In March of 2015, the World Health Organization’s International Agency for Research on Cancer (IARC) declared that glyphosate, the main ingredient in Monsanto’s Roundup weed-killer, is “probably carcinogenic to humans.”

Immediately, the finding created a huge ruckus, in part because Roundup and other glyphosate-based herbicides were once pitched as more benign, even as "biodegradable."

Monsanto also has a whole lot to lose from the linkage of its blockbuster herbicide to cancer. Perhaps not surprisingly, the company aimed its fury at the scientists of the IARC, calling it an “unelected, undemocratic, unaccountable, and foreign body.”

After the original designation, another branch of the WHO stated that, at the levels of expected human exposure, glyphosate is unlikely to cause cancer.

So between the uproar and the conflicting finding, how has the attacked cancer agency responded? By doubling down.


Our classification of the cancer hazards of glyphosate still stand. We are the authority to classify cancer substances.
— Dr. Kurt Straif, The International Agency for Research on Cancer

Dr. Straif added that IARC looks for three factors in making a carcinogenic finding: clear evidence for cancer in experimental animals, limited evidence for cancer in humans from real world exposures, and strong evidence that it can damage genes.

Dr. Straif also said: “Our evaluation was a review of all the published scientific literature on glyphosate and this was done by the world's best experts on the topic that in addition don't have any conflicts of interest that could bias their assessment.”

OK. But that’s just one IARC doctor. What have others said? Aaron Blair, the chairman of the IARC, said this in response to the conflicting designations: “There is not a single example of IARC being wrong, showing something is a probable carcinogen and then later it is proven not to be.”

Since the March 2015 designation as “probably carcinogenic” and the ensuing pushback by Monsanto and others, more than 90 scientists from various countries released a report explaining the comprehensive scientific methodology and findings that led to the IARC’s conclusion.

The report concludes that the “IARC [working group] evaluation of probably carcinogenic to humans accurately reflects the results of published scientific literature on glyphosate.”

One of the report authors, Dr. Maarten Bosland, the director of the Center for Global Health Outreach Department of Pathology at the University of Illinois at Chicago commented on the conflicted findings, saying that “the pushback has really come out of the industry based on things that are not scientifically sound.”

Watch the clip featuring Dr. Straif of the IARC below:

Do you have friends who have concerns about the use of Roundup? Let the numbers do the talking. Share this story.