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See the Postscript below.

A “roundup” of findings on the safety of glyphosate shows that the herbicide is very benign, highly unlikely to pose any real threat to humans, and far less toxic than many common household chemicals and even natural hazards in the environment. However, the debate over glyphosate is heavily politicized, as illustrated by the unsavory details surrounding a report issued last year by the International Agency for Research on Cancer (IARC), an arm of the World Health Organization (WHO). The IARC reclassified glyphosate as “probably carcinogenic to humans” based on a few cherry-picked, poorly-designed studies with weak statistical power. That finding is inconsistent with the vast preponderance research, which shows that glyphosate is not a significant threat to human health.

The Farmer’s Daughter provided a good summary of the issues shortly after the IARC’s ruling was announced last year. She offers the following quote from the U.S. Environmental Protection Agency (EPA):

The U.S. EPA classified glyphosate as Group E, evidence of non-carcinogenicity in humans. The U.S. EPA does not consider glyphosate to be a human carcinogen based on studies of laboratory animals that did not produce compelling evidence of carcinogenicity.

European regulators reached similar conclusions and are rather damning in their assessment of the IARC’s findings, though Brussels recently disregarded their findings and decided to ban the sale of glyphosate for gardening. In this post at Biology Fortified, Anastasia Bodnar discusses the low toxicity of glyphosate with links to several recent studies on its safety. And here is the Risk Monger blogs’s list of “ten reasons why glyphosate is the herbicide of the century“:

  1. Controlling invasive weeds leads to better agricultural yields
  2. Better yields = less land in production = more meadows and biodiversity
  3. Extremely low toxicity levels compared to (organic) alternatives
  4. Allows for no or low till farming – better for soil management
  5. Reduces CO2 emissions (compared to organic)
  6. Glyphosate saves lives
  7. It is much more affordable and effective than other options
  8. Glyphosate is off patent so no single company is profiting heavily from it
  9. Glyphosate-resistant crops allow for more ecological weed management practices
  10. There is overwhelming scientific evidence that glyphosate is safe for humans

How, then, did the IARC reach such a negative conclusion? Again from the Risk Monger, David Zaruk, the IARC hired just one external technical advisor, Christopher Portier, an activist previously employed by an NGO, the anti-pesticide Environmental Defense Fund (EDF). Portier has no technical background in toxicology, and the IARC apparently went to pains to avoid references to his affiliation with the EDF. Moreover, the IARC’s conclusion seems to have been preordained:

The IARC study rejected thousands of documents on glyphosate that had industry involvement and based their decision on carcinogenicity on the basis of eight studies (rejecting a further six because they did not like their conclusions).

The lead author of the report, Kathryn Guyton, gave a speech in 2014 in which she stated that herbicide studies slated for 2015 showed indications of a link to cancer. Just how did she know, so far ahead of time? And then there’s this revelation:

“According to the observer document, the glyphosate meeting started with the participants being told to rule out the possibility of classifying the substance as non-carcinogenic.

Zaruk believes there is internal pressure for the IARC study to be retracted. The organization has suffered a great loss of credibility in the scientific community over the report. In addition, WHO has remained neutral thus far, but they are expected to address the issue this month.

Zaruk and Julie Kelly provide a more succinct summary of the issues in “The Facebook Age of Science at The World Health Organization” at National Review. The suggestion made in the title seems to be that WHO’s decision might be swayed by public pressure, measured by Facebook “likes” by the superstitious, such as unknowing David Wolfe devotees, rather than science:

Environmentalists and organic companies tout phony studies claiming that glyphosate is found in everything from breast milk to bagels. … Meanwhile, farmers who use glyphosate to protect their crops and boost yields are caught in the crossfire. Even if glyphosate is banned, they will need to use another herbicide, probably more toxic, because the romantic notion of hand-weeding millions of acres of crops is promoted only by those who have never done it.

I’ll keep using Monsanto’s Roundup, thanks! Or a competitive brand of glyphosate. To close, here’s a quote from Matt Ridley’s Rational Optimist blog on the embrace of pseudoscience at the IARC and elsewhere (including social media):

Science, humanity’s greatest intellectual achievement, has always been vulnerable to infection by pseudoscience, which pretends to use the methods of science, but actually subverts them in pursuit of an obsession. Instead of evidence-based policymaking, pseudoscience specialises in policy-based evidence making. Today, this infection is spreading.

Postscript: On May 16, WHO announced that glyphosate is “unlikely to cause cancer in people via dietary exposure.Here is a Q&A from WHO regarding its assessment, explaining that it is based on risk as opposed to mere hazard, upon which the earlier IARC report was based. This is good news!