Researchers have detected antidepressant drugs in the brains of fish captured downstream of sewage-treatment plants.

Pharmaceuticals taint waterways because people excrete many of the drugs they take but treatment plants don’t extract all the chemicals (SN: 4/1/00, p. 212: More Waters Test Positive for Drugs). Concerned that antidepressants might be accumulating in fish, Melissa M. Schultz of the College of Wooster (Ohio), and Edward T. Furlong of the U.S. Geological Survey in Denver measured concentrations of several such medicines in river water and fish in Colorado. They tested for drugs including sertraline (Zoloft), fluoxetine (Prozac), and venlafaxine (Effexor).

Sertraline and fluoxetine, two of the most widely prescribed antidepressants, showed up downstream of sewage-treatment plants but only in low parts-per-trillion concentrations. To the researchers’ surprise, they found several less commonly prescribed antidepressants in significantly higher concentrations. For instance, venlafaxine reached concentrations as high as 1.4 parts per billion (ppb).

On the other hand, the higher-concentration waterborne antidepressants, such as venlafaxine, didn’t show up in fish, whereas sertraline and fluoxetine did—in concentrations up to 2.5 ppb in brain tissue. The chemists reported their findings last month in Montreal at the Society of Environmental Toxicology and Chemistry meeting.

The results were “certainly counterintuitive,” Furlong says. He adds that the team will now study why only some of these drugs appear to be getting into fish.

One concern, Schultz says, is that because these drugs target similar signaling compounds in the brain, their effects might be additive.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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