A national study by the U.S. Geological Survey of U.S. streams across 30 states shows they are polluted by the painkillers acetaminophen and ibuprofen, prescription medicines for cardiac disorders and hypertension, and female sex hormones used in birth control pills and hormone replacement therapy.

The national survey specifically targeted 95 organic wastewater contaminants. The researchers sampled 139 stream sites throughout the country, during 1999-2000. In addition to medications, caffeine and cotinine, a nicotine breakdown product, were also among the most frequently detected compounds. So too were cholesterol and coprostanol, steroids that can be indicative of fecal contamination.

Also present were the insect repellant DEET, triclosan, the active ingredient in antimicrobial soaps and detergents, a flame retardant (tri(2-chloroethyl) phosphate) and a detergent breakdown product with endocrine disruptive properties (4-nonylphenol).

Of the 95 target compounds, the researchers found 82 of them in at least one stream. And in 35 percent of streams, the scientists found 10 or more compounds. In one stream, they found 38 chemicals. The scientists expected to find most of the compounds eventually, but the high number of mixtures surprised them, says Dana Kolpin, a USGS research hydrologist.

Researchers tried to pick streams that were most likely to show some contamination. Most are downstream from wastewater treatment plants or livestock activity. Although concentrations of most of the compounds were low, typically less than one part per billion, previous research has shown that exposure to levels even lower than this can cause dangerous effects in aquatic species. The effects on humans who drink the water have not yet been determined.

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