Something we failed to take into account: prescription drugs that make us happy are not magically absorbed inside our bodies by a team of smiling rainbows. Nope. They eventually make their way to our toilets, where we flush them away to water treatment centers. There, infectious germs are eliminated and the water is released into streams, chemicals intact.
The fish on drugs aren’t happy about this. In fact, there is evidence that our antidepressants are making them anxious. In a recent study done at the University of Wisconsin−Milwaukee, male fathead minnows swimming in waters contaminated with fluoxetine (Prozac) became aggressive and homicidal, reports Brian Bienkowski of the Environmental News Network (June 12, 2013). Exposed to doses as low as one part per billion, males spent more time hiding under a tile, making them slower to catch prey and less likely to breed. Increased doses saw females producing fewer eggs and males becoming increasingly aggressive, sometimes killing females. When minnows are exposed during development, Bienkowski writes, the drug seems to scramble genetic expression.
Though the university’s study was controlled, levels of exposure tested were similar to those entering streams via treatment centers. Still, Bienkowski notes, there is not enough evidence yet to know whether or how pharmaceuticals are impacting fish in the wild.