poor sanitation)
4. An increase in elderly who are more susceptible to infection
5. Pollution, environmental degradation, changing weather patterns
6. Growth in international travel and commerce
7. Poverty and social inequality
II. Environmental Pollution and Disease
A. Persistence, bioaccumulation, and biological magnification of environmental
contaminants
Chapter 7
i.
Persistence is a characteristic of certain chemicals that are extremely stable
and may take years to be broken down in to simpler forms by natural
processes
ii. Bioaccumulation is the buildup of a persistent toxic substance
iii. Biological magnification is the increased concentration of toxic chemicals in
the tissues of organisms that are at higher levels in food webs
1. Toxic substances that exhibit all three of these characteristics include
certain pesticides (DDT), radioactive isotopes, heavy metals
(lead/mercury), flame retardants (PBDEs), and industrial chemicals
(PCBs)
2. Natural decomposers (bacteria) have not yet evolved ways to degrade
many synthetic pesticides, therefore leading to the accumulation of
pesticides in the environment and food web
B. Endocrine disrupters are chemicals that mimic or interfere with the actions of the
endocrine systems in humans and wildlife
1. Examples include chlorine-containing industrial compounds (PCBs
and dioxins), heavy metals (lead and mercury), pesticides (DDT,
kepone, dieldrin, chlordane, endosulfan), flame retardants (PBDEs),
and certain plastics and plastic additives such as phthalates
a. Phthalates are ingredients in cosmetics, fragrances, nail polish,
medications, and common plastics used in food packaging, toys
and household products
b. Phthalates have been implicated in birth defects and
reproductive abnormalities
c. Like hormones, they are active at very low concentrations and
appear to alter reproductive development in males and females
of various animal species
2. Hormones are chemical messengers produced by organism in minute
quantities to regulate growth, reproduction and other important
biological functions
III. Determining Health Effects of Environmental Pollution
A. All chemicals, even “safe” chemicals such as sodium chloride (table salt), are toxic if
exposure is high enough
B. The study of toxicants, or toxic chemicals, is called toxicology
i.
Toxicity is measured by the extent to which adverse effects are produced by
various doses of a toxicant
1. Acute toxicity, which ranges from dizziness and nausea to death,
occurs immediately to within several days following a single exposure
2. Chronic toxicity generally produces damage to vital organs, following
a long-term, low-level exposure to chemicals
ii. One complication of toxicology is that each individual’s genes largely
determine that person’s response to a specific toxicant
1. Environmental susceptibility genes affect how the body metabolizes
toxicants
2. Other gene variations allow certain toxicants to bind strongly – or less
so – to DNA
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iii.
Children and chemical exposure
1. Children are more susceptible to most chemicals than are adults
because their bodies are still developing and are not as effective in
dealing with toxicants
2. Pesticides and children
a. The EPA estimates that 84% of U.S homes use pesticide
products
b. More than 65,000 reports of exposure and possible poisoning
from household pesticides, involving children, occur each year
3. Identifying cancer-causing substances
a. Toxicology and epidemiology are the two most common
methods for determining whether a chemical causes cancer
b. Although epidemiological studies have the advantage that they
look at people who were actually exposed to the chemical,
several limitations still exist
i. It is difficult to reconstruct, or estimate, historical doses
ii. Various confounding factors exist (additional
exposures)
iii. Individuals respond differently
iv.
Chemical mixtures interact by additivity, synergy, or antagonism
1. Additivity – the effect is exactly what one would expect, given the
individual effects of each component of the mixture (1+1=2)
2. A synergistic chemical mixture has a greater combined effect than
expected (1+1=3)
3. An antagonistic interaction in a chemical mixture results in a smaller
combined effect than expected (1+1=1.3)
IV. Ecotoxicology: Toxicant Effects on Communities and Ecosystems
A. There has been a paradigm shift in the way people think about toxicant effects on
communities and ecosystems
i.
People used to think - and some still do – that “the solution to pollution is
dilution” (the dilution paradigm)
ii. Today virtually all environmental scientists have rejected the dilution
paradigm in favor of the boomerang paradigm – “what you throw away can
come back and hurt you”
B. Ecotoxicology (aka environmental toxicology) studies contaminants in the biosphere,
including their harmful effects on ecosystems
i.
Its scope is broad – from molecular interactions to global climate change
ii. It helps policymakers determine the costs and benefits of the many industrial
and technological “advances” that affect us and the ecosystems
1. Obtaining higher-level information is complicated because natural
systems are exposed to many environmental stressors
2. Also, natural systems must be evaluated for extended periods to
establish trends, and results must be clear enough for evaluation by
policymakers and the public
V. Decision Making and Uncertainty: Assessment of Risks
A. Risk management is the process of identifying, assessing, and reducing risks
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i.
Risk is the probability that a particular adverse effect will result from some
exposure or condition
ii. A hazard is a condition that has the potential to cause harm
iii. Effective risk management cannot be based on calculated risks alone, but must
also account for intuition, trust, and social conditions
B. Cost-benefit analysis of risks analyzes the estimated cost of some regulation to reduce
risk compared with potential benefits associated with that risk reduction
C. The precautionary principle is the idea that no action should be taken or product
introduced when the science is inconclusive and unknown risks may exist; it puts the
burden of proof on the developers
D. Ecological risk assessment involves hazard identification, dose-response assessment,
exposure assessment, and risk characterization
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In-Class Activities:
Instructor Notes for In-Class Activity 1
Title:
Contrasting Human Health Issues in the Developed and Developing
World
Time:
Materials:
Handouts:
5 – 10 minutes prep; 15 – 20 minutes in class
Tally master sheet or template (see below)
One
Procedures:
Distribute handouts to all students. Students will spend one or two
minutes filling out a worksheet that assesses the types of diseases and
other causes of death they have encountered at a personal level. They will
then tally their results in small groups, and discuss any uncertainties they
may have encountered. One student will then report back to the larger
group, and the instructor or a student will tally the list for the full class.
This list will represent diseases familiar to the US. The instructor can
then challenge the students to think about rates of the same diseases and
causes of death in less developed countries.
Fill out the worksheet. Then, working in groups of 3 - 4, tally your
Student
Instructions: group’s results, and talk about any uncertainties you may have. Choose
one member of your group to report back to the class.
After full class has been tallied, ask students to return to their group of 3
– 4, and discuss this question: how do you think these numbers would
differ in a less developed country (perhaps Bangladesh or Zaire). Why?
Would the differences be more pronounced among the young, middle
aged, or old?
Have groups take turn reporting their ideas back to the full class (number
of ideas per group will depend on total size of class).
Specific
Suggestions:
Objectives:
1. Prepare a master tally sheet for the classroom—whether an
overhead, PowerPoint slide or template to copy onto the board.
2. Feel free to add other “conditions” to the table below, or allow
students to add other conditions by adding blank lines.
3. Be sure to ask whether any students are from or have personal
contacts in developing countries.
Contrast health issues in highly developed and developing countries
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In-Class Activity 1: Handout
Condition
Know
someone who
has or has had
the condition
Know someone
who has died
from the
condition
Malaria
Obesity
Heart Disease
Diarrhea (infant)
Tuberculosis
Car accident
Polio
HIV / AIDS
Starvation
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Have heard of
someone in US
with the
condition
Have heard of
someone in US
who has died
from the
condition
Chapter 7
Instructor Notes for In-Class Activity 2
Title:
Estimating Bioaccumulation: DDT in a lake
Time:
5 - 10 minutes prep; 15 - 25 minutes in class (depends on students’ math
skills)
Calculators or computers with spreadsheets
One (see below)
Materials:
Handouts:
Procedures:
Students will calculate a hypothetical bioaccumulation of the common
lipophilic pesticide DDT as it progresses through the food chain from
algae to fish to humans. First, students will work through an example
calculation: a starting concentration of DDT found in algae is used that to
calculate the total amount of DDT consumed by a shrimp. The amount
consumed by the shrimp divided by the weight of the shrimp will yield
an approximate concentration of DDT in the shrimp. A similar
calculation will yield the concentration of DDT in a fish, and another will
yield the concentration in an adult human.
Complete the calculations on the worksheet below.
Student
Instructions:
Specific
Suggestions:
Objectives:
1. Assess the math skills of your students before doing this exercise.
If they have solid basic math skills, they should be able to do this
alone. Alternatively, have them work in small groups.
2. If you have access to computers, these equations can easily be set
up in a spreadsheet program.
3. For advanced students, consider varying the various consumption
rates and body weights, consider the case of children, and / or plot
the bioaccumulation in humans as they age.
Demonstrate how bioaccumulation can lead from small exposures to
large exposures through the food chain.
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In-Class Activity 2: Handout
Estimating Bioaccumulation: DDT in a Lake
(Note: this is a hypothetical example.)
A medium sized lake can serve as a major food source for a subsistence community. Suppose
that a community of about 100 people gets much of its protein from fishing on such a lake. Every
day, each person eats one or two fish, which weigh on average about 150 grams. The fish feed
primarily on shrimp, as well as insects and other small animals. You have learned that an alga
that is one of the primary food sources for shrimp in the lake is contaminated with DDT, a
persistent organic pesticide that farmers upstream have begun using to control ants in food crops.
You want to know how much of this DDT might eventually end up in members of the
community.
The following shows how to calculate the concentration of DDT in the shrimp, given the
concentration in algae and the eating habits of the shrimp.
Knowns:
 Algae contain about 0.0002 mg of DDT per gram of algae. That is about 0.2 parts per
million (ppm).
 Over its (short) life, a shrimp will grow to weigh about 1 gram
 The average shrimp eats about 10 grams of contaminated algae during its life.
The amount of DDT consumed by the shrimp can then be calculated:
DDT consumed by shrimp = amount algae consumed × concentration of DDT in algae
So
 DDT consumed by shrimp = 10 galgae × 0.0002 mgDDT per galgae = 0.002 mgDDT


Since a shrimp weighs 1 gram, the concentration of DDT in the shrimp is
0.002 mgDDT / gshrimp, or about 2 ppm

This assumes that ALL of the DDT consumed by the shrimp stays in its body (a “worst
case” assumption that is probably not true).
Now, use this same method to estimate the eventual concentration of DDT in fish and in humans,
given the following information:
 The average fish eats about 1.7 kg of shrimp as it grows to weigh 150 g.
 The average person eats 1 – 2 fish per day over a 60 year life.
 The average adult weighs about 70 kg.
 Note that you will have to compute the total amount of fish eaten by multiplying the
amount eaten per day by the number of days in the individual’s life.
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Instructor Notes for In-Class Activity 3
Title:
Creating and Interpreting Dose-Response Curves
Time:
Materials:
Handouts:
10 minutes prep; 15 - 25 minutes in class
None
Instruction sheet, graphs
Procedures:
Students will chart
Working in groups of 3-4, create a Dose-Response curve given the data
Student
Instructions: and instructions on the worksheet. Use this dose-response curve to
answer the questions on the worksheet. Discuss as a class.
Specific
Suggestions:
Provide students with multiple copies of the graph sheet.
Consider using additional real or hypothetical dose-response data so that
students will see a range of possible curves, including thresholds and
even hormetic (beneficial) effects as shown in the Environmental news
clip.
Objectives:
Describe how a dose-response curve helps determine the health effects of
environmental pollutants.
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In-Class Activity 3: Handout 1
Suppose that some mice are fed a chemical called EMBS every day for about two years. They
are then tested for cancer. The results of this test are listed in the table below. Note that animals
are usually given doses based on their body weights, so smaller animals would get relative small
total doses, but still the same in proportion to their weights.
Dose (mg EMBS /
kgmouse body weight / day)
0
3
6
12
Number of
mice
73
69
75
75
Number of mice
with tumors
0
7
16
30
P(Cancer)
0.10
 7 / 69
1. What do these data tell us about the carcinogenic potential of EMBS?
a. Can it cause cancer in mice?
b. Can it cause cancer in humans?
2. Fill in the fourth column, using the example provided as a guide
3. Graph the EMBS dose-response curve on the following page. Does EMBS appear to have
a threshold for mice?
4. Suppose you fed another group of mice 24 mg EMBS / kgmouse body weight / day. How many
would you expect to get cancer? Why?
5. Suppose you fed yet another group of mice 1 mg EMBS / kgmouse body weight / day. How
many would you expect to get cancer? Why?
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Instructor Notes for In-Class Activity 4
Title:
Populations and disease
Time:
Materials:
Handouts:
5 minutes prep; 60 minutes in or out of class
Internet access
None
Procedures:
Divide the students into groups and assign them a continent of the world.
They can either draw their continent out of a hat or sign up for one. The
continents are Australia, North America, South America, Africa, Asia,
Europe instead of Antarctic use the islands of the word.
After the students are divided into continents have them research the
populations for their continents and the various diseases for the current
time period. Have them make a graft or some visual to explain to the
class their findings. A second part to this activity is to go back 100 years
and find the population and what disease have gone through their
continent. Have the diseases changed, have the populations increased or
decreased etc. When they come up with these facts they can superimpose
them over the previous graft and relate the difference, if significant.
Student
Instructions:
Choose a continent from the following:
Australia
Asia
Africa
Europe
North America
South America
World islands (this is not a continent, but is full of information)
Research the population of your continent and the diseases of this time
period.
After completion draw a graph or some visual and present to the class
stating what the current population of your continent is and what are the
major diseases plaguing the population of your continent.
Second Step: Now research the above by going back 100 years and has
the population increased or decreased? What were the diseases back
then? Are the disease today mostly environmentally induced or are they
the same disease have evolved from one hundred years ago. Again after
completion put a visual, a graph, poster presentation, power point
together to present to the class.
Specific
Suggestions:
None
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Chapter 7
Objectives:



Define the population for a specific continent.
Define the disease of that population.
Describe the difference of population and disease from present time
to one hundred years ago.
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Instructor Notes for In-Class Activity 4
Title:
Cataloging Toxins in the Home
Time:
Materials:
Handouts:
0 minutes prep; 15 - 25 minutes in class
Internet access
None
Procedures:
Have students catalog toxins found in their living environments, and
discuss how well prepared they are to manage them.
Options: go on the internet to find “Material Safety Data Sheets”
(MSDS’s) for these substances
Have students check the lists they generate at home after they have
returned to their homes.
 Were they fairly accurate?
 Did they omit entire classes of materials?
 Did they consistently omit the same types of substances?
Working in groups as assigned by your instructor, generate a list of toxic
Student
Instructions: substances you have in your home. It may be useful to do this by thinking
room by room. If you live in a dorm, consider other toxic substances that
you might come in contact with.
1. How well do you understand the potential effects of these
substances
2. To what extent are you prepared to handle these materials,
including cleanup after spills?
3. How many of these do you know how to dispose of properly?
Specific
Suggestions:
None
Objectives:
Describe common but potentially toxic household materials and
appropriate management practices.
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Answers to Thinking About the Environment
End of Chapter Questions:
1. What are the three leading causes of death in the United States? How are they related to
lifestyle choices?
Ans: The three leading causes of death in the United States are cardiovascular diseases (of the
heart and blood vessels), cancer, and chronic obstructive pulmonary disease (of the lungs); these
diseases are noninfectious chronic health problems, and many are associated with aging. A
significant fraction of premature deaths in the United States are caused in part by individual
lifestyle habits involving poor diet, lack of exercise, and smoking.
2. Why are public health researchers concerned about “exporting” health problems associated
with developed countries to less developed countries?
Ans: Research suggests that many unhealthy lifestyles associated with developed countries,
including smoking, obesity and diabetes, are increasingly common in less developed countries.
As people in less developed countries adopt unhealthly lifestyles the rate of cardiovascular
diseases (of the heart and blood vessels), cancer, and chronic obstructive pulmonary disease (of
the lungs) increases.
3. A researcher who studies obesity once described the cause of obesity as a combination of
“computer chips and potato chips.” Explain what he meant.
Ans: Obesity is not only linked to what and how much you eat but how much physical activities
you engage in. Computers have made many people much less physically active then they were a
generation ago.
4. What was the first viral disease to be globally eradicated? What disease do health officials
hope will be eradicated soon?
Ans: During the 20th century smallpox was eliminated worldwide. Health officials hope that
polio will be eradicated soon.
5. What is a “pandemic,” and why does the potential for pandemics trouble many public health
officials?
Ans: A pandemic is a disease that reaches nearly every part of the world, and has the potential to
infect almost every person. A pandemic could kill millions or billions of people within a single
year. In an era of global travel a virus could be spread around the world very quickly.
6. Distinguish among persistence, bioaccumulation, and biological magnification.
Ans: Chemicals that exhibit persistence are extremely stable and may take many years to be
broken down into simpler forms by natural processes. Bioaccumulation is the buildup of a
persistent toxic substance in an organism's body, often in the fatty tissues. Biological
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magnification is the increased concentration of toxic chemicals in the tissues of organisms that
are at higher levels in food webs
7. How do acute and chronic toxicity differ?
Ans: Acute toxicity is adverse effects that occur within a short period after exposure to a
toxicant. Chronic toxicity is adverse effects that occur some time after exposure to a toxicant, or
after extended exposure to the toxicant
8. What is a dose-response curve? What can it tell us about effects at low doses if experimental
information is on high doses?
Ans: A dose of a toxicant is the amount that enters the body of an exposed organism. A doseresponse curve shows the effect of different doses on a population. Typically, scientists first test
the effects of high doses and then work their way down to a threshold level, the maximum dose
with no measurable effect (or, alternatively, the minimum dose with a measurable effect). It is
assumed that doses lower than the threshold level will not have an effect on the organism and are
safe. However, if experimental information only exists for high doses the curve will not tell us
how small doses effect a population.
9. Examine this cartoon criticizing cutbacks in pollution testing in the mid-1990s. What does
the cartoon suggest about the relative value of toxicological information and epidemiological
testing? Do you think this is a reasonable comparison? Explain your answer.
Ans: Answers will vary.
10. Describe three ways that chemical mixtures can interact. Which of these is usually assigned
when the effects of chemical mixtures are unknown?
Ans: Chemical mixtures interact by additivity, synergy, or antagonism. When a chemical mixture
is additive, the effect is exactly what one would expect, given the individual effects of each
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component of the mixture. If a chemical with a toxicity level of 1 is mixed with a different
chemical with a toxicity level of 1, the combined effect of exposure to the mixture is 2. A
synergistic chemical mixture has a greater combined effect than expected; two chemicals, each
with a toxicity level of 1, might have a combined toxicity of 3. An antagonistic interaction in a
chemical mixture results in a smaller combined effect than expected; for example, the combined
effect of two chemicals, each with toxicity levels of 1, might be 1.3. Toxicologists assign risk to
unknown mixtures by additivity. Such an approach usually underestimates but may sometimes
overestimate the risk involved, but it is the best approach currently available.
11. Describe the common methods for determining whether a chemical causes cancer.
Ans: Toxicologists expose laboratory animals such as rats to varying doses of the chemical and
see whether they develop cancer. Usually, two, three or four groups of animals are exposed to
different amounts or doses, including a “control group” that is not exposed. At the end of the
experiment (about two years for mice and rats), the animals are dissected, and the ratio of
animals with tumors to animals without in each group is recorded. Epidemiologists look at
historical exposures of humans to the same chemical, and see whether exposed groups show
increased cancer rates. Ideally, a cohort or group of individuals who were exposed to the
chemical are compared to an otherwise similar group who were not exposed.
12. Distinguish between the dilution paradigm and the boomerang paradigm.
Ans: The dilution paradigm motto would be “the solution to pollution is dilution.” In this
paradigm you could discard pollution into the environment and it would be diluted sufficiently to
cause no harm. Today virtually all environmental scientists have rejected the dilution paradigm
in favor of the boomerang paradigm: “what you throw away can come back and hurt you.” The
boomerang paradigm makes it unacceptable to discards toxicants into the environment. This
paradigm was adopted during the latter half of the 20th century after several well-publicized
events captured the public's attention. Notable among these events was the discovery that the
pesticide DDT was accumulating in birds at the top of the food web.
13. Select one of the two choices to complete the following sentence, and then explain your
choice: The absence of certainty about the health effects of an environmental pollutant (is/is not)
synonymous with the absence of risk.
Ans: Answers will vary.
14. Why might industrial interests be more strongly opposed to the precautionary principle than
are environmental advocacy organizations?
Ans: The precautionary principle is the idea that no action should be taken or product introduced
when the science is inconclusive but unknown risks may exist. The precautionary principle puts
the burden of proof on the developers of the new technology or substance, who must demonstrate
safety beyond a reasonable doubt. Therefore, industry interest would oppose the principle
because they feel it limits trade and new technology. Environmental advocacy groups feel human
health is the first priority and therefore, caution must be used.
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15. How are risk assessments for human health and ecological risk assessments for
environmental health alike? How do they differ?
Ans: Risk assessment involves using statistical methods to quantify the risks of a particular
action so that they can be compared and contrasted with other risks. Like human health risk
assessment, ecological risk assessment involves hazard identification, dose-response assessment,
exposure assessment, and risk characterization. Human health risk assessment may look at the
increased risk of developing cancer after exposure to contaminants in drinking water. In contrast
ecological risk assessment works on a wide scale, from individual animals or plants in a local
area to ecological communities across a large region.
16. Why is knowledge of ecotoxicology essential to human well-being? Why must we think in
terms of systems and interactions in order to understand both human and environmental health?
Ans: Since the environmental impacts of DDT was brought to light, many other environmental
problems have arisen. As a result the field of ecotoxicology was created to look at contaminants
in the environment. Knowledge of these contaminants is necessary to maintain human wellbeing. Expanding knowledge in ecotoxicology indicates many examples of linkages between
human health and the health of natural systems. If the health of natural systems is declining,
human health will also be adversely effected.
Answers to Review Questions
Human Health (p. 153)
1. What is the average life expectancy for a woman in Japan? a woman in Zambia? Explain the
difference.
Ans: In a highly developed country such as Japan, the average life expectancy for a woman is 85.
In contrast, in Zambia, a less developed country, the average life expectancy is 35 for women. A
Japanese child receives good health care, including vaccinations, and has sufficient nutrition for
growth and development. As Japanese people age, they may develop the chronic degenerative
diseases associated with aging, but they have access to quality health care, medications, and
rehabilitation services. Many Zambian children receive few immunizations or adequate nutrition
for normal growth and development; many children are underweight. Those Zambians who
survive middle age often die prematurely because they lack treatment for the chronic
degenerative diseases associated with aging.
2. What are three health issues for children in developing countries?
Ans: Malnutrition, unsafe water, and poor sanitation still prevail in many less developed
countries.
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Environmental Pollution and Disease (p. 157)
1.What are the differences among persistence, bioaccumulation, and biological magnification?
How are these chemical characteristics interrelated?
Ans: Chemicals that exhibit persistence are extremely stable and may take many years to be
broken down into simpler forms by natural processes. Bioaccumulation is the buildup of a
persistent toxic substance in an organism's body. Biological magnification is the increased
concentration of toxic chemicals in the tissues of organisms that are at higher levels in food
webs.
2. How did the 1980 chemical spill in Lake Apopka affect alligators?
Ans: Male alligators living in Lake Apopka in the years following the spill had low levels of
testosterone (an androgen) and elevated levels of estrogen. Their reproductive organs were often
feminized or abnormally small, and the mortality rate for eggs was extremely high.
Determining Health Effects of Environmental Pollution (p. 163)
1. What is toxicology?
Ans: Toxicology is the study of chemicals with adverse human health effects (toxicants).
2. Why are children particularly susceptible to environmental contaminants such as pesticides?
Ans: Children are more susceptible to most chemicals than are adults because their bodies are
still developing and are not as effective in dealing with toxicants. Children are also more
susceptible to chemicals because they weigh substantially less than adults. Children also tend to
play on floors and lawns, where they are exposed to greater concentrations of pesticide residues
and very young children are more likely to put items in their mouths.
Ecotoxicology: Toxicant Effects on Communities and Ecosystems (p. 165)
1. What environmental catastrophe was largely responsible for replacement of the dilution
paradigm by the boomerang paradigm?
Ans: According to the dilution paradigm, “the solution to pollution is dilution.” Environmental
scientists reject the dilution paradigm in favor of the boomerang paradigm, which is “what you
throw away can come back and hurt you.” The boomerang paradigm was adopted after the
discovery that the pesticide DDT was accumulating in birds at the top of the food web. The
implications were that DDT represented an unacceptable threat to ecosystem health and human
health.
2. What is ecotoxicology?
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Ans: Ecotoxicology is the study of contaminants in the biosphere, including their harmful effects
on ecosystems.
Decision Making and Uncertainty: Assessment of Risks (p. 169)
1. What is risk assessment?
Ans: Risk assessment is the process of estimating the probability of harm (such as injury,
disease, death, or environmental damage) occurring under certain circumstances.
2. What is the precautionary principle?
Ans: The precautionary principle is the policy that no action should be taken if there is any
reason to think harm might be caused. A new technology or chemical product suspected of
threatening human health or the environment should not be introduced until it is demonstrated
that the risks are small and that the benefits outweigh the risks.
3. What information does a cost-benefit analysis provide decision makers?
Ans: In a cost-benefit analysis, the estimated cost of some regulation is compared with potential
benefits. Cost-benefit analysis is an important mechanism to help decision makers formulate
environmental legislation, but it is only as good as the data and assumptions on which it is based.
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