Air pollution linked to a greater risk of autoimmune disease

A new study from the University of Verona in Italy has found evidence of a correlation between long-term exposure to air pollution and a heightened risk of autoimmune disease. 

Examples of autoimmune disease identified in the study include rheumatoid arthritis; multiple sclerosis; systemic lupus erythematosus; inflammatory bowel diseases; and connective tissue diseases such as osteoarthritis.

Environmental air pollution comes from sources such as vehicle exhaust and industrial output. Normally, these types of pollutants trigger the body to react to a specific disease, causing entity through adaptive immunity. However, in some cases, adaptive immunity can misfire, leading to inflammation in the body as well as tissue damage and in the long term, autoimmune disease. 

Over the last ten years, the prevalence of autoimmune disease has steadily increased, and the cause has remained a mystery. To investigate, the researchers gathered medical information on 81,363 men and women submitted from the national Italian fracture risk database (DeFRA) between 2016 and 2020.

Most of the participants were women (92 percent) with an average age of 65. Overall, 22 percent of the volunteers had at least one co-existing health condition. To understand how air pollution impacted their health, each participant was linked to a nearby air quality monitoring station.

The study evaluated the potential impacts of particulate matter, focussing on particulate matter levels of PM10 and PM2.5, the thresholds considered harmful to human health. Information on air quality was obtained from 617 monitoring stations in 110 Italian provinces. The results showed that 12 percent of participants had been diagnosed with an autoimmune disease between 2016 and 2020. 

The study also identified how the disease risk varies depending on exposure to particulate matter and changes over time. For example, exposure to PM2.5 was not associated with an increased risk of autoimmune disease. At the same time, PM10 was associated with a seven percent heightened risk for every 10µg/m3 (10 micrograms / cubic meter) increase in levels.

The study showed an increased risk of autoimmune disease under long term exposure. Specifically, long term exposure to PM10 above 30 µg/m3 and to PM2.5 above 20 µg/m3 were associated with up to 13% higher risk of autoimmune disease. 

The levels of particulate matter each participant was exposed to under a long term scenario resulted in specific diagnosis. For example, long term exposure to PM10 had a specific link to heightened risk of rheumatoid arthritis. Long term exposure to PM2.5 was associated with a heightened risk of rheumatoid arthritis, connective tissue diseases, and inflammatory bowel diseases.

Overall, prolonged exposure to traffic and industrial air pollutants resulted in a 40 percent higher risk of rheumatoid arthritis, a 20 percent higher risk of inflammatory bowel disease, and a 15 percent higher risk of connective tissue diseases.

While this study shed some light on the connections between long term air pollution and the risk of autoimmune disease, it cannot establish the root cause. As an observational study, the researchers noted some limitations that could have affected their findings. 

For example, the data they relied on did not include dates of each participant’s diagnosis, or when autoimmune symptoms first appeared. It was also noted that air quality monitoring may not reflect personal exposure to pollutants. 

Despite these limitations, the researchers pointed to existing studies that have already linked air pollution to immune system abnormalities. Previous studies have linked smoking and toxins in fossil fuel emissions to rheumatoid arthritis and other autoimmune diseases.

The study is published in the journal RMD Open.

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By Katherine Bucko, Earth.com Staff Writer