Fine Particulate Matter Air Pollution, Proximity to Traffic, and Aortic Atherosclerosis

Background: The initiation and acceleration of atherosclerosis is hypothesized as a physiologic mechanism underlying associations between air pollution and cardiovascular effects. Despite toxicologic evidence, epidemiologic data are limited. Methods: In this cross-sectional analysis we investigated exposure to fine particulate matter ( $\text{PM}_{2.5}$ ) and residential proximity to major roads in relation to abdominal aortic calcification, a sensitive indicator of systemic atherosclerosis. Aortic calcification was measured by computed tomography among 1147 persons, in 5 US metropolitan areas, enrolled in the Multi-Ethnic Study of Atherosclerosis. The presence and quantity of aortic calcification were modeled using relative risk regression and linear regression, respectively, with adjustment for potential confounders. Results: We observed a slightly elevated risk of arotic calcification (RR = 1.06; 95% confidence interval = 0.96-1.16) with a 10 μg/m³ contrast in $\text{PM}_{2.5}$ . The $\text{PM}_{2.5}-\text{associated}$ risk of aortic calcification was stronger among participants with long-term residence near a $\text{PM}_{2.5}$ monitor (RR = 1.11; 1.00-1.24) and among participants not recently employed outside the home (RR = 1.10; 1.00-1.22). $\text{PM}_{2.5}$ was not associated with an increase in the quantity of aortic calcification (Agatston score) and no roadway proximity effects were noted. There was indication of $\text{PM}_{2.5}$ effect modification by lipid-lowering medication use, with greater effects among users, and $\text{PM}_{2.5}$ associations were observed most consistently among Hispanics. Conclusions: Although we did not find persuasive associations across our full study population, associations were stronger among participants with less exposure misclassification. These findings support the hypothesis of a relationship between particulate air pollution and systemic atherosclerosis.