As tiny amounts of Prozac and other antidepressant drugs trickle from our wastewater into rivers and lakes, fish can become sluggish and isolated. Exposed to high concentrations, though, male fish turn violent, according to a recent report in the scientific journal Aquatic Toxicology.
When University of Wisconsin-Milwaukee ecologist Rebecca Klaper exposed fathead minnows to Prozac, she found that the drug impaired the fishes' brain function. At small doses, males hid from females under tiles, spending less time mating and more time looking for food. But as doses increased, the minnows turned ugly, killing two-thirds of the female fish. Those that died "had visible bruising and tissue damage," Klaper says in a statement.
Sewage systems aren't engineered to extract drugs, allowing prescription antidepressants to filter through freshwater ecosystems without fully breaking down. Nor is this an isolated problem -- an Associated Press investigation found traces of pharmaceuticals in the drinking water of two dozen U.S. metropolitan areas.