This is politics, not science
 

By KEITH R SOLOMON
Special to The Record
 

Headlines scream the following: The Green Law Scare, City Bylaws Ban Pesticides, Supreme Court OKs Municipal Bans of Pesticides. Pesticides are probably the most tested and closely regulated substances in the developed world today.
    An entire office of Health Canada in Ottawa, the Environmental Protection Agency in Washington, not to mention a host of other countries, provincial and state regulators oversee their approval, their movement in commerce, who may use them, where, and when they may be used.
    Why then are cities and towns, most with no source of expertise to judge health or environmental effects of these substances, enacting bans on their use by city employees and private citizens?
    They do this because they see this as the will of the public - the citizens who have elected them and some of whom believe that pesticides are causing illness in us and our environment.
    Scientists, such as myself, who use the scientific method, are in part to blame. As a scientist, I cannot offer absolute and irrefutable proof that pesticides are safe. All that science can do is say that one thing is more likely to happen than another, much more or much less likely, but never 100 per cent certain.
    No matter how well designed an experiment, no matter how many mice or fish are used, the scientist will always report the result with some uncertainy. This means that, for example, even if there is no real effect of the substance on the liver, in some experiments a very small adverse (positive) effect will be seen, while in others, a non-adverse (negative) effect will occur. This is because of natural variability in the test organisms and random events. The average of all of these experiments is close to zero but, for those who believe that an adverse effect should exist, the positive studies will be absolute proof.
    The scientific method, the test of the null hypothesis, is designed to keep scientists honest and detached from whatever their beliefs may be. No scientist is pleased to find that nothing is happening; it is much more exciting and satisfying to find interesting responses and effects.
    As was pointed out nearly four centuries ago by Francis Bacon, the father of the scientific method, it is part of human nature to diminish negative evidence and exaggerate the significance of positive evidence. Because of this, we tend to ignore the negative and focus on the positive, evidence that is, in the analogy describe above, essentially anecdotal.
    Some people believe in ghots, the paranormal and in the visitations of aliens, despite the countless years of study that have failed to show any evidence in support of these phenomena. They do this because they chose to believe the anecdotal evidence.
    The media are of little help because the possibility that some aspect of our daily life may cause injury or worse is the substance of headlines and increased circulation. This is a likely reason for the common misperception that pesticides cause all types of diseases in humans.
    A study may report a link between pesticide use and a disease such as cancer in humans. However, one positive study does not prove a cause-and-effect between the pesticide use and disease. Only if most studies consistently show this linkage, and other lines of evidence also support the conclusion, would this association be accepted as showing causality, as has been the case with smoking and lung cancer.
    Municipalities regulate many activities within their boundaries and the Supreme Court, on constitutional grounds, has seen fit to include the use of pesticides in these activities. The court did not judge scientific evidence, nor would it necessarily have the medical and scientific skills to interpret this information. Pesticides are some of many tools in the pest management toolbox. There are alternatives to pesticides, however, they may be less effective, more costly, and not necessarily free of health risks.
    As I do not live in one of the towns where bans have been proposed, I do not care one way or the other if they choose to not use pesticides. However, I do care when this is done in the name of science and concern for health effects when, realistically these do not exist.
    If the town councils and the majority of citizens do not want pesticides used in their homes and gardens, then all I ask is that they have the courage to admit that they do this for reasons of belief or politics, not on the basis of science.

    Keith Solomon is a professor in the environmental biology department (Centre for Toxicology) at the University of Guelph - ksolomon@tox.uoguelph.ca