Respiratory Exacerbations Increase with Chronic PM 2.5 Exposure in Current and Former Smokers
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Rationale
Short term exposure to fine particulates (PM 2.5 ) increases the risk of respiratory exacerbations, but the effects frequently resolve. The contribution of chronic, long-term exposure, to respiratory exacerbations is poorly defined.
Objectives
To assess the long-term effects of PM 2.5 on the risk of severe exacerbations in current and former smokers.
Methods
A longitudinal cohort of current and former smokers with and without COPD study were surveyed every six months for exacerbation events. PM 2.5 concentrations at participant geo-coded addresses were estimated using satellite, reanalysis, and ground-based monitoring sources.
Measurements and Main Results
The relative risk of severe exacerbation increased by a factor of 1.509 (CI: 1.209, 1.884; p = 0.00028) for every 10 μg/m 3 increase in long-term PM 2.5 exposure across all participants. The effect in the GOLD 0 participants was greater with a relative risk of 2.674 (1.836 -3.894, p<0.0001). Significant effect modifiers with greater impact of PM 2.5 included prior exacerbations, female sex, neighborhood characteristics and study period as well as smoking status, white race, disease severity, asthma diagnosis, and age at enrollment. Significant positive associations for exacerbations were identified at levels below 8 μg/m 3 . Weak evidence was found for the mediation of the association between PM 2.5 exposure and present exacerbations by a history of pre-enrollment exacerbations.
Conclusions
Persistent exposure to particulate air pollution is a significant risk factor for respiratory exacerbations in current and former smokers, and in patients with or at risk of COPD. The current primary annual EPA standard of 9μg/m 3 for PM 2.5 may be inadequate to prevent ongoing lung injury.
