LAUSR

white, live in more educated neighborhoods, and have fewer comorbidities. Supplemental analysis of estimated nonlinear associations with PM2.5 and cardiovascular mortality in the lowexposure subcohort indicated that the greatest increase in the HR occurred between 7 and 12 mg/m of PM2.5. In a general sense, the results of this cohort study of adults with COPD are somewhat consistent with other cohort studies of air pollution. Similar PM2.5–CVDmortality associations are observed in broad, population-based cohorts as in the full cohort of adults with COPD (Figure 1). Furthermore, adverse PM2.5–mortality associations are often observed even when long-term average concentrations are below the current annual U.S. PM2.5 national ambient air quality standard for PM2.5 of 12 mg/m 3 (3, 12). As Alexeeff and colleagues clearly note (11), their study contributes to the evidence that long-term exposure to PM2.5 air pollution is a risk factor for CVD and that the current long-term PM2.5 standard is not adequately protective— especially for adults with COPD.