1. Environment: The Science behind the Stories
Lecture Outlines
Chapter 14
Environment: The Science behind the Stories
4th Edition
Withgott/Brennan

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Four types of environmental hazards

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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 to antibiotics

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. Silent Spring began the debate over chemicals
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

24. 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

25. Endocrine disruptors mimic hormones
Hormones stimulate growth, development, sexual maturity
Synthetic chemicals
Block hormones
Mimic hormones

26. 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.

27. 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

28. Routes of chemical transport

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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.

36. 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 response

37. 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

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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

44. 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 situation
We fear nuclear power and toxic waste
But not smoking or overeating

45. 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

46. 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

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

48. 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

49. Two approaches for determining safety
Who should have to prove a product is safe: the manufacturers or government/citizens?

50. 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

51. 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

52. 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

53. 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

54. 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

55. 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

56. QUESTION: Review Which of the following is a cultural hazard?
Earthquake
Smoking
Virus
A pesticide
All are biological hazards
Answer: b

57. QUESTION: Review
Which of the following damages the brain and liver, causes learning problems, and comes from water flowing through certain pipes?
Radon
Asbestos
Lead
Polybrominated diphenyl ethers
Answer: c

58. QUESTION: Review 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
Answer: a

59. QUESTION: Review A “carcinogen” causes: Cancer Mutations Birth defects
Problems in the hormonal system
Answer: a

60. QUESTION: Review
A study that studies individual patients (i.e., autopsies) uses:
An epidemiological study
A case history approach
Mainly private funding sources
Probability and risk as major components of the study
Answer: b

61. QUESTION: Review
Which statement about endocrine disruptors is NOT true?
They may show unconventional dose-response curves.
They affect reproduction, development, and immunity.
Industry studies show how really harmful they are.
The endocrine system is vulnerable to very low levels of these disruptors.
Answer: c

62. 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 correct?
Smoking is dangerous and we are anxious about it.
Smoking is not dangerous, but we are anxious about it.
Fire is dangerous, and we are anxious about it.
Fire is not dangerous, but we are anxious about it.
Answer: d

63. 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 population?
About 5 units
About 10 units
About 15 units
You can’t tell from the graph.
Answer: b

64. QUESTION: Viewpoints
Should the United States be able to manufacture and export chemicals that have been banned in the United States?
No; if we won’t have it in the United States, we shouldn’t be able to make and export it to others.
Yes, because the money we get from selling it will help our economy.
Yes; let people decide what they want to do.
Yes; in fact, chemicals should not be banned in the United States either.
Answer: any

65. QUESTION: Viewpoints
How should the U.S. government regulate chemicals?
The government should force industries to prove their products are safe.
The government should prove a chemical is dangerous before it is taken off the market.
Industry knows chemicals best, so decisions such as this should be left up to the industry.
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.
Answer: any