Pesticide Exposure and Risk of Rheumatoid Arthritis among Licensed Male Pesticide Applicators in the Agricultural Health Study

BACKGROUND: The occupation of farming has been associated with rheumatoid arthritis (RA); pesticides may account for this association, but there are few studies. OBJECTIVES: We investigated associations between RA and use of pesticides in the Agricultural Health Study. METHODS: The study sample was drawn from male pesticide applicators enrolled in 1993–1997 who provided questionnaire data at baseline and at least once during follow-up (over a median 18 y; interquartile range 16–19). Incident RA cases ([Formula: see text]), confirmed by physicians or by self-reported use of disease-modifying antirheumatic drugs, were compared with noncases ([Formula: see text]) who did not report RA. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression, adjusting for enrollment age, state, smoking pack-years, and education. We evaluated the association of RA with the use of 46 pesticides and across 4 levels (never use and tertiles) of lifetime days of use for 16 pesticides with [Formula: see text] for ever use. RESULTS: Incident RA was associated with ever use of fonofos (OR = 1.70; 95% CI: 1.22, 2.37), carbaryl (OR = 1.51; 95% CI: 1.03, 2.23), and chlorimuron ethyl (OR = 1.45; 95% CI: 1.01, 2.07) compared with never use. Statistically significant exposure–response trends in association with RA were observed for lifetime days of use of atrazine [[Formula: see text] 1.62 (95% CI: 1.09, 2.40); [Formula: see text]] and toxaphene [[Formula: see text] 2.42 (95% CI: 1.03, 5.68); [Formula: see text]]. Exposure–response was nonlinear for fonofos [[Formula: see text] 2.27 (95% CI: 1.44, 3.57); [Formula: see text] 0.98 (95% CI: 0.54, 1.80); [Formula: see text] 2.10 (95% CI: 1.32, 3.36); [Formula: see text]] and suggestive for carbaryl ([Formula: see text]). CONCLUSIONS: Our results provide novel evidence of associations between exposure to some pesticides and RA in male farmers. https://doi.org/10.1289/EHP1013