What goes down the drain isn't really gone forever. Dabbed-on perfumes, excreted antibiotics, sunscreen lotion, and insect repellent all make their way into treated wastewater which is often sluiced back into the nation's streams. Now scientists with the U.S. Geological Survey (USGS) have documented for the first time the low-key presence of many of these drugs and personal care products in streams across the nation. The levels aren't enough to raise concerns for swimmers and tap-water drinkers, but the impact on wildlife is unknown.
Before the stream survey started in 1999, most research on pharmaceuticals and personal care products in streams had been done in Europe, says Herbert Buxton, one of the paper's co-authors and coordinator of the USGS's toxic substances hydrology program. U.S. researchers have been studying the effect of hormone-like pollutants, but only in a few areas. The USGS effort is the first attempt to look for organic pollutants in streams across the county.
Highly hygienic USGS scientists and technicians--"no potato chips, no coffee, no insect repellent," says Buxton--collected samples from 139 streams in 30 states. Eight of the streams were in relatively pristine regions; the rest were downstream from cities and large agricultural sites such as dairies and pig farms. The researchers developed five methods to analyze the samples for 95 organic chemicals including antibiotics, ibuprofen, fragrances, and hormonal residuals from birth-control pills.
The team detected 82 of the 95 compounds. Of the 139 streams, 80% contained at least one of the chemicals; more than a third of the streams had more than 10. All the concentrations were miniscule--in the part per billion range--the scientists report in the 15 March issue of Environmental Science and Technology. Only 14 of the contaminants are regulated, and none of the measured levels violated safety regulations. But even at these low concentrations, Buxton says, the effect of personal care products on river ecosystems is unknown.
For the estrogen-type pollutants, the potential impact is clearer. All the values reported in the study are high enough to change the sex of some kinds of fish, says aquatic toxicologist Daniel Schlenk at the University of California, Riverside. The problem with these trace amounts is that they may appear harmless in a quick test for toxicity--"but if after 28 days you have 100% females, that's a big effect," Schlenk says. The cumulative long-term effect of these pollutants may be more important than the dose at which 50% of a population of water fleas or minnows dies, he says.