LONDON, U.K. (Reuters) — A large long-term study on the use of glyphosate by agricultural workers in the United States has found no firm link between exposure to the pesticide and cancer.
Published in the Journal of the National Cancer Institute, the study found there was no association between glyphosate, the main ingredient in Monsanto’s Roundup, “and any solid tumours or lymphoid malignancies overall, including non-Hodgkin lymphoma and its subtypes.”
It said there was “some evidence of increased risk of acute myeloid leukaemia among the highest exposed group,” but added this association was not “statistically significant” and would require more research to be confirmed.
The findings are likely to affect legal proceedings taking place in the U.S. against Monsanto, in which more than 180 plaintiffs are claiming that exposure to Roundup gave them cancer, which Monsanto denies.
The findings may also influence a crucial decision due by the end of the year on whether glyphosate should be re-licensed for sale in the European Union.
EU countries had been scheduled to vote on the issue last week, but again failed to agree to a proposal for a five-year extension.
The EU decision has been delayed for several years after the World Health Organization’s International Agency for Research on Cancer reviewed glyphosate in 2015 and concluded it was “probably carcinogenic” to humans. Other bodies, such as the European Food Safety Authority, have concluded glyphosate is safe to use.
The research is part of a large and important project known as the Agricultural Health Study, which has been tracking the health of tens of thousands of agricultural workers, farmers and their families in Iowa and North Carolina.
Since the early 1990s, it has gathered and analyzed detailed information on the health of participants and their families, and their use of pesticides, including glyphosate.
Reuters reported in June how an influential scientist was aware of new AHS data while he was chairing a panel of experts reviewing evidence on glyphosate for IARC in early 2015.
But since it had not at that time been published, he did not tell the expert panel about it, and IARC’s review did not take it into account.
The publishing of the study Nov. 9 comes more than four years since drafts based on the AHS data on glyphosate and other pesticides were circulating in February and March 2013.
In a summary conclusion of the results, the researchers, led by Laura Beane Freeman, principal investigator of the AHS at the U.S. National Cancer Institute, reported that among 54,251 pesticide applicators in the study, 44,932, or 82.9 percent, of them used glyphosate.
“Glyphosate was not statistically significantly associated with cancer at any site,” the conclusion said.
The researchers said they believed the study was the first to report a possible association be-tween glyphosate and AML, but that it could be the result of chance and should be treated with caution.