Flushed contraceptive pills are leading to a fifth of male fish becoming "intersex", according to recent findings, with some male river fish even producing eggs.
Tests carried out by Professor Charles Tyler from the University of Exeter found that 20 percent of freshwater fish from 50 sites had "feminine characteristics". Tyler noted that some fish also had a reduced sperm count and displayed less aggressive behaviours, thus decreasing their chances of breeding successfully.
The contraceptive pill isn't the only product to blame, as ingredients from cleaning products, plastics and cosmetics have some part to play, too. In fact, according to Tyler's study, flushed anti-depressants have also been affecting the behaviour of river fish, altering some species' natural shyness and therefore changing the way they interact with predators.
Tyler – who will present his findings at the 50th anniversary symposium of the Fisheries Society in the British Isles today – told The Telegraph: "We are showing that some of these chemicals can have much wider health effects on fish that we expected. 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."