- Long-term exposure to ozone and road traffic are associated with increased risk for rheumatoid arthritis (RA), but particulate matter exposures are protective for development of RA, according to a large meta-analysis.
- Gaseous pollutants (nitrogen dioxide, carbon monoxide, and sulfur dioxide) had no association with RA.
Why this matters
- This is the first meta-analysis to investigate the relationship between long-term outdoor air pollutant exposures and RA.
- Meta-analysis of 8 studies (3 case-control and 5 cohort studies with total of >1,000,000 participants) after a search of PubMed, Embase, and Web of Science.
- Funding: National Natural Science Foundation of China.
- Ozone was associated with an increased risk for RA (per unit increase in ozone exposure: relative risk [RR], 1.16; 95% CI, 1.15-1.18), as was proximity to road traffic (RR, 1.34; 95% CI, 1.11-1.62).
- 2 types of air pollutants were associated with a decreased risk for RA:
- Particulate matter 2.5 μm in size (PM2.5) protected against incident RA (RR, 0.90; 95% CI, 0.81-0.99).
- Particulate matter 10 μm in size (PM10) protected against onset of seropositive RA (RR, 0.79; 95% CI, 0.69-0.92).
- Long-term exposure to nitrogen dioxide, carbon monoxide, and sulfur dioxide had no association with RA.
- Observational designs.