Does Roundup cause cancer?

Roundup maker Monsanto has been hit with several lawsuits from farmworkers and home gardeners who allege they were diagnosed with cancer after being exposed to the glyphosate-based weed killer.

Many of these Roundup lawsuits have resulted in payouts for the plaintiffs, including a $289 million award to a San Francisco–area groundskeeper in August 2018, and a $86 million award in May 2019 to a husband and wife from California. That payment was lowered from the original $2 billion figure awarded by a jury. 

Juries have not always sided with plaintiffs, however. A jury in December sided with Monsanto in a lawsuit filed by a woman claiming her exposure to Roundup caused her to develop cancer. The jury determined Monsanto was not responsible for the woman’s cancer.

In each of those cases, the plaintiffs claimed to have been diagnosed with non-Hodgkin’s lymphoma after using Roundup. But is there proof Roundup causes cancer?

Does Roundup cause cancer?

Glyphosate, the active ingredient in Roundup weed killer, has been linked to an increased risk of cancers such as non-Hodgkin’s lymphoma and leukemia.

The International Agency for Research on Cancer (IARC) classified glyphosate as a likely human carcinogen in March 2015, based on “limited” evidence of cancer diagnoses in humans exposed to the chemical in real-world conditions and “sufficient” evidence provided by studies of pure glyphosate on animals. The IARC is part of the World Health Organization (WHO).

The IARC came to its conclusions after reviewing about 1,000 studies, some of which examined people exposed to glyphosate through their jobs and others that were experimental studies on cancer.

Other studies have also linked cancer and glyphosate, according to Healthline.

In 2013, a study concluded the chemical triggered the growth and division of breast cancer cells, fueling the cancer. That study also concluded glyphosate fuels hormone-dependent cancer cell lines.

And a 2016 study involving researchers in Italy and Brazil concluded those exposed to glyphosate faced an increased risk of developing cutaneous melanoma.

In August 2022, a collaborative study between the Florida Atlantic University and Nova Southeastern University linked glyphosate with seizures.

Despite these studies, the Environmental Protection Agency (EPA) says it does not see evidence glyphosate, when used properly, poses a risk to public health.

“EPA continues to find that there are no risks to public health when glyphosate is used in accordance with its current label and that glyphosate is not a carcinogen,” the EPA said.

Others, however, disagree with the EPA’s conclusions.

The IARC’s March 2015 report, which prompted many lawsuits against the makers of Roundup, found a link does exist.

University of Washington researchers conducted their own analysis and concluded glyphosate exposure raises a person’s cancer risk by 41%, CNN reported.

Attorney Timothy Litzenburg, counsel representing the first cancer patient to sue Monsanto, told CNN that Roundup, not simply glyphosate, is the real issue.

“We are not alleging that our clients got cancer from glyphosate alone,” said Litzenburg. “Roundup contains animal fats and other ingredients that increase the carcinogenicity of the glyphosate.” He added the EPA doesn’t require adequate testing of Roundup’s formulation.

What types of cancer could Roundup cause?

Roundup has allegedly been linked to a number of types of cancer, including:

• Non-Hodgkin’s lymphoma
• B-cell lymphoma
• T-cell lymphoma
• Chronic lymphocytic leukemia (CLL)
• Hairy cell lymphoma

Lymphoma begins in the lymphatic system, which consists of lymph nodes and vessels that move a fluid called lymph through the body. The fluid contains infection-fighting white blood cells. There are more than 70 types of lymphoma.

Leukemia is cancer that grows in the body’s tissues that form blood, such as bone marrow or the lymphatic system, according to the Mayo Clinic. Leukemia, like lymphoma, typically involves white blood cells. A person with leukemia has bone marrow that produces an excess number of abnormal white blood cells that don’t function as they should.

Lawsuits have already been filed over Roundup cancer risk, with many who have been diagnosed with cancer awarded millions of dollars. A current class action lawsuit filed over the risk of Roundup cancer — not actually being diagnosed with it — is nearing a settlement agreement of $45 million.

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