Long-term exposure to air pollution is linked to a heightened risk of autoimmune disease, according to new research published in RMD Open.

The research found that environmental air pollution from vehicle exhaust and industrial output may trigger diseases such as rheumatoid arthritis, connective tissue diseases and inflammatory bowel diseases.

The prevalence of these conditions have steadily increased over the past decade, and to shed some light on why this may be, the researchers looked at data from the national Italian fracture risk database (DeFRA) and air quality monitoring stations across Italy. 

Long-term exposure to air pollutants was associated with a 40% higher risk of rheumatoid arthritis

Data was retrieved for more than 81,000 patients, 92% of whom were women with an average age of 65. Roughly a fifth (22%) had at least one co-existing health condition. 

The researchers were particularly interested in the impact of particulate matter, so, using data from the nearest air quality monitoring station, they analysed each person's exposure between 2013 and 2019.

Overall, long term exposure to traffic and industrial air pollutants was associated with an approximately 40% higher risk of rheumatoid arthritis, a 20% higher risk of inflammatory bowel disease, and a 15% higher risk of connective tissue diseases.

The study is observational and cannot establish a cause

The researchers acknowledge that the study is observational and cannot establish a cause, as well as noting several limitations.

These include: the lack of information on the dates of diagnosis and start of autoimmune disease symptoms; that air quality monitoring might not reflect personal exposure to pollutants; and that the findings might not be more widely applicable because study participants largely comprised older women at risk of fracture.

However, since air pollution has already been linked to immune system abnormalities, and smoking, which shares some toxins with fossil fuel emissions, is a predisposing factor for rheumatoid arthritis, they hold that the findings likely hold some credibility.