The journal Regulatory Toxicology and Pharmacology has formally retracted a sweeping scientific paper published in 2000 that became a key defense for Monsanto’s claim that Roundup herbicide and its active ingredient glyphosate don’t cause cancer.
Martin van den Berg, the journal’s editor in chief, said in a note accompanying the retraction that he had taken the step because of “serious ethical concerns regarding the independence and accountability of the authors of this article and the academic integrity of the carcinogenicity studies presented”.
The paper, titled Safety Evaluation and Risk Assessment of the Herbicide Roundup and Its Active Ingredient, Glyphosate, for Humans, concluded that Monsanto’s glyphosate-based weed killers posed no health risks to humans – no cancer risks, no reproductive risks, no adverse effects on development of endocrine systems in people or animals.
Regulators around the world have cited the paper as evidence of the safety of glyphosate herbicides, including the Environmental Protection Agency (EPA) in this assessment.
The listed authors of the paper were three scientists who did not work for Monsanto – Gary Williams, Robert Kroes and Ian Munro, and was held up by the company as a defense against conflicting scientific evidence linking Roundup to cancer. The fact that it was authored by scientists from outside the company, from seemingly independent researchers, gave it added validity.
But over the last decade, internal company documents, that came to light in litigation brought by plaintiffs in the US suffering from cancer, revealed Monsanto’s influence on the paper. The documents included an email from a company official discussing the research paper and praising the “hard work” of several Monsanto scientists as part of a strategy Monsanto called “Freedom to Operate” (FTO).
The corporate files showed how company officials celebrated when the paper was published.
In one email following the April 2000 publication of the Williams paper, Lisa Drake, then Monsanto government affairs official, described the toll the work of developing “independent” research papers took on multiple Monsanto employees.
“The publication by independent experts of the most exhaustive and detailed scientific assessment ever written on glyphosate … was due to the perseverance, hard work and dedication of the following group of folks,” Drake wrote. She then listed seven Monsanto employees. The group was applauded for “their hard work over three years of data collection, writing, review and relationship building with the papers’ authors”.
Drake further emphasized why the Williams paper was so significant for Monsanto’s business plans: “This human health publication on Roundup herbicide and its companion publication on ecotox and environmental fate will be undoubtedly be [sic] regarded as ‘the’ reference on Roundup and glyphosate safety,” she wrote in the email dated 25 May 2000.
“Our plan is now to utilize it both in the defense of Roundup and Roundup Ready crops worldwide and in our ability to competitively differentiate ourselves from generics.”
In a separate email, a company executive asked if Roundup logo polo shirts could be given to eight people who worked on the research papers as a “token of appreciation for a job well done”.
Monsanto’s Hugh Grant, who at that time was a senior executive on his way toward being named CEO and chairman, added his own praise, writing in an email: “This is very good work, well done to the team, please keep me in the loop as you build the PR info to go with it.”
In 2015, William Heydens, a Monsanto scientist, suggested that he and colleagues “ghost-write” another scientific paper. Monsanto could pay outside scientists to “edit & sign their names” to the work that he and others would do, Heydens wrote in an email. “Recall that is how we handled Williams Kroes and Munro 2000.”
The emails were spotlighted in jury trials in which plaintiffs suffering from cancer won billions of dollars in damages from Monsanto, which was bought by Bayer AG in 2018.
Gary Williams, one of the authors of the now retracted 2000 research paper, could not immediately be reached for comment. In 2017, Williams’s former employer New York Medical School said it found “no evidence” that a faculty member violated the school’s prohibition against authoring a paper ghostwritten by employees of Monsanto. The two other authors of the paper, Robert Kroes and Ian Munro, are deceased.
In explaining the decision to retract the 25-year-old research paper, Van den Berg wrote: “Concerns were raised regarding the authorship of this paper, validity of the research findings in the context of misrepresentation of the contributions by the authors and the study sponsor and potential conflicts of interest of the authors.”
He noted that the paper’s conclusions regarding the carcinogenicity of glyphosate were solely based on unpublished studies from Monsanto, ignoring other outside, published research.
Van den Berg did not respond to a request for comment.
When asked about the retraction, Bayer said in a statement that Monsanto’s involvement was adequately noted in the acknowledgments section of the paper in question, including a statement that referred to “key personnel at Monsanto who provided scientific support”. The company said the vast majority of thousands of published studies on glyphosate had no Monsanto involvement.
“The consensus among regulatory bodies worldwide that have conducted their own independent assessments based on the weight of evidence is that glyphosate can be used safely as directed and is not carcinogenic,” the company said.
An EPA spokesperson said that the agency was aware of the retraction but “has never relied on this specific article in developing any of its regulatory conclusions on glyphosate”.
The spokesperson said the EPA has “extensively studied glyphosate, reviewing more than 6,000 studies across all disciplines, including human and environmental health, in developing its regulatory conclusions”.
The updated human health risk assessment the agency is currently conducting for glyphosate is “using gold standard science”, the spokesman said. That assessment should be released for public comment in 2026 and will not rely on the retracted article.
“The retraction of this study is a long time coming,” said Brent Wisner, one of the lead lawyers in the Roundup litigation and a key player in getting the internal documents revealed to the public.
Wisner said the Williams, Kroes and Munro study was the “quintessential example of how companies like Monsanto could fundamentally undermine the peer-review process through ghostwriting, cherrypicking unpublished studies, and biased interpretations”.
“This garbage ghostwritten study finally got the fate it deserved,” Wisner said. “Hopefully, journals will now be more vigilant in protecting the impartiality of science on which so many people depend.”
News of the retraction of the study came in the same week the Trump administration urged the US supreme court to take up Bayer’s bid to curtail thousands of lawsuits claiming Roundup causes cancer.
In a brief filed at the court, the solicitor general, D John Sauer, said the company was correct that the federal law governing pesticides pre-empts lawsuits that make failure-to-warn claims over the products under state law.
Plaintiffs have said they developed non-Hodgkin’s lymphoma and other forms of cancer due to using Roundup and other glyphosate-based herbicides sold by the company, either at home or on the job.
This story is co-published with the New Lede, a journalism project of the Environmental Working Group.
