Government Scientist Withheld Evidence Popular Herbicide Doesn’t Cause Cancer

Published August 4, 2017

The Reuters news agency uncovered evidence a study by a World Health Organization scientist concluding the popular herbicide Roundup is a probable carcinogen is wrong. Reuters’ investigation found the lead scientist involved in the research withheld key data indicating the weed killer is safe, as the U.S. Environmental Protection Agency and European Food Safety Authority concluded in the 1970s when they approved Roundup for use.

The International Agency for Research on Cancer (IARC), a division of the World Health Organization, declared glyphosate (Roundup) a probable carcinogen in December 2015. Since then, citing the IARC’s findings as evidence, hundreds of plaintiffs have filed suit against Monsanto, Roundup’s manufacturer, saying the company failed to warn them about the risks from Roundup or that it caused their cancers.

Scientist Withheld Evidence

The Reuters investigation revealed Aaron Blair, a National Cancer Institute scientist emeritus and chair of the IARC review panel on glyphosate, withheld evidence of a large study indicating Roundup does not cause cancer.

Blair was a coauthor of the unpublished 2013 Agricultural Health Study (AHS), administered by the U.S. National Cancer Institute (NCI). NCI stood by its findings, telling Reuters its reason for not publishing the study was “space constraints.”

Court documents obtained by Reuters in one of the legal cases against Monsanto show Blair knew the unpublished research found no evidence of a link between glyphosate and cancer. The documents include a sworn deposition by Blair given in March 2017 in which he admitted the data would have altered IARC’s analysis and made it less likely glyphosate would satisfy the agency’s criteria for being classified as “probably carcinogenic.”

Political Classification?

Angela Logomasini, who manages, a project of the Competitive Enterprise Institute, says IARC’s classification process is not credible.

“This is just another example as to why IARC classifications should be completely disregarded,” said Logomasini. “Even in the absence of the data from the unpublished study, there is little reason to classify glyphosate as a carcinogen.

“IARC’s nonsensical classifications don’t consider whether human exposure is too low to have any effects on health,” Logomasini said. “Such exposure assessments are a critical part of risk assessment, and without them the classifications are meaningless.”

Logomasini says IARC’s conclusions are political, not scientific.

“IARC’s entire approach to assessing glyphosate underscores the fact these classifications are guided more by politics than science, and they have no value in helping understand actual risks,” Logomasini said. “Unfortunately, government bodies use these classifications to regulate and even ban products that pose low risk and provide important benefits.”

California Differs

Despite Reuters showing IARC’s findings were based on incomplete information, on June 27 the state of California placed Roundup on the list of chemicals it believes causes cancer. Under California’s Proposition 65, by 2018 Roundup will have to carry a warning label saying its ingredients are “known to the state of California to cause cancer and birth defects, and other reproductive harm.”

Citing Reuters’ investigation and U.S. and European government analyses determining Roundup to be safe, Monsanto is suing to block the Proposition 65 listing.

Michael McGrady ([email protected]) writes from Colorado Springs, Colorado.


Kate Kelland, “Cancer Agency Left in the Dark Over Glyphosate Evidence,” Reuters, June 14, 2017: