The pesticide debate needs to move beyond ideology and into specifics, says a McGill University chemistry professor.
“People don’t talk about numbers,” said Joe Schwarcz, director of the university’s Office for Science and Society, which is dedicated to demystifying science for the public.
“We need to talk about numbers.”
Speaking at Ag-West Bio Inc.’s second annual meeting, Schwarcz outlined how food consumers are inundated with a steady stream of studies telling them what they shouldn’t be eating, to the point where nothing seems safe.
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“We are confused because there is a lot of information out there and a lot of it is confusing.”
One of the hot button topics is pesticide residue, which has been linked to many health issues, but the danger associated with the use of farm chemicals needs to be put in perspective.
“By definition those things are toxic,” Schwarcz said.
“It’s just that pests are much smaller than humans and we think that the dose that is lethal to pests is not consequential to humans.”
Chemists can detect trace residues down to parts per trillion, which means they can find up to 36 pesticides on an apple.
However, that doesn’t mean all or any of them pose a health threat to the human eating the fruit.
“The only sufficient reason to worry about something is if you know it to be toxic and it is present in a dose known to be toxic,” Schwarcz said.
“Only the dose makes the poison.”
He said people don’t realize there are hundreds of naturally occurring potentially dangerous chemicals in the flesh of the apple.
“There are things like acetone and formaldehyde in there, which at high doses could be toxic.”
However, he said the key is that those naturally occurring chemicals in the fruit’s flesh are present in such small doses that they are of no consequence, much like the synthetic residues on the skin.
The Pest Management Regulatory Agency reviews farm chemicals to establish maximum residue limits to ensure the public isn’t exposed to toxic levels of pesticides.
“They don’t pull this out of a hat,” Schwarcz said.
“Look at the PMRA data and see what is the maximum permissible level. If it is less than that, then what are you worried about?”
Brenda Frick, prairie co-ordinator for the Organic Agriculture Centre of Canada, said there are plenty of things to worry about.
For one, there is still considerable scientific uncertainty about the risk of long-term exposure to pesticides, especially in children, who tend to fill up on food with higher levels of residue such as fruit and vegetables.
For another, despite the PMRA’s best efforts, people are still eating imported and domestic food that exceeds the maximum residue limits because government regulators can’t test everything.
Frick also has a problem with setting one acceptable limit for everybody.
“I know people vary tremendously in their sensitivity to things. Some people may be able to handle certain levels of exposure that other people would find problematic.”
Frick said it is not up to science to determine how much risk the general public is comfortable with, which is a decision for society at large.
However, Schwarcz said consumers need scientific guidance based on toxicology tests rather than relying on scare tactics employed by environmentalists.
While acknowledging that pesticides have had “a checkered history,” he said good health regulations are now in place to protect the public.
People should still make a practice of washing their fruit and vegetables, but the goal is to remove harmful bacteria rather than chemical residue.
He said while people in developing countries are dying of starvation, North Americans are unnecessarily fretting about pesticides in their food.
“We worry about trivia,” Schwarcz said.
“Why do people go bonkers about parts per trillion of pesticides?”
