AT A GLANCE

A new study published in Arthritis & Rheumatology suggests that exposure to certain insecticides and pesticides may increase the risk for rheumatoid arthritis (RA) among female spouses of licensed pesticide applicators.¹

“Growing evidence suggests farming and agricultural pesticide use may be associated with RA, but few studies have examined specific pesticides and RA among farm women, who may personally use pesticides or be indirectly exposed,” explain study authors Parks et al. “We investigated pesticide use and RA risk among female spouses of licensed pesticide applicators in the Agricultural Health Study.”

Among 32,126 participants enrolled during 1993–1997 from North Carolina and Iowa, incident RA cases were identified by way of follow-up questionnaires (1999–2021) and confirmed by medical records, relevant medication use, or Medicare claims data (1999–2016). Among these, Medicare claims data were definitively used for confirmation if questionnaire data on RA were unavailable. Subsequently, among participants with complete covariate data (n = 410 cases and 21,850 non-cases), the authors examined associations with pesticide classes and 32 specific pesticides (i.e., personal lifetime use reported at enrollment, updated in 1999–2003). Odds ratios with 95% confidence intervals were calculated, with adjustment for age, state, education, pack-years smoking, body mass index, and correlated pesticides (rho > 0.35).

According to the authors, their analysis revealed that incident RA was associated with the use of organochlorine (DDT [1.89; 1.30–2.75], lindane [1.97; 1.12–3.47]) and organophosphate insecticides (coumaphos [2.32; 1.29–4.19], malathion [1.21; 0.91–1.62]), the carbamate insecticide carbofuran (1.87; 0.97–3.63), and permethrin or pyrethroid insecticides use on crops (1.56; 0.92–2.64) or livestock (1.69; 1.07–2.68). Exposure to the fungicides captan (1.78; 1.13–2.83) and metalaxyl (2.49; 1.41–4.40) was also associated with RA. Conversely, RA was not associated with the use of herbicides other than metribuzin (1.88; 0.94–3.79).

“These findings indicate that persistent organochlorine insecticides and some pesticides also used in public health or residential settings may increase RA risk in women,” conclude the authors. “While insecticides are an important tool in controlling threats to crops and human health, our results provide evidence of potential risks. Further studies are warranted, especially for widely used insecticides, such as malathion, carbaryl, and pyrethroids, given ongoing residential and public health uses, such as mosquito control, and residential orpersonal uses such as permethrin-treated clothing.”

Reference

1.     Parks CG, Leyzarovich D, Hamra GB, et al. Associations of specific pesticides and incident rheumatoid arthritis among female spouses in the Agricultural Health Study (online ahead of print July 16, 2025). Arthritis Rheumatol.