Unexpected pollutants in lakes

While studying lake water for pesticide contamination, chemists at a Swiss agricultural research laboratory found an unexpected pollutant: clofibric acid, a drug for lowering cholesterol.

Clofibric acid is not manufactured in Switzerland, so industrial spillage was ruled out as a cause. The chemists checked other bodies of water, including rural mountain lakes and rivers that run through cities, and found very low concentrations of the drug everywhere.

Berlin researchers also found clofibric acid in local waters: "It laced some groundwater at concentrations of up to 4 milligrams per litre, or 4 parts per billion (ppb)... It also turned up in all the Berlin tap water they sampled-at up to 0.2 ppb."

Once they started looking, European researchers found lipid-lowering drugs, analgesics (including ibuprofen and diclofenac), beta-blocker heart drugs, chemotherapy drugs, antibiotics, and hormones in water bodies that supply drinking water. Higher concentations were found in more populated areas. Having ruled out indusial spillage, researchers realised that the drugs had come from human body wastes.

How much of a drug gets broken down by the body varies depending on the drug and on the individual. As much as 50% to 90% of a medicine, in its original form, may be excreted from the body. Sometimes, chemical reactions with the environment turn partly degraded drugs back into an active form. No one knows what the concentrations are in US waters, because no one is looking. The FDA does not require that water supplies be monitored to see if pharmaceutical concentrations match manufacturers' estimates.

Stuart Levy, who directs the Center for Adaptation Genetics and Drug Resistance at Tufts University (Boston, Mass.), has said that antibiotics at a parts-per-trillion concentration can affect Escherichia coli and other bacteria.

Meanwhile, Swiss researchers have found 0.5 micrograms per litre of fluoroquinolone antibiotics in sewage-treatment-plant- water--1,000 times higher than the parts-per-trillion figure to which Levy refers.