The move is part of an effort to harmonize Canadian pesticide rules with those of the United States, which tends to allow higher residue levels on its food: Canada's limits are stricter than those south of the border for 40 per cent of the residues it regulates.

Differences in residue limits, which apply to domestic and imported food, pose a potential "trade irritant," said Richard Aucoin, chief registrar of the Pest Management Regulatory Agency, which sets Canada's pesticide rules.

However, Canada will only relax its rules "where this poses no risks," he stressed.

The harmonization effort may even force Canada to raise some of its standards to match those in the U.S., he adds. However, he concedes, U.S. standards are stricter in only 10 per cent of cases.

The U.S. often allows more pesticide residues because its warmer climate means it is plagued by more pests, Mr. Aucoin said.

Canada won't be relaxing its limits for all of the cases in which they are stricter than those south of the border, but "will likely be asked to (change) them" for cases now being identified as priorities by growers, he says.

The agency is reviewing its limits on a case-by-case basis, he said.

The harmonization effort is drawing fire from environmental critics.

"Canada should never lower its standards in the name of harmonization," said David Boyd, an environmental lawyer and author of a 2006 study of international pesticide regulations.

"We should look to equal or surpass the best in the world, not only measure ourselves against the U.S.," where regulations are weaker than in jurisdictions such as the European Union, he said.

Canadian regulators and their U.S. counterparts have been working to harmonize their pesticide regulations since 1996, as part of the North American Free Trade Agreement.

Now the effort is being fast-tracked as an initiative under the Security and Prosperity Partnership, a wide-ranging plan to streamline regulatory and security protocols across North America. The SPP's 2006 report identified stricter residue limits as "barriers to trade."

Mr. Boyd's report, published by the B.C.-based David Suzuki Foundation, raised concerns about the levels of pesticide residue allowed both in the U.S. and Canada.

Comparing 40 U.S. limits with those set by Canada, the European Union, Australia and the World Health Organization, he found the U.S. had the weakest rules for more than half of the cases studied.

In some cases the differences were dramatic: The U.S. allows 50 times more vinclozolin on cherries as the E.U., and 100 times more lindane on pineapples.

Canada fared no better: For permethrin on leaf lettuce and spinach, the Canadian and U.S. limit was 400 times higher than in Europe, and the Canadian cap on methoxychlor was 1,400 times the European limit.

Both Canada and the U.S. also allow pesticides that have been banned by health officials not only in Europe but also in some developing countries, Mr. Boyd noted.

Methamidophos, for example, is permitted in Canada but banned in Indonesia and other developing nations, he found. (The pesticide is now being re-evaluated in Canada.)

Both countries also allow the use of atrazine, which has been found to cause sexual deformities and reproductive problems in frogs in concentrations of just a few parts per billion -- concentrations that have been found in Canadian drinking water, Mr. Boyd's report says.

Other pesticides have been associated with a risk of cancer, including breast cancer and childhood leukemia, autism, birth defects, organ damage and Alzheimer's disease.

Mr. Aucoin said residue limits are set according to exacting standards in Canada, adding that differences in ecosystems and patterns of use can account for the variation from country to country.

Also, it's just common sense for Canada to work most closely with its largest and nearest trading partner, he adds.

Besides, in practice, the question of official residue limits is moot in most cases because farmers are using fewer and fewer pesticides, he says.

"The trend in both Canada and the U.S. is to use less, not more," he said, explaining that the high cost of bug-killers has prompted farmers to cut back.

As a result, residue levels on imported produce are usually well below even the Canadian limits, he says.

The Canadian Food Inspection Agency, which monitors residue levels, has found "a relatively small number of violations" of Canada's maximum levels in recent years, he said.

Raising the official limits "will not change the amount of pesticides coming into the country," he concludes.

But Mr. Boyd questions how much we really know about the amount of pesticides coming across the border, saying his study raised questions about the effectiveness of Canada's monitoring system.

His study noted that the food inspection agency found residues in only 10 per cent of the produce it tested in 2004-05. In the same period, U.S. regulators found residues in 76 per cent of the fresh fruit and vegetables they tested. British officials found pesticides in 40 per cent of their produce in 2006.

In the cases of Canada and the U.S., less than one per cent of the residues exceeded the legal limits.

Even if those findings are accurate, Mr. Boyd says they are cause for concern.

"One or two per cent may not seem like very much, but you have to consider that people are eating fruits and vegetables several times a day, 365 days a year," Mr. Boyd said.

Pesticide residues also make their way into water and the air through dust particles, leading to a cumulative effect that regulators do not currently take into account, he says.

A 2006 study in the Annals of Neurology found even low exposure to pesticides increased the risk of contracting Parkinson's disease by 70 per cent, Mr. Boyd's study notes.

NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed without profit to those who have expressed a prior interest in receiving this information for research and educational purposes.

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