Fine particulate matter air pollution, proximity to traffic, and aortic atherosclerosis

Abstract

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 (PM2.5) 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 aortic calcification (RR = 1.06; 95% confidence interval = 0.96-1.16) with a 10 microg/m contrast in PM2.5. The PM2.5-associated risk of aortic calcification was stronger among participants with long-term residence near a PM2.5 monitor (RR = 1.11; 1.00-1.24) and among participants not recently employed outside the home (RR = 1.10; 1.00-1.22). PM2.5 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 PM2.5 effect modification by lipid-lowering medication use, with greater effects among users, and PM2.5 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.

Figure 1

Relative risks of detectable calcium for a 10-μg/m³ contrast in PM_2.5 and for residing near a major road estimated from 6 models with increasing adjustment for confounders. Crude: Adjusted for scanner technology only (see text). Model 2: Adjusted for scanner technology + age, gender, ethnicity Model 3: Model 2 + BMI (body mass index), smoking, diabetes Model 4: Model 3 + education, income Model 5: Model 4 + blood lipids, lipid-lowering medications Model 6: Model 5 + blood pressure, anti-hypertensive medications

Figure 2

Relative risks of detectable calcium for a 10-μg/m³ contrast in PM_2.5 and residing near a major road estimated from the fully adjusted model after stratifying by sex, age, diabetes, obesity, lipid-lowering medication (LLM) use, education, income, and ethnicity. The number of participants within each stratum is given in parentheses. ^* PM_2.5 interaction or trend p-value < 0.1. ^** PM_2.5 interaction or trend p-value < 0.05. ⁺ Near Road interaction or trend p-value < 0.1. ⁺⁺ Near Road interaction or trend p-value < 0.05. H = Hispanic; B = Black; W = White; C = Chinese

Figure 3

Change in Agatston score associated with a 10-μg/m³ contrast in PM_2.5 and residing near a major road estimated from 6 models with increasing adjustment for confounders. Crude: Adjusted for scanner technology only (see text). Model 2: Adjusted for scanner technology + age, gender, ethnicity Model 3: Model 2 + BMI (body mass index), smoking, diabetes Model 4: Model 3 + education, income Model 5: Model 4 + blood lipids, lipid-lowering medications Model 6: Model 5 + blood pressure, anti-hypertensive medications Note: outcome variable is log-transformed Agatston score among 851 participants with Agatston score > 0.

Figure 4

Change in Agatston score associated with a 10-μg/m³ contrast in PM_2.5 and for residing near a major road estimated from the fully adjusted model after stratifying by sex, age, diabetes, obesity, lipid-lowering medication (LLM) use, education, income, and ethnicity: participants with nonzero calcium. The number of participants within each stratum is given in parentheses. ^* PM_2.5 interaction or trend p-value < 0.1. ^** PM_2.5 interaction or trend p-value < 0.05. ⁺ Near Road interaction or trend p-value < 0.1. ⁺⁺ Near Road interaction or trend p-value < 0.05. H = Hispanic; B = Black; W = White; C = Chinese 0.

Figure 5

Change in Agatston score associated with a 10-μg/m³ contrast in PM_2.5 and for residing near a major road estimated from the fully adjusted model after stratifying by sex, age, diabetes, obesity, lipid-lowering medication (LLM) use, education, income, and ethnicity: all participants. The number of participants within each stratum is given in parentheses. ^* PM_2.5 interaction or trend p-value < 0.1. ^** PM_2.5 interaction or trend p-value < 0.05. ⁺ Near Road interaction or trend p-value < 0.1. ⁺⁺ Near Road interaction or trend p-value < 0.05. H = Hispanic; B = Black; W = White; C = Chinese