The ability of fish to breed has been drastically affected, a study reveals, by 'gender bending' chemicals which are washed into rivers and oceans as a result of human activities.
The findings from the four-year study, led by the universities of Exeter and Brunel, has important implications for understanding the impacts of these chemicals on ecosystem health and possibly on humans.
Endocrine disrupting chemicals (EDCs) disrupt the ways that hormones work in the bodies of vertebrates (animals with backbones), including humans.
They can be found in everything from female contraceptive drugs and hormone replacement therapy pills, to washing up liquid, with the most well studied EDCs being those that mimic oestrogen (female hormone).
EDCs have been seeping into rivers through the sewage system for decades and have an observed effect on fish, altering male biology to make them more female - hence the 'gender bending' reputation of these chemicals.
Until now, there has been no solid evidence to show the long-term impact of this effect on fish in the wild - but the new research focusing on wild roach in two UK rivers (Bourne and Arun) has provided new evidence.
Two large-scale breeding studies assessed the ability of fish to breed by using a genetic technique (DNA microsatellites) to match offspring produced to their parents.
It was found that intersex fish - those that had their sexuality compromised by EDCs and which contain both male (sperm) and female (eggs) sex cells - had their reproductive performance reduced by up to 76pc.
Charles Tyler, from the University of Exeter's Biosciences department, jointly led the research alongside Professor John Sumpter, from the Institute of Environment at Brunel University.
The study has been published in Environmental Health Perspectives online.