CHAPTER 17

1. CHAPTER 17 Environmental Hazards and Human Health

2. An introduction to hazards and human health • The highly virulent H5N1 avian flu first appeared in 1997 • Infecting poultry, other birds, and humans • Hundreds of millions of poultry have been slaughtered • The 2009 H1N1 swine flu outbreak spread rapidly • The World Health Organization declared a global influenza pandemic • 39 new diseases have spread from animals to humans • SARS, the Ebola virus, West Nile virus, hantavirus • New diseases will appear as we change the environment

3. The old enemies • The new, emerging diseases are not our greatest threat • The common, familiar ones take the greatest toll • Malaria, diarrhea, respiratory viruses, worms • Especially in developing countries • In developed countries, cancer is the killer most closely linked to the environment • Due to our exposure to chemicals • Environmental health: connections between environmental hazards and human disease and death

4. Links between the environment and health • Pollution: the presence of a substance in the environment that because of its composition or quantity prevents functioning of natural processes and produces undesirable environmental or health effects • Pollutant: any material that causes pollution • Usually by-products of some desirable action • Agriculture, comfortable homes, transportation, etc. • Pollution has increased due to population and consumption • Along with accumulation of nonbiodegradable products (e.g., plastic, synthetic organic chemicals)

5. Categories of pollution

6. Pollution is everywhere • Any part of the environment can be polluted • Almost anything can be a pollutant • The only criterion? The addition of a pollutant results in undesirable changes • Impacts can be: • Aesthetic: hazy air, litter • On ecosystems: fish or forest die-offs • On human health: water contaminated with waste • Local (a contaminated well) or global (ozone depletion) • Too much of a natural compound (e.g., fertilizer)

7. Our existence necessitates waste production • So…we need to… • Identify the material(s) causing the pollution • Identify the source(s) of the pollutants • Clean up the environment • Prevent pollutants from entering the environment • Avoid the pollution altogether • Transitioning to a sustainable society will require a technology transition from pollution-intensive to environmentally friendly processes

8. Environmental health • Environment: the whole context of human life • The physical, chemical, and biological setting of where and how people live • Home, air, water, food, workplace, climate, etc. • Hazard: anything that can cause: • Injury, disease, death to humans • Damage to personal or public property • Deterioration or destruction of environmental parts

9. Hazards, risk, and vulnerability • Undesirable consequences do not necessarily follow a hazard • Risk: the probability of suffering injury, disease, death, or some loss as a result of exposure to a hazard • Vulnerability: some people (e.g., the poor) are more vulnerable to certain risks • Risk = Hazard x Vulnerability • The presence of avian flu in poultry: a hazard that presents the risk of humans getting the disease • People working with poultry are more vulnerable

10. Dose response and threshold • The dose (level of exposure multiplied by the length of time of exposure) is linked with the response (effects) • If a chemical has a low toxicity, concern centers on chronic or carcinogenic effects • Human exposure to a hazard is a vital part of risk characterization • Exposure comes from the workplace, food, water, and environment • It is hard to get an accurate determination of exposure

11. Threshold level • There is usually a threshold level in the dose-response relationship • Organisms can usually deal with some level of a substance without suffering ill effects • Threshold level: the level below which there are no ill effects • Effects above this level depend on concentration and duration of exposure • It is high for short exposures, and lower as time increases

12. The threshold level

13. Threshold levels for carcinogens • The EPA takes a zero-dose, zero-response approach for carcinogens • There is no evidence of a threshold level for them • But lower doses are less likely to produce cancers • The field of toxicology is well established • It is the most important source of sound science for supporting regulations from the EPA and FDA • The NTP was established in 1978 • The world’s leader in assessing chemical toxicity and carcinogenicity

14. The picture of health • Health: a state of complete physical, social, and mental well-being • Not just the absence of disease or infirmity • Environmental health focuses on disease • Health: the absence of disease • Two measures are used to study disease • Morbidity: the incidence of disease in a population • Mortality: the incidence of death in a population • Epidemiology: the study of the presence, distribution, and prevention of disease in populations

15. Infectious Diseases • http://www.nbclearn.com/portal/site/learn/changing-planet

16. Public health • Federal government • Centers for Disease Control and Prevention (CDC) • Provides tools and information to protect health • Involved in health risk management and prevention • Each state has its own public-health agency • Can require shots, quarantines, monitoring diseases, etc. • The U.S. has a huge health care industry • Medicare, Medicaid, hospitals, physicians, etc.

17. Other countries • Most countries have a ministry of health that acts on behalf of its people to manage and minimize health risks • Health policies are limited by information and funding • Limited funds should go to strategies that achieve the greatest risk prevention • Countries have access to the WHO • Established by the UN in 1948 • Everyone should get the highest possible level of health • Staffed by professionals and governed by the World Health Assembly

18. Life expectancy • A universal indicator of health • In 1955, it was 48 years • It is now 68 years and will rise to 73 by 2025 • Longer lives: due to social, medical, economic advances • Epidemiologic transition: decreasing death rates accompany development • Infectious diseases are replaced by diseases of aging • But 92 million children still die each year • Common diseases kill 47% of people in poor countries • Industry and intensive agriculture have their own hazards

19. Environmental hazards • Four classes of environmental hazards: • Cultural, biological, physical, chemical • There are two ways to consider hazards to health • Lack of access to resources (clean water, food) • Exposure to hazards in the environment that brings risk of injury, disease, or death • Cultural hazards: many factors that cause death or disability are a matter of choice • People engage in risky behavior (smoking, drinking, drugs, don’t exercise, risky sexual practices, etc.)

20. Biological Hazards: Tuberculosis, malaria, and parasites • Mycobacterium tuberculosis infects one-third of all people • Tuberculosis has resurged due to complacency, HIV-weakened immune systems, and drug-resistant strains • Malaria kills 881,000 people each year • A mosquito infects a person with a protozoan parasite • Red blood cells are destroyed, leading to anemia, fever, chills, and malaise • 3.5 billion people suffer from parasitic worms • Hookworms and schistosomes

21. Physical Factors: In harm’s way • Hurricanes, earthquakes, volcanoes, etc • Much loss from natural disasters is due to poor environmental stewardship • Deforested hillsides • Building on floodplains, below volcanoes, on geologic faults, marshes, and mangrove forests • People assume disasters happen to other people • Stupid zones could be created for areas that shouldn’t be built • Areas prone to hurricanes, earthquakes, volcanoes, etc.

22. Chemical hazards • Industrialization has resulted in technologies that use chemicals • Cleaning agents, pesticides, fuels, medicines, paints, etc. • Exposure is through ingestion, breathing, the skin, direct use, or by accident • Toxicity: condition of being harmful, deadly, or poisonous • Depends on exposure and dose (the amount absorbed) • Different people have different thresholds of toxicity • Children and embryos are most sensitive

23. Industrial processes and hazards

24. Carcinogens • Many chemicals are hazardous even at very low levels • Heavy metals, organic solvents, pesticides • Acute poisoning episodes are understandable and preventable • But it is hard to determine effects of long-term exposure to low levels of substances • Carcinogens: cancer-causing agents • Cancer develops over decades, so it is hard to connect cause with the effect • There are 51 known and 188 suspected carcinogens • Developing nations have rising exposure to chemicals

25. Pathways of risk • What pathways lead from risks (of infection), exposure (to chemicals), and vulnerability (to hazards) to human deaths? • A very small number of risk factors cause the vast majority of premature deaths and disease • One major pathway for hazards: poverty • The world’s biggest killer in both developing and developed nations • People lack access to health care, clean water, nutritious food, healthy air, sanitation, and shelter

26. The 10 leading global risk factors

27. Public-health clinics

28. Priorities • Education, nutrition, and wealth do not explain everything • A nation may make deliberate policy choices to improve the health of its population • Instead of militarization or power sources • Costa Rica, China, and Sri Lanka have longer life expectancies and lower infant mortality than expected • They focused public resources on immunization, upgrading sewer and water systems, and land reform

29. U.S. deaths caused by smoking

30. Marlboro country? • Tobacco is the only product sold that kills half its users • It is clearly correlated with cancer and other lung diseases • It is responsible for 29% of U.S. cancer deaths • 5.4 million die worldwide each year • Synergistic effects: smokers living in polluted air or working with asbestos have higher rates of lung cancer • Black lung disease occurs mainly in smokers • Smoking costs the U.S. $193 billion/yr in health care costs and lost job productivity

31. Decreasing tobacco use • Raising taxes: the most effective measure to reduce tobacco use • Providing billions of dollars to state and federal governments • Other measures to reduce smoking include warnings, smoke-free workplaces, non-smoking areas, and banning smoking on domestic flights • The U.S. smoking population dropped from 42% to 19.8% since warnings began

32. Secondhand smoke • In 1999 the EPA classified environmental tobacco smoke (ETS), secondhand smoke, as a Class A (known) carcinogen • A serious and substantial public health risk • Specific steps now protect children in public places • The Occupational Safety and Health Administration is working to protect workers from ETS • In 1999, Congress gave the Food and Drug Administration sweeping power to regulate tobacco • Overcoming efforts of the powerful tobacco lobby

33. Legally speaking • The attorneys general of several states sued tobacco companies • In 1998, 46 states reached a $246 billion settlement • Tobacco companies would reimburse states for smoking-related illnesses • Help finance programs to discourage smoking • Other lawsuits have not been successful • Judges ruled that earlier court rulings forbade them from imposing fines

34. Risk and infectious diseases • Epidemiology is “medical ecology” • Epidemiologists trace a disease’s location, transmission, and consequences • Infectious diseases and parasites are more common in developing countries • Inadequate hygiene, inferior sewage treatment • A lack of resources for public-health infrastructure • Developed nations also have outbreaks of diseases • In 1993 Milwaukee’s (Wisconsin) water supply was contaminated by animal wastes, hospitalizing over 4,000

35. Tropical diseases • The tropics have ideal climates for insect-borne diseases • Mosquitoes are vectors for yellow fever, dengue fever, elephantiasis, Japanese encephalitis, West Nile, malaria • Malaria is the most serious • Control of malaria focuses on vector control: using pesticides on the Anopheles mosquito • Or treatment strategies: curing infected people • Malaria has been eradicated in the U.S. • DDT is a successful, yet controversial, control for mosquitoes in developing countries

36. Malaria incidence per 1,000 population, 2006

37. Net results • Giving children insecticide-treated nets over their beds reduces mortality from all causes • Bed nets, indoor DDT spraying, and effective drugs reduce malaria deaths • A cost-effective, large-scale intervention in Africa • The Plasmodium protozoan is becoming resistant to drugs • Chloroquine is now ineffective against malaria • ACT (artemisinin combination therapy) is effective • But resistance is appearing

38. Insecticide-treated bed net

39. Toxic risk pathways • Airborne pollutants are hard-to-control hazards • Hard to measure and avoid • Three categories of impacts • Chronic: pollutants cause gradual deterioration of physiological functioning over years • Acute: pollutants cause life-threatening reactions within hours or days • Carcinogenic: pollutants cause cellular changes leading to uncontrolled growth and division (cancer)

40. Developing countries • Developing nations have the most serious threat • Three billion use wood or dung for cooking and heating • Fireplaces, stoves, etc. are not properly ventilated • Exposing people to carbon monoxide, nitrogen and sulfur oxides, soot, benzene (a carcinogen) • Problems associated with indoor cooking: acute respiratory infections, chronic lung disease (asthma, bronchitis), lung cancer, birth defects • Solutions? Ventilated, efficient stoves • Using bottled gas or liquid fuels instead of biofuels

41. Hazard assessment: is this really a hazard? • Hazard assessment: the process of examining evidence • Linking a potential hazard to its harmful effects • Historical data are often used to calculate risks • A link may not be clear due to a time delay between exposure and effect • An epidemiological study tracks how a sickness spreads • Are people exposed to a hazard sicker than the unexposed? • Animal testing: uses animals to determine what might happen • Uses hundreds of animals (mice) over years at high costs

42. Animal testing

43. Objections to animal testing • Rodents and humans may have different responses to a chemical • Doses given to animals are much higher than humans are exposed to • Some people are opposed for ethical reasons • All chemicals shown to be human carcinogens are also carcinogenic in test animals

44. Just test people? • Chemical manufacturers used to pay people to test products • They are less expensive than animal testing • A National Academy of Sciences panel stated this was unjustifiable • The EPA banned such tests • The Bush administration pressed to allow testing • A 2006 EPA ruling allowed testing to restart • But forbids testing on children or pregnant women • The Natural Resources Defense Council is suing • The Obama administration may stop this testing

45. The precautionary principle • The precautionary principle: where an activity threatens harm to humans or the environment, precautionary measures should be taken even if some cause-and-effect relationships are not fully known • Proponents of the activity, not the public, should bear the burden of proof

46. Using the precautionary principle • It is well-established in Europe • It is the basis for environmental laws • It overlies some U.S. policies • Pharmaceuticals and pesticides • A substance is presumed guilty until proven innocent • It is not permitted until tests prove it is safe • It can implement stewardship in environmental health • But should not be a blanket policy • It can counter pressures from proponents • Use it where the penalty for being wrong is great

47. CHAPTER 17 Environmental Hazards and Human Health Active Lecture Questions

48. True or False: The existence of a hazard means that undesirable consequences will inevitably follow. a. True b. False Review Question-1

49. True or False: The existence of a hazard means that undesirable consequences will inevitably follow. a. True b. False Review Question-1 Answer

50. ______ is the incidence of disease in a population, while ______ is the incidence of death in a population. a. Mortality; morbidity b. Morbidity; immortality c. Morbidity; mortality d. Immortality; mortality Review Question-2