Pesticides, food additives and scientific lies

  • 14/03/1993

Pesticides, food additives and scientific lies MORE than 70 new chemicals are registered every hour in the US alone. The public - battered and bemused by daily press reports about the dangers of smoking, pesticides, pollution and food additives - looks to scientists to pronounce on the safety of this rising chemical tide. But the scientists do not know, either.

Scientists, of course, are ignorant about many things. Usually, they are willing to admit their ignorance, if only to justify funds for further research. But when it comes to risking exposure to chemicals, too many get seduced into making unjustifiable statements.

Example: "One person in every 10,000 will contract cancer from residues of ethylene dibromide (a grain fumigant) in flour." Or, "There will be a greater than a one in a 100,000 chances that Alar (pesticide) will cause cancer in children consuming apple juice." Uncertain truths Such statements are false, says Rodricks, and explains: "There are no means available to identify these types of risks with the degree of certainty suggested by the language used. Any risk assessor who contends that X people will contract cancer, where X is a single number, is either a liar or is highly incompetent."

As such statements are regularly made, it is evident that Rodricks" world - and ours - is full of incompetent or lying scientists and journalists.

An added complication in assessing risks arises from companies eager to profit from research; from environmentalists concerned about the threats to health from chemicals in the air, food, water, drugs, consumer products and the workplace, and from the public"s attitude to risk, which is not perceived simply as a matter of probability. Flying, for example, is often seen as more dangerous than the statistics indicate, because air crashes are dramatic and passengers helpless.

People also fear risks from new sources such as biotechnology, more than from established technologies. Furthermore, the threat of a natural risk is tolerated more than a man-made risk and some diseases are feared more than others. (Scientists regard such attitudes as irrational, but to accept the risk of smoking while objecting to the possibly lesser risk from a neighbouring factory is not necessarily illogical. It may be a perfectly sensible statement about the right to control one"s own environment.)

Pity, then, the regulatory authorities. They have to make decisions about the safety of particular chemicals in the face of a heady brew of commercial pressure, public misconception and scientific uncertainty.

There is not even a scientific consensus on the proper conduct of risk assessment. So the regulatory authorities find themselves adopting, as a matter of policy, assumptions that do not have universal acceptance in the scientific community. Some scientists, like some doctors, argue that it is better to offer reassurance than to create alarm by admitting ignorance. But they cannot be right for people should be educated -- not deceived --about science and its limitations.

Rodricks" book is a lucid contribution to such an education, which is also required, as he makes clear, for some of those involved in toxicology. It focusses on the science of toxicology and adopts an unemotive, non-partisan approach. His understatement, however, should not conceal the seriousness of his criticisms of current decision-making on environmental chemicals.

He argues for a change in the methods of scientific research, on the unassailable grounds that risk assessment is too important to be based on untested scientific assumptions. After all, the relationship between the results of tests on animals and humans can be imposed to twist results in one direction or the other to achieve desired policy results. Overall, Rodricks argues that existing fragmented, non-uniform systems of controlling chemicals do not serve the public interest.

The most important -- and possibly literally fatal -- flaw in the whole muddled business is the manner in which the impact of chemicals are assessed in isolation. It is the total picture that ultimately matters. Assessment of, say, a chemical additive in peanut butter may lead to a decision that it constitutes little risk to individual consumers. But that fails to take into account the cumulative effect on the human body of all sources of the chemical, of which the additive is only one.

Even more significantly, it fails to take into account the effect of the additive when it reacts with other chemicals that have been ingested. Yet many cancers seem to be caused by several factors, rather than by individual carcinogens.

What Rodricks does not say is that the speed of chemical proliferation is unacceptable, given the impossibility of controlling the rush of new chemicals or of informing the people who handle and use them of the possible dangers, or even of the antidotes. Untrammeled production is based on the postulate that despite some risks, chemicals have contributed much to raising living standards and the quality of life and so industry should be left to invent more and more of them. But Rodricks himself points out that toxicologists "know a great deal about a few chemicals, a little about many, and next to nothing about most."

Death risks in the US due to some activities and chemical exposures.

(per 100.000 at risk)

All causes, all ages
Smoking (cancer)
Smoking (other causes)
Motor vehicles
Rodeo performance
Chlorinated drinking water
4tbsp peanut butter/ day (aflatoxin)
3 oz charcoal-broiled steak/day
Hit by meteorite


Source: Calculated Risks

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