Glyphosate is a broad-spectrum
herbicide that is one of the most frequently applied pesticides in the world. Although there has been little consistent evidence of genotoxicity or carcinogenicity from in vitro and animal studies, a few epidemiologic reports have indicated potential health effects of
glyphosate. We evaluated associations between
glyphosate exposure and
cancer incidence in the Agricultural Health Study (AHS), a prospective cohort study of 57,311 licensed
pesticide applicators in Iowa and North Carolina. Detailed information on
pesticide use and other factors was obtained from a self-administered questionnaire completed at time of enrollment (1993-1997). Among private and commercial applicators, 75.5% reported having ever used
glyphosate, of which > 97% were men. In this analysis,
glyphosate exposure was defined as a) ever personally mixed or applied products containing
glyphosate; b) cumulative lifetime days of use, or "cumulative exposure days" (years of use times days/year); and c) intensity-weighted cumulative exposure days (years of use times days/year times estimated intensity level). Poisson regression was used to estimate exposure-response relations between
glyphosate and incidence of all
cancers combined and 12 relatively common
cancer subtypes.
Glyphosate exposure was not associated with
cancer incidence overall or with most of the
cancer subtypes we studied. There was a suggested association with
multiple myeloma incidence that should be followed up as more cases occur in the AHS. Given the widespread use of
glyphosate, future analyses of the AHS will allow further examination of long-term health effects, including less common
cancers.