Men will become infertile by the middle of the next century unless certain man-made chemicals are banned, zoologist Theo Colborn tells Robert Allen.

More than 30 years ago science fiction author Brian Aldiss wrote Greybeard, a novel about a world without fertile humans. And four years ago P. D. James took time out from writing crime stories to warn about the folly of ignoring the consequences of our technological progress, in a scary novel entitled The Children of Men. Set in 2021, James's narrator wonders why no one in the last years of the 20th century suggested that the fertility of the human race was dramatically changing. "When Omega came, it came with dramatic suddenness and was received with incredulity. Overnight it seemed, the human race has lost its power to breed."

The world Aldiss and James portrayed looms. A zoologist has come up with compelling evidence to suggest that the fertility of men is dramatically declining under the influence of synthetic chemicals present in pesticides, plastics and detergents. Theo Colborn is not being thanked for her research, even though she believes it is only a matter of time before the force of her message hits home and remedial action is taken.

Amid controversy and criticism - from the chemical industry that feels it is under attack and scientists who believe more research is necessary - Colborn, director of the wildlife and contaminants programme for the World Wildlife Fund, has shown that manmade chemicals are threatening the fertility, intelligence and survival of the human species. Human males, Colborn insists, will probably become infertile by the middle of the next century if the ban on the chemicals known to disrupt the endrocrine (hormone producing) system is not implemented as soon as possible.

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Although she has been trying to get her message across for over six years it is with the publication of Our Stolen Future, cowritten with John "Pete" Myers, director of the W. Alton Jones Foundation, and Boston Globe reporter Dianne Dumanoski ("who cried when I asked her to write this book with me because she has been unable to get the issue past her editors") that Colborn is beginning to make an impact. But despite its enthusiastic welcoming by Green supporters, she does not share their apocalyptic vision of an inevitable doomsday. "I don't think we are facing such a scenario because there are industrialists out there with a conscience and they will make the right decisions." But far from complimenting Colborn and her colleagues for compiling this evidence, many industrialists, scientists and bureaucrats, particularly in northern America, have accused her of confusing hypothesis with reality while others have set her up for ridicule.

As Our Stolen Future is published in Britain and Ireland, a month after its United States release, Colborn stresses that she still stands by the statement of July 1991 when she was joined by 20 other scientists to discuss the impact of synthetic chemicals on wildlife and humans. After the conference at Wingspread, Wisconsin - which featured experts in anthropology, ecology, comparative endocrinology, histopathology, immunology, mammalology, medicine, law, psychiatry, psychoneuroendocrinology, reproductive physiology, toxicology, wildlife management, and zoology - the 21 scientists announced "that a large number of man-made chemicals have the potential to disrupt the endocrine system of animals, including humans".

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These chemicals, which are in pesticides, plastics, detergents, cosmetics and environmental pollutants, are ubiquitous in modern society. Colborn estimates that as many as 500 measurable chemicals are now present in our bodies. As she puts it in her book, they are here, there and everywhere, even in the bodies of the Inuit in Arctic regions where there is no polluting industry.

"Many wildlife populations are already affected by these compounds," Colborn and her colleagues stated in 1991. "The impacts include thyroid dysfunction in birds and fish, decreased fertility in birds, fish, shellfish and mammals; decreased hatching success in birds, fish and turtles; gross birth deformities in birds, fish and turtles; metabolic abnormalities in birds, fish and mammals; behavioural abnormalities in birds; demasculinisation and feminisation of male fish, birds and mammals; defeminisation and masculinisation of female fish and birds and compromised immune systems in birds and mammals."

The book highlights the death, in 1988, of over 40 per cent of North Sea seals. In a controlled experiment, two groups of seals were fed fish (from catches destined for commercial sale), one group from the Atlantic, the other from the polluted Waddensee. Only four of the Waddensee group conceived compared with ten of the 12 females in the Atlantic group. It became clear to Colborn that they had stumbled on something very serious, that these chemicals were having a devastating effect on wildlife before it was born. The damage, Colborn noted, is permanent. Although her critics claim the effects on humans are not well known, Colborn is adamant these chemicals are affecting not only fertility but also intelligence. What are the consequences to society of a 5 per cent drop in IQ, she asks rhetorically, adding that she hopes it will not come to that.

Aside from placing her fate in industrialists she also believes that when economists get round to working out the human costs and toxicologists begin to look for illness in a different way, instead of concentrating on finding cell damage, everything will be fine. Toxicologists, Colborn argues, have to change the way they study the effects of chemicals on human health.

Colborn says it is no longer safe to assume the dose makes the poison. Although she admits that more research needs to be done, she says scientists already know that the body shuts down when it receives an overload of hormone-disrupting chemicals. Thus synthetic chemicals that disrupt the endocrine system are at their most dangerous at low levels. As Colborn stresses, these chemicals do not kill cells or attack DNA.

But many believe it is already too late. And even some of the sceptics have been convinced. Pierre Jouannet, director of the Centre d'Etude et de Conservation des Oeufs et du Sperme in Paris, did not believe that the average male sperm count had dropped 45 per cent from an average of 113 million per ml in 1940 to 66 million per ml in 1990. Jouannet had data on 1,350 Parisian men, all of whom had fathered at least one child and therefore had proved their fertility, so he analysed them, expecting to refute the claims of falling sperm count. To his astonishment he found that sperm counts in his group had dropped steadily at 2 per cent a year for the past 20 years. At the present rate of decline, he reported gravely, "It will take 70 or 80 years before it [the sperm count] goes to zero."

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Now there are agencies taking Colborn very seriously indeed. The US Environmental Protection Agency and the US National Institute of Environmental Health Sciences have put up over $8 million for further research into the chemicals known to disrupt hormones in wildlife, which Colborn and many other scientists insist are having the same impact on humans.

But at the same time money is being spent on alternative explanations. Earlier this year the Chlorine Chemistry Council, a subsidiary of the US Chemical Manufacturers Association, began a campaign to try to challenge Colborn's theory with an industry-led conference that sought to show that the natural world produces many more chemicals capable of disrupting human fertility.

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Scientists who disagree with Colborn say the amounts of synthetic chemicals in the environment are heavily outweighed by quantities of naturally occurring chemicals that have the same effect. Colborn and those who have studied the impact of endocrine-disrupting chemicals on human health acknowledge that many plants produce chemicals that can mimic hormones. It is her contention, however, that while those plants can have an oestrogenic effect on the animals and humans consuming them, they are easily broken down and excreted from the body. Synthetic chemicals, on the other hand, accumulate in the human body, causing low-level, long-term biological damage.

Patricia Whitten," Colborn asserts, "will shortly be publishing a paper on plant oestrogens that will answer these questions." Whitten, an anthropologist at the Laboratory of Reproductive Ecology and Environmental Toxicology at Emory University in Atlanta, Georgia, has been exploring the fundamental question about plant estrogens - whether humans ingest sufficient quantities to cause damage. Colborn is adamant that even her critics - Stephen Safe, a professor of toxicology at Texas University, springs to mind -are beginning to accept that different biological mechanisms are involved. Environmentalists who are worried that the heavy criticism may force Colborn to retract, have, she says, nothing to fear. Colborn says she stands by what she said a few years ago: "It is vital that we focus attention on preventing pollution instead of simply trying to control it after it has been created. We must consider how we use materials in industry, commerce and our domestic lives. If we don't, we are putting the diversity of life on earth on a fast track to extinction."

É«ºÐÖ±²¥ CHEMICAL VILLAINS

That certain chemicals are capable of mimicking sex hormones appears to have been accepted by a large body of the scientific community. Man-made chemicals such as organochlorine pesticides (DDT, for example, which was used in large quantities until the 1960s when it was restricted in the western world) head the list of environmental oestrogens.

The Danish Environmental Protection Agency has identified classes of pesticide commonly used as environmental oestrogens. PCBs (used as industrial chemicals in capacitors and transformers) are among five classes of industrial chemicals now known as environmental oestrogens. Alkylphenol polyethoxlates (non-ionic surfactants used in detergents, emulsifiers, wetting agents and dispersing agents in household products and in agricultural and industrial products such as herbicides and paints; also used as spermicides in contraceptive foams, jellies and creams) and phthalate esters (used to make plastics flexible, including PVC) are other chemicals responsible for xeno- oestrogenic behaviour.

Chemicals found in food wrapping, tin cans and even in some face creams and dental fillings have also come under the microscope. This source of exposure to oestrogenic chemicals via food was discovered when Spanish scientists found that bisphenol-A leaches from the inner lining of food cans into many vegetables. According to Colborn, US production of carbon-based chemicals topped Pounds 435 billion in 1992 with global production estimated to be four times that amount. To put this in perspective, between 1940 and 1982 production of synthetic materials increased roughly 350 times. About 1,000 new synthetic chemicals enter the market each year.

many without adequate testing.

Robert Allen is a journalist, researcher and lecturer who is writing a book on the impact of dioxin exposure on health and is the publisher of Toxcat, a journal on toxic pollutants.

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Our Stolen Future will be reviewed in The É«ºÐÖ±²¥S later this month.