Air pollution can increase inflammation and raise the risk of rheumatoid arthritis flare-ups, according to a study of patients in South Korea published in the journal Annals of the Rheumatic Diseases. Researchers found that exposure to airborne dust, soot and smoke aggravated symptoms in people living with the long-term joint condition.
The study tracked 1,070 rheumatoid arthritis patients in South Korea over a four-year period. During the trial, scientists evaluated data from 12,583 medical appointments and measured disease activity against ambient levels of six major air pollutants, including nitrogen dioxide, ozone, carbon monoxide, PM2.5 and PM10 particulate matter.
The strongest connection to heightened symptoms appeared with PM2.5 particles. Higher concentrations of these microscopic pollutants were associated with more severe symptoms and a higher frequency of disease flare-ups among the participants.
Particulate matter PM2.5 refers to tiny airborne particles measuring 2.5 micrometres or smaller in diameter, which are commonly produced by vehicle exhaust, industrial emissions and power generation. Other major pollutants monitored in the study, such as nitrogen dioxide, ozone and carbon monoxide, are standard indicators used globally to assess urban air quality.
Rheumatoid arthritis is an autoimmune disease in which the immune system mistakenly attacks healthy tissue lining the joints, causing inflammation, pain and progressive joint damage. Flare-ups represent periods when symptoms become temporarily sharper and more debilitating, often restricting patient mobility.
Biological impact of polluted air
The increased risk of a flare-up became particularly noticeable after patients were exposed to polluted air for more than two weeks. Investigators suggested that microscopic particles can pass from the lungs into the bloodstream and circulate throughout the body, elevating oxidative stress and triggering inflammatory responses.
Oxidative stress is an imbalance between harmful free radical molecules and protective antioxidants in human tissue, which can damage cells and worsen existing inflammatory conditions. The Annals of the Rheumatic Diseases is a peer-reviewed medical journal that publishes research on joint and musculoskeletal diseases.
Precautionary measures and health risks
The authors of the study advised people with rheumatoid arthritis to avoid staying outdoors for extended periods on days when air pollution levels are high, whenever possible.
The findings build on earlier research by scientists showing that high temperatures and polluted air together significantly increase the risk of heart attacks and strokes.
