Drugged to death

waterways across the us are contaminated by a number of antibiotics, caffeine, painkillers and other drugs, finds a recent study conducted by the us Geological Survey (usgs). The study targeted 95 organic wastewater contaminants and sampled 139 stream sites in 30 us states during 1999-2000. The 95 pollutants were picked on the basis of estimates about the quantities used, toxicity, potential hormone activity, suspected persistence in the environment and the availability of reference standards. "The study indicted that chemicals used in households, agriculture and industry can enter the environment through a variety of wastewater sources," said usgs research hydrologist Dana Kolpin, who headed the study. "It begins a process of exploring the occurrence of these chemicals in our nation's streams," said Robert Hirsch, usgs associate director for water ( www.nytimes.com , March 28, 2002).

Concentrations of most of the compounds were found to be less than one part per billion. Previous research has shown that exposure to levels even lower than these can cause harm to aquatic species. The most frequently detected compounds included:

• coprostanol, a steroid

• n-n-diethyltoluamide, an insect repellent

• caffeine, a stimulant

• cotinine, a nicotine breakdown product

• triclosan, an antimicrobial dis infectant

• tri (2-chloroethyl) phosphate, a fire retardant

• triclosan, the active ingredient in antimicrobial soaps and detergents

• 4-nonylphenol, a detergent breakdown product

"Overall, steroids, non-prescription drugs and a chemical found in insect repellents were the chemical groups most frequently detected," Kolpin said. "Detergent metabolites and steroids were generally measured at higher concentrations than the other chemical groups, but concentrations measured in this study generally were very low -- less than one part per billion." Of the 95 target compounds, the researchers found 82 of them in at least one stream. In 35 per cent of streams tested, the scientists found 10 or more compounds, and in one case, 38 chemicals were present in a single water sample.

The results of the study are intended to set a baseline for future research to examine questions such as how far downstream from their sources can these chemicals be found, or how concentrations of these chemicals vary with climate, land use, stream flow rates, or waste characteristics and treatment methods. When toxicity is taken into account, the measured concentrations of reproductive hormones may have implications for the health of aquatic organisms, according to Kolpin and his colleagues. "This is important new data," said Tamar Barlam, an infectious disease specialist at the Washington dc-based Center for Science in the Public Interest. "We know that bacteria are more likely to become resistant to drugs if they continue to encounter antibiotics. The next step is to see if there is a connection between contamination of waterways and antibiotic resistant infections in people."

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