Fish found in American waterways appear to show genetic and neurological changes due to rising levels of antidepressant medications in the water.
A report, published un Environmental Health News, says scientists at the University of Wisconsin-Milwaukee have found changes in fathead minnows from laboratory exposures at levels mimicking typical wastewater discharges.
Antidepressants enter US waterways through sewer systems, and the systems are not designed or operated to deal with this sort of material. Federal regulation does not see them as pollutants, either.
EHN, however, says the U.S. Environmental Protection Agency (EPA) has put antidepressants and other medications on a list for possible regulation because of the risks they may pose to wildlife.
The research exposed fish to Prozac, Effexor and Tegretol, at varying doses that they may expect to meet downstream from wastewater discharges.
Scientists could tell whether the minnows were experiencing anxiety from the fishes' odd behaviour - this included swimming unusually long distances and making more directional changes as they went.
This sort of behaviour may have significant impact on the feeding and reproducing of the fish and, therefore, the population.
When male minnows were exposed to low doses of Prozac, for example, they ignored females, took more time in feeding and spent more time hiding. At higher does, they were aggressive to other fish, sometimes even killing the females.
The drugs also affected females' egg production in negative ways.
Researchers found "architectural changes" in the minnows' brains and, from that, came up with the idea that the medications alter the genes that control nerve growth.
The report also shows that the antidepressants concentrate in tissues of some fish, such as rainbow trout.
The EHN's work is not the first to find behavioural disruption from pharmaceutical pollution.
Prozac has been found to make shrimp less aware of predators, and Swedish researchers reported that benodiazepines, such as Valium, promote antisocial and aggressive behaviour in perch.