Roundup Safety Study Retracted Decades After Publication

Editors are questioning the validity of a study that has been used for decades to support claims that glyphosate is safe for humans and not carcinogenic.

Dating back to April 2000, the medical journal Regulatory Toxicology and Pharmacology published a study indicating that glyphosate, the active ingredient in Roundup weed killer, was safe for humans.

However, internal Monsanto documents produced during discovery in the Roundup litigation suggest that the company played an undisclosed role in writing the study. These revelations led the journal to issue a retraction notice on December 5. 

Dr. Martin van den Berg, the journal’s co-editor-in-chief, said the findings raised serious concerns about the study’s credibility and the integrity of the research.

Roundup is a popular weed-killing herbicide that contains the active ingredient glyphosate, which has been used for decades by farmers, landscapers and homeowners. While it has long been marketed as safe for routine use, a growing body of research has linked glyphosate exposure to an increased risk of cancer, a danger the manufacturers never disclosed on the product’s label.

The manufacturer, Monsanto, a subsidiary of Bayer, has faced tens of thousands of Roundup lawsuits filed by former users who alleged that long-term exposure to glyphosate led to the development of non-Hodgkin’s lymphoma and other forms of cancer. As a result, Bayer and Monsanto have paid more than $10 billion in settlements to resolve a large number of claims.

However, thousands of additional cases remain unresolved, and new Roundup claims continue to be filed as additional users receive cancer diagnoses.

The retracted study, credited to Gary M. Williams, Robert Kroes and Ian C. Munro, had long been cited as evidence that Roundup posed no risk. However, litigation over the weed killer later revealed that Monsanto had secretly ghostwritten portions of the paper without disclosing its involvement to the journal.

Monsanto’s undisclosed role in shaping the study was not the only issue. The retraction notice explains that the paper’s conclusion that glyphosate was not carcinogenic relied “solely on unpublished studies from Monsanto,” while failing to account for other long-term toxicity and cancer research that was available at the time.

“The paper had a significant impact on regulatory decision-making regarding glyphosate and Roundup for decades. 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.”

– Dr. Martin van den Berg, co-editor-in-chief, Regulatory Toxicology and Pharmacology

The journal also criticized the study for lacking independent authority, noting that it failed to disclose Monsanto’s influence, misrepresented the authors’ contributions, raised concerns about potential financial incentives, and presented ambiguous findings. Editors further questioned how the researchers evaluated and weighed the available evidence.

Roundup Cancer Lawsuits

Bayer and Monsanto have been hit by a series of multi-million dollar verdicts in Roundup cancer lawsuits in recent years. Facing trouble convincing juries, Bayer has urged U.S. lawmakers to grant special legal protections against future lawsuits, warning it may otherwise withdraw the product from the U.S. market.

The manufacturers have repeatedly attempted to convince courts to dismiss Roundup lawsuits, arguing that the company should be exempt from liability under existing federal preemption laws. However, judges have repeatedly shot down the company’s legal theory, and lawsuits continue to move forward through the U.S. court system.

One of those verdicts involves a $1.2 million jury award granted to John L. Durnell in Missouri state court, who alleged that Roundup exposure caused his non-Hodgkin’s lymphoma. Monsanto’s attempt to overturn the verdict was rejected by a state appellate court in February. The company is now asking the U.S. Supreme Court to review the case, arguing that conflicting lower-court rulings on federal preemption require clarification, while seeking to have the verdict reversed.

At the beginning of the month, U.S. Solicitor General D. John Sauer filed an amicus brief (PDF) intervening on the government’s behalf, supporting Bayer and Monsanto’s motion to have the verdict overturned on preemption grounds. The high court has yet to decide if it will take up the case.

Following billions paid out in Roundup settlements, Bayer announced in 2021 that it would reformulate Roundup and remove the active ingredient glyphosate from consumer versions of the weedkiller. However, there doesn’t appear to be any end in sight for liability the company may face, as juries continue to hear evidence about how long Monsanto knew about the potential cancer risks.

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