If you drink water from a municipal system in the United States, the water must meet the purity standards mandated by the Safe Drinking Water Act of 1974. The U.S. Environmental Protection Agency sets and enforces standards for approximately 90 different contaminants in drinking water and reviews no more than 30 unregulated contaminants every five years. Current standards protect you from many hazards, but do not guarantee complete safety.
Primary Standards
The EPA's primary standards of drinking water quality address the most hazardous contaminants from three classes of toxins. Dangerous infective pathogens, radioactive contaminants and chemical poisons receive the strictest controls. Your drinking water may contain low levels of contaminants from all three categories, but in amounts not considered a risk to health. If you drink water with a pollution level the EPA deems safe, you should be protected from immediate acute illness and chronic illness caused by long-term exposure. Primary standards only protect you from contaminants on the EPA's controlled list, however. Your drinking water could contain untested and unregulated hazardous contaminants.
Secondary Standards
Your drinking water could meet the primary standards and still show unpleasant qualities. The EPA sets guidelines regarding odor, taste and color along with other aesthetic factors. The EPA does not enforce secondary standards. Water officially considered safe to drink could be discolored, smell bad or foam. Safe water could also contain unusual amounts of iron, fluoride, copper and harmless suspended solids. Current regulations encourage municipal water providers to deliver water that looks pure and clean, but accepts water that only meets primary health standards. Home filtration systems improve the appearance of drinking water, but may not significantly raise health standards.
Unregulated Contaminants
The EPA considers no more than 30 new contaminants during any five-year review cycle. Before the EPA places a pollutant on the list of contaminants governed by primary standards, studies must prove that it causes illness in humans and contaminates drinking water. Research must determine what level causes illness and what level of contamination is safe before the EPA will enforce a new primary standard. Current unregulated candidates include the hepatitis A virus, responsible for severe liver disease, and Salmonella enterica, a bacterium that causes food poisoning. Chemicals under consideration include the insecticide acephate and the fungicide captan, as well as industrial solvents, hormones and antibiotics.
Localized Problems
Problems in or near your home could add hazards to drinking water that met primary standards before it entered your plumbing. Older homes could contain lead pipes or copper plumbing with lead solder joints. Acidic water leaches lead from the pipes as it passes through. Leaking water mains admit pollutants from groundwater before drinking water reaches your house. Mixing water from the hot side of the tap with cooking or drinking water adds dangerous minerals concentrated inside your hot-water tank. Testing a water sample collected in your own home measures the true quality of your water supply.
References
- EPA; Basic Information about Regulated Drinking Water Contaminants and Indicators; March 29, 2011
- EPA; Unregulated Contaminant Monitoring Program; March 8, 2011
- University of Florida Extension; Drinking Water Standards; Judith C. Stewart, et al.; 2009
- EPA; Contaminant Candidate List 3 -- CCL; May 5, 2011
- EPA; Drinking Water Contaminants; May 4, 2011
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