We have allowed as many as 100,000 synthetic chemicals to be sprayed into our environments, with only limited testing against just a few health threats. In Britain, our bodies could contain as many as 500 of these chemicals. In the United States the aggregate volume of the chemicals has now topped three million tons a year, or over 11kg per American. Nearly 1.5 million tons of just one category of chemicals, polychlorinated biphenyls (PCBs), have been spread around the world through their use in paints, pesticides, plastics and electrical equipment. Every day a breast-feeding baby in Europe or North America receives five times the PCB intake deemed permissible for an adult.
In short, we may have set up a host of "chemical time bombs", ticking so discretely that nobody hears them - except for people like the authors of this remarkable book. If only part of their scientific analyses proves correct, theirs will be as dire as virtually any other environmental warning of the past decades. But blowing the whistle is rarely without cost. The chemical industry has been wheeling out its biggest guns to blow away the book's findings. More power to the authors, then, for their courageous stance.
For almost 50 years, nature has been warning us of something wrong with the reproductive habits of many species. For instance, the "gay gulls" in California, where females have been pairing up, ostensibly because males no longer care about mating. It turns out that males now have parts of females' egg-laying equipment. The double-crested cormorant has revealed gross birth defects such as club feet, crossed bills, crooked spines and missing eyes. Nor are only birds affected. Alligators in Florida are producing eggs that often fail to hatch, apparently because many male alligators now feature female hormones and micro-penises. Also in Florida, certain turtles seem to be turning hermaphrodite. Among many mammals and fish, too, males appear to have been demasculinised if not feminised.
The feature common to these aberrations is that the creatures are all top carnivores, meaning that they "biomagnify" the impact of pollutants. A persistent chemical becomes concentrated in tissue as it moves from environment to plant, then to herbivore, carnivore and finally top carnivore. In Lake Ontario, its accumulation in body fat can be 25 million times greater in a herring gull than in the lake's water. The human being is top carnivore par excellence; and in 20 countries, human sperm counts have dropped by half in just two generations.
These phenomena are what the authors call "derailed development". Many synthetic chemicals can mimic hormones, which upsets the endocrine systems and thus the reproductive organs and patterns of animals. Worse, they are effective at a concentration equivalent to one drop of gin in 660 railway-tanker trucks of tonic. Endocrine systems are, to quote the authors, "the biological equivalent of the information superhighway", carrying messages that regulate reproduction, immune systems and behaviour patterns. Some of the chemicals act on endocrine systems as "thugs that sabotage vital communication. They mug the hormone messengers or impersonate them. They jam signals. They scramble messages. They sow disinformation. They wreak all manner of havoc." Probably worst of all, most forms of havoc still lie beyond our ken since we have not bothered to look for them. Governments have been preoccupied with the acute toxicity and the carcinogenic capacity of industrial chemicals to the extent that they have hardly bothered to check on other threats. More subtle, and hence more pernicious risks arise with the hormone disruptors, including such chemicals as DDT, dieldrin, PCBs (with more than 200 forms), dioxin (75 forms) and the alkylphenols (used to stabilise plastics). These chemicals attack organisms while still embryos or fetuses - precisely at the stage of their life-cycles when they are most vulnerable.
At least half of the chemicals can steadily and insidiously build up in body fat. Over 50 of them have been identified as "hormone disruptors". Some mimic the female hormone oestrogen, others block the male hormone testosterone, still others attack an entire range of hormones. Not only do the chemicals appear in abundance in products from pesticides and plastics to detergents and cosmetics, they can "leach out" of items such as plastic wrappings and into food and drink for humans.
Equally significant could be the immunosuppressive impact of pesticides. According to the short book by Robert Repetto and Sanjay Baliga, many pesticides can compromise the body's ability to fight infection. Inuit children in the northern Hudson Bay area of Canada, nursed on human milk laced with organochlorines such as DDT, not only face a highly elevated risk of infection, but in some cases are so immunocompromised that they cannot be vaccinated because they simply do not produce any antibodies. All this is especially pertinent to those developing countries where synthetic pesticides are still widely used and where infectious diseases are a leading cause of death.
True, these conclusions are far from conclusive. As Theo Colborn and her colleagues constantly remind us, there is plenty of room for doubt. But the case for the prosecution is so strong and backed by so much empirical evidence, that the reader is reminded of other instances where scientific scepticism seemed eventually to fly in the face of reason: ozone layer depletion and the Antarctic hole; freak weather phenomena as a harbinger of global warming. The authors emphasise it will take much research before scientists can come up with "smoking gun" evidence of linkages between chemical pollutants and human abnormalities. What to do in the meantime? If we put safety first and deny ourselves the chemicals, one thing is certain: there will be a specific and hefty price to pay via agriculture and industry. No more blemish-free fruits and vegetables, no more convenient packaging with culprit plastics and so on. Not so certain is what we will gain: we simply do not know what the benefits will be, let alone their economic value.
This is often the trouble with environmental problems. Increasingly, we find ourselves in a position where we have to act in twilight. But let us beware the asymmetry of evaluation. If we wait until there is definite evidence of damage, and continue to run the risks, we shall effectively be saying we believe the risks to be tolerable - despite the ever-more emphatic warnings to the absolute opposite. So should we turn the situation around and require the chemical manufacturers to assume the burden of proof? Let them demonstrate that their products are indeed harmless in whatever circumstances. If the industrialists cannot prove their point, they should not be allowed to put their products on the market. Of course this will cost us in the form of increased prices. But are not the concealed costs of the alternative becoming too great? Has the time arrived for certain scientific activities to be considered guilty until proven innocent? Appalling as this will seem to those who want to "pursue science wherever it leads", it may be a necessary course of action as well as the biggest price of all to pay. The 100,000 synthetic chemicals enable us to intervene in some of life's most vital processes. Certain chemical pollutants could even undermine human intelligence. "Those whom the gods wish to destroy they first make mad."
Norman Myers is honorary visiting fellow, Green College, Oxford.
Pesticides and the Immune System
Author - Robert Repetto and Sanjay Baliga
ISBN - 1 56973 087 3
Publisher - World Resources Institute/Earthscan
Price - £15.00
Pages - 100