EPA Concludes Glyphosate Is Not Likely to Be Carcinogenic to Humans

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By Patrick Maxwell, M.S. and Travis Gannon, Ph.D.

In December 2017, the US Environmental Protection Agency (EPA) released the draft human health risk assessment for glyphosate, the active ingredient in Roundup. The human health assessment concluded that “glyphosate is not likely to be carcinogenic to humans” and found “no other meaningful risks to human health” when used in accordance with label instructions.

Findings from the human health assessment align with nearly every major regulatory body in the world including Canada, Europe, Germany and the United Nations; however, the EPA conclusion contradicts the World Health Organization’s International Agency for Research on Cancer (IARC), who classified glyphosate as a “Class 2A probable carcinogen to humans” in 2015. The IARC decision generated considerable attention and fueled concerns over human health risks associated with glyphosate use around the globe. Unlike other regulatory agencies, IARC disclosed little about its review process, making it difficult to determine how IARC arrived at its decision. Yet, as part of litigation proceedings, many IARC ‘draft’ documents surfaced and when compared with the published reports, several critical edits were identified by Reuters and Forbes calling the legitimacy of the IARC classification into question.

By its own description, IARC is a hazard-based organization meaning they evaluate the possibility of something causing cancer and not the probability. Hence, IARC does not consider potential exposure levels, which is a drastically different approach compared to the EPA. Moreover, it’s important to put the IARC grouping system into context. IARC classifies substances in five categories, based on the strength of evidence for their carcinogenicity. While the IARC system is valuable for its simplicity, it only conveys how strong the evidence is that a substance causes cancer and substances in the same group can vary widely in their propensity to increase the risk of developing cancer.

For obvious reasons, the human health assessment generated enormous attention; however, a second component (the ecological risk assessment and supporting documents) have not yet been released. Nevertheless, the EPA commented on the ecological assessment suggesting, “there is potential for effects on birds, mammals, and terrestrial and aquatic plants”. While the updated ‘draft’ has yet to be released, the preliminary ecological risk assessment released in 2015 raised concerns, one of which was the uncertainty surrounding toxicity data for a class of surfactants (polyethoxylated tallow amines) used in select glyphosate formulations (e.g. Roundup). While it may seem inconsequential, the vast majority of toxicity studies used technical material (glyphosate alone) and not a commercial formulation. This creates a dilemma for the EPA as the bulk of toxicity data for glyphosate may not fully characterize the hazard end products (commercial formulations) may present.

In the digital age, the ability to search for and disseminate information has allowed society to connect on a scale once inconceivable. While few can argue the benefits the internet provides, it undoubtedly played a role in the negative public perception around pesticides and the IARC classification of glyphosate as a probable carcinogen is no exception. Today, an individual may encounter anti-pesticide articles based on faulty science and/or personal agendas disguised as a legitimate source that may lead them to form a negative sentiment towards the topic. Scientists can dispute false claims and publish peer-reviewed research, but the reality is that less of those articles will gain traction compared to flashy headlines, like “Glyphosate is Killing Your Child”.

For years, glyphosate has generated contentious debate and although the EPA findings will not satisfy all sides, it illustrates the immense responsibility that falls on the agency. People are quick to criticize the agency, yet all the data they use to formulate their conclusions are grounded in science and publically accessible. Ultimately, the allegations leveled against IARC demonstrate the necessity for subjectivity and transparency in the regulatory decision-making process. Finally, EPA is scheduled to publish their proposed registration review decision for glyphosate in 2019 which will outline any proposed mitigation measures, if needed.