19- 1

1. 19-1

2. Identify the major types of environmental health hazards and the goals of environmental health Describe the types, abundance, distribution, and movement of toxicants in the environment Discuss the study of hazards and their effects, including case histories, epidemiology, animal testing, and dose-response analysis Assess risk assessment and risk management Compare philosophical approaches to risk Describe policy and regulation in Canada and elsewhere Upon successfully completing this chapter, you will be able to

3. Central Case: The Asbestos Dilemma Asbestos has been used widely in buildings in Canada and now its use is regulated The world’s largest asbestos deposit is in Asbestos, Quebec Chrysotile asbestos may or may not be as harmful to health (99% of world’s asbestos trade) Health Canada says it is safe; WHO and Canadian Cancer Society say it is not $1 billion export industry for Canada

4. Environmental Health 19-4

5. Environmental hazards can be chemical, physical, biological, or cultural Chemical = synthetic chemicals such as pesticides, disinfectants, pharmaceuticals Harmful natural chemicalsalso exist Physical hazards = occur naturally in our environment Earthquakes, volcanoes, fires, floods, droughts We can’t prevent them, but we can prepare for them and reduce risk We increase our vulnerability by deforesting slopes (landslides), channelizing rivers (flooding), etc.

6. Environmental hazards can be chemical, physical, biological, or cultural (cont’d) Biological = result from ecological interactions Viruses, bacteria, and other pathogens Infectious disease = other species parasitize humans, fulfilling their ecological roles We can’t avoid risk, but we can reduce it Cultural = result from the place we live, our socioeconomic status, our occupation, our behavioral choices Smoking, drug use, diet and nutrition, crime, mode of transportation

7. Risky Business weighingtheissues • Do you live in a part of Canada that is “naturally” hazardous? Check your region on Figure 9.2 to see if the natural disasters shown on the map match your experience of life in that part of the country. • Can you determine which aspects of the natural environment make your region vulnerable to that particular type of hazard? • Do you know what kinds of preparations have been undertaken by governments in your province or territory to minimize risk to the public?

8. Disease is a major focus of environmental health

9. Disease is a major focus of environmental health (cont’d) • Infectious diseases kill 15 million people per year • Half of all deaths in developing countries • Developed countries have better hygiene, access to medicine, and money • Vector = an organism that transfers pathogens to a host

10. Disease is a major focus of environmental health (cont’d) • Our mobility spreads diseases (e.g. In 2003 SARS was imported from Hong Kong) • Airline travel • Diseases are evolving resistance to antibiotics • Climate change will expand the range of diseases • To predict and prevent diseases, experts deal with complicated interrelationships

11. Environmental health hazards exist indoors as well as outdoors Radon = a highly toxic, radioactive gas that is colorless and undetectable without specialized kits Causes lung cancer Lead poisoning From water going through lead pipes, lead-based paint on popular brand-name children’s toys from China Damages organs; causes learning problems, behavior abnormalities, and death PBDEs polybrominated diphenyl ethers Computers, TVs, plastics, furniture Endocrine disruptors, brain and nervous system

12. Toxicology is the study of poisonous substances Toxicology = the study of the effects of poisonous substances on humans and other organisms Toxicity = the degree of harm a toxicant can cause “The dose makes the poison” = toxicity depends on the combined effect of the chemical and its quantity Analogous to pathogenicity or virulence = the degree of harm of biological hazards that spread disease Toxicant = any toxic agent

13. Toxicology is the study of poisonous substances (cont’d) Environmental toxicology deals with toxic substances that come from or are discharged into the environment Studies the health effects on humans, other animals, and ecosystems Focus mainly on humans, using other animals as test subjects Can serve as indicators of health threats Don’t forget, chemicals have given us our high standard of living

14. Toxic Agents In The Environment 19-14

15. Toxic agents in the environment The environment contains countless natural chemicals that may pose health risks Radon gas seeping from bedrock, toxic chemicals stored or produced in living organisms But, synthetic chemicals are also in our environment

16. Synthetic chemicals are ubiquitous in our environment • Synthetic chemicals are all around us, about 100,000 are in common use • Every one of us has traces in our body • Not all pose human health risk but very few have been tested for harmful effects (as low as only 10%) • Risk of exposure to pesticides not learned until 1960s • DDT 19-16

17. Silent Spring began the public debate over synthetic chemicals Rachel Carson published Silent Spring in 1962 generated significant social change Presented the risks of DDT 1960s: pesticides were mostly untested and were sprayed over public areas Canada banned DDT in 1985 but still produced in the U.S. and exported to developing countries

18. The Circle of Poison weighingtheissues It has been called the “circle of poison.” Although Canada banned DDT in 1985 and the United States in 1972, U.S. companies still manufacture and export the compound to many developing nations. Thus, pesticide-laden food can be imported back into the United States and to other countries, including Canada. • How do you feel about this? Is it unethical for one country to sell to others a substance that it has deemed toxic? • Are there factors or circumstances that might change the view you take? • Compare this with Canada’s exportation of asbestos, discussed in the Central Case. What are the similarities and differences?

19. Toxicants come in several different types Carcinogens = cause cancer Mutagens = cause DNA mutations Can lead to severe problems, including cancer Teratogens = cause birth defects Allergens = overactivate the immune system Neurotoxins = assault the nervous system Endocrine disruptors = interfere with the endocrine (hormone) system

20. Endocrine disruption may be widespread Mimic hormones May be causing: Feminization of male animals Drop in sperm counts Testicular cancer Rise in breast cancer rates Neurological problems

21. Endocrine disruption research has generated debate • Research results are uncertain, which is inherent in any young and developing field • Negative findings pose economic threats to chemical manufacturers • Banning a top-selling chemical could cost a company millions of dollars • Bisphenol-A, found in plastics, can cause birth defects, but the plastics industry protests that the chemical is safe (Canada first country to declare it unsafe) • Studies reporting harm are publicly funded, but those reporting no harm are industry funded

22. Toxicants may concentrate in water • Runoff carries toxins from large land areas to small volumes of surface water • Chemicals can leach into the soil • Chemicals enter organisms through drinking or absorption • Aquatic organisms are effective pollution indicators

24. Airborne toxicants can travel widely • Pesticide drift = airborne transport of pesticides • Synthetic chemical contaminants are found globally • They appear in arctic polar bears, Antarctic penguins, and people living in Greenland

25. Some toxicants are persistant Toxins can either degrade quickly or remain unaltered and persist for decades Rates of degradation depends on temperature, moisture, and sun exposure Breakdown products = toxicants degrade into simpler products May be more or less harmful than the original substance DDT degrades into DDE, which is also highly persistent

26. Toxicants may accumulate over time and up the food chain Bioaccumulation = toxicants build up in animal tissues Biomagnification = toxicants concentrate in top predators Near extinction of peregrine falcons and brown pelicans

27. Not all toxicants are synthetic • Chemical toxicants 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 toxicants may be more readily metabolized and excreted by the body than synthetic ones

28. Studying The Effect of Hazards 19-28

29. Wildlife studies use careful observations in the field and lab • Museum collections provide data from times before synthetic chemicals were used • Measurements from animals in the wild can be compared to controlled lab experiments • Conspicuous mortality events can trigger research • 1998-2001: Research showed California sea otters died from parasites carried in sewage runoff containing cat litter

30. Human studies rely on case histories, epidemiology, and animal testing • Case histories = process of observation and analysis of individual patients • Epidemiology = large-scale comparisons among groups of people, generally for a long period of time • Studies between exposed and unexposed people last for years • Manipulative experiments = lab experiments that expose subjects to toxicants to establish causation • Animals used as models (e.g. rats, mice)

31. Dose-response analysis is a mainstay of toxicology • Dose = the amount of toxicant the test animal receives • Response = the type or magnitude of negative effects of the animal • Dose-response curve = the plot of dose given against response • LD50/ED50= the amount of toxicant required to kill (affect) 50% of the subjects • Threshold = the dose level where certain responses occur

34. 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 • Standards are set by Health Canada • Do not account for risks to fetuses, infants, children, older adults, and the immunocompromised

35. The type of exposure can affect the response • Acute exposure = high exposure for short periods of time to a hazard • Easy to recognize • Stem from discrete events: ingestion, oil spills, nuclear accident • Chronic exposure = low exposure for long periods of time to a hazard • Hard to detect and diagnose • Affects organs gradually: lung cancer, liver damage • Cause and effect may not be easily apparent

36. Mixes may be more than the sum of their parts • Synergistic effects = interactive impacts that are more than or different from the simple sum of their constituent effects • Mixed toxicants can sum, cancel out, or multiply each other’s effects • New impacts may arise from mixing toxicants

37. Risk Assessment And Risk Management 19-37

38. Risk is expressed in terms of probability • Policy and management decisions consider economics, ethics, and political pressure • Risk is expressed in terms of probability, a quantitative description of the likelihood of a certain outcome • Probability entails • Chance and frequency that an organism will encounter it • Amount of exposure to the threat • An organism’s sensitivity to the threat

39. Our perception of risk may not match reality

40. Risk assessment = the quantitative measurement of risk and the comparison of risks involved in different activities or substances Scientific study of toxicity Assessing the likely extent of exposure to the substance (frequency, concentrations, and length of exposure) Studies are often performed by industry-associated scientists, which may undermine the study’s objectivity Risk assessment analyzes risk quantitatively

41. Risk management combines science and other social factors • Risk management = decisions and strategies to minimize risk • Costs vs. benefits • Benefits are economic and easy to calculate • Health risks (costs) are hard-to-measure probabilities of a few people being affected

42. Philosophical And Policy Approaches 19-42

43. Two approaches exist for determining safety • Innocent until proven guilty approach: product manufacturers must prove a product is safe • Benefits: now slowing down technological innovation and economic advancement • Disadvantage: putting into wide use some substances that may later on turn out to be dangerous

44. Two approaches exist for determining safety (cont’d) • Precautionary principle approach: substances are harmful until they are shown to be harmless • Identifies troublesome toxicants before they are released • But, this may impede the pace of technology and economic advance

45. Philosophical approaches are reflected in policy • Most nations use a mix between the two approaches • The precautionary principle has long been a foundation of Canada’s approach • e.g. Health Canada declared BPA a toxic substance • The same is not true of the United States

46. Toxicants are also regulated internationally • United Nations • 1992: Basel Convention agreement on hazardous materials • International Code of Conduct on the Distribution and Use of Pesticides • World Health Organization • Rotterdam Convention (hazardous chemicals and pesticides) • International treaties • Stockholm Convention on Persistent Organic Pollutants • European Union • Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) Program

47. Conclusion • International agreements inspire hope that governments will act to protect the world’s people, wildlife, and ecosystems • Solutions often come easily when they do not arise from government regulations alone • Consumer choice may be best way to influence industry’s decision making • Once scientific results are in, society’s approach to risk management will determine policy decisions • We will never attain complete scientific knowledge of any risk • Synthetic chemicals have brought us innumerable modern conveniences • A safer and happier future depends on knowing the risks and replacing harmful subtances with safer ones

48. QUESTION: Review Which of the following is a biological hazard? • Earthquake • Smoking • Virus • A pesticide • All are biological hazards

49. QUESTION: Review A “vector” is defined as … • A highly toxic, radioactive compound • An organism that transfers pathogens to a host • A compound with fire-retardant properties • A compound that mimics natural substances

50. QUESTION: Review Toxicity is … • The study of the effects of poisonous substances • Any toxic agent • Any substance that causes environmental degradation • The degree of harm a substance can cause