Is Glyphosate Causing Cancer?

What the WHO concluded, the landmark study that was retracted, and what the independent science shows

The Glyphosate Series - Part 3 of 5

The question of whether glyphosate causes cancer has been at the center of one of the most contentious scientific and legal battles of the past decade.

On one side: regulatory agencies in the U.S. and Europe that have largely maintained glyphosate does not pose a cancer risk. On the other: the World Health Organization, independent researchers, and tens of thousands of plaintiffs in courtrooms across America.

Understanding this debate requires knowing who funded what - because in few areas of public health does the distinction between industry-funded and independent research matter more.

What the WHO Concluded in 2015

In 2015, the International Agency for Research on Cancer (IARC) - the cancer research arm of the World Health Organization - classified glyphosate as "probably carcinogenic to humans," placing it in Group 2A. The classification was based on three bodies of evidence:

1. Sufficient evidence of cancer in animals - multiple rodent studies showing increased rates of malignant tumors at glyphosate-exposed doses

   
   

2. Strong evidence of genotoxicity - glyphosate and its formulations caused DNA and chromosomal damage in human cells in laboratory studies, consistent with cancer-causing mechanisms

   
   

3. Limited but positive evidence in humans - multiple case-control studies showing associations between glyphosate exposure and non-Hodgkin lymphoma, a cancer of the lymphatic system

The IARC working group included 17 independent scientists from 11 countries. No members had undisclosed financial relationships with pesticide manufacturers.

The U.S. EPA disagreed, maintaining its position that glyphosate is not likely carcinogenic at typical exposure levels. The regulatory divide set the stage for years of scientific and legal conflict.

The Fraudulent Study That Propped Up "Safe" for 25 Years

In December 2025, the journal Regulatory Toxicology and Pharmacology retracted a widely cited 2000 paper that had been a cornerstone of glyphosate's safety record for a quarter century. The paper concluded that glyphosate did not pose a cancer risk and was cited repeatedly by regulators worldwide to dismiss the IARC findings.

The retraction came after researchers documented serious ethical violations: the study was ghostwritten by Monsanto employees; authors had undisclosed financial relationships with the company; the paper relied on unpublished, unverified industry studies; and long-term research that contradicted the safety conclusion was deliberately excluded.

For 25 years, one of the most influential pillars of glyphosate safety was built on compromised science.

Trial after trial had surfaced internal Monsanto documents showing a deliberate strategy to manufacture doubt about glyphosate's risks - a playbook that mirrors what the tobacco and lead industries used for decades.

What the Independent Science Shows

2019 meta-analysis: A pooled analysis published in Mutation Research found that people with high glyphosate exposure had a 41 percent increased risk of developing non-Hodgkin lymphoma compared to those with low or no exposure. This held even after accounting for other pesticide exposures.

2023 systematic review: A review using the ten key characteristics of carcinogens framework found that glyphosate and its formulations met multiple criteria, including genotoxicity, oxidative stress, disruption of hormone signaling, and immunosuppression. The authors concluded that the mechanistic evidence for glyphosate as a probable human carcinogen had strengthened significantly since 2015.

Chromosome damage in male farmers: A 2023 study published in Environmental Health Perspectives found that glyphosate exposure in male farmers was associated with expanded mosaic loss of chromosome Y - a type of DNA damage linked to cancer risk. This represented important new evidence of a biological mechanism connecting glyphosate exposure to cancer in living humans.

Jury verdicts: More than $11 billion has been paid by Bayer in settlements with approximately 100,000 plaintiffs who claimed glyphosate exposure caused their non-Hodgkin lymphoma. Juries have awarded billions more in individual verdicts, including a $2 billion judgment in Georgia in March 2025. Juries hear the full evidence - including internal company documents - and have repeatedly found that Monsanto failed to warn consumers of a known cancer risk.

Why the Regulatory Disagreement Persists

If independent science supports a cancer link, why do the EPA and European agencies still say glyphosate is safe? Several factors contribute:

●      Regulatory agencies rely heavily on the body of studies submitted by the manufacturer as part of the registration process. These studies are not always publicly available for independent verification.

●      The retracted Williams et al. (2000) paper was a key citation in regulatory reviews for decades. Its influence on the official safety record cannot be fully unwound retroactively.

●      IARC and regulatory agencies use different methodologies. IARC assesses whether a substance is capable of causing cancer under any circumstances. Regulatory agencies assess risk at typical real-world exposure levels. These are different questions - and the distinction is often lost in public communication.

●      Regulatory timelines are slow, and comprehensive re-evaluation of a widely approved pesticide faces significant industry lobbying pressure.

This does not mean the EPA is corrupt or that cancer from oatmeal is inevitable. It means the regulatory picture is incomplete, the foundational study has been retracted, and independent researchers have identified mechanisms and associations that deserve serious weight in any honest assessment of risk.

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In Part 4, we look at what is happening right now in courts and legislatures across America - including a Supreme Court case scheduled for oral arguments in April 2026 that could determine whether Bayer faces any accountability at all for the harm its product has caused.

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Lis Rodriguez is a Registered Dietitian Nutritionist and integrative and functional medicine practitioner. She founded Professional Nutrition Consulting, PLLC in 2009 and writes about environmental nutrition, public health, and whole-person wellness at LisRodriguez.com.

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References

International Agency for Research on Cancer. (2015). IARC monographs volume 112: Evaluation of five organophosphate insecticides and herbicides. World Health Organization. https://www.iarc.who.int/featured-news/media-centre-iarc-news-glyphosate/

Schinasi, L. H., & De Roos, A. J. (2023). Invited perspective: Important new evidence for glyphosate hazard assessment. Environmental Health Perspectives, 131(12), 121305. https://pmc.ncbi.nlm.nih.gov/articles/PMC10699408/

Zhang, L., Rana, I., Shaffer, R. M., Taioli, E., & Sheppard, L. (2019). Exposure to glyphosate-based herbicides and risk for non-Hodgkin lymphoma: A meta-analysis and supporting evidence. Mutation Research - Reviews in Mutation Research, 781, 186-206. https://doi.org/10.1016/j.mrrev.2019.02.001

CSG South. (2025). Lawsuits and legislation: What's happening with glyphosate-based herbicides.https://csgsouth.org/policies/lawsuits-and-legislation-whats-happening-with-glyphosate-based-herbicides/

Farm Action. (2026). Supreme Court showdown: Farmers' rights vs. corporate power. https://farmaction.us/supreme-court-showdown-farmers-rights-vs-corporate-power/