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by, Michael Castore
In September 2016, the Environmental Protection Agency (EPA) issued a position paper preliminarily finding glyphosate to not likely be carcinogenic. The purpose of this follow up is to reinforce the conclusion that the debate over whether glyphosate is a carcinogen, is not and cannot be concluded with the information currently available. Thus, our approach toward regulating any herbicidal chemical that; 1) disputedly has carcinogenic effects and 2) makes its way up a food chain that leads directly to human consumers; should be precautionary. At least until more studies are conducted and conclusions based on them have a chance to gain relative acceptance throughout the pertinent scientific community.
Two months later, The Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel (Panel) concluded their review of EPA’s position on glyphosate. On instruction from the EPA, the Panel considered, “a set of scientific issues being evaluated by the EPA regarding…the carcinogenic potential of the herbicide glyphosate.” Multiple members of the Panel expressed concerns documented in their final report regarding EPA’s approach, data, and findings on the issue of glyphosate’s potential carcinogenicity. For instance, “Panel members expressed concerns, that EPA’s discussion of the epidemiological evidence appeared to discount statistical findings and overemphasize non-statistical criteria. Thus, some Panel members believed that there is limited but suggestive evidence of a positive association between glyphosate exposure and risk.” The Panel recommended that EPA revise its conclusion to, “something along the lines of the following: ‘Based on the weight-of-evidence from epidemiological studies and meta-analyses, the Agency cannot exclude the possibility that observed positive associations between glyphosate exposure and risk of NHL suggest human carcinogenic potential of glyphosate, even though study limitations and concerns about potential biases remain.’” In other words, the studies, data, and methodologies the EPA relied upon to reach the conclusion that glyphosate is not carcinogenic to humans is tentative at best.
Lastly, to solidify the conclusion that glyphosate may in fact be carcinogenic, I will quote the authors of a study the EPA relied upon to conclude glyphosate is not carcinogenic. The authors of the study in questions, Dr Roos et al. (Authors), responded to negative criticism from their peers in the scientific community concerning the conclusion glyphosate is not mutagenic. The Author’s response reiterated the narrow scope of the findings in the study and offered other factors as to why certain other studies indicating glyphosate formulations are carcinogenic. “We stated in our article the conclusion of the U.S. Environmental Protection Agency (U.S. EPA 1993) and the World Health Organization (1994) that glyphosate is not mutagenic, but because that conclusion focused on the active ingredient, glyphosate, and not formulated products such as Roundup (Monsanto Company, St. Louis, MO), we also cited several studies which show potentially greater toxic effects of Roundup than glyphosate.” The Authors went on to say, “Our article (De Roos et al. 2005) does not purport to be a comprehensive review of the toxicology literature, and because of space limitations imposed by the journal, we did not discuss several studies showing potentially toxic effects of several glyphosate-based pesticide products through disruption of cell-cycle control mechanisms, which may be relevant for cancer as well as noncancer health outcomes (Marc et al. 2002, 2004).”
The argument that the conclusion glyphosate is not likely carcinogenic has been diminished by the Panel’s final report. Moreover, the scope of studies relied upon by the EPA do not seem to include formulations of glyphosate, which is the form consumers normally interact with the chemical as is the case with “Roundup.” Rather, upon further research, some of the omitted studies found glyphosate, when formulated, to likely be more carcinogenic than when studied in isolation. Personally, I have not come to a conclusion as to whether glyphosate is or is not carcinogenic because I do not believe the evidence currently available is definitive enough to base a prudent conclusion on.
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 https://www.epa.gov/pesticides/scientific-advisory-panel-report-glyphosate-available (Minutes & final report can be found here)