When Aaron Blair sat down to chair a week-long meeting of 17 specialists at the International Agency for Research on Cancer in France in March 2015, there was something he wasn’t telling them.
The epidemiologist from the U.S. National Cancer Institute had seen important unpublished scientific data relating directly to a key question the IARC specialists were about to consider: Whether research shows that the weedkiller glyphosate, a key ingredient in Monsanto’s best-selling RoundUp brand, causes cancer.
Previously unreported court documents reviewed by Reuters from an ongoing U.S. legal case against Monsanto show that Blair knew the unpublished research found no evidence of a link between glyphosate and cancer. In a sworn deposition given in March this year in connection with the case, Blair also said the data would have altered IARC’s analysis. He said it would have made it less likely that glyphosate would meet the agency’s criteria for being classed as “probably carcinogenic.”
But IARC, a semi-autonomous part of the World Health Organization, never got to consider the data. The agency’s rules on assessing substances for carcinogenicity say it can consider only published research—this new data, which came from a large American study on which Blair was a senior researcher, had not been published.
The lack of publication has sparked debate and contention. A leading U.S. epidemiologist and a leading UK statistician—both independent of Monsanto—told Reuters the data was strong and relevant and they could see no reason why it had not surfaced.
Monsanto told Reuters that the fresh data on glyphosate could and should have been published in time to be considered by IARC, and that the failure to publish it undermined IARC’s classification of glyphosate. The legal case against Monsanto, taking place in California, involves 184 individual plaintiffs who cite the IARC assessment and claim exposure to RoundUp gave them cancer. They allege Monsanto failed to warn consumers of the risks. Monsanto denies the allegations.
The company also goes beyond saying the fresh data should have been published. It told Reuters the data was deliberately concealed by Blair, but provided no specific evidence of it being hidden.
Blair told Reuters the data, which was available two years before IARC assessed glyphosate, was not published in time because there was too much to fit into one scientific paper. Asked whether he deliberately did not publish it to avoid it being considered by IARC, he said that was “absolutely incorrect.” He said a decision not to publish the glyphosate data had been taken “several months” before IARC chose to conduct a review of the chemical.
The National Cancer Institute also cited “space constraints” as the reasons why the new data on glyphosate was not published.
The absence of the data from IARC’s assessment was important. IARC ended its meeting in 2015 by concluding that glyphosate is a “probable human carcinogen.” It based its finding on “limited evidence” of carcinogenicity in humans and “sufficient evidence” in experimental animals. It said, among other things, that there was a “positive association” between glyphosate and blood cancers called non-Hodgkin lymphoma. IARC told Reuters that, despite the existence of fresh data about glyphosate, it was sticking with its findings.
The agency’s assessment is at odds with other international regulators who have said the weedkiller is not a carcinogenic risk to humans. It led to a delay in Europe on a decision on whether to re-license or ban EU-wide sales of pesticides containing glyphosate. That decision is still pending. In the meantime, some countries have tightened restrictions on the weedkiller’s use in private gardens and public spaces and on crops before harvest.