Pesticide ban needs evidence

Hey there, time traveller!
This article was published 3/2/2012 (3315 days ago), so information in it may no longer be current.

Editorial

Manitoba's government is leaning toward banning the use of cosmetic pesticides. Conservation Minister Gord Mackintosh says he is favouring regulations similar to those in Ontario, where herbicides are kept under lock and key in home and garden centres. But first he wants to hear from Manitobans how a ban might roll out here. Manitobans deserve an informed debate and Mr. Mackintosh should ask the provincial medical officer of health to compile the latest evidence on the risks of common exposure to such chemicals, the use Manitobans make of pesticides and alternatives and the experience of other jurisdictions where bans are in place.

Manitoba is a late comer to this issue. During the last decade, Canadian municipalities increasingly banned the use of cosmetic pesticides -- chemicals used primarily on lawns and gardens -- and today only four provinces have not moved to restrict their sale. One of them, British Columbia, is poised to adopt a ban.

Although the public discussion is often rife with talk of environmental concerns, bans on cosmetic use of pesticides can only be about human health -- urban use of pesticides involves a tiny part, perhaps 10 per cent, of pesticide use in Canada. Non-urban use, specifically in food production, involves the greatest use of pesticides.

In 2002, Toronto's then-medical officer of health, Dr. Sheela V. Basrur, compiled a good summary of the science on the risks pesticides pose to human health. Dr. Basrur, in advance of Toronto's bylaw on pesticide use, noted there was increasing evidence of associations between pesticides and diseases such as non-Hodgkin's lymphoma, especially in occupations involving repeated exposure. More worrisome, evidence was mounting that children are particularly vulnerable to exposure and to the compounded effect of multiple pesticide chemicals, due to their immature immune systems and organs.

That is compelling physician groups to warn governments and parents about the exposure of children to pesticides. Tests for risks to human health, conducted for manufacturers registering pesticides federally, rely on animal experiments. Human organs mature slowly, so many people have noted the tests on animals, which mature quickly, cannot describe toxicity levels for children.

Scientific proof of harm, however, is limited. Studies point to "associations" between exposure and disease or impaired endocrine and immune systems. Research is developing on the effect of multiple chemicals in the environment on human health, especially that of children. That mounting evidence in the early 2000s prompted regulatory agencies in Canada and elsewhere to phase out products using the organophosphates chlorpyrifos or diazinon.

Epidemiological studies, which look at large populations over time, on the impact of pesticides are scant and there are widely recognized weaknesses in those that exist; small samples, for example, make drawing conclusions about broad populations risky.

That is why groups that use scientific evidence to draw conclusions about pesticides pull their punches. They carefully note that the associations are growing and give cause for concern and action by regulatory agencies, and warn the public to limit exposure. The pesticide industry states that the federal public health branch puts manufacturers through rigorous controls to ensure human health is not at risk. Dr. Basrur concluded -- 10 years ago -- that the pest management regulatory agency had standards considered among the most up-to-date.

Cosmetic pesticides are used by 47 per cent of Manitobans, the second-highest rate in Canada. That's not surprising, given that Manitoba is among those provinces where usage is not heavily restricted or banned. A made-in-Manitoba review of the current state of health research on the subject would be practical, as it would make for informed debate. It would also inform Manitobans, especially parents, of the developing evidence that weighs in favour of cautious use and limited exposure.