Glyphosate: Hazard vs. Risk
A recent report was published by Myers et al., in the Environmental Health Perspectives expressed concern with potential human and environmental health risks posed by glyphosate; this article emphatically emphasized glyphosate’s potential link to cancer and endocrine related effects. These conclusions were based on a biased and selective interpretation of the state of the current regulatory science, with a deliberate focus on hazard and not on actual risk. More specifically, they emphasize the detection of glyphosate and its metabolites in the food supply showing increased exposure and point to studies that reveal possible endocrine system-mediated and developmental impacts from glyphosate exposure. While these statements appear compelling, especially the linkages between glyphosate exposure and adverse health effects, they are based on selective interpretation of a small subset of data as compared to the volume of toxicity and exposure data that support scientifically peer reviewed regulatory risk assessments for glyphosate.
Should the Public Be Concerned about Cancer and Endocrine Effects?
The report by Myers et al., 2016 claims that glyphosate residues and its metabolite are found in crops at harvest and in processed foods, noting that residue levels were identified “by the USDA in 2011 that reveal residues of glyphosate in 90.3% of 300 soybean samples, and its metabolite in 95.7% of samples.” However, more recent updates published by the USDA in their annual Pesticide Data Program (PDP) report indicate that pesticide residues overall are not a food safety concern for the United States. The recent 2016 PDP report found our food to be safe, with pesticide residue levels low enough to pose no human health risks, even for infants. The U.S. Department of Agriculture tested for pesticides in 10,619 samples of food in 2014. The large majority of pesticide residue levels were found to be at or below tolerance levels set by the U.S. Environmental Protection Agency in all but 0.36% of the samples, a very different percentage than cited by this article.
Myers et al. states that studies from human and animal toxicity studies collectively indicate that glyphosate exposure leads to an increased incidence of cancer based largely on conclusions drawn by the World Health Organization’s International Agency for Research on Cancer (IARC) who recently classified glyphosate as “probably carcinogenic to humans”. Included in this same IARC 2A classification are things like eating red meat, exposure to emissions from high frying temperatures, and working as a hair dresser or barber. This IARC cancer classification is based primarily on “hazard” potential, which greatly differs from the “risk-based” conclusions drawn by multiple international regulatory agencies that glyphosate is not carcinogenic to humans.
In 2014, USEPA stated that in its review of over 55 human epidemiological studies conducted on the possible cancer and non-cancer effects of glyphosate, that “the body of scientific research from animal and human data does not provide any evidence to demonstrate that glyphosate causes cancer, and the data set does not warrant any change in USEPA’s cancer classification for glyphosate, which is classified as a group E or evidence of non-carcinogenicity for humans” (USEPA, 1991). This is the same conclusion reached in 2004 by the United Nations’ Food and Agriculture Organization and affirmed this year by Germany’s pesticide regulatory officials.
More recently, on November 12, 2015, European Food Safety Authority (EFSA) announced that it had completed its reassessment of glyphosate, and had issued its conclusion on its website that glyphosate is unlikely to pose a carcinogenic hazard to humans (http://www.efsa.europa.eu/en/press/news/151112). Similar many other regulatory agencies, EFSA’s report concluded that glyphosate is unlikely to pose a carcinogenic concern to humans.
In addition to the potential cancer linkage, the Myers et al. 2016 report indicated the inability of current test methods to address potential adverse effects triggered by disruption of the endocrine system. What this report failed to mention is that glyphosate was among the 52 List 1 chemicals screened by the USEPA Endocrine Disruption Screening Program across a battery of assays that have been scientifically validated and internationally accepted and harmonized. The battery of Tier 1 assays includes a range of in vitro and in vivo assays that address effects across species, exposure durations, and sensitive life stages. In addition to the Tier 1 assay data, other scientifically relevant information (OSRI), including general toxicity data and open literature studies of sufficient quality, were considered in this weight of evidence (WoE) assessment. Based on a weight of evidence evaluation, the USEPA concluded in June 2015 that for glyphosate, there “was no convincing evidence of potential interaction with the estrogen, androgen or thyroid pathways” (USEPA 2015).
Collectively, the data reviewed by multiple regulatory authorities, reviewed by expert peer reviewing committees, do not support a cancer or endocrine disrupting potential from glyphosate exposure. In 2016, the USDA Pesticide Data Program continues to report safe levels of pesticide residues found in our food supply. Neither the exposure nor hazard potential has been confirmed by the extant data set. Based on these conclusions, the global pesticide dossier, and hazard and exposure assessments continue to support the safe registration of glyphosate and use of this herbicide on food commodities according to the pesticide label.
AUTHOR: Mary Manibusan, Exponent
Myers, J., Antoniou, M., Blumberg, B, et al. (2016). Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environmental Health 15:19, p 1-13. http://ehjournal.biomedcentral.com/articles/10.1186/s12940-016-0117-0
U.S. Environmental Protection Agency (EPA). EDSP Weight of Evidence Conclusions on the Tier 1 Screening Assays for the List 1 Chemicals. June 29, 2015. http://www.epa.gov/sites/production/files/2015-06/documents/glyphosate-417300_2015-06-29_txr0057175.pdf
USEPA. 1991. Memorandum on Second Peer Review of Glyphosate. Office of Pesticide Programs, Cancer Assessment Review Committee. October 30, 1991.
US Department of Agriculture (USDA). Pesticide Data Program (PDP) Annual Report. 2016. https://www.ams.usda.gov/sites/default/files/media/2014%20PDP%20Annual%20Summary.pdf