Ambient air pollution and pulmonary vascular volume on computed tomography: The MESA Air Pollution and Lung cohort studies

Background: Air pollution alters small pulmonary vessels in animal models. We hypothesised that longterm ambient air pollution exposure would be associated with differences in pulmonary vascular volumes in a population-based study. Methods: The Multi-Ethnic Study of Atherosclerosis recruited adults in six US cities. Personalised longterm exposures to ambient black carbon, nitrogen dioxide (NO₂), oxides of nitrogen (NO_x), particulate matter with a 50% cut-off aerodynamic diameter of <2.5 μm (PM2.5) and ozone were estimated using spatiotemporal models. In 2010-2012, total pulmonary vascular volume was measured as the volume of detectable pulmonary arteries and veins, including vessel walls and luminal blood volume, on noncontrast chest computed tomography (TPVVCT). Peripheral TPVVCT was limited to the peripheral 2 cm to isolate smaller vessels. Linear regression adjusted for demographics, anthropometrics, smoking, second-hand smoke, renal function and scanner manufacturer. Results: The mean±SD age of the 3023 participants was 69.3±9.3 years; 46% were never-smokers. Mean exposures were 0.80 μg·m^-3 black carbon, 14.6 ppb NO₂ and 11.0 μg·m^-3 ambient PM2.5. Mean±SD peripheral TPVVCT was 79.2±18.2 cm³ and TPVVCT was 129.3±35.1 cm³. Greater black carbon exposure was associated with a larger peripheral TPVVCT, including after adjustment for city (mean difference 0.41 (95% CI 0.03-0.79) cm³ per interquartile range; p=0.036). Associations for peripheral TPVVCT with NO₂ were similar but nonsignificant after city adjustment, while those for PM2.5 were of similar magnitude but nonsignificant after full adjustment. There were no associations for NO_x or ozone, or between any pollutant and TPVVCT. Conclusions: Long-term black carbon exposure was associated with a larger peripheral TPVVCT, suggesting diesel exhaust may contribute to remodelling of small pulmonary vessels in the general population.