Study shows flushed traces of anxiety drug affect fish behavior

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Swedish researches have found that the popular anti-anxiety drug oxazepam is having a measurable effect on aquatic wildlife. Trace amounts of the drug end up in waterways after being flushed through insufficient sewage treatment. The drug remains biochemically active in the wild, and the new study shows that it makes fish populations bolder, more anti-social and prone to feed at higher rates.

Researchers tested European Perch by duplicating the concentration of the drug found in local surface waters — about a microgram per kilogram of fish weight. Perch are typically mild, shy and hunt in schools, but researches observed that exposed Perch "exhibited increased activity, reduced sociality, and higher feeding rate." Their report went on to say that "as such, our results show that anxiolytic drugs in surface waters alter animal behaviors that are known to have ecological and evolutionary consequences."

But this oxazepam isn't the only drug that finds its way into waterways. "A variety of pharmaceuticals enter waterways by way of treated wastewater effluents and remain biochemically active in aquatic systems. Several ecotoxicological studies have been done, but generally, little is known about the ecological effects of pharmaceuticals."

Researcher Tomas Brodin and his colleagues believe it is necessary to improve sewage treatment to capture active drugs and limit contamination. Their study has been published in the journal Science.