ENVIRONMENTAL SCIENCE UNIT 7 POLLUTION AND HUMAN HEALTH

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 effectsbb

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