Glyphosate herbicide safety study withdrawn 25 years after publication

Health Canada says its decision to approve a popular weed killer will not be affected by the retraction of a major research paper.

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

Journal Regulatory Toxicology and Pharmacology paper withdrawn Last week, citing documents made public through litigation in the US

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

“It’s really a foundational document based on which many regulatory agencies decide whether glyphosate is safe or not.”

The retraction notice cites documents made public through litigation in the US that suggest employees of Monsanto, which makes Roundup, may have helped write the article without proper approval – a practice known as ghostwriting.

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

The recall notice states that the conclusions on whether glyphosate causes cancer are “based solely on Monsanto’s unpublished studies.”

The journal’s editor wrote that it was “unclear how much of the authors’ conclusions were influenced by outside contributions from Monsanto without proper acknowledgement.”

Health Canada cites comprehensive review

The study has been cited more than 700 times in scientific publications – including Health Canada’s 2017 re-assessment of glyphosate use, which concluded that the chemical is “unlikely to pose a human cancer risk.”

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

Olivastri is calling on Health Canada to ban the sale of glyphosate while the health minister orders an expedited special review of the pesticide.

Health Canada said in a written statement that “withdrawal of this review will not impact the findings of our previous review” as the department had also independently assessed the primary data sources used in the 2000 review paper.

“Health Canada’s re-evaluation of glyphosate included more than 1,300 studies. It included studies from the published scientific literature – including several studies on carcinogenicity and human epidemiological studies – industry-provided studies, and information from other regulatory authorities,” the statement said.

Herbicide use on canola and wheat

The department said it monitored glyphosate levels in humans and found they were “more than 1,000 times below screening levels” and would trigger further analysis.

A spokesperson for Health Minister Marjorie Mitchell said she had nothing to add to Health Canada’s response.

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

“What we see in the emerging science on this pesticide is it is linked to a variety of harms,” ​​he said.

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

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

It is commonly applied as a weedicide on crops such as canola and wheat, 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 saying it “stands firmly 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 to co-chair Health Canada’s pest management regulatory agency in 2022. He said he had initially accepted but had to back out when he learned that the committee was not allowed to ask questions.

He noted that while both Health Canada and the U.S. Environmental Protection Agency have concluded that glyphosate is safe, the United Nations’ International Agency for Research on Cancer, a division of the World Health Organization, classified glyphosate as “probably carcinogenic to humans” in 2015.

“If it’s a carcinogenic chemical, if it’s toxic, and three-quarters of the public is being exposed to it, then it needs to be treated as a real, immediate problem,” he said.

Lanphear said it’s a good reason to step back to review the latest science.

“Every time we learn something new about a result – such as risk, potential carcinogenicity – the regulatory agency must reevaluate it,” he said.