Wang M, Aaron CP, Madrigano J, et al. – In this cohort study, conducted between 2000 and 2018, that involved 5,780 participants in 6 US metropolitan regions followed up for a median of 10 years, researchers evaluated the longitudinal correlation of ambient ozone (O₃), fine particulate matter (PM_2.5), oxides of nitrogen (NO_x), and black carbon exposure with variation in percent emphysema evaluated through CT imaging and lung function. Mean ambient concentrations of PM_2.5 and NO_x—but not O₃—declined substantially during follow-up. At study baseline, ambient concentrations of O₃, PM_2.5, NO_x, and black carbon were significantly correlated with larger rises in percent emphysema per 10 years. During follow-up, ambient O₃ and NO_x concentrations—but not PM_2.5 concentrations—were also significantly related to higher rises in percent emphysema. Ambient O₃ concentrations—but not other pollutants—at baseline and during follow-up were significantly correlated with a higher decrease in forced expiratory volume in 1 second per 10 years. Hence, long-term exposure to ambient air pollutants was significantly related to rising emphysema evaluated quantitatively using CT imaging and lung function.