lecture outlines...© 2011 pearson education, inc. this lecture will help you understand: •...

© 2011 Pearson Education, Inc.

Lecture Outlines

Chapter 14

Environment:The Science behind the

Stories

4th Edition

Withgott/Brennan


This lecture will help you understand:

• Environmental health and hazards

• Toxic substances in the environment

• Hazards and their effects• Risk assessment and risk

management• Philosophical approaches

to risk• Regulatory policy in the

U.S. and internationally


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


Bisphenol A mimics estrogen

• BPA mimics estrogen, a female hormone- In lower levels than set by regulatory agencies

• Researchers, doctors, and consumer advocates want regulation- The chemical industry insists it is safe

• Some countries and states have banned it- Many companies are removing it voluntarily


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


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

host- We can’t avoid risk, but we can reduce infection


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

transportation- Health factors (e.g., living near toxic waste) are often

correlated with poverty


Four types of environmental hazards


Indoor environmental health hazards

• Radon = a highly toxic, radioactive gas that is colorless and undetectable - It can build up in

basements• Asbestos = a mineral that

insulates, muffles sounds, and resists fire- Asbestosis = scarred

lungs that cease to function


Lead poisoning• Lead poisoning = caused by lead, a heavy metal

- Damages the brain, liver, kidney, and stomach- Causes learning problems, behavior abnormalities, and

death• 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


A recently recognized hazard

• Polybrominated diphenyl ethers (PBDEs) = has fire-retardant 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


Disease is a major focus of environmental health• 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


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


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

spreading - Some develop

resistance toantibiotics


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


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


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


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

ecosystems


Balancing risks and rewards

• There is a tradeoff between the risk and reward of most hazards- 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


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


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


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


Silent Spring began the debate over chemicals

• 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

In the 1960s, untested pesticides were sprayed over public areas, with assumption they would do no harm


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


Endocrine disruptors mimic hormones

• Hormones stimulate growth, development, sexual maturity

• Synthetic chemicals - Block hormones- Mimic hormones


Many products mimic female hormones

• Bisphenol A binds to estrogen receptors

• Phthalates in plastics disrupt hormones- Toys, perfumes,

makeup- Birth defects, cancer,

reproductive effects- In the bodies of

everyone in the U.S.


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

absorption- Aquatic organisms (fish, frogs, etc.) are good pollution

indicators• Contaminants in streams and rivers enter drinking water

and the air


Routes of chemical transport


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


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

substance- DDT degrades into DDE, which is also highly

persistent and toxic


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


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


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


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


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 them

• New techniques may replace some live-animal testing- Human cell cultures,

bacteria, etc.


Dose-response analysis

• Dose = amount of substance the test animal receives

• Response = the type or magnitude of negative effects

• Dose-response curve = the dose plotted against the response

• Dose-response analysis = measures the effect a toxicant produces or the number of animals affected- At different doses


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 occur- Organs can metabolize or

excrete low doses of a toxicant

Scientists extrapolate downward from animal studies to estimate the effect on humans


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 chemicals


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


Individuals vary in their responses to hazards

• 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


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

time- More common but harder to detect and diagnose- Affects organs gradually: lung cancer, liver damage- Cause and effect may not be easily apparent


Mixes may be more than the sum of their parts

• 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


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 outcome


Perceptions of risk may not match reality

• 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 situation- We fear nuclear power

and toxic waste- But not smoking or

overeating

Everything we do involves some risk


Analyzing risk quantitatively

• Risk assessment = the quantitative measurement of risk - Compares risks involved in different activities or

substances - 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 summaries


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


The process of risk management

Because of the lack of equivalency in measuring costs and benefits, risk management stirs up debate


Two approaches to determining safety

• Innocent-until-proven-guilty approach: assumes a substance is harmless- Helps technological innovation and economic

advancement- 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

advance


Two approaches for determining safety

Who should have to prove a product is safe: the manufacturers or government/citizens?


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


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


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


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

further• 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


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


Conclusion

• 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


QUESTION: Review

Which of the following is a cultural hazard?

a) Earthquakeb) Smokingc) Virusd) A pesticidee) All are biological hazards


QUESTION: Review

Which of the following damages the brain and liver, causes learning problems, and comes from water flowing through certain pipes?

a) Radonb) Asbestosc) Leadd) Polybrominated diphenyl ethers


QUESTION: Review

Toxicology is:

a) The study of the effects of poisonous substancesb) Any toxic substancec) Any substance that causes environmental degradationd) The degree of harm a substance can cause


QUESTION: Review

A “carcinogen” causes:

a) Cancerb) Mutationsc) Birth defectsd) Problems in the hormonal system


QUESTION: Review

A study that studies individual patients (i.e., autopsies) uses:

a) An epidemiological studyb) A case history approachc) Mainly private funding sourcesd) Probability and risk as major components of the study


QUESTION: ReviewWhich statement about endocrine disruptors is NOT true?

a) They may show unconventional dose-response curves.

b) They affect reproduction, development, and immunity.

c) Industry studies show how really harmful they are.d) The endocrine system is vulnerable to very low

levels of these disruptors.


QUESTION: Interpreting Graphs and DataOur 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 correct?

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.


QUESTION: Interpreting Graphs and DataIf 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 population?

a) About 5 unitsb) About 10 unitsc) About 15 unitsd) You can’t tell from

the graph.


QUESTION: Viewpoints

Should the United States be able to manufacture and export chemicals that have been banned in the United States?

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.


QUESTION: ViewpointsHow 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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