Hypothesis
Heavier lifetime use of glyphosate would be associated with higher cancer incidence, as IARC's 2015 'probably carcinogenic' classification and some earlier studies suggested.
What failed
In a prospective cohort of 54,251 licensed applicators (44,932 glyphosate users, 5,779 incident cancers among them) followed to 2012–13, glyphosate use was not significantly associated with cancer at any site. Only a non-significant raised risk of acute myeloid leukaemia appeared in the highest exposure quartile (RR 2.44, 95% CI 0.94–6.32).
Broken assumption
Glyphosate use raises cancer incidence in the people most heavily exposed to it.
Why
The paper reports no statistically significant association at any site after controlling for other pesticide use; the AML signal did not reach significance under any lag and is flagged as needing confirmation.
From the published paper: Andreotti et al. JNCI Journal of the National Cancer Institute, 2017. ↗Public domain