Channel 2's Consumer Investigator Jim Strickland exposed health concerns about chemicals in the product months ago.

Ingredient in popular weed killer raises cancer risk, study finds

Researcher ‘even more convinced’ glyphosate causes non-Hodgkin lymphoma

The first day of spring is a little more than a month away. Before you pull out the weed killer for your yard and garden, however, you should check the label.

A recent meta-analysis by researchers at the University of Washington has found being “highly exposed” to glyphosate — found in common weed killers like Roundup — increases a person’s cancer risk by 41 percent.

Glyphosate is the most widely used herbicide around the world.

In March 2015, the International Agency for Research on Cancer classified glyphosate as “probably carcinogenic to humans.”

This, IARC wrote, was based on “limited” evidence of cancer in humans (from real-world exposures that actually occurred) and “sufficient” evidence of cancer in experimental animals (from studies of “pure” glyphosate). 

IARC also concluded there was “strong” evidence for genotoxicity, both for “pure” glyphosate and for glyphosate formulations.

In March 2017, California added gyphosate to its list of chemicals to cause cancer.

In the recent study, the Washington researchers conducted a new meta-analysis that included the most recent update of the Agricultural Health Study cohort published in 2018, along with five case-control studies, using the highest exposure groups when available in each study.

The researchers also included a 2018 agricultural health study that found “glyphosate was not statistically significantly associated with cancer” even though there was an increased risk of acute myeloid leukemia among those who used it the most.

The most recent findings, published in the online journal Mutation Research/Reviews in Mutation Research, says the link between glyphosate and non-Hodgkin lymphoma is stronger than previously thought.

“Our analysis focused on providing the best possible answer to the question of whether or not glyphosate is carcinogenic,” senior author Lianne Sheppard, a professor in the UW departments of Environmental & Occupational Health Sciences and Biostatistics, said in a press release. “As a result of this research, I am even more convinced that it is.”

Bayer, which bought glyphosate-maker Monsanto, has adamantly rejected any cancer claims and said the new study is "flawed" and uses "cherry-picked data" in a statement to Carey Gillam, a journalist and researcher for U.S. Right to Know, who wrote about the new findings in the Guardian.

» Does Roundup kill more than just weeds? Lawsuits claim it also causes cancer

» Unsafe amounts of weed killer chemical found in some oat-based food, report finds
» Weed killer ingredient going on California list as cancerous

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