Fish are hung up to dry in Hong Kong's Aberdeen Harbor on October 13, 2014. A new study says that some freshwater male fish are displaying female characteristics as a result of chemicals being flushed into river streams. File Photo by Stephen Shaver/UPI | License Photo

July 3 (UPI) -- Cleaning agents and contraceptives flushed down household drains are turning male fish into females, according to a new study.

Professor Charles Tyler of the University of Exeter in Britain said male river fish are displaying more feminine traits, including reduced sperm and producing eggs because of the chemicals being introduced to their environment.


"We are showing that some of these chemicals can have much wider health effects on fish that we expected," Tyler said, according to The Telegraph. "Using specially created transgenic fish that allow us to see responses to these chemicals in the bodies of fish in real time, for example, we have shown that oestrogens found in some plastics affect the valves in the heart."

Tyler said that tests have shown that 20 percent of freshwater fish at 50 different sites has higher feminine characteristics and the offspring of these fish tended to be more susceptible to chemical alteration.

RELATED Common insecticide is harming animal life in wetlands and waterways

In addition to having effects on gender, Tyler said that medications like anti-depressants have made some fish more social, which can sometimes be deadly.

"Other research has shown that many other chemicals that are discharged through sewage treatment works can affect fish, including antidepressant drugs that reduce the natural shyness of some fish species, including the way they react to predators," Tyler said.

The effects of chemicals on fish gender has been a topic of concern for scientists for several years.

In 2010, The Potomac Conservancy in Washington, D.C. called for more research to be done after it was found that more than 80 percent of male bass fish in the Potomoc River exhibited female traits, such as eggs in their testes, likely due to a "toxic stew" of chemicals.

"We have not been able to identify one particular chemical or one particular source," said Vicki Blazer, a fish biologist with the US geological survey, according to The Guardian. "We are still trying to get a handle on what chemicals are important."