Male fertility fears over pollution in water supply

Half of all the male fish in lowland rivers are changing sex as a result of pollution, alarming new official research suggests. The findings raise serious questions as to whether the pollution is getting into drinking water and affecting human fertility.

The research – to be published by the Environment Agency this month – shows that male fish are developing female characteristics in rivers all over the country. In some stretches all the male fish have been feminised.

Scientists conducting the research blame a particularly powerful form of oestrogen in urine from the contraceptive pill, which is flushed through sewage works into the rivers. Some fear that the "exquisitely potent" chemical may be contaminating part of the one third of all of the country's drinking water that is taken from rivers.

The water industry and the agency strongly deny that this situation – revealed by a joint investigation by The Independent on Sunday and BBC TV's Countryfile – could damage health. But environmentalists fear that the fertility of some men could be affected by years of drinking the water. Sperm counts have been falling dramatically in Britain over the past half-century. Yesterday Peter Ainsworth, the shadow environment secretary, said: "Danger to human fertility cannot be ruled out" and called for an urgent programme of research on the threat. The agency said that it was taking the pollution "very seriously" and would unveil an action programme later this month.

The research, financed by the Department of Environment Food and Rural Affairs and the official Natural Environment Research Council, has examined roach from 10 rivers over the past five years. They found feminised "intersex" males in all of them – the rivers Lea in Hertfordshire (from which London takes much of its drinking water), Blackwater in Essex, Arun in West Sussex, Avon in Bristol, Rea in Shropshire, Wreake in Leicestershire, Nene in the East Midlands, Ouse in North Yorkshire and Aire and Calder in West Yorkshire.

It found that, on average, just under 50 per cent of the male fish had developed eggs in their testes, and/or female reproductive ducts – a finding they believe is likely to be typical of roach and other species of fish all over the country. In stretches of the Aire and Nene all the male fish were affected in this way: even in relatively unpolluted waters 7 to 8 per cent were affected.

The fish did not change back after being put into clean water, suggesting that the changes were permanent. About one tenth of male fish were sterile, and about another quarter had damaged sperm.

The research suggests that the main culprit is ethanol oestradiol, a synthetic oestrogen used in the contraceptive pill which the scientists say can feminise fish at levels of as low as one part per billion. Conventional sewage treatment is ineffective at removing it from water.

Professor Charles Tyler of Exeter University, one of the leaders of the research, says that it is "so exquisitely potent that some of the very concentrations where we are seeing effects on fish are below the detection limit that is presently in place for testing our drinking water. So we cannot be sure that some of these compounds, albeit at very low concentrations, aren't getting into our drinking water".