Sperm counts are falling dramatically across Britain and the rest of industrialised world, and scientists are increasingly convinced that pollution is to blame.

Sperm counts are falling dramatically across Britain and the rest of industrialised world, and scientists are increasingly convinced that pollution is to blame.

Studies around the world have shown that average sperm counts in men have dropped by more than half over the past 50 years – from about 160 million per millilitre of semen to 66 million.

The Medical Research Council reports that the fertility of Scottish men born since 1970 was 25 per cent less than those born in the 1950s, with sperm counts continuing to drop by two per cent a year.

Other research by the US Government's Environmental Protection Agency shows that, proportionately, a man now produce only about a third as much sperm as a hamster.

Scientists increasingly blame a whole class of hormone-disrupting chemicals. Evidence suggests that they cause cancer and damage the immune system, as well as impairing fertility. And they are ever more ubiquitous.

DDT and other pesticides disrupt hormones, as do PCBs, used in countless products worldwide, from plastics and paint to electrical equipment.

Other components of plastics have been found to leach hormone-disrupters including phthalates, which have been found in a wide range of foods including baby milk.

Furthermore, an investigation by the BBC's Countryfile and The Independent on Sunday has revealed research, to be published this month, that shows that artificial oestrogens, used in contraceptive pills and emitted through sewage works, appear to be changing the sex of half the fish in Britain's lowland rivers.

Scientists and environmentalists fear that the powerful chemicals are getting into drinking water and affecting human fertility. One third of Britain's drinking water comes from rivers; most of it is taken from below sewage works.

The Environment Agency denies that there is any danger. Water UK, which represents the water companies, says that no hormone-disrupting chemical has ever been detected in British drinking water, and that fish placed in the water to test it did not become feminised.

But some scientists say that the chemicals may not have been detected, because there is no routine testing for them in drinking water, and because the equipment used in Britain is not sensitive enough.

Research at the University of Ulm, in West Germany, using more sophisticated techniques, found small amounts in four out of every 10 samples tested. And environmentalists fear that effects in people may occur over much longer periods than those used to test the fish.

Dr Susan Jobling of Brunel University, who led the research, says: "Unlike in fish, it is going to take 20 years to see if my children have been affected by developmental exposure to this same cocktail of chemicals."