Common weed killer ups risk of some cancers by 40%

Exposure to glyphosate—the world’s most widely used, broad-spectrum herbicide and the primary ingredient in the weed killer Roundup—increases the risk of some cancers by more than 40 percent, according to new research.

Various reviews and international assessments have come to different conclusions about whether glyphosate leads to cancer in humans.

Now, researchers have conducted an updated meta-analysis—a comprehensive review of existing literature—and focused on the most highly exposed groups in each study. They found that the link between glyphosate and non-Hodgkin lymphoma is stronger than previously reported.

“Our analysis focused on providing the best possible answer to the question of whether or not glyphosate is carcinogenic,” says senior author Lianne Sheppard, a professor in the environmental and occupational health sciences and biostatistics departments at the University of Washington. “As a result of this research, I am even more convinced that it is.”

By examining epidemiologic studies published between 2001 and 2018, the team determined that exposure to glyphosate may increase the risk of non-Hodgkin lymphoma by as much as 41 percent. The authors focused their review on epidemiological research in humans but also considered the evidence from laboratory animals.

“This research provides the most up-to-date analysis of glyphosate and its link with Non-Hodgkin Lymphoma, incorporating a 2018 study of more than 54,000 people who work as licensed pesticide applicators,” says coauthor Rachel Shaffer, a doctoral student in the environmental and occupational health sciences department.

“These findings are aligned with a prior assessment from the International Agency for Research on Cancer, which classified glyphosate as a ‘probable human carcinogen’ in 2015,” Shaffer says.

The agricultural industry started using glyphosate in 1974. Its use soared, particularly since the mid-2000s when the practice of “green burndown” began, in which glyphosate-based herbicides are applied to crops shortly before harvest. As a consequence, crops now are likely to have higher residues of glyphosate.

Researchers say more studies are needed to account for the effects of increased exposures from green burndown, which may not be fully captured in the existing studies reviewed in this new publication.

Their findings appear in the journal Mutation Research/Reviews in Mutation Research. Additional coauthors are from the University of California, Berkeley and the Icahn School of Medicine at Mount Sinai in New York. The National Institutes of Environmental Health Sciences and the University of Washington Retirement Association Aging Fellowship funded the research.

Source: University of Washington