Tipsy Fish: When Anti-Anxiety Meds Get Into Rivers

By Veronique GreenwoodFeb. 15, 2013

The modern pharmacopeia is a glorious thing—drugs have helped many people with depression and anxiety, not to mention cancer and other life-threatening diseases. But what goes down your throat must eventually come out, er, elsewhere—especially since drugs are designed specifically so they won’t break down on the pharmacy shelves or in a patient’s body. Starting in the 1990s, with the advent of super-sensitive chemical-detection technology, scientists began discovering that a lot of this medical chemistry is surviving wastewater treatment plants and flowing into waterways. That, in turn, raised a basic and troubling question: What’s it doing to the fish?

Typically, the impact of industrial chemistry on wildlife is tested using fairly basic measures of toxicity. If it doesn’t kill animals outright or prevent them from reproducing—as DDT did by causing birds to lay thin-shelled eggs—it’s not considered a clear and present threat. But with more and more psychotropic drugs like antidepressants and anti-anxiety drugs flowing from factories, into consumers and out into the wild, environmental scientists have begun to worry that the meds may be affecting animal behavior too. In a paper published this week in the journal Science, Swedish researchers report that they put that question to the test—and they came up with some troubling answers.

The scientists, all affiliated with Sweden’s Umeå University, began by testing perch, a species of schooling fish, living downstream from a wastewater treatment plant. The investigators were specifically looking for traces of the anti-anxiety drug oxazepam, which has been observed in waste water before. They found the drug in the water and, when they examined muscle samples of the fish, saw it there too—but in six times the concentration it is in the river, suggesting that it builds up in the animals’ bodies over time. Next, they started afresh with a school of perch they hatched from eggs and, when they had grown, put them through a battery of tests to measure behavioral qualities thought important for perch survival, such as schooling and danger avoidance. Then they split the school into three groups: the first would live in a tank with clean water, the second would swim in water with a same concentration of oxazepam on the order of what was found in the river, and the third would get water with 500 times the river’s concentration.