One edit concerned a 1983 study in mice. IARC’s published monograph contains a fresh statistical analysis calculation as part of its review of that study. The original investigators found no statistically significant link between glyphosate and cancer in the mice. IARC’s new calculation reached the opposite conclusion, attributing statistical significance to it.
This new calculation was inserted into the final published assessment, but was not in the draft version seen by Reuters. The change gave the working group more evidence on which to base its conclusion that glyphosate was probably carcinogenic.
In further discussion of the same 1983 study, IARC’s final published report refers to expert pathologists on a panel commissioned to re-analyze the work of the original investigators. The IARC draft notes that these pathologists “unanimously” agreed with the original investigators that glyphosate was not related to potentially precancerous tissue growths in the mice. IARC’s final report deletes that sentence.
Reviewing a second mouse study, the IARC draft included a comment saying the incidence of a type of animal cancer known as hemangiosarcoma was “not significant” in both males and females. IARC’s published monograph, by contrast, inserts a fresh statistical analysis calculation on the data in male mice, and concludes that the findings were statistically significant.
Influential Monograph
IARC’s assessment that glyphosate is a probable human carcinogen is an outlier. In the 40 or so years since the weedkiller first came to the market, glyphosate has been repeatedly scrutinized and judged safe to use.
A year after IARC issued its evaluation, a joint United Nations and World Health Organization panel reviewed the potential for glyphosate in food to cause cancer in people. It concluded the weedkiller was “unlikely to pose a carcinogenic risk to humans.”
The U.S. EPA, which first assessed glyphosate in the 1980s and has reviewed it several times since, says it has “low toxicity for humans.” The European Food Safety Authority and the European Chemicals Agency, which advise the 28 members of the EU, have also assessed glyphosate within the past two years and ruled it safe.
But IARC’s Monograph 112 has had great influence.
It is weighing heavily on a pending European Union decision—due by the end of the year and possibly to be made next week—on whether glyphosate should be relicensed for sale across the 28 member states. France, one of the bloc’s agricultural powerhouses, has said it wants the weedkiller phased out and then banned, provoking protests by its vocal farmers, who argue glyphosate is vital to their business.
A failure to renew glyphosate’s license by the end of the year would see an EU ban kick in on Jan. 1, 2018.
In the U.S., Monsanto—the firm that first developed and marketed glyphosate – is facing litigation in California involving at least 184 individual plaintiffs who cite the IARC assessment and claim exposure to RoundUp gave them a form of cancer known as non-Hodgkin lymphoma. They allege Monsanto failed to warn consumers of the risks. Monsanto denies the allegations. The case is ongoing.
Members of the U.S. Congress, concerned about what they described as IARC’s “inconsistent” standards and determinations for classifying substances as carcinogenic, last year launched investigations into American taxpayer funding of IARC. The investigations are ongoing.
In Europe, IARC has become embroiled in a public spat with experts at the European Food Safety Authority, which conducted its own review of glyphosate in November 2015 and found it “unlikely to pose a carcinogenic hazard to humans.”
With IARC monograph meetings, some outside observers are selected and allowed to witness proceedings, but they are banned from talking about what goes on. Journalists are generally not allowed in.
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