'Pesticides are most serious environmental threat' - UN advisor

Nicholas Ashford, a leading environmental scientist and health adviser to the United Nations told a recent closed meeting at the Health and Safety Executive (HSE) that pesticides may pose a far more serious threat to public health than has previously been thought. Jeff Howell reports on an interview with Professor Ashford after the meeting.

Professor Ashford - calling for an immediate reduction in pesticide use

Professor Nicholas Ashford of Massachusetts Institute of Technology (MIT), a leading researcher into the multiple chemical sensitivity (MCS) theory of illness, was on his way to Amsterdam to address the first international conference on children's health and environment. Stopping over in London to address a closed HSE seminar, Professor Ashford said:
    "I think pesticides are the most serious problem we have today in the industrial countries."
    Professor Ashford, co-author (with Claudia Miller) of the book Chemical Exposures: low levels and high stakes, explained that pesticides-particularly organophosphates, implicated in the deaths of farmers involved in sheep dipping, and permethrin, sprayed in around 5,000 British homes every week as a woodworm treatment-may be the most common initiators of MCS, an illness which leaves sufferers sensitised to other common chemical substances such as detergents, tobacco smoke and traffic fumes. There is no known cure for the condition.
    In the recently-published second edition of the book, Ashford and Miller introduce a new theory for this sensitisation process, which they call toxicant induced loss of tolerance (TILT). In some cases, sensitised patients have been found to react to levels of chemicals so low that they are undetectable by all the usual laboratory testing methods; this means that their symptoms baffle doctors who, unable to diagnose a classic cause-and-effect sickness, frequently conclude that the illness must be a mental problem.
    Professor Ashford said that the huge rise in pesticide use since the second world war could be responsible for an untold number of illnesses with a common range of symptoms, such as skin rashes, breathing problems, cancers and birth defects. Other research has suggested that MCS may affect millions of sufferers in the industrialised countries; studies in the US have shown that around one-third of the population-up to 60 million people-may be affected in some way.
    Professor Ashford, who is professor of Technology and Policy at MIT, a Fellow of the American Association for the Advancement of Science, and an advisor to the UN Environmental Programme, told the HSE meeting that since the first edition of the book was published in 1991, there had been a mass of published research on MCS, and that the new second edition presented compelling evidence that this condition should be recognised as a certifiable illness.
    Addressing the idea that sensitivity to chemicals might be all in the mind of the sufferer, Professor Ashford told the meeting: "The last seven years of research has not furthered the case for psychosomatic origins at all-but it has definitely furthered the case for physiological origins".
    Professor Ashford said: "We now understand more about the mechanism of chemical effects on human health. It is not a question of a single substance poisoning an organism"-as measured by the acute toxicity tests used to licence pesticides-"but rather a multi-stage process which interferes with a whole system". He explained that MCS, like endocrine disruption and cancer, was probably initiated by exposure to one chemical, such as a pesticide, and then promoted by subsequent contact with others. He likened the current research into MCS by toxicologists and clinical ecologists as being like an audience viewing a three-act play; "The toxicologists are leaving after the first act; how can they know what's going to happen in the end? And the doctors and clinical ecologists are walking in half way through the second act; they see what's going on, but it makes no sense to them".
    Professor Ashford said: "Pesticides are nerve poisons; they damage the brain and they are also known to be endocrine disruptors. Why isn't the research being done now to discover the true effects of pesticides on human health?" He called for the formation of a European Union environment unit to study the problem in Europe, and for an immediate reduction in pesticide use until the effects are better understood.
    The HSE has commissioned a British study of multiple chemical sensitivity from the Institute of Medicine, which is expected to report before the end of the year.

Nicholas Ashford and Claudia S Miller, Chemical Exposures: low levels and high stakes, 2nd Edition, Wiley, New York, 1998.

Jeff Howell is a writer and broadcaster on pesticides used in the home environment.

[This article first appeared in Pesticides News No. 41, September 1998, page 16]