Exposure to Pesticides Increases Risk of Rheumatoid Arthritis in Women

Written by Angeline A. De Leon, Staff Writer. This study identifies several potential risk factors such as specific agricultural pesticides, solvents, and chemical fertilizers that may increase the risk of rheumatoid arthritis in women, while a lifetime livestock exposure (as a child and adult), as compared to no livestock exposure involving animal contact may be protective.

Rheumatoid arthritis (RA) is a chronic inflammatory disorder affecting the lining of joints. This autoimmune disease causes painful swelling as well as potential bone erosion and joint deformity¹. Environmental risk factors, such as exposure to smoking and alcohol intake, are known to influence development of RA, however, certain occupational hazards, particularly in the field of agriculture, are now recognized to also play a role². Farming, involving regular field exposure and use of chemical fertilizers and solvents, has been linked to higher levels of RA³, with toxicology reports indicating the potential for specific types of pesticides to affect the immune system differentially⁴. Moreover, among men and women, RA risk due to occupational pesticide exposure appears to vary⁵. Some studies also suggest that early childhood exposure to livestock may play a protective role against other autoimmune diseases⁶, while other studies report the opposite, that livestock farming may actually increase risk². Therefore, it is unclear whether RA is exclusively associated with crop farming. A previous longitudinal cohort study found suggestive but non-significant associations between RA in women working in agriculture and exposure to specific varieties of pesticides⁷. In an extended study, researchers at the National Institute of Health conducted an investigation examining the relationship between RA and pesticide exposure among female spouses of licensed pesticide applicators.

In a longitudinal cohort study, RA-diagnosed spouses of private pesticide applicators (n = 275) were compared to non-cases (n = 24,018). At baseline, subjects completed questionnaires assessing lifetime and childhood residential farm history, time personally spent mixing or applying pesticides, use of non-specific household pesticides, and engagement in various farm tasks during the past year. At follow-up, women completed a questionnaire asking about childhood contact with farm animals.

Results revealed that women with RA were more likely to have reported lifetime use of pesticides vs. none at all (Odds Ratio = 1.4, 95% Confidence Interval: 1.0 to 1.6). Among the pesticides examined, maneb/mancozeb (agricultural fungicide) as well as glyphosate (crop desiccant) were linked to incident RA, relative to no pesticide use (OR = 3.3, 95% CI: 1.5 to 7.1; OR = 1.4, 95% CI: 1.0 to 2.1, respectively). In addition, an association was reported between incident RA and application of chemical fertilizers (OR = 1.7, 95% CI: 0.97 to 3.6) and cleaning with solvents (OR = 1.6, 95% CI: 1.1 to 2.4). However, RA was shown to have an inverse relationship with lifetime livestock exposure (as a child and adult), as compared to no livestock exposure (OR = 0.48, 95% CI: 0.24 to 0.97).

Based on study findings, researchers report that among female spouses of licensed pesticide applicators, exposure to any specified pesticide is linked to increased risk of RA. Evidence suggests that certain pesticides, including maneb and glyphosate, were specifically associated with RA, however, there also appears to be an interesting protective effect of prior contact with livestock. The impact of pesticide exposure in relation to other autoimmune diseases warrants further examination, and future studies will need to determine whether a potential dose-response relationship exists with certain types of pesticides.

Source: Parks CG, Hoppin JA, De Roos AJ, et al. Rheumatoid arthritis in agricultural health study spouses: associations with pesticides and other farm exposures. Environmental Health Perspectives. 2016; 124(11): 1728-1734. DOI: 10.1289/EHP129.

Environmental Health Perspectives (EHP) is a peer-reviewed journal published monthly with support from the U.S. National Institute of Environmental Health Sciences (NIEHS). … EHP is a fully open-access journal; its content is available free of charge online.

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Posted July 31, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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