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HUMANS HEALTH AND WATER POLLUTION: CHEMICAL CONTAMINANTS
Most chemicals designed to dissolve grease and oil are called organic solvents. These extremely toxic substances, such as carbon tetrachloride, tetrachloroethylene, and trichloroethylene (TCE), are used to clean clothing, painting equipment, plastics, and metal parts. Many household products, such as stain and spot removers, degreasers, drain cleaners, septic system cleaners, and paint removers, also contain these toxic chemicals.
Organic solvents work their way into the water supply in different ways. Consumers often dump leftover products into the toilet or into street drains. Industries pour leftovers into large barrels, which are then buried. After a while, the chemicals eat their way out of the barrels and leach into the groundwater system.
A number of hazardous materials can be recycled or treated to remove or minimize toxicity. For example, lubricating, hydraulic, and fuel oils can be refined to produce clean fuels that can be used in diesel engines or industrial boilers. Many chemical wastes can be treated to destroy hazardous components, such as heavy metals, cyanides, hexavalent chromium, and toxic organics, or to recover them for safe disposal. These processes are often costly, however, and often industries may not be willing to pay the costs associated with safe disposal of toxic materials.
One related group of toxic substances contains chlorinated hydrocarbons. The most notorious of these substances are the polychlorinated biphenyls (PCBs), their cousins the polybromated biphenyls (PBBs), and the dioxins.
PCBs
PCBs are fire resistant and stable at high temperatures and were therefore used for many years as insulating materials in high-voltage electrical equipment such as transformers. PCBs bioaccumulate, meaning that the body does not excrete them but rather stores them in fatty tissues and the liver. PCBs are associated with birth defects, and exposure to them is known to cause cancer. The manufacture of PCBs was discontinued in the United States in 1977, but approximately 500 million pounds of PCBs have been dumped into landfills and waterways, where they continue to pose an environmental threat.
Dioxins
Dioxins are chlorinated hydrocarbons that are contained in herbicides (chemicals that are used to kill vegetation) and produced during certain industrial processes. Dioxins have the ability to bioaccumulate and are much more toxic than PCBs.
The long-term effects of bioaccumulation of these toxic substances include possible damage to the immune system, increased risk of infection, and elevated risk for cancer. Exposure to high concentrations of PCBs or dioxins for a short period of time can also have severe consequences, including nausea, vomiting, diarrhea, painful rashes and sores, and chloracne, an ailment in which the skin develops hard, black, painful pimples that may never go away.
Pesticides
Pesticides are chemicals that are designed to kill insects, rodents, plants, and fungi. Americans use more than 1.2 billion pounds of pesticides each year, but only 10 percent actually reach the targeted organisms. The remaining 1.1 billion pounds of pesticides settle on the land and in our water supplies. Pesticide residues also cling to many fresh fruits and vegetables and are ingested when people eat these items.
Most pesticides remain in the environment and accumulate in the body. A recent study found a correlation between breast cancer and Dieldrin, a popular pesticide used until the 1970s. The women in the study who had the highest traces of Dieldrin in their blood were twice as likely as women with the lowest levels to develop breast cancer. Other potential hazards associated with exposure to pesticides include birth defects, cancer, liver and kidney damage, and nervous system disorders.
Lead
The Environmental Protection Agency has issued new standards intended to reduce dramatically the levels of lead in U.S. drinking water. These standards are already in place in many municipalities and will eventually reduce lead exposure for approximately 130 million people. The new rules stipulate that tap water lead values must not exceed 15 parts per billion (the previous standard allowed an average lead level of 50 parts per billion). When water suppliers identify problem areas, they will have to lower the waters acidity with chemical treatment because acidity increases water\'s ability to leach lead from the pipes through which it passes, or they will have to replace old lead plumbing in the service lines.
One way to reduce the possibility of ingesting lead if it does exist in your home\'s water system is to run the tap water several minutes before taking a drink or cooking with it to flush out water that has been standing overnight in lead-contaminated lines. Although leaded paints and ceramic glazes used to pose health risks, particularly for small children who put painted toys in their mouths, the use of leads in such products has been effectively reduced in recent years.
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GENERAL HEALTH
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