Male river fish are displaying feminised traits and even producing eggs, the study found. Some have reduced sperm quality and display less aggressive and competitive behaviour, which makes them less likely to breed successfully.
The chemicals causing these effects include ingredients in the contraceptive pill, by-products of cleaning agents, plastics and cosmetics, according to the findings.
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.
Charles Tyler from the University of Exeter is to present his findings in a keynote lecture this week. He will explain that the offspring of such “transgender” or “intersex” fish can also be more sensitive to the effects of these chemicals in subsequent exposures.