Pesticides may be behind many ailments, but the government will not investigate, says Richard North

Poisoning the wells of science

A victim of the Spanish "toxic oil syndrome" disaster, interviewed on the admirable Yorkshire Television documentary Poisoned Lives in 1991 expressed her disillusion: When I hear the word 'scientist', it's as if I get an allergic reaction. And the word 'expert', well, I go cold whenever someone says 'an expert says this', I worry that it is not true. It's something that was said in the interests of some economic pressure group. I think science is a fine thing, it's a shame that it can be corrupted like this."

That disaster, in which thousands suffered grotesque neuro­logical disturbances and several hundred died, was officially attributed to contaminated cooking oil. However, two researchers employed on post-epidemic studies found that many victims had not consumed the suspect oil, though all had eaten tomatoes or cucumbers from a nursery in southern Spain which used an organo-phosphorous (OP) pesticide. Symptoms of the "syndrome" were entirely compatible with acute OP poisoning.

Dr Mark Purdey, who farms organic cattle in Somerset, notes a similarity between this incident, and the current bovine spongiform    encephalopathy (BSE) or "mad cow", epidemic, which has now affected more than 100,000 cattle.

This is officially explained as being due to a suspect protein, but the ministry concedes that 2,000 of the cattle never consumed this. Dr Purdey has found that BSE too is remarkably similar to chronic organo-phosphorous poisoning, and notes a series of co­incidences. Not least of these is that the BSE epidemic started two years after OP compounds began to be used as sheep dip pesticides. Another striking feature is that the BSE epidemic in Britain, as the ministry agrees, has been most intense in areas such as the south­west which were designated as Warble Fly Eradication Zones in the 1980s. Here farmers were com­pelled by the ministry to treat their cattle with OP insecticides from the same chemical family as those used in the sheep-dips. As the OP sheep-dips are now thought by some to be implicated in a variety of complaints, from ME to asthma, Dr Purdey believed that the compounds might be causing BSE.

So confident was he that this was a plausible hypothesis to explain the continuing epidemic, that in April 1992, when one of his cows which had been over-wintered on a chemically managed farm showed signs of BSE he treated it with the cocktail of drugs that was issued to Gulf war soldiers as an antidote to organo-phosphorous nerve gas. His cow responded within 90 minutes, and sustained improvement until further drugs were withheld because experts could not agree to the treatment continuing. When the cow was slaughtered, it was confirmed as a BSE sufferer.

Such data might it would be supposed, excite the interest of be­leaguered officials from the ministry, who are finding it increasingly difficult to explain why cases of BSE continue to rise. Instead, until recently, Dr Purdey has met a wall of official indifference.

What he came up against, however, is more profound than a simple rejection of a plausible hypothesis. He was confronted by a disturbing attitude in the official scientific method. When a problem is found, the traditional scientific approach, which has served mankind well, is to assemble facts, from which a hypothesis is formulated, on which basis controls are devised. But crucially, the hypothesis must be treated as provisional. Attempts must be made to knock it down — not least by monitoring the effect of the controls introduced. Only if the hypothesis survives can it be treat­ed as sound, and then only as the best approximation to the truth.

In we case of BSE, a hypothesis was hastily arrived at during the 1988-9 food scares, which were fuelled by the claims of Professor Richard tacty of Leeds University that transmission to humans could lead to the death of millions. Ministers — first John MacGregor and then John Gummer — worked on the hypothesis that BSE was caused by cows' consumption of under-processed, scrapie-infected sheep protein. Feed tenderers were blamed, and the use of such feed was banned.

It is hard to fault the ministers, faced as they were with acute public concern, the relative lack of knowledge, and the imminent collapse of the beef market It is also hard to argue that their intervention was excessive. The pressure to do something was inexorable.  But here politics and science part company. For once hypotheses are used as the basis of policy, they tend to be taken not as the best approximation to the truth, but as unalterable fact.  They become a mantra, and departure from this is akin to heresy. Those who disagree are ignored or ridiculed, while the scientific estab­lishment is funded not to test the hypothesis, but to support it

While Dr Purdey's thesis may not prove any more valid than the official doctrine of infected feed, it is at least plausible. And if information on OP residues in cattle and sheep were obtained and collated with BSE incidence, it might either support his thesis or put it to rest. But of more than 10,000 tests on carcass meat by the Veterinary Medicines Directorate in the first three months of this year, a mere 28 looked for pesticide residues. Furthermore, the samples taken were of a type least likely to disclose pesticide residues.