Fire Smoke and Nitrogen Oxide Linked to Increased Risk of Rheumatoid Arthritis

A new study published online on January 12, 2025, in Arthritis & Rheumatology has unveiled significant links between exposure to air pollutants and the risk of developing rheumatoid arthritis (RA) and rheumatoid arthritis-associated interstitial lung disease (RA-ILD). Utilizing data from the US Veterans Affairs dataset, the study analyzed records from October 2009 to December 2018. Researchers examined 9,701 patients with RA, with a mean age of 65 years and 86% being men, and 531 patients with RA-ILD, with a mean age of 69 years and 91% being men. Additionally, the study included a control group of 68,851 individuals.

The study, led by Dr. Vanessa L. Kronzer from the Division of Rheumatology at Mayo Clinic, focused on the association between air pollution exposure and RA risk. Key pollutants studied included fire smoke containing particulate matter smaller than 2.5 microns (PM2.5) and elevated nitrogen oxide levels. The results indicated that nitrogen oxide exposure was linked to a 16% increased risk for RA, while fire smoke exposure nearly doubled the risk for RA-ILD.

Specifically, the risk for RA-ILD was notably higher when concentrations reached or exceeded 0.28 μg/m³. Investigations revealed that exposure to fire smoke within one to three years prior to an RA diagnosis correlated with a 12% increased risk. Similarly, a 13% increased risk was associated with exposure occurring three to five years before diagnosis.

The research also identified that ozone and PM10 were particularly associated with seronegative RA, while carbon monoxide, overall PM2.5, and sulfur dioxide demonstrated negative associations with RA. The findings underscore the complexity of pollutant interactions with autoimmune diseases such as RA.

“Programs for controlling and reduction of air pollutants, along with screening adapted for at-risk population, can potentially result in positive effects on health outcomes,”

• the authors of an accompanying editorial

The study received financial support from various grants and awards, including contributions from the Veterans Affairs, the Rheumatology Research Foundation, and the National Institutes of Health. This comprehensive support highlights the importance of understanding environmental impacts on health conditions like rheumatoid arthritis.