In the U.S., a California judge took the IARC assessment into account in a separate legal case in March when ruling that the state can require RoundUp to carry a warning label that it may cause cancer. Monsanto is now facing further litigation from hundreds of plaintiffs across the U.S. who say glyphosate gave them or their loved ones non-Hodgkin lymphoma, citing the IARC assessment as part of their claims.
Yet if the IARC panel experts had been in a position to take into account Blair’s fresh data, IARC’s analysis of the evidence on glyphosate would have been different, Blair acknowledged in the court documents reviewed by Reuters.
The unpublished research came from the Agricultural Health Study, a large and significant study, led by scientists at the U.S. National Cancer Institute, of agricultural workers and their families in the U.S. Asked by Monsanto lawyers in March whether the unpublished data showed “no evidence of an association” between exposure to glyphosate and non-Hodgkin lymphoma, Blair replied: “Correct.”
Asked in the same deposition whether IARC’s review of glyphosate would have been different if the missing data had been included, Blair again said: “Correct.” Lawyers had put to him that the addition of the missing data would have “driven the meta-relative risk downward,” and Blair agreed.
Scott Partridge, Monsanto’s vice president of strategy, told Reuters the IARC glyphosate review “ignored multiple years of additional data from the largest and most comprehensive study on farmer exposure to pesticides and cancer.”
The Agricultural Health Study was particularly pertinent, he said, because it examined real-life human exposure to glyphosate, whereas much of the scientific research IARC analyzed involved laboratory tests on rodents.
IARC told Reuters that its evaluations follow strict scientific criteria and that its carcinogen classification system “is recognized and used as a reference all around the world.” It reiterated that in the interests of transparency it considers only published data.
Reuters asked two independent statistical experts to review the data, which has still not been published, though the National Cancer Institute told Reuters researchers are currently working on an updated analysis of it. Neither of the two experts had seen the data before and both said they had no conflict of interest over glyphosate.
David Spiegelhalter, a professor of the Public Understanding of Risk at Britain’s University of Cambridge, said there was “no apparent scientific reason” for not publishing the data. Bob Tarone, a retired statistician who worked alongside Blair and others at the National Cancer Institute for 28 years before moving to the for-profit International Epidemiology Institute, said he could find “no ready explanation in terms of the available scientific evidence” for the data not to have been published.
Tarone had already raised the issue in a little-noticed paper in the European Journal of Cancer Prevention last year. He wrote that IARC’s classification of glyphosate as probably carcinogenic to humans was the result of “a flawed and incomplete summary” of the evidence.
In an email to Reuters, IARC declined to say whether Blair informed IARC staff about the unpublished data, whether he should have, and whether that data might have changed IARC’s evaluation of glyphosate had it been published in time. The agency said it had no plans to reconsider its assessment of the chemical.
Glyphosate is what’s known as a non-selective herbicide, meaning it kills most plants. Discovered by the Monsanto chemist John E. Franz in 1970, glyphosate is no longer under patent, is supplied by numerous companies and is now the world’s most widely used weedkiller, deployed in agriculture, forestry and domestic gardening. Monsanto and other companies have developed genetically engineered seeds that can tolerate glyphosate, allowing farmers to apply it to entire fields without destroying crops.