A group of chemicals called endocrine disruptors are the most likely cause of falling sperm counts and increasing testicular cancer in adults, and disruptive behaviour* and lower IQs in children, according to Fred Vom Saal of Missouri University (US). Tests on human cell cultures replicated in mice showed that exposing a foetus to just one billionth of a gram in the first weeks of pregnancy (in the early stages mammal embryos develop very similarly) has serious health consequences, the most noticeable in mice being reduced sperm counts and enlarged prostate glands.

These effects were first highlighted in the children of women who had eaten fish containing similar levels of hormone mimickers from North America's Great Lakes. They were less able than other children to handle unpleasant events, exhibiting symptoms very similar to 'road rage'. Rats fed with the same levels displayed the same behaviour.

Endocrine disrupters are also being blamed for the increases in male breast cancer and infertility in Denmark, where 10-15% couples are now having difficulty conceiving. Tests on human cell cultures showed that exposure to just one billionth of a gram of bisphenol-A could lead to serious health consequences.

A major source of bisphenol-A is the inner plastic coating in food cans. When cans of baked beans, for instance, are heated to 250° to sterilise the food, enough bisphenol-A is released into the food to provide a dose of 90 parts per million. Lower concentrations given to a female rat during the first seven days of pregnancy produced male offspring with reduced sperm counts and enlarged prostates.

Hormone mimickers have been in use for 50 years when we began to use the pesticide DDT. Theo Colborn, director of the World Wildlife Fund's Contaminants Programme, fears that we are only now beginning to reap the consequences.

Ed.- Bisphenol-A leaches out of plastic at a rate which increases with use and is found (e.g.) in baby bottles, tin can linings, some toys and plastic food containers.

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The debate over the safety of bisphenol-A continues to rage, as studies finding adverse effects prove impossible to replicate or are contradicted by Industry-funded studies which are then, themselves, criticised on grounds of scientific procedure. The matter has been further complicated by the suggestion that it is not scientific to assume a straight dose-effect relationship. The suggestion is that low doses of endocrine disruptors may cause greater damage than higher doses.

Very low doses may cause damage by stimulating hormones and binding to hormone receptor sites whereas slightly higher doses may over-stimulate the hormone system, leading to a reduction in the number of receptors and a down-regulation of the hormone mechanism.The result is an inverted U dose response rather than the linear dose-effect relationship assumed by traditional risk assessment techniques.