Long-term exposure to air pollution is linked to a higher risk of autoimmune disease, reported a new study.
Autoimmune diseases, like multiple sclerosis, happens when the body attacks its own cells because it can't tell them apart from foreign cells.
Researchers found that long-term exposure to air pollution from traffic and industrial air pollutants was associated with about a 40% higher risk of rheumatoid arthritis and a 20% higher risk of inflammatory bowel disease, which refers to Crohn's disease and ulcerative colitis.
The study also reported a 15% higher risk of connective tissue diseases, such as lupus.
The World Health Organisation deemed air pollution one of the greatest environmental risk to health in a 2021 report.
Air pollution is a major cause of premature death and disease - and is the single largest environmental health risk in Europe, says the European Environment Agency.
Published in RMD Open, the study analysed data from an Italian database that monitored the risk of fractures.
Researchers reviewed comprehensive medical information about 81,363 people between June 2016 and November 2020.
About 12% of patients were diagnosed with an autoimmune disorder during that period.
Each person was matched with information on air quality from monitoring stations near their postcode.
The study was particularly interested in the potential impact of particulate matter (PM10 and PM2.5), which are emitted by cars and industrial output as with power stations.
Scientists looked at thresholds generally considered harmful to human health.
The study concluded that long-term exposure to particulates above these levels was associated with, respectively, a 12% and 13% higher risk of developing an autoimmune disease.
Overall, long term exposure to air pollutants was linked 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.
Researchers cautioned that this was an observational study, and as such, can't establish cause.
They said other factors might be involved, such as lack of information on the dates of diagnosis and start of autoimmune disease symptoms or that air quality monitoring might not reflect personal exposure to pollutants.
Also, the findings might not be more widely applicable because the study's participants largely comprised older women at risk of fracture.
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