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By Agroempresario.com
German multinational Bayer has firmly rejected the conclusions of a new study suggesting that glyphosate—the active ingredient in the company’s flagship herbicide, Roundup—can cause multiple forms of cancer in rats, even at low exposure levels. The study, led by the Cesare Maltoni Cancer Research Center of the Ramazzini Institute, claims to provide robust evidence in support of the International Agency for Research on Cancer’s (IARC) 2015 assessment, which classified glyphosate as “probably carcinogenic to humans.”
The research involved exposing Sprague-Dawley rats to three different glyphosate concentrations via drinking water. Two commercial formulations were used: Roundup BioFlow, used in the European Union, and Ranger Pro, sold in the United States. Both are manufactured by Bayer.
According to Dr. Daniele Mandrioli, co-author of the study and director of the Cesare Maltoni Center, “rat bioassays are among the most predictive toxicological models for human carcinogens.” The study observed an increase in benign and malignant tumors across several organs, including the liver, kidneys, thyroid, pancreas, adrenal glands, mammary glands, and spleen.
Bayer swiftly issued a statement in response:
“While we are still reviewing the report, it is already clear this study has serious methodological flaws, which is consistent with the Ramazzini Institute’s long history of making misleading claims about the safety of various products.”
The company pointed to past assessments by the U.S. Environmental Protection Agency (EPA) and the European Food Safety Authority (EFSA) that discredited the Ramazzini Institute’s scientific rigor. Bayer emphasized that the EPA had previously rejected studies from the institute for failing to meet scientific standards in regulatory review.
In 2010, the EPA suspended four studies after the U.S. National Toxicology Program identified discrepancies in cancer diagnoses in previous Ramazzini studies. Likewise, the EFSA criticized a 2016 Ramazzini paper claiming sucralose induced cancer in mice, stating the available data did not support such conclusions.
Despite criticism, the glyphosate study was conducted in collaboration with respected institutions including Boston College, George Mason University, King’s College London, the Icahn School of Medicine at Mount Sinai, the Scientific Centre of Monaco, the University of Bologna, the Italian National Institute of Health, and Italy’s National Food Safety Committee.
Dr. Mandrioli stated that their findings “reinforce the IARC’s classification,” noting that tumors appeared even at glyphosate levels currently considered safe. The most concerning result, he added, was that leukemia deaths among rats exposed from prenatal stages occurred within their first year of life—comparable to cancers developing before the age of 40 in humans.
However, Sprague-Dawley rats are known for a predisposition to spontaneous tumor growth, raising questions about how directly the study’s results apply to human health. Critics also recall the controversial Séralini study from 2012, which linked glyphosate to tumors in rats but was retracted in 2014 over concerns about methodology.
Glyphosate has been registered with the EPA since 1974. The agency’s most recent assessment in 2020 confirmed earlier findings that “glyphosate is unlikely to be a human carcinogen” and poses “no risks of concern” when used as labeled. Nonetheless, the agency acknowledged ecological risks, particularly for non-target plants affected by drift.
Following a 2020 lawsuit filed by the Natural Resources Defense Council (NRDC), the Ninth Circuit Court of Appeals vacated the EPA’s interim decision, citing an insufficient cost-benefit analysis. As a result, the EPA withdrew its interim approval and is currently revisiting both the environmental and carcinogenic impacts of glyphosate.
In the European Union, glyphosate remains divisive. While the European Commission renewed its approval for another 10 years in 2023, disagreement persists among member states. Neither EFSA nor the European Chemicals Agency (ECHA) classify glyphosate as carcinogenic, but public pressure and new studies keep the chemical under intense scrutiny.
Beyond the scientific debate, Bayer continues to face legal pressure over Roundup. The company has settled more than 100,000 lawsuits, costing nearly $11 billion, but still has about 67,000 cases pending.
Some verdicts have favored Bayer, but plaintiffs have also secured roughly $4 billion in damages. Most recently, an appeals court in Missouri upheld a $611 million award to three plaintiffs who claimed that Roundup caused their cancer. Bayer has pledged to appeal that decision.
On its official website and in public statements, Bayer continues to stand by the safety of its glyphosate products:
“For more than 50 years, leading health regulators around the world have repeatedly concluded that our glyphosate products can be used safely, and that glyphosate is not carcinogenic.”
The glyphosate controversy reflects a larger divide between regulatory institutions, scientific communities, and public sentiment. As Bayer defends its flagship herbicide and continues legal appeals, new research like that from the Ramazzini Institute is reigniting concerns about potential health risks at low exposure levels.
With environmental and consumer safety groups calling for stricter regulation, the coming years could bring significant shifts in how glyphosate is approved, used, and litigated across jurisdictions.
The question remains: will global regulators and courts continue to uphold glyphosate’s safety record, or will emerging evidence and legal precedents force a reevaluation of one of the world’s most widely used herbicides?
