by Elana Gotkine

Specific pesticides are associated with an increased risk for rheumatoid arthritis among older adults, according to a study published online Dec. 2 in Scientific Reports.

Christine G. Parks, Ph.D., M.S.P.H., from the National Institutes of Health in Durham, North Carolina, and colleagues examined RA risk among licensed pesticide applicators from North Carolina and Iowa in relation to lifetime use of 45 pesticides reported at enrollment (1993 to 1997; updated 1999 to 2003).

The researchers identified 161 (0.7 percent) incident cases with two or more RA claims, ≥30 days apart, after 12 months or longer without RA claims, among 22,642 applicators aged 67 years and older. In models adjusted for age, state, education, smoking, and correlated pesticides, risk was elevated for use of nine pesticides: four insecticides (malathion, phorate, carbaryl, and carbofuran); four herbicides (alachlor, metolachlor, S-Ethyl dipropylthiocarbamate, and metribuzin); and one fungicide (benomyl). For greater intensity-weighted lifetime days use of malathion and carbofuran, exposure-response was seen.

"Our findings support the hypothesis that specific pesticides may contribute to RA risk," the authors write. "Replication of these findings in other populations and experimental studies is needed, given the potential implications for other autoimmune diseases and millions of tons of pesticide active ingredients produced and used in the U.S. and globally."

More information: Christine G. Parks et al, Associations between pesticide use and rheumatoid arthritis among older farmers in the Agricultural Health Study, Scientific Reports (2024). DOI: 10.1038/s41598-024-76179-2

Journal information: Scientific Reports 

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