Glyphosate registrants defended their products as safe to use in comments submitted this week to the Department of Health and Human Service's Agency for Toxic Substances and Disease Registry (ATSDR), which issued a report in April saying it could not “rule out” an association between exposure to glyphosate-based products and the risk of cancer.

The Joint Glyphosate Task Force, made up of 20 members with registrations for technical grade glyphosate, the active ingredient in Bayer's Roundup, reiterated its longstanding position that the substance is safe to use, is not a reproductive toxicant or endocrine disrupter, and is unlikely to cause cancer.

Glyphosate is currently the world's best-selling herbicide, used in more than 90 countries and on more than 150 crops, according to data from the U.S. Geological Survey.  Glyphosate use in agriculture has tripled since 1997, largely due to the increasing popularity of Roundup Ready® crops (including corn, soybeans and cotton), which have been genetically modified to tolerate glyphosate.

In comments on ATSDR’s toxicological profile, the JGTF also questioned the validity of studies cited by the agency that suggested glyphosate or formulations containing it may cause genetic damage. The International Agency for Research on Cancer concluded in a 2015 monograph that glyphosate is “probably” a human carcinogen and that there was “strong evidence” of genotoxicity.

The JGTF recommended ATSDR construct a “table of genotoxicity conclusions” from various studies so as to “highlight the very isolated, unusual and unique aspect of the IARC monograph conclusion as well as the use or non-use of a weight of evidence approach in arriving at the genotoxicity conclusions.”

ATSDR cited studies indicating that 3-4% of glyphosate enters the blood through skin, well above the less-than-1% rate cited by EPA. The JGTF said “although there is not a dermal absorption study available for glyphosate alone, multiple in vitro dermal absorption studies with formulations confirmed a low dermal absorption of glyphosate.”

“Dermal penetration experiments, where glyphosate was left undisturbed on skin surfaces of experimental animals and on human skin in vitro, indicate a percutaneous absorption of less than 2%,” the JGTF said in its comments.

The Center for Food Safety (CFS), in its comments, said tests commissioned by Monsanto on two glyphosate formulations produced widely divergent results on dermal absorption. “That absorption of glyphosate can differ by a factor of 8 in tests on just two formulations suggests that all glyphosate formulations should be tested for dermal absorption of the active ingredient,” CFS said. “It is interesting to note that EPA still does not have a single study on dermal absorption of glyphosate (either technical or formulation) in its database.”

CFS also called ATSDR’s treatment of glyphosate’s carcinogenic potential “disappointing. Rather than conduct an independent assessment, the agency has chosen to summarize EPA’s deeply flawed treatment of the subject.” EPA has concluded glyphosate is not likely to cause cancer in people.

“Weighing the totality of the animal, human epidemiological and genotoxicity evidence, likely to be carcinogenic is the classification that best fits glyphosate according to EPA’s 2005 cancer assessment guidelines,” CFS said.

Several growers also weighed in, urging the continued use of glyphosate.

“On behalf of cotton producers across the rolling plains of west Texas and the 1 million acres of upland cotton we produce, I want to reiterate the importance of glyphosate to our producers,” noted Lauren Decker. “Glyphosate is a critical tool against many noxious weeds in our fields. We would ask that you continue to allow us to use glyphosate for weed control across our growing area.” To view all comments received on the docket, click here.

ATSDR’s toxicological profile became the subject of controversy in 2017 when a 2015 email surfaced in which an EPA pesticide official said in an email he should “get a medal” if he could “kill” the ATSDR report.

EPA recently reaffirmed its conclusion that glyphosate is not likely to be carcinogenic to humans in a draft registration review document.

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