Is International Agency for Research on Cancer’s (IARC) glyphosate ruling based on ‘flawed’ assessment?

Reports from Reuters and Mother Jones say that the International Agency for Research on Cancer’s (IARC) decision to mark glyphosate as a “probable carcinogen” was made without assessing recent crucial data.

Reuters says that one of the scientists leading IARC’s review, Aaron Blair, an epidemiologist from the US National Cancer Institute, did not mention a study that discovered no evidence of a link between glyphosate and cancer.

According to the Reuters story, Blair was a senior researcher on the Agricultural Health Study that looked at around 89,000 agricultural workers, farmers and their families in Iowa and North Carolina. The news agency has also seen court documents that feature Blair saying this data would likely have altered IARC’s assessment.

Reuters asked two independent researchers to review the data, with David Spiegelhalter, a University of Cambridge professor of the Public Understanding of Risk, saying he could see “no apparent scientific reason” that would have prevented its publication.

“[IARC has] a board of people whose job it is to assess evidence, so they should be able to do that before it’s published”

Professor Michael Eisen

The second researcher, Bob Tarone, who worked at the National Cancer Institute for 28 years, wrote in a 2016 paper in the European Journal of Cancer Prevention that IARC’s classification of glyphosate was the result of “a flawed and incomplete summary” of the evidence.

IARC only considers published studies, and Reuters found this crucial research project had not been made available for publication. IARC told the news agency that, despite the existence of fresh data, it would stand by its earlier findings.

Non-profit news organisation Mother Jones also looked into the IARC’s decision not to consider unpublished material, speaking to Michael Eisen, a professor of genetics, genomics, and development at the University of California-Berkeley.

Eisen, who is a transparency in science advocate, told Mother Jones, “This is a board of people whose job it is to assess evidence, so they should be able to do that before it’s published. The broader issue is that they seem eager to have reached the conclusion that they reached.

“They don’t seem interested in getting to the bottom of these things. These decisions seem based in politics.”


Glyphosate is the world’s most widely used weed control substance, but is it carcinogenic? Find out the truth about whether glyphosate causes cancer here.