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Herbicides such as glyphosate have helped make weedfree fields like this one possible
<p>Herbicides such as glyphosate have helped make weed-free fields like this one possible.</p>

Expert panels say IARC glyphosate report flawed, excludes key data

&ldquo;The conclusions reached by the expert panels and&nbsp;IARC&nbsp;clearly differ,&rdquo; the expert panel members said in a report published in the journal Critical Reviews in Toxicology. &ldquo;However, this is not due to differences in process but rather the result of the exclusion from the&nbsp;IARC&nbsp;review process of key data or differences in interpretation of the data.&rdquo;

A report issued by four independent expert panels says a monograph that concluded glyphosate is “probably carcinogenic to humans” ignored key data that would have proven its findings were in error.

The monograph, published by the International Agency for Cancer Research in March of 2015, generated headlines around the world that said glyphosate or Roundup could cause cancer and raised questions about the U.S. pesticide regulatory system.

The new study, which was funded by Monsanto, which makes glyphosate, the active ingredient in its Roundup herbicide, said members of the expert panels found a “review of the totality of the evidence” indicated the data do not support the IARC’s conclusion that glyphosate is a probable human carcinogen.

“The conclusions reached by the expert panels and IARC clearly differ,” the expert panel members said in a report published in the journal Critical Reviews in Toxicology. “However, this is not due to differences in process but rather the result of the exclusion from the IARC review process of key data or differences in interpretation of the data.”

The expert panels paper, which was published Wednesday (Sept. 28), was released as the House Committee on Oversight and Government Reform sent a letter to the National Institutes of Health requesting information on funding given to the International Agency for Research on Cancer.

Inconsistent with other research

“IARC’s standards and determinations for classifying substances as carcinogens, and therefore cancer-causing, appear inconsistent with other scientific research and have generated much controversy and alarm,” said the letter released by Committee Chairman Jason Chaffetz, R-Utah.

“Despite this record of controversy, retractions and inconsistencies, IARC receives substantial taxpayer funding from the National Institutes of Health. NIH’s grant database reflects that the agency has given IARC several millions of dollars since 1992, including over $1.2 million so far this year.”

Rep. Chaffetz cited the IARC’s findings on glyphosate, noting that its claims that the commonly-used herbicides were in contrast with research from other organizations, including the European Food Safety Authority and the U.S. Environmental Protection Agency, that found the compound to be safe.

EPA has generated controversy of its own in its handling of reports on glyphosate in recent months. The agency has generally said glyphosate was not a human carcinogen in studies going back to 1986.

More recently, EPA has been conducting further assessments of glyphosate as part of the requirement it review all registered pesticides every 15 years. A report titled “Final Cancer Assessment Document” appeared on an EPA website last April 29 but was subsequently withdrawn after officials said the document was not final.

New EPA paper

Two weeks ago, the agency released a 227-page paper outlining its proposed position on the safety of glyphosate in advanced of a FIFRA Scientific Advisory Panel that is scheduled to be convened in Washington Oct. 18-21. It has said it will make a final determination on whether glyphosate should or should not be considered “probably carcinogenic to humans” in 2017.

While the expert panels report was funded by Monsanto, the panels are themselves made up by independent experts who have written numerous peer-reviewed articles on the toxicity of chemical compounds, articles that are in short supply in the IARC-cited literature.

“As a preface to the remainder of the document, the process by which IARC identifies and reviews data must be compared with that employed by the expert panels,” the expert panels’ paper said. “IARC only reviews data included in: ‘reports that have been published or accepted for publication in the openly available scientific literature’ or ‘data from governmental reports that are publicly available.’

“In addition, IARC reviews and assesses these data in the context of hazard (i.e. inherent carcinogenic potential) not risk (i.e. the likelihood of carcinogenic effects at exposure levels humans may encounter). As a result, the conclusion of IARC is often solely associated with hazard.”

In contrast to IARC toxicology, mechanism, and exposure, the paper said the expert panels evaluated all of the available scientific data, including the results of a number of unpublished reports, some of which have been submitted to and reviewed by regulatory authorities. These reports document GLP- and OECD/FDA Redbook guideline compliant studies, conducted to assess the genotoxic and carcinogenic potential of glyphosate.

Balanced assessment

“In essence, these studies provide the highest quality of documentation and verification; hence, a balanced assessment requires the inclusion of such studies in the review process,” the paper said, adding that in addition to the identification of hazard potential, the expert panels assessed exposure data to provide a perspective from which to comment on potential risk.

“In the absence of carcinogenic hazard, however, no risk is present regardless of exposure,” it said. “The conclusions reached by the expert panels and IARC clearly differ. However, in the opinion of the expert panel(s) this is not due to differences in process (hazard versus risk assessment), but rather the result of the exclusion from the IARC review process of key data (animal bioassay and genotoxicity) or differences in the interpretation of the data that was assessed particularly in regard to the animal bioassay results.

“Given these differences, even without the data IARC did not include, there is no support for IARC’s conclusion that glyphosate is “probably carcinogenic to humans.” This critique is presented and discussed in the context of the expert panels’ assessment of the totality of the data.”

To read the expert panels’ report, visit


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