Glyphosate herbicide safety study retracted 25 years after publication

wellness Canada says its determination to sanction a pop mourning band killer won't be affected by the retraction of a key research paper.

The 25-year-old study said the main ingredient in Roundup — the herbicide glyphosate — is safe for humans.

The journal Regulatory Toxicology and Pharmacology retracted the paper last week, citing documents made public through litigation in the U.S.

"It was like a bomb dropped," said Beatrice Olivastri, CEO of Friends of the Earth Canada.

"It's really a foundational paper against which a lot of regulatory agencies made decisions about whether or not glyphosate was safe."

The retraction notice cited documents made public through litigation in the U.S. That suggest employees of Monsanto, which makes Roundup, may have helped write the article without proper acknowledgment — a practice known as ghostwriting.

The documents also suggest Monsanto may have paid the study's authors.

The retraction notice said the conclusions on whether glyphosate causes cancer were "solely based on unpublished studies from Monsanto."

The journal's editor wrote it is "unclear how much of the conclusions of the authors were influenced by external contributions of Monsanto without proper acknowledgments."

The study has been cited more than 700 times in scientific publications — including Health Canada's 2017 re-evaluation of glyphosate use, which concluded that the chemical was "unlikely to pose a human cancer risk."

That review approved the use of glyphosate-based herbicides until 2032.

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Olivastri is calling on Health Canada to impose a moratorium on glyphosate sales while the health minister orders an expedited special review of the pesticide.

Health Canada said in a written statement that "the retraction of this review does not affect our previous review conclusions" because the department also independently evaluated the primary data sources used in the 2000 review paper.

"Health Canada's re-evaluation of glyphosate included more than 1,300 studies. This included studies from published scientific literature — including many studies on carcinogenicity and human epidemiology studies — industry-supplied studies, and information from other regulatory authorities," the statement said.

The department added it monitors glyphosate levels in humans and has found they are "more than 1,000 times below the screening level" that would trigger further analysis.

A spokesperson for Health Minister Marjorie Michel said she has nothing to add to Health Canada's response.

Cassie Barker, a senior program manager at Environmental Defence, echoed the call for Health Canada to review the latest science.

"What we see in the emerging science on this pesticide is links to a wide range of harms," she said.

Glyphosate use is increasing. Roughly 50 million kilograms of the chemical are sold in Canada each year, making it the most widely used pesticide in the country and in the world.

It has been on the market since the 1970s and can be found in more than 160 pest control products in Canada.

It's commonly applied to crops like canola and wheat as a weed-killer, and is used by the forestry industry to clear vegetation where softwood lumber is being harvested.

In response to questions about this story, Bayer sent a statement by email that said it "firmly stands behind the safety of glyphosate-based products," which have been used for nearly 50 years.

"Leading health regulators around the world, including Health Canada, have repeatedly concluded that glyphosate is not a carcinogen and that glyphosate products are safe when used according to label directions," the statement said.

Monsanto said in a statement of its own that its involvement in the paper "did not rise to the level of authorship" and that its authors had full control over the study's manuscript.

Bruce Lanphear, a professor in the faculty of health sciences at Simon Fraser University, said ghostwriting is "part of the playbook" of the pesticide industry.

Lanphear was invited in 2022 to co-chair Health Canada's Pest Management Regulatory Agency. He said he accepted initially but had to pull out when he learned the committee was not allowed to ask questions.

He pointed out that while Health Canada and the U.S. Environmental Protection Agency both have concluded that glyphosate is safe, the UN's International Agency for Research on Cancer, a division of the World Health Organization, classified glyphosate as "probably carcinogenic to humans" in 2015.

"If this is a carcinogenic chemical, if it's toxic, and three-quarters of the public are being exposed, that should be treated as a real, urgent problem," he said.

Lanphear said the retraction is a good reason to review the latest science.

"Every time we learn something new of consequence — like exposure, like potential carcinogenicity — the regulatory agency should re-evaluate it," he said.

Sarah Ritchie is a reporter with The Canadian Press.

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