Lecture Outlines
Chapter 14
The Science behind the
4th Edition
© 2011 Pearson Education, Inc.
This lecture will help you understand:
• Environmental health and
• Toxic substances in the
• Hazards and their effects
• Risk assessment and risk
• Philosophical approaches
to risk
• Regulatory policy in the
U.S. and internationally
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Central Case: Poison in the bottle: is
bisphenol A (BPA) safe?
• BPA causes cancer, nerve
damage, and miscarriages
- In extremely low doses
• It is in hundreds of products
- Cans, utensils, baby
bottles, laptops, toys
• BPA leaches into food,
water, air, and bodies
- 93% of Americans have
it in their bodies
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Bisphenol A mimics estrogen
• BPA mimics estrogen, a female hormone
- In lower levels than set by regulatory agencies
• Researchers, doctors, and consumer advocates want
- The chemical industry insists it is safe
• Some countries and states have banned it
- Many companies are removing it voluntarily
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The four types of environmental hazards
• Environmental health = assesses environmental factors
that influence human health and quality of life
- Including natural and human-caused factors
• Physical hazards = occur naturally in our environment
- Earthquakes, volcanoes, fires, floods, droughts
- We can’t prevent them, but we can prepare for them
- We increase our vulnerability by deforesting slopes
(landslides), channelizing rivers (flooding), etc.
- We can reduce risk with better environmental choices
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Chemical and biological hazards
• Chemical hazards = synthetic chemicals such as
pharmaceuticals, disinfectants, pesticides
- Harmful natural chemicals (e.g., venom) also exist
• Biological hazards = result from ecological interactions
- Viruses, bacteria, and other pathogens
- Infectious disease = species parasitize humans,
fulfilling their ecological roles
- Vector = an organism that transfers a pathogen to a
- We can’t avoid risk, but we can reduce infection
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Cultural (lifestyle) hazards
• Cultural = result from where we live, our socioeconomic
status, our occupation, our behavioral choices
- We can minimize some, but not all, of these hazards
- Smoking, drug use, diet and nutrition, crime, mode of
- Health factors (e.g., living near toxic waste) are often
correlated with poverty
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Four types of environmental hazards
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Indoor environmental health hazards
• Radon = a highly toxic,
radioactive gas that is
colorless and undetectable
- It can build up in
• Asbestos = a mineral that
insulates, muffles sounds,
and resists fire
- Asbestosis = scarred
lungs that cease to
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Lead poisoning
• Lead poisoning = caused by lead, a heavy metal
- Damages the brain, liver, kidney, and stomach
- Causes learning problems, behavior abnormalities, and
• Exposure is from drinking water that flows through lead
pipes or from lead paint
Education led to declines
in poisoning, but China
still used it in toy paint
until recently
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A recently recognized hazard
• Polybrominated diphenyl ethers (PBDEs) = has fireretardant properties
- Used in computers, televisions, plastics, and furniture
- Persist and accumulate in living tissue
- Mimic hormones and affect thyroid hormones
- Also affect brain and nervous system development and
may cause cancer
• Concentrations are rising in breast milk
- Now banned in Europe, concentrations have decreased
- The U.S. has not addressed the issue
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Disease is a major focus of environmental
• Despite our technology,
disease kills most of us
• Disease has a genetic and
environmental basis
- Cancer, heart disease,
respiratory disorders
- Poverty and poor
hygiene foster illnesses
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Infectious diseases kill millions
• Infectious diseases kill 15
million people/year
- Half of all deaths in
developing countries
• Money lets developed
countries have access to
hygiene and medicine
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Infectious and noninfectious diseases
• Lifestyles in developed nations affect diseases
- U.S. smoking dropped 38%
- But obesity has doubled
• Public health decreases some infectious diseases
- Some (AIDS) are
- Some develop
resistance to
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Diseases, the environment, and society
• Our mobility spreads diseases
- West Nile Virus spread
from Africa to all lower
48 U.S. states in 5 years
• New diseases are emerging
- H5N1 avian flu, H1N1
swine flu
• Climate change will expand the range of diseases
• To predict and prevent diseases, experts deal with
complicated interrelationships
- In technology, land use, and ecology
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Health workers fight disease
• The best way to reduce disease? Improve the basic living
conditions of the poor
- Food security, sanitation, clean drinking water
• Expanded access to health care
- Health clinics, immunizations, pre- and postnatal care
• Education campaigns work in rich and poor nations
- Public service and governments give advice
- Packaging and ads advise us on smoking, etc.
- Sex and reproductive health education slows
population growth and spread of HIV/AIDS
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Working together to fight disease
• Agencies, organizations, and governments work together
- The United Nations, the World Health Organization,
U.S. Agency for International Development, etc.
- Private organizations donate millions of dollars
- Pharmaceutical companies research new medicines
Sanitation and drinking
water are improving
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Toxicology studies poisonous substances
• Toxicology = the study of the effects of poisonous
substances on humans and other organisms
• Toxicity = the degree of harm a toxicant can inflict
• Toxicant = any toxic substance (poison)
- “The dose makes the poison” = toxicity depends on the
combined effect of the chemical and its quantity
• Environmental toxicology = deals with toxic substances
that come from or are discharged into the environment
- Studies health effects on humans, other animals, and
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Balancing risks and rewards
• There is a tradeoff between the risk and reward of most
- We must judge how these compare
- We use bisphenol A despite its health risks
- Are safer and affordable alternatives available?
• Don’t forget, chemicals have given us our high standard
of living
- Food, medicine, conveniences
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Toxic substances in the environment
• The environment contains
natural chemicals that may pose
health risks
• Toxins = toxic chemicals made
in tissues of living organisms
• But synthetic chemicals are also
in our environment
- Every human carries traces of
industrial chemicals
The U.S. makes or imports 250 lb of
chemicals for every person in the country
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Chemicals are in the air, water, and soil
• 80% of U.S. streams contain 82 contaminants
- Antibiotics, detergents, drugs, steroids, solvents, etc.
• 92% of all aquifers contain 42 volatile organic
compounds (from gasoline, paints, plastics, etc.)
- Less than 2% violate federal health standards for
drinking water
Pesticides are present in
streams and groundwater
in levels high enough to
affect aquatic life
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Synthetic chemicals are in all of us
• Every one of us carries traces of hundreds of industrial
chemicals in our bodies
- Including toxic persistent organic pollutants restricted
by international treaties
• Babies are born “pre-polluted” – 232 chemicals were in
umbilical cords of babies tested
• Not all synthetic chemicals pose health risks
- But very few of the 100,000 chemicals on the market
have been tested
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Silent Spring began the debate over
In the 1960s, untested
pesticides were sprayed over
public areas, with assumption
they would do no harm
• Rachel Carson’s Silent Spring (1962) showed DDT’s
risks to people, wildlife, and ecosystems
• Chemical companies challenged the book
- Discrediting Carson’s personal reputation
• DDT was banned in the U.S. in 1973
- But is still made in the U.S. and exported
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Toxicants come in different types
• Carcinogens = cause cancer
- Hard to identify because of the long time between
exposure and onset of cancer
• Mutagens = cause DNA mutations
- Can cause cancer
• Teratogens = cause birth defects in embryos
• Neurotoxins = assault the nervous system
• Allergens = overactivate the immune system
• Endocrine disruptors = affect the endocrine
(hormone) system
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Endocrine disruptors mimic hormones
• Hormones stimulate growth,
development, sexual maturity
• Synthetic chemicals
- Block hormones
- Mimic hormones
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Many products mimic female hormones
• Bisphenol A binds to
estrogen receptors
• Phthalates in plastics
disrupt hormones
- Toys, perfumes,
- Birth defects, cancer,
reproductive effects
- In the bodies of
everyone in the U.S.
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Toxins may concentrate in water
• Runoff carries toxins from land to surface water
• Chemicals in the soil can leach into groundwater
- Contaminating drinking water
• Chemicals enter organisms through drinking or
- Aquatic organisms (fish, frogs, etc.) are good pollution
• Contaminants in streams and rivers enter drinking water
and the air
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Routes of chemical transport
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Airborne substances can travel widely
• Chemicals can travel by air
- Their effects can occur far
from the site of use
• Pesticide drift = airborne
transport of pesticides
• Synthetic chemicals are
found globally
- In arctic polar bears,
Antarctic penguins, and
people in Greenland
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Some toxicants persist
• Toxins can degrade quickly and become harmless
- Or they may remain unaltered and persist for decades
- Rates of degradation depend on the substance,
temperature, moisture, and sun exposure
• Breakdown products = simpler products that toxicants
degrade into
- May be more or less harmful than the original
- DDT degrades into DDE, which is also highly
persistent and toxic
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Toxicants can accumulate and biomagnify
• Toxicants in the body can be
excreted, degraded, or stored
- Fat-soluble toxicants are
stored in fatty tissues
• Bioaccumulation = toxicants
build up in animal tissues
• Biomagnification =
concentrations of toxicants
become magnified
- Near extinction of peregrine
falcons and bald eagles
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Not all toxicants are synthetic
• Toxic chemicals also exist naturally and in our food
- Don’t assume natural chemicals are all healthy and
synthetic ones are all harmful
• Some scientists feel that natural toxicants dwarf our
intake of synthetic chemicals
- Natural defenses are effective against synthetics
• Environmentalists say synthetic toxins:
- Are harder to metabolize and excrete
- Persist and accumulate
- Enter people in ways other than in food
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Wildlife studies integrate field and lab work
• Museum collections provide data from times before
synthetic chemicals were used
• Measurements from animals in the wild can be compared
to controlled experiments in the lab
Alligators and frogs show
reproductive abnormalities
due to endocrine
disruption from pesticides
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Human studies
• Case history approach = studies individual patients
- Autopsies tell us about lethal doses
- Don’t tell about rare, new, or low-concentration toxins
- Don’t tell about probability and risk
• Epidemiological studies = large-scale comparisons
between exposed and unexposed groups
- Studies can last for years
- Yield accurate predictions about risk
- Measure an association between a health hazard and an
effect – but not necessarily the cause of the effect
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Manipulative experiments show causation
• Animals are used as test subjects
• Mammals share evolutionary history
- Substances that harm rats and mice probably harm us
• Some people object to animal tests
- Medical advances would be
far more difficult without
• New techniques may replace
some live-animal testing
- Human cell cultures,
bacteria, etc.
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Dose-response analysis
• Dose-response analysis = measures the effect a
toxicant produces or the number of animals affected
- At different doses
• Dose = amount of substance
the test animal receives
• Response = the type or
magnitude of negative effects
• Dose-response curve = the
dose plotted against the
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Dose response curves
• LD50/ED50= the amount of toxicant required to kill
(affect) 50% of the subjects
- A high number indicates low toxicity
• Threshold dose = the level where certain responses
- Organs can metabolize or
excrete low doses of a
Scientists extrapolate
downward from animal
studies to estimate the
effect on humans
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Strange dose-response curves
• Sometimes a response decreases as a dose increases
- U- or J-shaped or an inverted-U dose-response curve
• Counterintuitive curves occur with endocrine disruptors
- The hormone system is geared to respond to minute
concentrations (e.g., hormones)
- The endocrine system is
vulnerable to extremely
low concentrations of
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Endocrine disruptions pose challenges
• Unconventional dose-response curves are hard to study
- Or use to set safety standards for toxic substances
• Theo Colburn’s Our Stolen Future (1996) describes how
synthetic chemicals may be changing hormones
• Thousands of studies show that endocrine disruptors
affect reproduction, development, immune functions,
nervous systems, etc.
Industry-funded research
shows no problems, while
government research shows
harmful effects
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Individuals vary in their responses to
• Different people respond differently to hazards
- Affected by genetics, surroundings, etc.
- People in poor health are more sensitive
- Sensitivity also varies with sex, age, and weight
- Fetuses, infants, and young children are more sensitive
• The Environmental Protection Agency (EPA) sets
standards for responses based on adult responses
- Often, standards are not low enough to protect babies
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The type of exposure affects the response
• Acute exposure = high exposure to a hazard for short
periods of time
- Easy to recognize
- Stem from discrete events: ingestion, oil spills,
nuclear accident, etc.
• Chronic exposure = low exposure for long periods of
- More common but harder to detect and diagnose
- Affects organs gradually: lung cancer, liver damage
- Cause and effect may not be easily apparent
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Mixes may be more than the sum of their
• We can’t determine the impact of mixed hazards
- They may act in ways that cannot be predicted from
the effects of each in isolation
- Mixed toxicants can sum, cancel out, or multiply
each other’s effects
• Synergistic effects = interactive impacts that are
greater than the sum of their constituent effects
- New impacts may arise from mixing toxicants
- DDE may cause or inhibit sex reversal, depending on
the presence of other chemicals
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We express risk in terms of probability
• Exposure to health threats doesn’t automatically produce
an effect
- Rather, it causes some probability (likelihood) of harm
• A substance’s threat depends on its identity and strength
- Chance and frequency of an encounter
- An organism’s exposure and sensitivity to the threat
• Risk = the probability that some harmful outcome will
result from a given action, event, or substance
• Probability = describes the likelihood of a certain
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Perceptions of risk may not match reality
Everything we do involves some risk
• We try to minimize risk
- But perception may
not match reality
- Flying versus driving
• We feel more at risk
when we do not control a
- We fear nuclear power
and toxic waste
- But not smoking or
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Analyzing risk quantitatively
• Risk assessment = the quantitative measurement of risk
- Compares risks involved in different activities or
- It identifies and outlines problems
• Risk assessment has several steps:
- The scientific study of toxicity
- Assessing an individual or population’s exposure to
the substance (frequency, concentrations, length)
• Teams of scientific experts review hundreds of studies
- Regulators and the public benefit from informed
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Risk management
• Risk management = decisions and strategies to
minimize risk
• Federal agencies manage risk
- The U.S. has the Centers for Disease Control (CDC),
the EPA, the Food and Drug Administration (FDA)
• Scientific assessments are considered with economic,
social, and political needs and values
• Comparing costs and benefits is hard
- Benefits are economic and easy to calculate
- Health risks (costs) are hard-to-measure probabilities
of a few people suffering and lots of people not
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The process of risk management
Because of the lack of equivalency in measuring costs
and benefits, risk management stirs up debate
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Two approaches to determining safety
• Innocent-until-proven-guilty approach: assumes a
substance is harmless
- Helps technological innovation and economic
- But it allows dangerous substances to be used
• Precautionary principle: assumes a substance is harmful
until it is shown to be harmless
- Identifies troublesome toxicants before being released
- May impede the pace of technology and economic
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Two approaches for determining safety
Who should have to prove a product is safe:
the manufacturers or government/citizens?
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Philosophy affects policy
• Different nations use different policies for regulating
synthetic substances
• Europe incorporates the precautionary principle
• The U.S. uses the innocent-until-proven-guilty approach
• Federal agencies involved in tracking and regulating
synthetic chemicals include:
- The FDA: monitors food, food additives, cosmetics,
drugs, medical devices
- The EPA: regulates pesticides and chemicals not
covered by other laws
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EPA regulation is only partly effective
• The Toxic Substances Control Act (1976) = the EPA
monitors chemicals made in or imported into the U.S.
- The EPA can ban substances that pose excessive risk
• Many health advocates think the TSCA is too weak
- Of 83,000 chemicals, only five have been restricted
- To push for more testing, toxicity must already be
proven, but testing is minimal
• Only 10% of chemicals have been tested for toxicity
- Fewer than 1% are regulated
- Almost none have been tested for endocrine,
nervous, or immune system damage
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FIFRA (1974)
• The Federal Insecticide, Fungicide, and Rodenticide Act
- Charges the EPA with “registering” new pesticides
manufacturers want to market
• The EPA asks the manufacturer to provide information
on safety assessments
- The EPA examines ingredients, use, etc. to determine
risks to people, other organisms, water, or air
- It approves, denies, or sets limits on the chemical’s
sale and use and approves language used on the label
• Hazardous chemicals are approved if economic benefits
outweigh hazards
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Europe’s REACH program
• The EU’s REACH program (Registration, Evaluation,
Authorization, and Restriction of Chemicals) shifts the
burden of proof for safety to industry
• Helps industries research and develop safer products
- Chemicals will be approved, deemed unsafe, or tested
• 1,500 chemicals will be replaced with safer ones
• REACH will cost industry $3.8–7 billion over 11 years
- Health benefits will be $67 billion over 30 years
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The Stockholm Convention on Persistent
Organic Pollutants (POPs)
• Enacted in 2004 and ratified by over 150 nations
• POPs = toxic, persistent chemicals
- Bioaccumulate and biomagnify
- Can travel long distances
• The “dirty dozen” = the 12 most dangerous POPs
• The Stockholm Convention sets guidelines for phasing
out these chemicals
- Encouraging transition to safer alternatives
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• International agreements show that governments are
working to protect society, wildlife, and ecosystems
from toxic chemicals and environmental hazards
• But solutions need more than government regulations
- Consumer choice affects industries
• Once scientific results are in, society’s approach to risk
management determine what policies are enacted
• A safe and happy future depends on knowing the risks
some hazards pose
- Then replacing those substances with safer ones
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Which of the following is a cultural hazard?
A pesticide
All are biological hazards
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Which of the following damages the brain and liver, causes
learning problems, and comes from water flowing through
certain pipes?
Polybrominated diphenyl ethers
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Toxicology is:
The study of the effects of poisonous substances
Any toxic substance
Any substance that causes environmental degradation
The degree of harm a substance can cause
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A “carcinogen” causes:
Birth defects
Problems in the hormonal system
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A study that studies individual patients (i.e., autopsies)
An epidemiological study
A case history approach
Mainly private funding sources
Probability and risk as major components of the study
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Which statement about endocrine disruptors is NOT true?
a) They may show unconventional dose-response
b) They affect reproduction, development, and
c) Industry studies show how really harmful they are.
d) The endocrine system is vulnerable to very low
levels of these disruptors.
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QUESTION: Interpreting Graphs and Data
Our perception, and the reality, of risk often do not
match. Given this graph (reality), and your knowledge of
sources of anxiety (perception), which statement is
a) Smoking is dangerous and
we are anxious about it.
b) Smoking is not dangerous,
but we are anxious about it.
c) Fire is dangerous, and we are
anxious about it.
d) Fire is not dangerous, but we
are anxious about it.
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QUESTION: Interpreting Graphs and Data
If the “low” dose = 5 units of a chemical, the “medium”
dose = 10 units, and the “high” dose = 15 units, how much
of the chemical is required to kill 50% of the study
About 5 units
About 10 units
About 15 units
You can’t tell from
the graph.
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QUESTION: Viewpoints
Should the United States be able to manufacture and
export chemicals that have been banned in the United
a) No; if we won’t have it in the United States, we
shouldn’t be able to make and export it to others.
b) Yes, because the money we get from selling it will
help our economy.
c) Yes; let people decide what they want to do.
d) Yes; in fact, chemicals should not be banned in the
United States either.
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QUESTION: Viewpoints
How should the U.S. government regulate chemicals?
a) The government should force industries to prove their
products are safe.
b) The government should prove a chemical is dangerous
before it is taken off the market.
c) Industry knows chemicals best, so decisions such as
this should be left up to the industry.
d) As long as the product makes money and jobs for the
industry, it should be allowed, even if some people get
sick or die from it.
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