Medicinal waters: Where ibuprofen goes.

Last year, when Swiss chemists were looking for pesticide residues in lakes, they instead turned up the heart drug clofibric acid (SN: 3/21/98, p. 187). Several months later, they identified another pharmaceutical in Swiss rivers and lakes: diclofenac, an anti-inflammatory drug. In both cases, human urine appeared to be the source of the water-polluting drugs.

Mulling over their findings, Hans-Rudolf Buser and his colleagues at the Swiss Federal Research Station in Wadenswil became curious. Why weren't they also finding ibuprofen, a much more common anti-inflammatory drug?

In the August 1 ENVIRONMENTAL SCIENCE & TECHNOLOGY, these chemists report finding a critical difference in the environmental fates of the three drugs. While clofibric acid and diclofenac pass through municipal water-treatment facilities unscathed, ibuprofen doesn't. In Switzerland, wastewater-treatment plants "seem to get rid of maybe 95 percent or so" of the ibuprofen, Buser says. That's important, he notes, because unlike diclofenac, ibuprofen appears resistant to photolysis, or breakdown upon exposure to sunlight. Clofibric acid also resists photolysis, which is why it can be found entering the ocean up to thousands of miles from its source.

Buser's group also showed that the waterborne ibuprofen is from human excretion, not direct dumping. Manufacturing produces two mirror-image versions of the ibuprofen molecule. Although only the left-handed molecule is pharmacologically active, Buser notes, the marketed drug contains a mix of both the left- and right-handed forms. His team now reports finding only the left-handed ibuprofen, together with products that form through the body's action on the drug, in water entering wastewater-treatment plants. Because the right-handed form is altered in the body, this means that the ibuprofen had passed through people. Fortunately, he says, waste-treatment plants degraded the two forms and their by-products equally well.