1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 14 Environmental Health and Toxicology Part A PowerPoint ® Slides prepared by Jay Withgott and Kristy Manning Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

2. This lecture will help you understand: Environmental health hazards Environmental health goals Synthetic and natural toxicants Study of hazards and their effects Risk assessment and risk management Policy and regulation

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Central Case: Alligators and Endocrine Disruptors at Lake Apopka, Florida Biologist Louis Guillette found alligators with reproductive abnormalities in a Florida lake. The lake had been contaminated with pesticides. Research revealed that chemicals in the lake were disrupting the animals’ reproductive hormones.

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Environmental health Environmental health: RISK ASSESSMENT: Assesses environmental factors that influence human health and quality of life. RISK MANANGEMENT: Seeks to prevent adverse effects on human health and ecological systems. Contains environmental toxicology within its scope.

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Environmental health hazards Synthetic and natural toxicants are only one type of environmental health threat. Others are: Physical hazards (floods, blizzards, landslides, radon, UV exposure) Chemical hazards (disinfectants, pesticides) Biological hazards (viruses, bacterial infections) Cultural or lifestyle hazards (drinking, smoking, bad diet, crime in neighborhood)

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Environmental health hazards

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Infectious disease In communicable or transmissable disease, a pathogen attacks a host, either directly or through a vector (e.g., mosquito that transfers a malaria parasite to hosts) … and the pathogen can be transmitted from one host to another. Infectious disease causes 25% of deaths in the world and nearly half of deaths in developing nations.

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Infectious disease 2nd-leading cause of death worldwide 6 diseases account for 80% of infectious disease deaths

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings West Nile Virus West Nile Virus has spread rapidly since 1999.

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Many health hazards exist indoors Substances in plastics and consumer products Lead in paint and pipes Radon Asbestos PBDE fire retardants

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Synthetic chemicals are everywhere in our environment Many thousands have been produced and released. Some persist for long time periods or travel great distances. 2002 USGS study: 80% of U.S. streams contain up to 82 wastewater contaminants, which include antibiotics, perfumes, detergents, drugs, steroids, disinfectants, etc.

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Synthetic chemicals Of the 100,000 synthetic chemicals on the market today, very few have been thoroughly tested for harmful effects.

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Synthetic chemicals are numerous

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Rise of synthetic chemicals Widespread synthetic chemical production after WWII People are largely unaware of the health risks of many toxicants. The potent insecticide DDT was sprayed widely in public areas, even on people.

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Silent Spring and Rachel Carson Carson’s 1962 book alerted the public that DDT and other pesticides could be toxic to animals and people. Further research led the EPA to ban DDT in 1973. These developments were central to the modern environmental movement.

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of toxicants: Teratogens The drug thalidomide, used to relieve nausea during pregnancy, turned out to be a potent teratogen, and caused thousands of birth defects before being banned in the 1960s. “Thalidomide baby” Butch Lumpkin learned to overcome his deformed arms and fingers to become a professional tennis instructor.

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings All toxicants are not synthetic Although toxicology tends to focus on man- made chemicals, it’s important to keep in mind that there are plenty of natural toxicants. Many are toxins produced by animals or plants for protection against predators and pathogens.

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk Risk = the mathematical probability that some harmful outcome will result from a given action, event, or substance Probability = a quantitative description of the likelihood of a certain outcome Harmful outcome could be defined as injury, death, environmental damage, economic loss, etc.

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Perception different from reality Our perception of risks tends not to match statistical reality. smoking plane crash

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Perception different from reality © Scope Report 27 - Climate impact assessment, Chapter 16, Figure 16.5, ed. by RW Kates, JH Ausubel, and M Berberi J Wiley & Sons Ltd, UK (1985). Adapted from: Slovic et al. Rating the risks. Environment, 21(3) 14-39 (1979).

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk assessment Analyzes risks quantitatively Measures and compares risks involved in different activities or substances Helps identify and prioritize serious risks Helps determine threats posed to humans, wildlife, ecosystems

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk assessment Involves: Dose-response analysis or other tests of toxicity Assessing likely exposure to the hazard (concentration, time, frequency)

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk management Consider risk assessments in light of social, economic, and political needs and values. Weigh costs and benefits, given both scientific and nonscientific concerns. Decide whether or not to reduce or eliminate risk.

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk assessment and risk management inform policy Following risk management, policy decisions are made.

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Risk assessment and risk management inform policy

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Philosophical approaches “Innocent until proven guilty”: Assume harmless until shown to be harmful Precautionary principle:Precautionary principle Assume harmful until shown to be harmless

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Implications for product testing “Innocent until proven guilty”: Industry can introduce any products it wants. Government bears the burden of proof to show if products are dangerous. Precautionary principle: Industry cannot introduce a product until it is very thoroughly tested and shown convincingly to be harmless.

28. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Implications for product testing Industry has pressured government to take an “innocent- until-proven- guilty” approach. Environmental advocates have pressured government to follow the precautionary principle.

29. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Federal agencies and risk management In the U.S., most risk management is conducted by federal and state agencies. Particularly: Environmental Protection Agency and Food and Drug Administration

30. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Policy on toxicants Key agencies and products they regulate: Food and Drug Administration (FDA) -food, additives, cosmetics, drugs, medical devices Environmental Protection Agency (EPA) -FIFRA: Federal Insecticide, Fungicide and Rodenticide Act -TSCA: Toxic Substances Control Act -pesticides, industrial chemicals, and any synthetic chemicals not covered by other agencies Occupational Health and Safety Administration (OSHA) -workplace hazards

31. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings EPA regulation: Pesticides (FIFRA) Pesticides to be introduced to market in the U.S. need to be registered with the EPA. Registration involves risk assessment and risk management. EPA assesses research from the manufacturer along with any outside research. EPA can set restrictions on use, or even ban a product.

32. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings EPA regulation: Industrial chemicals (TSCA) EPA is charged with monitoring 75,000 industrial chemicals. Too many chemicals, too little time, people, resources Only 10% of chemicals on the market are thoroughly tested. Only 2% are screened for carcinogens, mutagens, teratogens. <1% are government regulated. ~0% are tested for endocrine, nervous, or immune effects.

33. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings “The dirty dozen” POPs Aldrin(insecticide) Chlordane(insecticide) DDT(insecticide) Dieldrin(insecticide) Dioxins(industrial by-product) Endrin(insecticide) Furans(industrial by-product) Heptachlor(insecticide) Hexachlorobenzene (fungicide, industrial by-product) Mirex(insecticide, fire retardant) PCBs(industrial chemical) Toxaphene(insecticide)

34. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Viewpoints: Industry or government? Warren Porter Marian Stanley “Given the inherent inadequacies of the testing process and the uncertainty of the economic impacts, both government and industry should share the responsibility of testing to ensure public safety.” “Manufacturers often voluntarily conduct new studies to support the continued safe use of their chemicals. … It is important that the EPA and manufacturers work together in evaluating chemicals.”

35. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Toxicology The study of poisonous substances and their effects on humans and other organisms Toxicologists assess and compare toxic agents, or toxicants, for their toxicity, the degree of harm a substance can inflict. Analagous to a pathogenicity or virulence of the biological hazards that spread infectious disease. Environmental toxicology focuses on effects of chemical poisons released into the environment.

36. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Environmental toxicology Studies toxicants that come from or are discharged into the environment, and: Health effects on humans Effects on animals Effects on ecosystems Animals are studied: For their own welfare As “canaries in a coal mine” to warn of effects on humans

37. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of toxicants Carcinogens: cause cancer Mutagens: cause mutations in DNA Teratogens: cause birth defects Allergens: cause unnecessary immune response Neurotoxins: damage nervous system Endocrine disruptors: interfere with hormones

38. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Toxicants take many routes through the environment

39. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Minimata Disease

40. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Toxicants concentrate in water Surface water and groundwater can accumulate toxicants. Runoff from large areas of land drains into water bodies, becoming concentrated. Toxicants in groundwater or surface water reservoirs used for drinking water pose potential risks to human health.

41. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Airborne toxicants Volatile chemicals can travel long distances on atmospheric currents. PCBs are carried thousands of miles from developed nations of the temperate zone up to the Arctic, where they are found in tissues of polar bears and seals.

42. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transport to the Arctic: “Global distillation”

43. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Persistence Some chemicals are more stable than others, persisting for longer in the environment. DDT and PCBs are persistent. Bt toxin in GM crops is not persistent. Temperature, moisture, sun exposure, etc., affect rate of degradation. Most toxicants degrade into simpler breakdown products. Some of these are also toxic. (DDT breaks down to DDE, also toxic.)

44. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Poisons accumulate in tissues The body may excrete, degrade, or store toxicants. Fat-soluble ones are stored. DDT is persistent and fat soluble, … so builds up in tissues: bioaccumulation. Bioaccumulated chemicals may be passed on to animals that eat the organism—up the food chain…

45. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Poisons move up the food chain At each trophic level, chemical concentration increases: biomagnification. DDT concentrations increase from plankton to fish to fish-eating birds.

46. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Studying effects of hazards Toxicologists study effects in several major ways: Wildlife toxicology studies Human epidemiological studies Dose-response studies in the lab

47. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Wildlife toxicology Determine causes of mortality in die-off events (e.g., toxoplasma) or Test animals in the lab for response to toxicants or Correlate chemical presence and animal presence in the field

48. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human epidemiology Human studies rely on: Case history = observation and analysis of individual patients Epidemiological studies = long-term, large-scale comparisons of different groups of people Animal testing

49. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human epidemiology Advantages: Realistic All real-life factors included Disadvantages: Statistically correlational only; does not prove causation Takes many years to get results

50. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mixing toxicology with anthropology Children were tested for pesticide effects. Drawings by nonexposed children Drawings by exposed children

51. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Dose-response analysis Method of determining toxicity of a substance by measuring response to different doses Lab animals are used. Mice and rats breed quickly, and give data relevant to humans because they share mammal physiology with us. Responses to doses are plotted on a dose-response curve.

52. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Dose-response curve LD 50 = dose lethal to 50% of test animals Threshold = dose at which response begins

53. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Dose-response curve Dose-response curves allow us to predict effects of higher doses. By extrapolating the curve out to higher values, we can predict how toxic a substance may be to humans at various concentrations. In most curves, response increases with dose. But this is not always the case; the increase may not be linear. With endocrine disruption, it may decrease.

54. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Factors affecting toxicity Not all people are equal. Sensitivity to toxicant can vary with sex, age, weight, etc. Babies, older people, or those in poor health are more sensitive. Type of exposure: acute = high exposure in short period of time chronic = lower amounts over long period of time

55. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mixtures of toxicants Substances may interact when combined together. Mixes of toxicants may cause effects greater than the sum of their individual effects. These are called synergistic effects. A challenging problem for toxicology: There is no way to test all possible combinations! (And the environment contains complex mixtures of many toxicants.)

56. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Conclusion International agreements are a hopeful sign that governments will prevent environmental hazards. But solutions can come more easily when they do not arise from government regulation alone. Consumer choice can influence industry if consumers have scientific information. But we will never attain complete knowledge of risks. A safer future depends on knowing risks, phasing out harmful substances, and replacing them with safer ones.

57. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Endocrine disruption Some chemicals, once inside the bloodstream, can “mimic” hormones. If molecules of the chemical bind to the sites intended for hormone binding, they cause an inappropriate response. Thus these chemicals disrupt the endocrine (hormone) system.

58. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Endocrine disruption The hormone system is geared to working with tiny concentrations of hormones … … so, it can respond to tiny concentrations of environmental contaminants. Have chemicals in the environment acted as endocrine disruptors in humans?

59. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Frogs, people, and atrazine Frogs show reproductive abnormalities in response to small doses of the herbicide atrazine, researcher Tyrone Hayes has found. Others suggest that atrazine may have effects on humans as well. The fierce criticism from atrazine’s manufacturer reflects the high stakes in environmental toxicology.

60. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Declining sperm counts? A 1992 study summarized results of sperm count studies worldwide since 1938. Data showed a significant decrease in men’s sperm counts over 50 years.

61. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Testicular cancer Others hypothesize that endocrine disruptors are behind the rise in testicular cancer in many nations.