Types of Pollutants Found in Drinking Water
The Green Guide
Even a pristine mountain stream can contain pathogens carried by livestock or wild animals, or toxic minerals that leach naturally from the ground. However, the most common sources of the drinking water contaminants listed on the next page include human sewage, industrial waste, pesticide runoff, backyard dumping and leaching from municipal landfills. Another area of grave concern is the leaking of pollutants from underground storage tanks, which hold everything from gasoline and heating oil to chemical and nuclear waste. According to recent U.S. Environmental Protection Agency (EPA) estimates, up to one-quarter of the 3-10 million underground storage tanks in the U.S. are likely to be leaking.
Following is a list of selected contaminants and the effects of exposure through drinking water:
Pathogens are microorganisms--bacteria, viruses, and protozoa--that enter drinking water from human sewage or animal feces. They cause diseases ranging from dysentery and hepatitis to Legionnaire's disease. Pathogens such as the bacteria E. coli in water sicken an estimated 940,000 people a year, kill several hundred and can cause miscarriages. Pathogens contaminate water through failure by water companies and government agencies to protect watersheds, to filter or adequately disinfect water or guard against treatment plant or animal feedlot overflow. At present the most effective disinfectant is chlorine.
Chlorine, however, does not kill two protozoa, Giardia lamblia and Cryptosporidium parvum, which can result in chronic illness or death to AIDs patients and others with weakened immune systems. Find out if your water system monitors for protozoa. To be safe, boil drinking water or use a tap water filter that removes particles of 1 micron or less. Bottled water labeled "micro-filtered" may not be protozoa-proof.
Inorganic chemicals and toxic metals
LEAD: According to the EPA, more than 800 U.S. cities have water that exceeds the EPA's "action level" for lead. Over half of U.S. cities still use lead-lined pipes or copper pipes with lead soldering, which are the primary sources of lead in drinking water. Even at low intake levels, lead can cause fetal damage and delayed neurological and physical development in children, and high blood pressure, heart attacks, kidney damage, reproductive dysfunction and strokes in adults.
VOLATILE ORGANIC COMPOUNDS (VOCs) are a special class of synthetic organic chemicals which include solvents like benzene, carbon tetrachloride, trichloroethylene, p-dichlorobenzene, and the building block of PVC plastic, vinyl chloride. Many VOCs are known or suspected carcinogens and can also affect the nervous system. VOCs evaporate readily, and thus can be inhaled while you shower.
ARSENIC, a well-known poison, is also classified as a known human carcinogen by the EPA. It can cross the placenta and accumulate in the body. Arsenic enters the water supply from smelting of many ores, such as copper and iron, and through its use as a wood preservative. Three hundred thousand people in the U.S. may be drinking water containing higher than the EPA's maximum allowable limit of 50 parts per billion of arsenic. High levels of intake can lead to abnormal fetal development and cardiovascular disease. The Northwest and Southwest have the lowest concentrations of arsenic in water.
CADMIUM, like lead, can be leached out of pipes, especially by soft, acidic water. Used for electroplating, in paint and pigments, and in the manufacture of PVC as well as nickel-cadmium batteries, cadmium enters the water supply from leaking landfills and fertilizer runoff (where it is a trace contaminant). Intake of cadmium, which accumulates in the body over time, is associated with hypertension and kidney damage.
Non-metallic inorganics include asbestos from cement water mains; cyanide from insecticides, metal refining, and pigment and plastic manufacture; and nitrates. Water contaminated with nitrates from nitrogen fertilizers is most common in farming areas, and can enter municipal watersheds through farm runoff. Infants who drink nitrate-tainted water can contract "blue-baby syndrome."
Synthetic organic chemicals (SOCs) are man-made chemicals that contain carbon. SOCs in some drinking water include pesticides like atrazine and alachlor (both suspected carcinogens), notorious industrial chemicals like dioxins and PCBs, and plastic-related chemicals such as phthalates and styrene. A 1995 study by the Environmental Working Group in Washington, D.C. found that approximately 10.2 million people in the Midwest, 1.5 million in Louisiana and 2.4 million in the Chesapeake Bay region drink water contaminated with weed killers; as a result, EWG concludes, 3.5 million people face cancer risks 10 to 100 times higher than the federal benchmark.
Chlorine and its by-products. Chlorine, an effective and currently necessary disinfectant, is added to all water supplies at treatment facilities to neutralize bacteria. Unfortunately, chlorine, reacting with organic chemicals left in the water by soil and decaying vegetation, also forms a group of chemicals called disinfection by-products (DBPs) or trihalomethanes (THMs). DBPs/THMs may be associated with 10,000 or more rectal and bladder cancers each year in the U.S., and are linked to pancreatic cancer as well. These chemicals may also cause major birth defects.
Fluoride is naturally occurring in some waters, and is also added to water supplies to fight tooth decay. Too much fluoride can cause mottling of teeth. Since fluoride is removed from the body by the kidneys, people with kidney disease who drink lots of water with fluoride can accumulate fluoride in their bones producing skeletal fluorosis, which can eventually have a crippling effect. There is some suggestion that fluoride is correlated with increased rates of cancer, though the evidence is not clear. Local drinking water programs are required to announce to the public when the fluoride level reaches more than 2 ppm; at this level the possibility of moderate to severe dental mottling increases. There is much debate over whether the risks of fluoridation outweigh its benefits
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