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POLLUTION AND HUMAN HEALTH ENVIRONMENTAL SCIENCE UNIT 7 ENVIRONMENTAL EFFECTS ON HEALTH • Pollution can cause illness in two ways • Directly by poisoning • Lead poisoning • Lung cancer • Indirectly by infectious diseases that are spread in polluted environments • Cholera • River blindness • People in developed countries suffer less from environmental causes of poor health • In developing countries, environmental causes of poor health are largely due to parasites and bacteria in polluted water and insect-borne diseases • Malaria TOXICOLOGY • Toxicology – study of toxic substances including their nature, effects, detection, methods of treatment, and exposure control • Toxicologists determine the following: • Whether the concentration of any particular chemical in the environment is high enough to be harmful • How much of the pollutant is in the environment and how much gets into the body • What concentration of the toxin damages the body • Individual’s response depends on: • Number of times a person is exposed • Person’s size • How well the person’s body breaks down the chemical • Dose-response curve shows relative effect of various doses of a drug/chemical on one or more organisms • Threshold dose • Exposure < threshold dose has no adverse effect • Exposure > threshold dose usually leads to adverse effects EPIDEMIOLOGY • Epidemiology – study of the spread of diseases • Epidemiologists collect data from health workers on when and where cases of a disease have occurred • Health officials determine risk posed by specific hazards • Risk assessment – estimate of the risk posed by a specific substance • • • • Compile and evaluate existing info Determine how people might be exposed Determine toxicity of the substance Characterize the risk that the substance poses to public • Risk assessments may lead to EPA regulations POLLUTION FROM NATURAL SOURCES • Some pollutants occur naturally • Radon gas (radioactive) may seep into buildings from granite • Causes estimated 15,000 – 22,000 cancer deaths each year in U.S. • Particulates such as dust, soot, etc. are most common natural pollutants • Particulates become trapped in air sacs in lungs, causing irritation that can worsen lung conditions such as chronic bronchitis and emphysema • Dust storms, volcanoes, wildfires • Heavy metals • Dangerous heavy metals include arsenic, cadmium, lead, mercury • Cause nerve damage • High levels of selenium can cause birth defects POLLUTION FROM HUMAN ACTIVITIES • Only 10% of commercial chemicals have been tested for toxicity • About 1,000 new chemicals introduced every year • Quality of life in U.S. is better than most other places b/c most vehicles and factories have pollution control devices • New health risks are discovered frequently • Example: Scientists now believe that chemical pollution may be at least part of the cause of Parkinson’s disease and Alzheimer’s disease • Burning fuels introduces enormous amounts of pollutants into the air • CO, particulates • Contributes to many premature deaths from asthma, heart disease, etc. • Long-term exposure to soot particles raises a person’s risk of dying from lung and heart diseases • Pesticides allow more food production but are often dangerous to humans in large doses • Most modern pesticides are organophosphates and break down quickly in the environment • Toxic, especially to children CHEMICALS THAT DISRUPT HORMONES • Ecotoxicology – study of effects of pollutants on organisms • Studies genetic, cellular, or reproductive changes in organisms exposed to specific pollutants • Many pollutants disrupt the endocrine system • Glands that produce hormones • Hormones control most life processes • Hormone mimics – pollutants that behave like natural hormones • Hormone disrupters – pollutants that prevent natural hormones from functioning normally • Hormone mimics have been found in male trout and eels that contained egg-yolk proteins usually produced only by females • Found downstream from sewage treatment plants • Estrogen-like chemicals that induce male fish to make female proteins • Come from detergents and urine of women taking contraceptive pills • Hormone disrupters interfere with sex hormones • Phthalates - used in cosmetics like hair dyes and fingernail polish • Alligators in a polluted Florida lake had such abnormally small male sex organs and low testosterone levels that they could not reproduce • The herbicide atrazine disrupts sexual development of frogs • Killer whales and beluga whales are developing reproductive problems, tumors , and sexual abnormalities • Imposex in snails • Imposex – females develop male sexual organs • Causes sterility and declines in populations • Tributyltin (TBT)is linked to imposex in dogwhelk snails • TBT is common additive in antifouling paints • When TBT was banned for yachts, boats, and fish cages, the dogwhelk populations bounced back • Waste disposal remains inadequate • Wastewater from cities carry oil and toxic chemicals into waterways • Waste incineration emits toxic products to the air • Mining can release toxic contaminants into waterways • Landfills are leaking • Some sewage treatment plants release raw sewage into waterways after heavy rains • Radioactive waste from nuclear power plants
