Summary
Differences in the carcinogenic evaluation of glyphosate between the International Agency for Research on Cancer (IARC) and the European Food Safety Authority (EFSA), J Epidemiol Community Health doi:10.1136/jech-2015-207005, March 2016.
The International Agency for Research on Cancer (IARC) working groups (WG) concluded that glyphosate is a ‘probable human carcinogen’, putting it into IARC category 2A due to sufficient evidence of carcinogenicity in animals, limited evidence of carcinogenicity in humans and strong evidence for two carcinogenic mechanisms.
- The IARC WG found an association between non-Hodgkin lymphoma (NHL) and glyphosate based on the available human evidence.
- The IARC WG found significant carcinogenic effects in laboratory animals for rare kidney tumours and hemangiosarcoma in two mouse studies and benign tumours in two rat studies.
- The IARC WG concluded that there was strong evidence of genotoxicity and oxidative stress for glyphosate, entirely from publicly available research, including findings of DNA damage in the peripheral blood of exposed humans.
The Renewal Assessment Report (RAR) by the European Food Safety Authority (EFSA) concluded (Vol. 1, p.160) that ‘classification and labelling for carcinogenesis is not warranted’ and ‘glyphosate is devoid of genotoxic potential’.
- EFSA classified the human evidence as ‘very limited’ and then dismissed any association of glyphosate with cancer without clear explanation or justification.
- Ignoring established guidelines cited in their report, EFSA dismissed evidence of renal tumours in three mouse studies, hemangiosarcoma in two mouse studies and malignant lymphoma in two mouse studies. Thus, EFSA incorrectly discarded all findings of glyphosate-induced cancer in animals as chance occurrences.
- EFSA ignored important laboratory and human mechanistic evidence of genotoxicity.
- EFSA confirmed that glyphosate induces oxidative stress but then, having dismissed all other findings of possible carcinogenicity, dismissed this finding on the grounds that oxidative stress alone is not sufficient for carcinogen labelling.
The most appropriate and scientifically based evaluation of the cancers reported in humans and laboratory animals as well as supportive mechanistic data is that glyphosate is a probable human carcinogen. On the basis of this conclusion and in the absence of evidence to the contrary, it is reasonable to conclude that glyphosate formulations should also be considered likely human carcinogens. The classification, labelling and packaging (CLP) criteria (Table 3.6.1, p.371) allow for a similar classification of Category 1B when there are ‘studies showing limited evidence of carcinogenicity in humans together with limited evidence of carcinogenicity in experimental animals’.
In the RAR, almost no weight is given to studies from the published literature and there is an over-reliance on non-publicly available industry-provided studies using a limited set of assays that define the minimum data necessary for the marketing of a pesticide. The IARC WG evaluation of probably carcinogenic to humans accurately reflects the results of published scientific literature on glyphosate and, on the face of it, unpublished studies to which EFSA refers.
Most of the authors of this commentary previously expressed their concerns to EFSA and others regarding their review of glyphosate to which EFSA has published a reply. This commentary responds to the EFSA reply.