Exposure to PM2.5 pollution is associated with an increased disease activity and flare risk in rheumatoid arthritis, a chronic autoimmune disease marked by joint inflammation and joint damage, according to a new study.
Findings published in the journal Annals of the Rheumatic Diseases underscore the importance for healthcare providers and policymakers to recognise the impact air pollution can have on how one manages the condition.
Factors such as genetics, immune system changes and environmental exposures can contribute to whether one develops rheumatoid arthritis, with many of the environmental factors being modifiable.
Researchers, including those from the Seoul National University College of Medicine, said smoking is one of the well-established risk factors, while climatic factors, such as air temperature and humidity, and certain pollutants, including silica, have also been implicated in developing the autoimmune condition.
Over 1,000 patients with rheumatoid arthritis from across 12,583 outpatient visits over four years (2021-2024) at a South Korean medical centre were tracked.
Air pollution exposure was estimated using monthly concentrations of six major air pollutants — sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), PM10 and PM2.5 — which were matched with disease activity and flare outcomes recorded at each outpatient visit.
PM2.5 was identified as a key contributor to increased disease activity in rheumatoid arthritis.
“Among (the) six pollutants, PM2.5 was significantly associated with an increased risk of flare and with (a) higher Disease Activity Score based on 28 joints (DAS28) with C-reactive protein (CRP), Clinical Disease Activity Index, 28-tender joint count, and 28-swollen joint count,” the authors wrote.
“In addition, the association between PM2.5 and DAS28-CRP was more pronounced among women and nonsmokers,” they said.
Further, a prolonged cumulative exposure to PM2.5 over more than two weeks was associated with an increased risk of flare in rheumatoid arthritis.
“Our study has important implications for public health policy making. While further studies are warranted to determine whether improving air quality can reduce disease activity in RA (rheumatoid arthritis) patients, we would recommend these patients avoid prolonged exposure to poor air quality, particularly high PM2.5 levels,” lead researcher Eun Bong Lee, from the department of internal medicine, Seoul National University College of Medicine, said.
Being smaller than red blood cells in size, PM2.5 particles can easily travel from the lungs into the bloodstream, circulating to distant organs.
The particles can then trigger the overproduction of harmful molecules called reactive oxygen species, thereby inducing cellular stress, damaging DNA, and sparking inflammatory responses in organs, the researchers explained.
In an accompanying editorial, Jeffrey A. Sparks, from the division of rheumatology, inflammation, and immunity at Mass General Brigham / Brigham and Women’s Hospital, and Harvard Medical School in the US, and not involved with the study, said, “This is one of the largest studies to use robust methods to link air pollutants with RA disease activity.” Sparks added that the study has significant clinical, biologic, and public health implications, given the increasing levels of air pollutants, and further reinforces that inhalants may have broad implications for risk and progression of RA and other autoimmune diseases.
“From a clinical perspective, this may offer avenues to lower the risk of RA flares by avoiding air with poor quality and provide some potential explanation for otherwise idiosyncratic RA flares,” Sparks said.
Published – August 05, 2026 06:42 pm IST