Does Everything Cause Cancer?

Just a little over a year ago, the International Agency for Research on Cancer (IARC) made headlines around the world by finding that the common weed killer glyphosate, the key ingredient in Roundup®, is “probably carcinogenic.”

That controversial finding packed a wallop because glyphosate is a staple for food growers today.  The ramifications for farmers, food companies and nearly everybody who eats were – and are – enormous.

At the time, my company and many others protested that the finding by IARC – a French-based affiliate of the World Health Organization (WHO) – was without merit. We cited “the overwhelming weight of evidence on the other side.” We noted the absence even of a mechanism for glyphosate to cause cancer in humans.  And we highlighted the fact that regulatory agencies all over the world had looked at the same studies reviewed by IARC (and more, because IARC limited the scope of their review to a small amount of self-selected data) and arrived at the opposite conclusion: Glyphosate is not a carcinogen.

But of course, the passions surrounding issues like the use of pesticides, genetically modified crops (GMOs), and the role of corporations like our own in agriculture are so intense that it can be difficult for people on one side of the issues to listen to people on the other. And it’s simply a truism that accusations – whether against products or companies or individuals – tend to leave a stain, even if they’re later proved baseless. 

How fascinating, then, to read two recent reports published in April by Reuters that delve into IARC’s other findings, its modus operandi, and some of the criticisms it’s facing from within the scientific community. 

The longer of the two articles is called “How the World Health Organization’s cancer agency confuses consumers.” It starts by noting that over the last four decades, IARC has assessed 989 substances and activities – from arsenic to working the night shift – for their carcinogenicity. Of those 989, the number that IARC has found are “probably not carcinogenic to humans” is … one. 

Alcoholic beverages? “Carcinogenic,” says IARC.  Traditional Asian pickled vegetables? “Possibly carcinogenic.”  Working the night shift? “Probably carcinogenic.”  Consuming red meat? “Probably carcinogenic.” Processed meat? “Carcinogenic.”  Lighting a wood fire in your home’s fireplace? “Probably carcinogenic.”

(And as this article is being written, IARC is meeting to consider whether “coffee, mate, and other very hot beverages” are carcinogenic.)

Take comfort, however:  The agency found that an ingredient in nylon used in stretchy yoga pants and toothbrush bristles was “probably not” cancer-causing. That ingredient was the one out of the 989 that passed muster.

What a relief!

As for the other 988: IARC has found that 487 are carcinogenic to humans, probably carcinogenic to them, or possibly carcinogenic.  Another 501 are “not classifiable” as to their carcinogenicity because the evidence is inadequate. That doesn’t get them off the hook, however.  “Not classifiable,” the IARC says on its website, “often means that further research is needed.”

So that’s the context of IARC’s judgment on glyphosate. The odds that this organization will find that a given substance or process is not carcinogenic are almost one in a thousand. Hopefully this context will be more part of the conversation around IARC’s upcoming judgment on coffee – or else there will no doubt be another wave of unnecessary alarm.

Reuters also took a careful look at how IARC goes about its business.  Here’s what they found. 

IARC classifications are determined by “expert working groups” the organization assembles to review existing research and issue a report called a “monograph.” Sometimes, the members of the expert working groups, however, are not necessarily in the best position to be objective.  Often, they include the very same scientists who did the research that’s under review.  Here is what Reuters found.

“Between 2012 and 2015, for example, IARC published or started 18 monographs involving 314 scientists.  A Reuters analysis found that at least 61 of those scientists served on monograph working groups that considered their own scientific research. The analysis did not include the number of scientists on working groups that reviewed the research of close colleagues.”

This is something like having students grade their own and their friends’ tests. It’s like having one team’s catcher at a baseball game also serve as the umpire.

Defending this approach, IARC says the working groups are nevertheless able to maintain their scientific detachment in this setup.

But some scientists, including Bob Tarone, Biostatistics Director at the International Epidemiology Institute, are skeptical.  Tarone, who also once served as statistician at the National Cancer Institute, told Reuters: “It’s absurd to assert there are no issues of bias related to self-interest, reputation or careerism. …it’s just human nature.”

Finally, guess what? In its second story on this topic, Reuters reported the working group that assessed glyphosate included as an “invited specialist” Christopher J. Portier.  Actually, as a check of the makeup of the working group shows, Portier was the only invited specialist. It so happens that Portier is a senior contributing scientist to the Environmental Defense Fund (EDF), which was founded on opposition to pesticides.   He was also the chair of an IARC meeting in 2014 where the agency’s 2015 priorities – including an evaluation of glyphosate –were established.

“Critics,” Reuters reported, “say Portier’s EDF connections represent a conflict of interest and argue IARC should not have allowed him to be involved in the glyphosate evaluation.”  But IARC and Portier both defended this arrangement by saying that Portier didn’t actually participate in the evaluation; presumably he merely advocated for his position.

But hold that thought and consider what happened after IARC made its report in March of 2015.

At the request of the European Commission, The European Food Safety Authority (EFSA) undertook its own assessment of glyphosate.  EFSA is a European Union (EU) agency that provides EU member states with independent scientific advice about risks associated with the food chain. Last November, EFSA published its response.

Glyphosate, it said, is “unlikely to pose a carcinogenic hazard to humans and the evidence does not support classification with regard to its carcinogenic potential.”  

In other words, EFSA flatly rejected IARC’s position.      

Then Portier took it on himself to be the lead signatory in an eight-page letter to EFSA, objecting to its finding and defending the IARC assessment IARC says he didn’t write or even participate in. EFSA responded with a 14-page letter of its own, rebutting Portier et al., point by point.

Since IARC classified glyphosate, regulatory authorities in Europe, Canada, Japan and Australia have publicly reaffirmed that glyphosate does not cause cancer. What’s more, just a couple weeks ago, the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) concluded that “glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet.”  In fact, three out of four WHO bodies have concluded that glyphosate does not cause cancer.

But what do you think is the ratio between the number of people who, thanks to IARC and Portier’s activism, have heard that glyphosate is “probably carcinogenic,” versus the number who have a grip on the flaws in the method by which that warning was issued?

My formal, scientific guess: a gazillion to one.