The study entitled, Statistical Modeling Suggests That Anti-Androgens in Wastewater Treatment Works Effluents Are Contributing Causes of Widespread Sexual Disruption in Fish Living in English Rivers,” and published in the journal Environmental Health and Perspectives identifies a group of river pollutants that cause testosterone to stop working. These chemicals, released from wastewater treatment operations into rivers and other surface waters are responsible for the feminization of male fish and abnormalities in male reproductive organs. Previous studies have attributed these problems in male fish to estrogenic compounds also found in surface waters.

However, this study is the first to identify anti-androgens with the feminization of male fish. It also indicates that male feminization may be the result of a rather more complicated interaction taking place between different classes of pollutants, resulting in an endocrine disrupting chemical cocktail.

“We have identified a new group of chemicals in our study on fish, but we do not know where they are coming from or what they are. We’ve only been able to measure their testosterone-blocking potential” said Susan Jobling, PhD, of Brunel University, one of the authors of the study.

The scientists analyzed anti-androgenic activity in samples of river water taken near 30 sewage outflows. They were able to demonstrate statistically that this activity could be linked with feminized fish found in the same rivers. Several chemicals in widely-used pharmaceuticals and pesticides are known to have anti-androgenic activity. They include several compounds found in agricultural pesticides.

Relatively high levels of anti-androgenic chemicals were detected near sewage outflows, suggesting they came from domestic sources. One possibility is that drugs excreted from the body may end up in rivers. However, the scientists also believe that the anti-androgens may also be seeping into rivers as run-off from agricultural land.

Feminization of male fish is a phenomena documented in recent decades in many rivers and surface waters in the US and Britain. Studies have long pointed to chemical contaminants such as pesticides and other endocrine disrupting chemicals, as having the potential for wreaking such hormonal chaos. Many pesticides have been implicated, including . Other animals like polar bears, big cats, alligators and frogs have been observed with abnormalities in their reproductive organs, which have been attributed to environmental contaminants. Research has also shown that pregnant women exposed to environmental contaminants gave birth to babies with male reproductive defects.