The Environment and Health - Chemical contamination
The continuing proliferation of chemicals, many of them toxic, suggests the dimensions of the problems relating to water pollution. One estimate by the EPA's Office of Toxic Substances indicated that more than 70,000 chemicals are manufactured or processed commercially in the United States. About 1,000 new chemical compounds are added annually. Literally hundreds of these compounds find their ways into the nation's water supply, some in potentially dangerous concentrations.
How directly and to what degree chemical contaminants contribute to America's health bill cannot be gauged with accuracy. But the roles of these contaminants as carcinogens is widely accepted. Federal health officials have estimated that environmental carcinogens, including those in water, account for 55 to 60 percent of all U.S. cancer cases annually. Some estimates run much higher.
A study by the U.S. Geological Survey reported that small amounts of seven toxic metals were present in many of the nation's lakes and streams, with dangerous concentrations occurring occasionally. The metals are mercury, arsenic, cadmium, chromium, cobalt, lead, and zinc. Aside from being generally poisonous, some of these metals are implicated in specific health problems. Cadmium, as one example, has been linked to hypertension caused by kidney malfunction. Some other substances represent special situations.
Because mercury is heavier than water, experts thought for years that it could be dumped into lakes, the oceans, and waterways. In theory, the mercury would lie harmlessly on the bottom. In reality, bacteria can convert some of the metallic part of the element into water-soluble form. The new compound enters the food chain and ends up in fish. When dangerous levels of this form of mercury were found in some waters and in food fish, warnings were issued regarding canned tuna and swordfish. The government later announced that 97 percent of the tuna on the market was safe to eat. But lakes and rivers across the country were closed to commercial and sport fishing.
An extremely toxic substance, mercury can, even in small concentrations, produce blindness, paralysis, and brain damage. The U.S. Food and Drug Administration has established the safe limit of mercury in food at half a part per million—about the equivalent of a thimbleful in an Olympic-sized swimming pool.
Among the chief water pollutants today are the polychlorinated biphenyls (PCBs), highly toxic chemicals used industrially in carbonless copying paper and as an additive in lubricants, paints, printing inks, coatings, waxes, and many other products. PCBs, which are biodegradable (capable of decomposing) only over a period of years, have been found in unusually large quantities in waterways downstream from manufacturing plants. The EPA banned the direct discharge of PCBs into any U.S. waterway in 1977 after tests showed that fish in some rivers, like the Hudson, had levels of PCBs far higher than the permissible levels.
No one knows what the long-term effects of ingesting small quantities of PCBs will be. But the chemical is a suspected carcinogen. PCB's have also caused severe skin and eye irritations and have been implicated in reproductive disorders, kidney damage, and liver ailments. Researchers believe that the millions of pounds of PCBs in the nation's water or in landfills will take many years to dissipate.
Sewage treatment plants around the country also face the major health challenge of disposing of the sludge, or solid matter, that is removed from sewage in the treatment process. Sludge contains not only human wastes but the residues of petroleum products, detergents, toxic heavy metals such as cadmium, lead, and zinc, and many other contaminants. Disposal methods range from dumping on land to burning and to composting for use as fertilizer. But environmental experts maintain that the use of sludge as fertilizer constitutes a health hazard; and major food processors will not accept food grown with sludge as fertilizer. In refusing such food, the companies are following guidelines set by the National Food Processors Association, which has expressed concern for farm workers’ health and for the health of the consumer.
The sludge comes from an estimated 6.8 billion gallons of sewage flushed daily into America's sewers. The sewage itself contains microorganisms that can endanger health. You may be risking gastrointestinal upsets if you swim at a beach that is posted with a sign proclaiming “polluted water.” Scientists warn that the fish caught in sewage-polluted coastal waters and harbors may not only be cancerous, they may also be carcinogenic. A number of states including Michigan and New York have restricted or banned sales of tainted fish such as naturally grown carp, catfish, and striped bass.
With the increasing reliance on supertankers to carry industrial and heating oil from abroad, the danger of major water-polluting oil spills in coastal areas has grown substantially. Several of these huge ships have gone aground and broken apart under heavy pounding by sea waves. Their cargoes have spilled into the oceans, where currents usually carry them many miles before they float ashore or sink to the ocean floor. The oil reaching land fouls beaches and kills water birds. Similar accidents on inland waterways have polluted rivers and lakes, killing fish and spoiling recreational areas.