Manitoba pesticide ban misguided: toxicologist

Legislation would ban cosmetic use | Leading toxicologist says the Manitoba government plan shows a lack of expertise

The Manitoba government announcement to ban cosmetic pesticides provided several quotes in a news release that included comments from doctors, parents and anti-pesticide activists.


It even included a comment from a well known children’s entertainer.


“Congratulations Manitoba for your new pesticide ban. Your children and families will thank you for this, for generations to come,” said Raffi in the release.


However, the release failed to include comments from toxicologists or a toxicology society, even though toxicologists study the adverse affects of chemicals on living organisms, like humans.


James Bus, a U.S. toxicologist who has studied pesticides for 35 years, said the Manitoba ban demonstrates an absence of expertise. 


“The level of sophistication in terms of understanding the science and appropriately making judgments about the science, usually diminishes as you (become more local),” said Bus, former president of the U.S. Society of Toxicology and the American Board of Toxicology, a member of scientific advisory boards for the U.S. Environmental Protection Agency and the Food and Drug Administration and the author of dozens of publications, books and scientific reviews on the toxicity of pesticides


“You would expect, at your federal level, to have your most sophisticated scientific expertise…. When you’re making decisions at the community level, you often find zero expertise.”


The Manitoba legislation will allow property owners to use pesticides on their lawns, but only provincially approved bio-pesticides.


The regulations do not apply to farms and forestry operations. The province said there would also be exemptions for certain practices and conditions, such as for gardens, golf courses and to control noxious weeds, poisonous or invasive plants


Manitoba farm groups have criticized the pesticide ban, called the science inconclusive and the rhetoric inflammatory.


“MBP (Manitoba Beef Producers) has concerns regarding the artificial distinction being made between so called cosmetic use of pesticides and agricultural use,” the Manitoba Beef Producers said in a letter to the province. 


“We do not believe that products can be considered safe in one environment and toxic in another. It is our view that this distinction between different uses of products sends an unfortunate (and ultimately dangerous) mixed message to the public at large.”


Bus, who has received multiple awards during his scientific career with Dow Chemical, Michigan State University and the Upjohn Company, said there is no evidence that common lawn herbicides like 2,4-D cause cancer or any health problems in children.


“There is no regulatory agency in the world… that regards 2,4-D as a human carcinogen or as a threat to children’s health.”


Bus said Health Canada through the Pest Management Regulatory Agency establishes exposure limits based on “extremely conservative” evaluation of the science. 


For 2,4-D for example, agency scientists review data from experiments where mice and rats are fed a diet containing 2,4-D for a two-year period. The animals are monitored for adverse health outcomes, including cancer.


“Those studies (identify) what we call a no observed effect level,” Bus said. “In those studies the overall no observed effect level… was five milligrams per kilogram of body weight, per day. That’s the dose (of 2,4-D) by which the regulators use to make their judgments.”


The PMRA then divides the five mg per kg figure by 100, to build a generous safety factor into the exposure standard for humans, which is 0.05 mg per kg.


Exposure experiments demonstrate homeowners are rarely exposed to 0.05 mg of 2,4-D per kg of body weight, when label instructions are followed.


Keith Solomon, a University of Guelph toxicologist, published a study in 1992 on human exposure to 2,4-D. Solomon and Shelley Harris recruited 10 volunteers to sit, stand and roll on a plot of grass 24 hours after a 2,4-D application. Five volunteers wore long sleeves and pants and five volunteers wore shorts and bare feet.


“No detectable residues were found in urine samples supplied by volunteers exposed to sprayed turf 24 hours following application,” Solomon wrote.


In the same experiment Solomon had volunteers go on the grass one hour after 2,4-D was applied. The scientists detected 2,4-D in the urine of volunteers who were barefoot and wore shorts, but the levels were well below the no effect level from rat experiments.


“The dose those individuals received was still 1,000 times lower than the five mg per kg of body weight,” Bus said.

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  1. sheri on

    Drowning our planet in pesticides is not something we all strive for.. Just cause people can swim in the stuff doesn’t mean we need to smother the planet with it.. Err on the side of caution or they may be like antibiotics in a few decades.

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