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 ( n =220), confirmed by physicians or by self-reported use of disease-modifying antirheumatic drugs, were compared with noncases ( n =26,134) 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 OR≥1.2 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 [ORtertile3 = 1.62 (95% CI: 1.09, 2.40); p trend =0.01] and toxaphene [ORtertile3 = 2.42 (95% CI: 1.03, 5.68); p trend =0.02]. Exposure–response was nonlinear for fonofos [ORtertile1 = 2.27 (95% CI: 1.44, 3.57); ORtertile2 = 0.98 (95% CI: 0.54, 1.80); ORtertile3 = 2.10 (95% CI: 1.32, 3.36); p trend =0.005] and suggestive for carbaryl ( p trend =0.053).

CONCLUSIONS: Our results provide novel evidence of associations between exposure to some pesticides and RA in male farmers. https://doi.org/10.1289/EHP1013.