Chemical threat to intelligence

Our intelligence, good behaviour and ability to reproduce are all under threat from the post-war boom in mass-produced synthetic chemicals, argues a best-selling book published in Britain this week.

Our Stolen Future explains how man-made substances which mimic our natural hormones, or disrupt their normal workings, have caused chaos among wild animal populations.

But there is growing evidence that they are also lowering human sperm counts and disrupting the normal development of babies' brains in the womb. The book's three authors claim a substantial part of the population may already be suffering lowered intelligence, learning difficulties and attention deficits because of these chemicals, which exert their effects at extremely low concentrations.

The book has been compared with Silent Spring, Rachel Carson's 1962 warning about how DDT and other pesticides were wiping out wildlife and threatening humans.

Our Stolen Future may cause greater alarm. The first print run of 25,000 copies in the United States this year sold out.

The book is a synthesis of research findings. Dr Theo Colborn, the book's lead author, who works for a private environmental foundation in Washington DC, said she had read about 10,000 papers and reports in the past eight years.

"It may soon be possible to conclude, if not prove, based on the weight of the evidence, that hormone-disrupting chemicals are linked to testicular cancer, falling sperm counts, and learning disabilities and attention deficits in children," says the book.

Scientists have discovered 51 types of synthetic chemical which interfere with the natural workings of hormones in animals or people. Some of these are already banned or restricted because they are known to be toxic to humans and wildlife - or to be carcinogenic.

These include PCBs, once manufactured in huge quantities for electrical transformers and capacitors, DDT, and dioxins produced when chlorine- containing compounds are burnt at low temperature.

Although the manufacture of PCBs was banned in most developed countries more than 10 years ago, it is still widespread - and found at levels of one part per million in the breast fat of women all over the world.

Consequently, says the book, a breast-feeding baby gets "five times the allowable daily level of PCBs set by international health standards for a 150 pound adult".

New hormone disruptors are also coming to light. A substance called nonylphenol mimics the female sex hormone oestrogen at very low concentrations. It is used in plastics and is also a breakdown product of industrial detergents, pesticides and personal care products. Another oestrogen mimic, bisphenol A, has been found leaching from the plastic lining of food cans.

"I think the problems are going to get worse if we wait for governments and policymakers to act," Dr Colborn said. "We have to go back to the drawing board on how we produce and manage these chemicals."

'Our Stolen Future' by Theo Colborn, John Myers and Dianne Dumanoski, Little Brown, pounds 18.99.