health

1. health • WHO defines as “state of complete mental, physical, and social well-being” • environmental health focuses on disease; as a result, health is usually defined as absence of disease • two measures are used in the study of disease in societies: • morbidity—incidence of disease in a population • mortality—incidence of death in a population • epidemiology—study of the presence, distribution, and prevention of disease in populations

2. life expectancy • universal indicator of health • 1955 average was 48 years • today, average is 67 years • expected to be 73 years in 2025 • progress is result of social, medical, and economic advances (epidemiologic transition) • 20% of annual deaths in the world are children under the age of 5 in the developing world • infectious diseases responsible for 54% of deaths in developing countries, but only 7% in developed countries

3. environmental hazards • two ways to consider hazards: • 1. lack of access to necessary resources • Ex. lack of access to clean water and nourishing food is harmful to a person • 2. exposure to hazards in the environment • cultural hazards • matter of choice, or at least can be influenced by choice • examples include eating too much, using harmful drugs, smoking, sunbathing, choosing hazardous occupations

4. environmental hazards • biological hazards • history: black plague, smallpox, antibiotics, immunizations • ~25% of global deaths are due to infectious and parasitic diseases • physical hazards • hurricanes, tornadoes, floods, forest fires, earthquakes, landslides, volcanic eruptions • some can be anticipated, others are a consequence of where people choose to live

5. environmental hazards • biological hazards • history: black plague, smallpox, antibiotics, immunizations • ~25% of global deaths are due to infectious and parasitic diseases • physical hazards • hurricanes, tornadoes, floods, forest fires, earthquakes, landslides, volcanic eruptions • some can be anticipated, others are a consequence of where people choose to live

6. environmental hazards • chemical hazards • industrialization has brought a host of technologies that use chemicals such as cleaning agents, pesticides, fuels, paints, and medicines • manufacture, use, and disposal of these chemicals often brings humans into contact with them • exposure is either by ingestion of contaminated foods or drinks, breathing contaminated air, absorption through the skin, direct use, or by accident • toxicity (condition of being harmful, deadly, or poisonous) depends not only on exposure, but also on the dose • people have different thresholds of toxicity for given substances • Ex. children are often at greater risk; embryos are even more sensitive

7. carcinogens • cancer-causing agents • because cancer often develops over a period of 10-40 years, it is often difficult to connect the cause with the effect • in the U.S., 23% of all deaths in 2003 were traced to cancer • cancer is a cell line that has lost its normal control over growth • at least 3 dozen genes have been studied that can bring about malignant cancer • two-hit hypothesis

8. Chapter 15.3Risk Assessment • 2002 WHO report: “Focusing on risks to health is the key to preventing disease and injury.” • risk assessment—process of evaluating the risks associated with a particular hazard before taking some action in a situation in which the hazard is present • risk can be expressed as days of lost life expectancy • may also be expressed as probability of dying from a specific hazard

9. environmental risk assessment by the EPA • risk assessment began at the EPA in the mid-1970s as a way of addressing the cancer risks associated with pesticides and toxic chemicals • currently has four steps: • hazard assessment • dose-response assessment • exposure assessment • risk characterization

10. hazard assessment • process of examining evidence linking a potential hazard to its harmful effects • for automobile accidents, link is clear • other cases are not as clear; may be time delay between first exposure and final outcome • Ex. establishing link between exposure to chemical and cancer

11. animal testing • test involving several hundred animals (usually mice) takes about 3 years and costs more than $250,000 • if a significant number develop tumors after being fed substance, then the substance is either a possible or probable carcinogen • three objections to animal testing • rodents and humans may have very different responses to a chemical • doses used on animals are often much higher than those humans would be exposed to • testing on animals is unethical

12. dose response assessment • when animal tests or human studies show a link between exposure to a chemical and an ill effect, the next step is to analyze the relationship between the concentrations of chemicals in the test (dose) and both the incidence and severity of the response • unless there is reason to assume otherwise, a linear response is used to determine an acceptable level of exposure

13. exposure assessment • involves identifying human groups already exposed to the chemical, learning how their exposure came about, and calculating the doses and length of time of their exposure

14. risk characterization • pulls together all the information gathered in the first three steps to determine the risk and any uncertainties • risk is commonly expressed as probability of a fatal outcome due to the hazard • Clean Air Act directs the EPA to regulate chemicals that have a cancer risk of greater than one in a million for the people who are subject to the highest doses • FDA applies same standard to regulate chemicals in food, drugs, and cosmetics • final estimate always recognizes degree of uncertainty

15. risk management • involves: • (1) a thorough review of the information available pertaining to the hazard in question and the risk characterization of the hazard • (2) a decision as to whether the weight of the evidence justifies a regulatory action • a regulatory decision will usually depend on: • 1. cost-benefit analysis • 2. risk-benefit analysis • 3. public preference

16. as always… • …the precautionary principle

17. LD50 • the amount or dose of a chemical (toxic substance) that kills half the test population (test organisms/specimens)

18. threshold level of toxicity • The dose (level) below which no toxic (lethal) effects are observed and/or above which the toxic (lethal) effects are apparent.

19. Chapter 18.1The Solid-Waste Problem • municipal solid waste: total of all materials thrown away from homes and commercial establishments • different from nonhazardous industrial waste • includes wastes from construction and demolition projects, sewage treatment sludge, wastes generated from industrial processes

20. methods of disposal • until the 1960s, almost all waste was burned in open dumps • burning reduced volume and increased lifespan of dump • produced clouds of smoke and served as breeding ground for rats, flies, and other pests • open dumps were replaced in 1960s and 70s with incinerators • huge furnaces burned waste more completely at high temperatures

21. path of trash • U.S. in 2003 • 55.4% = landfill • 30.6% = recycling or composting • 14% = combustion • percentage of recycled materials is increasing in U.S. • countries with greater population densities (i.e. Japan) burn a much higher percentage

22. landfills • landfill: waste is put on or in the ground and is covered with soil • each day’s fill is covered with at least 6 inches of soil • helps control air pollution and pests • first landfills did little to consider ecology, water cycle, or potential for hazardous products when waste components react

23. problems of landfills • subjected to biological and physical factors in the environment and undergo change over time • problems: • leachate • methane production • incomplete decomposition • settling

24. leachate • leachate: as water percolates through the landfill, various chemicals dissolve and are carried by the solution • likely to include residues of decomposing organic matter with iron, mercury, lead, zinc, and other metals from rusting cans and batteries, along with paints, pesticides, cleaning fluids, and other chemicals • areas like Florida, where the groundwater is often just below the surface, have experienced extensive water pollution as a result of unlined landfills

25. methane production • because it is about 2/3 organic material, MSW is subject to natural decomposition • buried wastes do not have access to oxygen, meaning decomposition is anaerobic • produces biogas mixture that is about 2/3 methane, with some hydrogen and carbon dioxide • mixture is highly flammable • may explode under certain conditions • some cities have installed gas wells to tap the landfill gas • methane is purified and used for fuel

26. incomplete decomposition • common plastics in MSW resist decomposition • polymers of petroleum-based compounds that cannot be broken down by microbes • (biodegradable plastic polymers have now been developed from cornstarch and soybeans) • demand for products based on two factors: • 1. price of oil • 2. demand for environmentally friendly packages • biodegradable materials such as newspaper and wood often degrade slowly or not at all in landfills (mostly due to lack of moisture)

27. settling • occurs as waste compacts and decomposes • issue for landfills that have been converted to playgrounds and golf courses • creates shallow depressions

28. Chapter 18.1 (cont.)Siting New Landfills • from 1988 to 2002, number of municipal landfills declined from ~8000 to 1767 • increase in size of landfills combined with increase in recycling means that landfill capacity is not a problem in the U.S. • however, “regional dislocations” occur • as old landfills close, it’s increasingly difficult to to find land for new ones

29. outsourcing • problem with finding new sites has some undesirable consequences • 1. drives up costs of waste disposal • 2. leads to inefficient practice of long-distance transport of trash • trash is often carried across state or national lines, leading to resentment from citizens of the locations receiving the waste • 10 states import more than 1 million tons of MSW per year, while 8 states export more than 1 million tons per year

30. combustion • because of its high organic content, waste can be burned • process is really waste reduction, not waste disposal • after incineration, ash must still be disposed of

31. advantages of combustion • can reduce weight of trash by 70% and volume by 90% • toxic or hazardous substances are concentrated into two streams of ash • fly ash • captured from the combustion gases by air pollution control equipment • contains most of the toxic substances; can be safely put in a landfill • bottom ash • from the bottom of the boiler • can be used as fill in some construction sites • no changes are needed in consumer behavior or trash collection procedures

32. advantages of combustion (cont.) • 2/3 of combustion facilities are waste-to-energy (WTE) facilities equipped with modern emission control technologies • when burned, unsorted MSW releases about 35% as much energy as coal • facilities often do resource recovery, which separates some materials before (and sometimes after) combustion

33. drawbacks of combustion • air pollution and offensive odors • facilities are expensive to build • combustion ash is often loaded with metals and other hazardous substances • even if it generates electricity, process wastes both energy and materials unless recycling and recovery are part of operation

34. an operating facility • plant receives about 3000 tons of MSW per day • PROCESS • 1. incoming waste is inspected, and recyclable and bulky materials are removed • 2. waste is then shredded into pieces with a width of 6 inches or less • 3. magnets remove 2/3 of ferrous metals for recycling • 4. waste is blown into boilers

35. an operating facility • PROCESS (cont.) • 5. water circulated through the walls of the boilers produces steam, which drives turbines for generating electricity • 6. after waste is burned, bottom ash is conveyed to processing facility where further sorting of metals occurs (recovers brass, aluminum, gold, copper, and iron) • 7. combustion gases are neutralized to remove sulfur dioxide and other gases • 8. fly ash and bottom ash residues are put into landfills

36. Chapter 18.2Solutions to the Solid Waste Problem • source reduction • defined by EPA as “the practice of designing, manufacturing, purchasing, or using materials (such as products or packaging) in ways that reduce the amount or toxicity of trash created” • accomplishes two goals: • 1. reduces amount of waste • 2. conserves resources • amount of waste per person reached peak of 4.5 pounds in 1990

37. examples of source reduction • reducing the weight of many items has reduced the amount of materials used in manufacturing • disposable diapers contain 50% less paper pulp • aluminum cans contain 1/3 of the aluminum they had 15 years ago • electronic communication and data storage has reduced paper consumption

38. reasons to recycle • saves energy and resources • Ex. one ton of recycled steel cans saves 2500 lb of iron ore, 1000 lb of coal, and more than 5400 BTU of energy • Ex. one ton of recycled paper saves 17 trees, 6953 gallons of water, 463 gallons of oil, and 4000 kilowatts of energy • decreases pollution • Ex. making recycled paper requires 64% less energy and generates 74% less air pollution and 35% less water pollution than wood from trees

39. what gets recycled • paper (48% recovery) • glass (19% recovery) • plastic (5.2% recovery) • aluminum (22% recovery) • yard waste (56% recovery) • old tires (36% recovery)

40. bottle laws • facilitate the recycle or reuse of beverage containers • while every state has proposed bottle laws at some point, only 11 have passed • in every case, the proposals have met fierce opposition from beverage and container industries, as well as other special interest groups • in states with bottle laws, 75% of containers are returned • repeated attempts have been made to pass a national bottle law • opponents argue that law would threaten recent successes in curbside recycling

41. PETE and HDPE • two recyclable plastics most commonly used: • 1. PETE (polyethylene terephthalate; #1) • when recycled, turned into carpets, jackets, and new PETE bottles • 2. HDPE (high density polyethylene; #2) • when recycled, used in sheet plastic and recycling bins • in recycling process, plastics must be melted down and poured into molds; some contaminants from original containers may carry over • critics argue that recycling plastic is more expensive than starting over from scratch

42. integrated waste management • source reduction, waste-to-energy combustion, recycling, materials recovery facilities, landfills, and composting all have roles to play in waste management • EPA sponsors WasteWise program which establishes partnerships with schools, local governments, and businesses to reduce waste • EPA’s PAYT program encourages “unit pricing” which charges customers for waste they dispose

43. dose response and threshold • in investigating a suspect chemical, a toxicologist would conduct tests on animals, investigate human involvement with the chemical, and present information linking the dose with the response • dose: level of exposure multiplied by the length of time over which exposure occurs • response: acute or chronic effect, or the development of tumors • LDL0: lowest dose at which death occurred in animal testing

44. threshold level • in dose-response relationship, there is usually a threshold • organisms are able to deal with certain levels of many substances without suffering ill effects • threshold level: level below which no ill effects are observed • above this level, effect of a substance depends on concentration and duration of exposure • for carcinogens, EPA generally takes a zero-dose, zero-response approach • however, the lower the dose, the more likely it is that the response cannot be distinguished from the background level of cancers in a population

45. heavy metals • most dangerous include lead, mercury, arsenic, zinc, cadmium, tin, chromium, and copper • common in metalworking or metal-plating shops, electronics, pesticides, and some medicines • once common in paint pigments, glazes, inks, and dyes due to brilliant colors • extremely toxic because, as ions in certain compounds, they are soluble in water and may be readily absorbed by the body (usually inhibit the function of enzymes)

46. Minamata • tragic episode in early 1970s revealed potential for biomagnification of mercury and other heavy metals • in the mid-1950s, cats in the small fishing village of Minamata, Japan began to show spastic movements, followed by partial paralysis, coma, and death • at first, most thought the syndrome was specific to felines • however, same symptoms began to appear in humans • chemical company near the village was discharging wastes containing mercury into a river that flowed into a bay where villagers fished • mercury settled with detritus, then absorbed and bioaccumulated by bacteria, then biomagnifed up the food chain • in the end, 50 died and 150 suffered bone and nerve damage

47. Chapter 19.2A History of Mismanagement • worsening pollution (both chemical and sewage) through the 1950s and 1960s increased recognition of adverse health effects • graphic example was fire on the Cuyahoga River which flows through Cleveland • led to passage of Clean Air Act (1970) and Clean Water Act (1972) • created dilemma-- if companies can’t vent waste into the atmosphere or flush into waterways, what should they do with it?

48. methods of land disposal • in the early 1970s, there were three primary land-disposal methods: • 1. deep-well injection • 2. surface impoundment • 3. landfills • with use of safeguards, each of these methods has merits and each is still widely used for hazardous waste disposal

49. deep-well injection • involves drilling a hole thousands of feet below groundwater into a porous geological formation or brine • well consists of concentric pipes and casings that isolate the wastes as they are injected • over time, the wastes will often undergo reactions with naturally occurring materials that make them less hazardous • method is currently used for VOCs, pesticides, fuels, and explosives • use has declined, but is better than most other methods for keeping toxic wastes from contaminating the hydrologic cycle and the food web

50. Resource Conservation and Recovery Act (1996) • amendment in Act led EPA to conduct a study of surface impoundments • ~18,000 surface impoundments in use at 7500 facilities • at least 2/3 contained hazardous chemicals with carcinogenic and other human health concerns • most impoundments were only a few meters above groundwater (more than ½ did not have adequate liners) • more than 20 million people lived within 2 km of an impoundment • 10% were located within 500 feet of drinking water wells