New Study Appears To Confirm Link Between Roundup and Cancer

Evidence about the side effects of glyphosate in Roundup on rats is seen as supporting evidence for IARC decision to classify the weedkiller as a human carcinogen.

The findings of a new study appear to add to the growing evidence that exposure to glyphosate, the active ingredient in Roundup weed killer products, can increase a person’s risk of cancer.

In a report published in the medical journal Environmental Health on June 10, Italian researchers detail experiments on rats, which show a dose-dependent increase in the development of tumors when exposed to glyphosate. Dose-dependent relationships are often considered strong evidence of a causal relationship.

The study comes as Bayer and its Monsanto subsidiary continue to face tens of thousands of Roundup lawsuits, each claiming that the manufacturers failed to provide adequate warnings about the link between Roundup and cancer, specifically the risk that users may develop non-Hodgkins lymphoma.

More than 90,000 consumers have filed claims after they were diagnosed with non-Hodgkins lymphoma from Roundup, and Bayer has already agreed to pay more than $10 billion in Roundup settlements. However, the litigation appears to have no end in sight, with a steady stream of trials scheduled involving individuals who declined the settlement offers, as well as new claims that continue to be filed as former users develop non-Hodgkin’s lymphoma.

In the new study, researchers looked at the side effects of glyphosate exposure from various different herbicides, including Roundup, Bioflow and RangerPro.

Led by Philip J. Landrigan, Fiorella Belpoggi and Daniele Mandrioli of the Cesare Maltoni Cancer Research Center in Italy, the team tested the rats at corresponding levels of exposure that a human would face under European Union acceptable daily glyphosate intake limits of 0.5 mg per kilogram of body weight per day.

“In all 3 treatment groups, statistically significant dose-related increased trends or increased incidences of benign and malignant tumors at multiple anatomic sites were observed compared to historical and concurrent controls. These tumors arose in haemolymphoreticular tissues (leukemia), skin, liver, thyroid, nervous system, ovary, mammary gland, adrenal glands, kidney, urinary bladder, bone, endocrine pancreas, uterus and spleen (hemangiosarcoma). Increased incidences occurred in both sexes.”

–Carcinogenic effects of long-term exposure from prenatal life to glyphosate and glyphosate-based herbicides in Sprague–Dawley rats

According to the data, most of the tumors were rare in these types of rats, with a background incidence rate of less than 1%, including leukemia. Early life exposure to glyphosate led to increased risk of multiple tumors and early death, the researchers warned.

Roundup Cancer Warnings

The findings come more than a decade after the World Health Organization’s International Agency for Research on Cancer (IARC) issued a Roundup cancer warning in March 2015, classifying glyphosate as a “probable carcinogen.”

The researchers in this latest study specifically pointed to their findings as new evidence that the IARC was correct in its assessment, which linked the weed killer to an increased risk of non-Hodgkins lymphoma.

Bayer has continued to defend the safety of Roundup, even as it settled tens of thousands of claims. However, following numerous failures in federal courts nationwide, including the Supreme Court, recent reports indicate the company has turned its efforts to the states, trying to convince them to provide lawsuit protection. Its efforts have already resulted in liability protections in Georgia and North Carolina, with similar measures being considered by several other states.

The company has also filed a Writ of Certiorari with the U.S. Supreme Court that argues the failure to warn claims should be barred by federal preemption, since the herbicide was approved by federal regulators.

It is the company’s third attempt to get the U.S. Supreme Court to weigh in on the litigation, with the petition coming after the Missouri Supreme Court rejected a similar Roundup appeal in February, when it upheld a $1.25 million Roundup damage award from October 2023.

To cut off the potential for future claims, Bayer also announced that it would reformulate Roundup in 2021, with plans to remove the active ingredient glyphosate from consumer versions of the weed killer. However, without additional settlements, the company is likely to continue facing new lawsuits for years, as former users develop non-Hodgkin’s lymphoma following use of the old Roundup formulations.