Mark D. Harris, MD, FACR

The precise etiopathogenesis of immune-mediated disease (IMIDs) is not clearly elucidated. IMIDs are estimated to affect 5% of the world’s population with rates significantly increasing over the last decade. A common postulated theory of autoimmunity is that a genetically susceptible individual loses immune regulation and tolerance possibly related to an external environmental signal or trigger, such as an infection, occupational exposure or — mounting evidence reveals — environmental pollutants.

Adami and colleagues at the University of Verona, in Italy, have identified that exposure to traffic and industrial pollutants was associated with an approximately 40% higher risk for rheumatoid arthritis, a 20% higher risk for inflammatory bowel disease and a 15% higher risk for connective tissue disease.

The study, published in RMD Open in March 2022, had access to a large osteoporosis-based fracture risk assessment database, with information entered by 3,500 physicians on 81,363 patients. Data on air pollution particulate matter — PM10 and the smaller-sized PM2.5 concentrations — were derived from the Italian Institute of Environment Protection and Research. Adverse health threshold pollutant levels were determined to be 30 µg/m³ for PM10 and 20 µg/m³ for PM2.5.

The study found that particulate levels above the concentration thresholds correlated with an approximately 13% risk for developing an IMID. Higher levels of PM exposure may also correlate with increased risk. There appears to be a 7% higher risk for having an IMID for every 10 µg/m³ increase in PM10 concentrations.

This may not be surprising to many rheumatologists who have long been aware of tobacco smoke inhalation as a significant risk in the pathogenesis and risk for developing RA. The authors note that emissions from fossil fuels, such as diesel exhaust, share toxins with cigarette smoking and convey risk of poor response to biologic therapies in RA.

Although it is impossible to assign causality to the association between autoimmunity and environmental pollutants, there is evidence to establish a link that requires further understanding of the toxic milieu we interact with daily and is a field pleading for quality research to direct future public health policy.

Karen McKerihan, MSN, NP-C

Not knowing much about pollution and particulate matter, I decided to check out the EPA website. Per the EPA website, particulate matter (PM), also known as particle pollution, are solid and liquid droplets found in the air. These substances are comprised of many different chemicals. PM10 are considered inhalable particles and are 10 micrometers or smaller. PM2.5 are considered fine inhalable particles.

Knowing these facts gave me a better understanding of what was used as air quality measures in this study. It was intriguing to read the discussion on the work that has already been done trying to understand the relationship between air quality and immune-mediated inflammatory diseases (IMIDs).

One observation that I found fascinating is the association between air pollution and a higher risk for flares and poorer responses to biologic treatments. This study ended just a few months after the COVID-19 pandemic began. It would be intriguing to see data comparing rates of IMIDs before and after the COVID-19 pandemic with the wide use of masks. Would there be any changes noted in the incidence and rates of IMIDs, disease flares and response to biologic treatments? I look forward to seeing more data.