Respiratory Exacerbations Increase with Chronic PM2.5 Exposure in Current and Former Smokers

RationaleShort-term exposure to fine particulates (PM2.5) transiently increases the risk of respiratory exacerbations, but the contribution of chronic, long-term particulate exposure to respiratory exacerbations is poorly defined. ObjectivesTo assess long-term effects of PM2.5 exposure on risk of severe respiratory exacerbations. MethodsA longitudinal cohort of current and former smokers with and without COPD were surveyed every six months for severe exacerbation events. PM2.5 concentrations at participant addresses were estimated using satellite, reanalysis, and ground-based monitoring data sources. Measurements and Main ResultsThe relative risk of severe exacerbation increased by a factor of 1.516 (CI: 1.226, 1.873; p = 0.00012) for every 10 g/m3 increase in long-term PM2.5 exposure across all participants. The effect in the non-COPD participants was greater, with a relative risk of 2.639 (CI: 1.840, 3.756; p<0.0001). Significant effect modifiers with greater effect of PM2.5, included prior exacerbations, female sex, and neighborhood characteristics and as well as smoking status, white race, disease severity, asthma diagnosis, and age at enrollment. Significant positive associations for PM2.5 on exacerbations were identified at levels below the EPA primary annual standard for PM2.5 of 9.0 g/m3. ConclusionsPersistent exposure to fine particulates is a significant risk factor for severe respiratory exacerbations in current and former smokers, and in patients with or at risk of COPD. The effect of fine particulates on the risk of severe exacerbations appears to be greater in those current and former smokers without COPD. The EPA annual PM2.5 standard may be inadequate to prevent ongoing lung injury.