Air Pollution Linked to Spikes in Rheumatoid Arthritis Activity and Flare Risk

A novel study shows that exposure to air pollution, especially fine particulate matter like dust, soot, and smoke (PM_2.5), is associated with increased disease activity and flare risk in rheumatoid arthritis (RA). The findings from an articleopens in new tab/window in the Annals of the Rheumatic Diseasesopens in new tab/window (ARD), The EULAR Journal, published by Elsevier, underscore the importance for healthcare providers and policymakers to recognize its impact on the management of RA.

RA is a chronic autoimmune disease characterized by joint inflammation and joint damage; also, widespread systemic symptoms can affect other parts of the body beyond the joints. Globally, it affects about 0.5% to 1% of the adult population. Many factors contribute to the development of RA, such as genetics, immune system changes, and environmental exposures. These environmental factors may play a critical role in both the onset and exacerbation of RA; importantly, many of them are modifiable. Smoking is one of the well-established risk factors, while climatic factors, such as air temperature and humidity, and certain pollutants, like silica, have also been implicated.

Previous epidemiological studies have shown an association between air pollution and an increased risk of developing RA. A team of investigators in South Korea has conducted research to evaluate the effects of air pollution on disease activity and flare occurrence in patients with established RA and explore its underlying mechanisms.

In an accompanying editorialopens in new tab/window Jeffrey A. Sparks, MD, MMSc, Division of Rheumatology, Inflammation, and Immunity, Mass General Brigham / Brigham and Women’s Hospital, and Harvard Medical School, comments, “This is one of the largest studies to use robust methods to link air pollutants with RA disease activity. Considering rising levels of air pollutants, these results have significant clinical, biologic, and public health implications. They also further reinforce that inhalants may have broad implications for risk and progression of RA and perhaps 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.”

This prospective cohort study tracked 1,070 RA patients across 12,583 real-world outpatient visits over four years (2021–2024) at a major South Korean medical center. Air pollution exposure was estimated using monthly concentrations of six major air pollutants (sulfur dioxide, SO₂; nitrogen dioxide, NO_2; ozone, O_3; carbon monoxide, CO; paritculate matter with a diameter of 10 µm, PM_10; and paritculate matter with a diameter of 2.5 µm,PM_2.5), which were matched with disease activity and flare outcomes longitudinally recorded at each outpatient visit.

The statistical analysis was adjusted for demographic characteristics, serologic status (the presence of specific antibodies typical for RA in the blood), medication use, socioeconomic factors, and meteorological variables. For sensitivity analysis to better control for time-invariant confounding and avoid potential reverse causation inherent in the monthly analysis, a case-crossover design using daily air pollutant concentrations preceding each visit was applied, using conditional logistic regression to assess changes within the same patient.

“Our study found that higher PM_2.5 concentration was associated with increased disease activity and flare risk, notably prolonged exposure to elevated PM_2.5 over more than two weeks,” explains lead investigator Eun Bong Lee, MD, PhD, Division of Rheumatology, Department of Internal Medicine, Seoul National University College of Medicine, and Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Republic of Korea.

The investigators identified PM_2.5 as the key contributor to increased RA disease activity. Because these microscopic particles are smaller than red blood cells, they can easily travel from the lungs into the bloodstream, circulating to distant organs. They can then trigger the overproduction of harmful molecules called reactive oxygen species, thereby inducing cellular stress, damaging DNA, and sparking inflammatory responses in organs.

Dr. Lee concludes, “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 patients, we would recommend these patients avoid prolonged exposure to poor air quality, particularly high PM_2.5 levels.”

ARD Editor-in-Chief Josef Smolen, MD, from the Medical University of Vienna, adds: “As always, this paper underwent thorough peer review, and it was nice to learn that all reviewers agreed on the importance and interest of these findings. Nevertheless, we should be aware that the observations pertain to the studied Korean population, with a specific genetic background and under specific environmental circumstances. Whether these data hold true in other regions of the world should be a focus of future investigations. However, it is an excellent starting point for our better understanding of factors that may play a role in influencing disease activity and therapeutic responses of patients with RA. And: it is an important wake-up call: the environment is likely an essential contributor to pain and inflammation in the patients for whom we care.”

Notes for editors

The article is “Effects of air pollution on disease activity in patients with rheumatoid arthritis,” by Sung Cheol Jung, Jeffrey R. Curtis, Seojin Yang, Yunhee Choi, Min Hyuk Lim, Saram Lee, Sung Ik Cho, Jin Kyun Park, Jun Won Park, and Eun Bong Lee (https://doi.org/10.1016/j.ard.2026.06.018opens in new tab/window).

The article is openly available at https://ard.eular.org/article/S0003-4967(26)00364-X/fulltextopens in new tab/window.

The editorial is “Air pollution and rheumatoid arthritis disease activity: linking pathogenesis and progression,” by Jeffrey A. Sparks (https://doi.org/10.1016/j.ard.2026.07.018opens in new tab/window).

The editorial is openly available at https://ard.eular.org/article/S0003-4967(26)00475-9/fulltextopens in new tab/window.

The article and editorial appear online ahead of volume 85, issue 10 (October 2026) of the Annals of the Rheumatic Diseases, published by Elsevier.

Full text of the article and editorial is also available to credentialed journalists upon request; contact Eileen Leahy at +1 732 406 1313 or [email protected]opens in new tab/window. Journalists wishing to interview the authors should contact Youngju Park, Media Relations Department, Seoul National University Hospital, at [email protected]opens in new tab/window. Jeffrey A. Sparks, MD, MMSc, may be reached for comment at [email protected]opens in new tab/window.

This research was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (RS-2025-02215880) and by Bio-Data Industry Professional Training Program through the Korea Institute for Advancement Technology (KIAT) funded by the Ministry of Trade, Industry and Energy (RS-2025-02214034).

About Annals of the Rheumatic Diseases (ARD)

Annals of the Rheumatic Diseasesopens in new tab/window (ARD), an official journal of EULARopens in new tab/window, is an international peer reviewed journal committed to promoting the highest standards of scientific exchange and education. It is the leading rheumatology journal publishing a combination of high-quality scientific papers, including original research, reviews, recommendations, viewpoints, and more. Clinical, basic, and translational science across the inflammatory and non-inflammatory musculoskeletal conditions are part and parcel of this spectrum.

About EULAR

EULARopens in new tab/window is the European umbrella organization representing scientific societies, health professional associations, and organizations for people with rheumatic and musculoskeletal diseases (RMDs). EULAR aims to reduce the impact of RMDs on individuals and society, as well as improve RMD treatments, prevention, and rehabilitation. To this end, EULAR fosters excellence in rheumatology education and research, promotes the translation of research advances into daily care, and advocates for the recognition of the needs of those living with RMDs by EU institutions.

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