For years, the Canadian Cancer Society has argued in favour of bans on the cosmetic use of pesticides around homes and gardens. But it has remained silent on the country's biggest use of bug and weed killers: on farms.
Now, the society is considering weighing in on whether these sprays pose a cancer risk to farmers, other rural residents near them, and to the wider public from eating foods carrying pesticide residues.
To that end, the society is holding a conference starting today at which it has assembled experts to advise it on whether cosmetic-pesticide restrictions, which now exist in Ontario, Quebec and many municipalities, should be followed by tougher action against the use of the sprays in agriculture. The society doesn't have a view on the related issue of whether organically grown foods are a better option, a topic that will also be discussed.
"We're bringing the world's leading scientists together to help us understand the science and what we know and don't know and where we could take action, if it's warranted," said Heather Logan, the society's director of cancer-control policy.
In deliberating on possible cancer risks of pesticides, the society is wading into one of the most vociferously contested fields of science and regulation. Health Canada and the pesticide industry say that products licensed for use are extensively tested, and present no risk to farmers or consumers.
"In terms of any risk, health risk, Health Canada will only approve pesticides that do not pose a health risk, provided that the label directions are followed," said Connie Moase, a director in the Pest Management Regulatory Agency, Health Canada's watchdog.
But pesticide opponents, including some respected public-health groups, argue that pesticides are strong poisons designed to kill if used as directed. They contend that Health Canada and industry play down research linking occupational exposures to bug and weed sprays to greater risks of many cancers, such as non-Hodgkin's lymphoma.
Those worried about pesticides also say the cancer society policy is contradictory because it deems use on residential lawns and gardens as dangerous and needing to be banned, while ignoring the far greater use on farms. One estimate, by the U.S. Environmental Protection Agency in 2005, found that about five times more 2,4-D, the main weed killer subject to cosmetic-pesticide bans, was used on farms as on lawns.
"It's very hard to argue that the cosmetic use of pesticides poses a public-health risk, including cancer risk, and not examine what is going on in the rural and agricultural communities," said James Brophy, an adjunct professor at the University of Windsor.
Prof. Brophy has published research indicating that women who worked on farms in Southwestern Ontario have about three times the breast-cancer risk of those without an agricultural background.
For the cancer society, lending its credibility to campaigns to eliminate cosmetic pesticide use was easy.
The bans were needed because "there is some potential for increased cancer" with the use of these products around homes and "no health benefit whatsoever," Ms. Logan said. "The only benefit that you get is looking at your lawn without any weeds. The issue of non-cosmetic exposure is very different."
The cancer society, in its monitoring of recent scientific literature, considers some cancers to be linked to pesticides. The connection is strongest for those, such as farmers, who have occupational exposures. "There does appear to be a potential of an increased risk of a number of cancers" from them, Ms. Logan said. The diseases include colorectal, prostate, lung, ovarian and some types of blood cancers.
The cancer risks for rural residents near farms and for those eating trace pesticide residues on food are less clear-cut, according to Ms. Logan.
