Study: Estrogen-Like Chemicals Turning Male Fish Into Females

Household chemicals and pharmaceuticals could be jeopardizing freshwater fish populations in the U.K., according to a newly released study.

Researchers from the University of Exeter found that one-fifth of male fish tested at 50 sites in the country's rivers showed some female characteristics, including egg production.

The analysis blamed hundreds of substances found at sewage plants known to mimic estrogen, including chemicals from birth control pills, cosmetics, plastics and cleaning agents.

Male fish with intersex characteristics can have lower sperm quality as well as display less aggressive or competitive behavior — which could make them less likely to breed successfully.

The authors added that subsequent generations of affected fish appear more sensitive to continued exposure to those chemicals.

“We are showing that some of these chemicals can have much wider health effects on fish that we expected," Exeter physiologist Charles Tyler said in a statement.

Researchers said that anti-depressants can also find their way from human waste to water supplies and affect fish, including how they reach to predators.

Scientists previously noted that estrogen and estrogen-like substances can impact fish even at extremely low concentrations, but a study by Canadian researchers last year suggested that upgraded water treatment systems could rehabilitate local fish populations relatively quickly.