How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate-based herbicides?

Environmental Sciences Europe

Table 2 Number of genotoxicity assays cited in core tables by IARC 2017, EPA 2016, or in Monsanto-commissioned reviews

Assay type and compound tested	Number of studies considered by IARC	Cited by
Assay type and compound tested	Number of studies considered by IARC	MON reviews	EPA Sept 2016
Exposed humans
Formulated GBHs	5	5	0
Human cells in vitro
Glyphosate	10	8	7
AMPA	2	2	0
Formulated GBHs	4	2	3
Non-human mammals in vivo
Glyphosate	11	10	10
AMPA	1	1	0
Formulated GBHs	13	13	13
Non-human mammalian cells in vitro
Glyphosate	5	5	5
AMPA	1	1	0
Formulated GBHs	2	2	2
Non-mammalian systems in vivo
Glyphosate	12	7	1
AMPA	2	2	0
Formulated GBHs	40	21	4
Non-mammalian systems in vitro
Glyphosate	8	3	4
Formulated GBHs	2	2	2
Total all categories	118	84	51
As percent of total IARC		71%	43%
Total of all mammalian categories	54	49	40
As percent of total IARC		91%	74%

1. IARC totals are from the detailed accounting of all studies considered by the IARC Working Group in the glyphosate section of Monograph 112 [4]. Information on the studies are taken from Tables 4.1–4.6 and the discussion of studies on oxidative stress in humans in Sect. 4.2.3 (a) (i) of the monograph
2. “MON Reviews” include four published studies: Brusick et al. [22]; Kier and Kirkland [27]; Heydens et al. [26]; and Williams et al. [14]. The references in these four, Monsanto-commissioned reviews were cross-checked against the list of IARC studies
3. “EPA Sept 2016” refers to the September 12, 2016 “Glyphosate Issue Paper: Evaluation of Carcinogenic Potential” [3]. All studies cited in this EPA document, including in its Appendix F which contains studies on formulated glyphosate-based herbicides, were cross-checked against the studies cited by IARC and in the Monsanto-commissioned reviews