A scientific journal has retracted a cornerstone “safety” paper Monsanto and Bayer used in lawsuits to defend Roundup, citing “serious ethical concerns.”
A cornerstone “safety” paper long used to defend Monsanto’s Roundup weed killer has been formally retracted, more than 25 years after its publication and eight years after internal company documents revealed Monsanto employees secretly shaped the research. The retracted article, published in 2000 in Regulatory Toxicology and Pharmacology by Gary M. Williams, Robert Kroes, and Ian C. Munro, concluded that glyphosate does not pose a health risk to humans at typical exposure levels. The paper, which Roundup cancer attorneys asserted was ghostwritten, was a key reference for regulators worldwide.
The journal withdrew the paper over “serious ethical concerns” and questions about the validity and independence of its findings, citing undisclosed Monsanto ghostwriting, reliance almost exclusively on Monsanto-generated data, and failure to incorporate other available toxicity and carcinogenicity studies.
What is the Williams, Kroes & Munro Paper?
Monsanto commissioned the Williams, Kroes, and Munro paper specifically to counter troubling findings from Dr. James Parry, a genotoxicity expert the company hired in 1999 after the Italian government raised concerns about Roundup’s genotoxic potential. Monsanto wanted Dr. Parry to review studies on glyphosate and Roundup formulations, including multiple Italian papers on glyphosate's potential genotoxicity.
What Dr. Parry found created a problem for the company: He concluded that glyphosate could induce genetic mutations, chromosomal breaks, or chromosomal rearrangements that have the potential to cause cancer. He recommended a battery of additional tests that Monsanto could conduct to better understand these genotoxic risks. The scientific conclusions stirred panic at Monsanto. Internal emails from Monsanto toxicologist, Dr. Donna Farmer, noted that Parry’s work left the company in a “genotox hole.”
Dr. William Heydens, a senior Monsanto scientist, wrote candidly to colleagues in a September 1999 email: “Let's step back and look at what we are really trying to achieve here. We want to find/develop someone who is comfortable with the genetox profile of glyphosate/Roundup and who can be influential with regulators and Scientific Outreach operations when genotox issues arise. My read is that Parry is not currently such a person, and it would take quite some time and $$$/studies to get him there.”
As for the studies Dr. Parry suggested Monsanto undertake, Heydens wrote, “[w]e simply aren't going to do the studies Parry suggests… we should seriously start looking for one or more other individuals to work with.” Heydens added, “we are currently very vulnerable in this area.”
Monsanto never conducted any of the additional tests that Parry suggested. More significantly, Monsanto never shared Dr. Parry's report or his recommendations with the U.S. Environmental Protection Agency (EPA), a violation of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which requires manufacturers to report “factual information regarding unreasonable adverse effects on the environment” to EPA on an ongoing basis.
Instead of following Parry's recommendations, Monsanto retained Dr. Gary Williams, a pathologist from New York Medical College. The resulting 2000 paper titled “Safety Evaluation and Risk Assessment of the Herbicide Roundup and Its Active Ingredient, Glyphosate, for Humans” reached the exact opposite conclusions from Parry's assessment.
Williams, Kroes & Munro concluded that glyphosate-based weed killers posed no health risks to humans—no cancer risks, no reproductive risks, no adverse effects on development or endocrine systems. Most critically for Monsanto's purposes, it dismissed genotoxicity concerns entirely.
Why the Williams, Kroes & Munro Glyphosate Study Was Retracted
For decades, regulators and industry groups pointed to the Williams, Kroes, & Munro paper as a hallmark review supporting the safety of glyphosate and Roundup. But internal Monsanto emails made public by Wisner Baum during Roundup cancer litigation told a very different story. The documents, known around the world as the Monsanto Papers, showed that Monsanto employees ghostwrote or drafted large portions of the article while outside academics were listed as the official authors.
In one of the Monsanto Papers documents, a February 2015 email from Monsanto scientist William Heydens, company employees discuss having scientists add their names to a new study, “keeping the cost down by us doing the writing and they would just edit & sign their names so to speak.”
Heydens ended the email by saying: “Recall that is how we handled Williams Kroes & Munro, 2000.”
The journal’s retraction notice emphasized that there is no clear record of which sections were written by Monsanto employees and which, if any, were independently authored by the named scientists. This created “uncertainty about the integrity of the conclusions drawn.”
The editor-in-chief also noted that the paper based its risk assessment “solely on unpublished studies from Monsanto” and omitted other long-term toxicity and carcinogenicity research that was readily available by 1999. That selective use of evidence, combined with undisclosed corporate involvement and potential financial conflicts, led the journal to state it had lost confidence in the results and conclusions.
Is the Glyphosate Study Retraction a Win for Public Health?
The Williams, Kroes & Munro paper was treated as a definitive assessment of glyphosate’s human health risks, especially in pro-industry circles. An analysis published in September of 2025 found that the article ranked in the top 0.1% of glyphosate-related studies by citation count and continued to be cited at high rates even after Monsanto’s hidden role came to light in the Roundup cancer litigation.
Regulators in the United States, Europe, and other parts of the world repeatedly relied on its conclusions in deciding to keep glyphosate on the market without stronger health warnings. Put more simply, regulatory policy and risk communication were shaped for decades by a paper whose independence and methodology are now formally discredited.
The retraction underscores how corporate-authored science, when presented as neutral and peer-reviewed, can distort the evidence base that agencies use to evaluate public health threats. But the retraction means less than it appears because the journal itself is systematically corrupt, according to reporter Paul Thacker.
Regulatory Toxicology and Pharmacology functioned for decades as what Thacker calls an industry platform for “corporate messaging dressed up as peer-reviewed science.” The journal has been run by Gio Gori, a tobacco consultant who was paid over $30,000 by the Tobacco Institute to write a 1991 paper downplaying secondhand smoke dangers. Gori published the paper in his own journal.
In other words, the problem was not limited to Monsanto’s ghostwriting; it was also the fact that the paper was published in a journal specifically designed to legitimize industry-funded research defending “tobacco, pesticides, chemicals, endocrine disruptors, air pollution.”
“This saga demonstrates that Monsanto's behavior wasn't aberrant,” says Wisner Baum senior partner, Michael L. Baum, who served on the trial teams in the first three Roundup trials. “The company exploited an existing framework designed to legitimize corporate science. Moving from Dr. Parry’s scientific findings to the now retracted Williams, Kroes & Munro paper was not something Monsanto improvised; it was a well-established playbook where inconvenient findings get replaced and whitewashed with compliant messaging published through captured journals.”
“A Turning Point in Holding Corporations Accountable”
Wisner Baum managing partner R. Brent Wisner, who helped expose Monsanto’s internal communications during Roundup cancer trials, said the retraction validates years of work uncovering the truth behind the company’s scientific defense strategy.
"The retraction of the Williams paper is a vindication of what we’ve been saying for years: Monsanto prioritized protecting its profits over protecting public health. This study was the linchpin of their defense strategy—they ghostwrote it, buried studies that contradicted their narrative, and then used it for 25 years to convince regulators around the world that glyphosate was safe. The retraction exposes not just Monsanto’s malfeasance, but the broken peer-review process and regulatory framework that allowed corporate-authored ‘science’ to masquerade as independent research. This is a turning point in holding corporations accountable for the integrity of the scientific record.”
Impact on Ongoing Glyphosate Lawsuits
Bayer, which acquired Monsanto in 2018, continues to face tens of thousands of Roundup cancer claims in state and federal courts despite having already paid nearly $11 billion to resolve earlier waves of litigation. Recent estimates suggest more than 60,000 cases are still pending nationwide. At the same time, the company is seeking relief through the courts and Congress, arguing that federal pesticide law should preempt state-law failure-to-warn claims. Bayer is also actively lobbying for legislation that would shield pesticide manufacturers from many future lawsuits.
The retraction of the Williams paper removes a key pillar of Monsanto and Bayer’s scientific defense. Glyphosate attorneys have long argued that the study should not be treated as credible independent science because of Monsanto’s undisclosed role and selective use of data. With the journal now agreeing that serious ethical and methodological problems undermine the paper’s conclusions, it will be harder for Bayer to rely on that paper as evidence that glyphosate is safe when used as directed.
The retraction also reinforces the conclusions from the International Agency for Research on Cancer (IARC), which classified glyphosate as a “probable human carcinogen” in 2015 after reviewing both published and internal industry studies. Subsequent court decisions and jury verdicts have credited that assessment and other independent research in finding that Roundup exposure can increase the risk of non-Hodgkin lymphoma.
A Reckoning for Corporate-Backed Science?
The Williams paper may not be the last glyphosate article to face scrutiny. Researchers who petitioned for this retraction have already asked another journal to withdraw a paper over similar concerns about undisclosed Monsanto involvement. Toxicologists and public health experts warn that multiple glyphosate reviews and commentaries may have been shaped, to varying degrees, by company input that was not transparent to readers or regulators.
For its part, Regulatory Toxicology and Pharmacology has previously faced criticism as a pro-industry outlet that corporations rely on for product-defense work. Critics have called for stronger conflict-of-interest policies and more rigorous editorial review for industry-funded submissions. The delay, now more than eight years from public disclosure of Monsanto’s ghostwriting to formal retraction, highlights systemic weaknesses in how the scientific record is corrected when serious misconduct or undisclosed corporate control is uncovered.
