The journal Regulatory Toxicology and Pharmacology retracted a widely cited 2000 review that concluded glyphosate/Roundup was not carcinogenic, citing undisclosed authorship, selective evidence use, and possible undisclosed payments. Internal Monsanto emails revealed during U.S. litigation suggest company staff helped draft the paper without clear attribution. Bayer defends the review; scientific authorities remain split on glyphosate's cancer risk due to differing evaluation methods.
25 Years Later — Landmark 2000 Glyphosate Review Retracted Over Authorship and Disclosure Concerns
A key study on the safety of glyphosate, the cancer-causing chemical used in the pesticide Roundup, has been retracted due to serious ethical concerns. The journal accuses the authors of having ties to glyphosate manufacturer Monsanto. Wolf von Dewitz/dpa
Regulatory Toxicology and Pharmacology has formally retracted a widely cited 2000 review that concluded glyphosate (marketed widely as Roundup) was not carcinogenic. The retraction, announced in early December, follows new questions about who actually prepared the paper, undisclosed contributions, and potential conflicts of interest tied to Monsanto, the company that marketed Roundup.
Background
The 2000 review was long treated as an influential summary of evidence used in regulatory debates about glyphosate safety. Elsevier, the journal's publisher, said the paper had been regarded as a landmark review. Editor-in-chief Martin van den Berg wrote that the editorial team concluded the paper's conclusions could no longer be relied on because of concerns about authorship, data selection and disclosure.
Why the Paper Was Retracted
- Undisclosed Authorship: Court-disclosed internal Monsanto emails suggest company employees helped draft the review without being listed as co-authors.
- Selective Evidence: The review’s assessment of carcinogenicity relied largely on Monsanto-sponsored studies that found no tumour-inducing effects and omitted other long-term studies available at the time.
- Misrepresentation of Contributions: Text describing the authors’ contributions appears to have been prepared by Monsanto staff but was not transparently acknowledged.
- Possible Undisclosed Payments: Litigation documents indicate the three named authors may have received financial compensation from Monsanto that was not disclosed in the paper.
- Failed Communication: The journal says it attempted to contact the sole surviving author, Professor Gary Williams, but received no response.
“Given its status as a cornerstone in the assessment of glyphosate's safety, it is imperative that the integrity of this review article and its conclusions are not compromised,” the journal said in its retraction statement.
Reaction and Context
Bayer, which acquired Monsanto in 2018, defended the original review, saying no Monsanto employee was listed as an author and that the company’s relationship to the paper had been disclosed. Bayer emphasized that glyphosate is one of the most extensively studied herbicides in recent decades and maintains that regulatory agencies have found it safe when used according to rules.
Scientific assessments of glyphosate remain divided: the International Agency for Research on Cancer (IARC) classifies glyphosate as a "probable human carcinogen," while regulators such as the European Food Safety Authority (EFSA) and Germany’s Federal Institute for Risk Assessment (BfR) have concluded that typical human exposures pose no relevant cancer risk. These differences reflect distinct evaluation approaches—hazard identification (IARC) versus exposure-based risk assessment (EFSA, BfR).
Why This Matters
The 2000 review has had outsized influence on regulators and public debate for decades: recent research in Environmental Science & Policy notes it remains among the top 0.1% most-cited papers in glyphosate research. Because the paper was treated as a cornerstone piece of evidence, doubts about its authorship, transparency and evidence selection have important implications for the scientific record and regulatory history.
Current Status and Implications
The European Union has extended glyphosate’s approval until the end of 2033, though some member states restrict non-agricultural uses. In the United States, courts have awarded large damages in several cases where plaintiffs linked Roundup use to cancer. The retraction does not itself settle questions about glyphosate’s safety, but it removes a high-profile review from the body of literature relied upon in regulatory and public-health discussions.
What’s Next: Researchers, regulators and courts may reassess evidence that previously leaned on this review. The episode highlights the importance of transparent authorship, conflict declarations and comprehensive evidence review in studies that influence public policy.
