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In a large cohort of U.S. female nurses followed for many years, exposure to various air pollutants did not increase the likelihood of rheumatoid arthritis (RA). These results were published in Arthritis Care & Research.

RA is an autoimmune disease. An autoimmune disease occurs when the immune system—which normally protects the body from infection—turns against some of the body’s own tissues. Other examples of autoimmune diseases are Type I diabetes, lupus, Sjogren syndrome, Grave’s Disease, and multiple sclerosis.

In the case of RA, the immune system attacks the synovium (the tissue that lines joint capsules) and causes inflammation. It’s unclear what starts this process, but some combination of genetic and environmental factors is likely to play a role. Factors that increase the likelihood of RA include being female, smoking, and having a family history of rheumatoid arthritis.

To explore the role of air pollution in RA, researchers evaluated information from the Nurses’ Health Study. The study involved more than 111,000 female nurses who have been providing health information since 1976.

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Exposure to air pollution was calculated based on each woman’s residential addresses. Information was collected about outdoor levels of particulate matter and gaseous pollutants.

During follow-up, there were 858 new diagnoses of RA among study participants. Overall, there was no relationship between exposure to different air pollutants and risk of RA.

These results suggest that in this population of socioeconomically advantaged, middle-aged and older women, air pollution did not increase the risk of RA.

Reference: Hart JE, Kallberg H, Laden F et al. Ambient air pollution exposures and risk of rheumatoid arthritis in the Nurses’ Health Study. Arthritis Care & Research. Early online publication February 11, 2013.