By Janet Raloff
From Minneapolis, at the Second International Conference on Pharmaceuticals and Endocrine Disrupting Chemicals in Water.
Last year, federal scientists reported preliminary data showing that many rivers and streams in the United States contain traces of prescription drugs and household chemicals. Now, these researchers have found that many of these largely ignored pollutants are making their way through community waste-treatment and drinking-water plants, possibly even all of the way through the kitchen tap.
Deborah M. Moll and her colleagues at the Centers for Disease Control and Prevention in Atlanta, together with scientists of the U.S. Geological Survey, analyzed local streams, treated wastewater, and drinking-water supplies for 47 compounds typically found in municipal wastes. These ranged from caffeine to bisphenol-A, a compound used in polycarbonate plastics.
Thirty-eight of the chemicals, some 80 percent, turned up at least once. In one wastewater sample, concentrations of a combustion pollutant, benzo(a)pyrene, exceeded a limit set by the Environmental Protection Agency. Sixteen pollutants even appeared in samples of drinking water from the three surveyed water-treatment plants serving residents of the Atlanta area.
Overall, drinking-water concentrations of these pollutants proved low — 1.2 parts per billion at most. Six samples had the flame retardant tri(2-chloroethyl)phosphate and five contained phthalic anhydride, used in making plastics. The combustion products fluoranthene and pyrene each appeared in three drinking-water samples, as did triclosan, an antibacterial agent in household products (SN: 5/27/00, p. 342: Popularity of germ fighter raises concern). An antioxidant known as 2,6-di-tert-butylphenol and an ingredient in plastics called ethanol-2-butoxy-phosphate also showed up in three samples.
Moll notes that four of the pollutants in some drinking water are also suspected hormone mimics: benzo(a)pyrene, the flame retardant, triclosan, and para-nonylphenol, which is in some detergents.
The scientists also surveyed the same waters for 42 different prescription and over-the-counter drugs. Owing to the streams’ locations, Moll said, any drugs in them probably trace to human excretion.
Overall, her group identified 17 drugs in the samples, with a couple of them hosting residues of 10 pharmaceuticals. Among those drugs that survived passage through waste-treatment facilities — but not drinking-water-treatment plants — were diltiazem, which is used to regulate blood pressure; metformin, an antidiabetes drug; gemfibrozil, a cholesterol-lowering drug; and dehydronifedipine, a breakdown product of a drug for angina.
Only two prescription drugs — the antibiotics trimethoprim and sulfamethoxazole — made it into drinking water, and only in trace amounts.
Three nonprescription drugs also showed up in some of the drinking-water samples: caffeine, acetaminophen, and a breakdown product of nicotine.
These studies generally are consistent with earlier Canadian findings that North American municipal wastewater-treatment plants fail to eliminate many potentially toxic chemicals (SN: 4/1/00, p. 212: More Waters Test Positive for Drugs). As such, people who swim or work in rivers and urban lakes risk exposure to such agents.
While drinking drug-laced water may not sound appetizing, it probably offers almost no risk of toxicity in the short term, notes chemist Thomas A. Ternes of the Institute for Water Research and Water Technology in Wiesbaden, Germany. Even drinking 2 liters of the tainted water every day over a lifetime, he says, wouldn’t cumulatively deliver the equivalent of a single prescribed dose of any of the polluting drugs.
However, Ternes was less sanguine about the new report’s finding of traces of antibiotics in drinking water. He notes that such tiny exposures are precisely the type that foster development of bacteria resistant to these drugs.
