Exposure to Occupational Inhalants and the Risk of Developing Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Our plain-English summary of Exposure to Occupational Inhalants and the Risk of Developing Rheumatoid Arthritis: A Systematic Review and Meta-Analysis, by Q. Liu, X. Song, E. Mauro, et al (Arthritis & Rheumatology, 2026).

The study

• Authors: Q. Liu, X. Song, E. Mauro, Y. Jiang, K. Shchetynsky, L. Klareskog, L. Alfredsson, X. Jiang
• Journal: Arthritis & Rheumatology
• Published: 2026;78(4):830-847
• Type of article: Systematic review, Meta-analysis
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint pain, swelling, and stiffness. Although smoking is a well-established risk factor for RA, the role of occupational inhalants in RA development is less well recognized. This study aimed to systematically review and synthesize existing evidence on the association between occupational inhalants and the risk of developing RA.

Methods: We conducted a systematic review and meta-analysis following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching MEDLINE, Embase, and Web of Science from database inception to November 20, 2024. Eligible studies were cross-sectional, were case-control and cohort designs, were population-based, reported original data on occupational inhalant exposures and RA, measured exposures, included a comparison group, and used reliable RA ascertainment methods. Studies relying solely on self-reported RA or focusing on treatment, prognosis, sick leave, or death were excluded. Two reviewers independently conducted literature screening, data extraction, and risk-of-bias assessment using the Newcastle-Ottawa Scale. Random-effects meta-analyses with relative risk were performed for cohort and case-control studies, and heterogeneity was assessed using the I2 statistic.

Results: In total, 31 studies met inclusion criteria, and 25 were included in meta-analyses across 10 types of occupational inhalants. Significant associations with RA risk were observed for exposure to silica, asbestos, solvents, pesticides, fertilizers, animal dust, and engine exhaust (relative risks ranging from 1.25 to 1.49). Moderate-to-high heterogeneity was observed in seven meta-analyses.

Conclusion: Occupational inhalants are associated with increased RA risk, underscoring the importance of workplace prevention strategies and further research into biologic mechanisms.

© 2025 The Author(s). Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology.

In plain English

This was a systematic review and meta-analysis of published studies on whether breathing in substances at work is linked to developing rheumatoid arthritis (RA), an autoimmune joint disease. The authors searched three databases up to November 20, 2024, and included 31 studies (15 case-control, 12 cohort, 4 cross-sectional). They pooled results from 25 case-control and cohort studies for 10 types of workplace inhalants, including seven results on asbestos. Seven inhalants (asbestos, silica, solvents, pesticides, fertilizers, animal dust and engine exhaust) were statistically significantly associated with higher RA risk, with relative risks from 1.20 to 1.49. For asbestos, the pooled relative risk was 1.39 (95% CI 1.05 to 1.84), and results varied widely between the asbestos studies. Textiles, oil mist and wood dust did not reach statistical significance. The authors found no significant differences between men and women or between antibody-positive and antibody-negative RA. They concluded that occupational inhalants are associated with increased RA risk. They noted possible recall bias and exposure misclassification, varying results across studies, little dose-response data, and that inhalants often occur together at work.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Systematic review and meta-analysis (random-effects) of published observational studies; cross-sectional studies were reviewed but left out of the pooled analyses
• Who was studied: 31 published studies (15 case-control, 12 cohort, 4 cross-sectional), published 1994 to 2022, mostly from Sweden (13) and the US (10), found by searching MEDLINE, Embase and Web of Science up to November 20, 2024. 25 studies were pooled in meta-analyses.
• Exposure: Occupational inhalants. Ten types were meta-analyzed: silica, pesticides, asbestos, solvents, oil mist, fertilizers, wood dust, textiles, animal dust and engine exhaust. There were 51 inhalant-RA associations in total, seven of them for asbestos. The asbestos studies included one on vermiculite/asbestos in Libby residents. The article does not specify asbestos fiber types.
• Main results:
  • Seven of the 10 inhalants (silica, asbestos, solvents, pesticides, fertilizers, animal dust and engine exhaust) were significantly associated with an increased risk of developing RA. The relative risks ranged from 1.20 to 1.49 (the abstract states 1.25 to 1.49).
  • Asbestos: the pooled relative risk for developing RA was 1.39 (95% CI 1.05 to 1.84), based on seven studies.
  • Fertilizers showed the highest pooled risk (RR = 1.49, 95% CI 1.13 to 1.97), followed by engine exhaust (RR = 1.45, 95% CI 1.19 to 1.76).
  • Silica had a pooled RR of 1.36 (95% CI 1.18 to 1.56). Pesticides had a pooled RR of 1.32 (95% CI 1.02 to 1.70).
  • The associations for textiles, wood dust and oil mist were not statistically significant.
  • Heterogeneity between studies was high for silica, textile and asbestos.
  • For asbestos, RRs were slightly higher for seropositive than seronegative RA, and slightly higher in men than in women. Overall, the authors found no significant differences by serostatus or by sex.
• The authors' conclusion: The authors concluded that occupational inhalants are associated with increased RA risk. They called for workplace prevention strategies and further research into biologic mechanisms.
• Limitations the authors state:
  • Recall bias and exposure misclassification may affect studies that relied on self-reported data or job-exposure matrixes.
  • There was moderate and high heterogeneity among some of the included studies.
  • The included studies rarely explored dose-response relationships.
  • Many inhalants occur together in workplaces, which makes it hard to isolate the effect of any single exposure.
  • Publication bias could be assessed only for silica, and the funnel plot may have been underpowered.

Topics

Medical terms in this study, explained in our Lexicon: Systematic Review, Meta-Analysis, Prognosis, Relative Risk.

Related studies

• Association of Agricultural, Occupational, and Military Inhalants With Autoantibodies and Disease Features in US Veterans With Rheumatoid Arthritis — A.V. Ebel, G. Lutt, et al. (2021)
• Occupations and exposures in the work environment as determinants for rheumatoid arthritis — A.R. Olsson, T. Skogh, et al. (2004)
• Effects of Libby amphibole asbestos exposure on two models of arthritis in the Lewis rat — K.D. Salazar, C.B. Copeland, et al. (2012)
• Rheumatoid lung changes associated with asbestosis — A.G. Rickards, G.M. Barrett (1958)
• Rheumatoid pneumoconiosis (Caplan's syndrome) in an asbestos worker — W.G. Tellesson (1961)
• Is Male Rheumatoid Arthritis an Occupational Disease? A Review — D. Murphy, D. Hutchinson (2017)

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