Carotid Intima-Media Thickness and Long-Term Exposure to Traffic-Related Air Pollution in Middle-Aged Residents of Taiwan: A Cross-Sectional Study

BACKGROUND: Associations between long-term exposure to air pollution and carotid intima-media thickness (CIMT) have inconsistent findings. OBJECTIVES: In this study we aimed to evaluate association between 1-year average exposure to traffic-related air pollution and CIMT in middle-aged adults in Asia. METHODS: CIMT was measured in Taipei, Taiwan, between 2009 and 2011 in 689 volunteers 35–65 years of age who were recruited as the control subjects of an acute coronary heart disease cohort study. We applied land-use regression models developed by the European Study of Cohorts for Air Pollution Effects (ESCAPE) to estimate each subject’s 1-year average exposure to traffic-related air pollutants with particulate matter diameters ≤ 10 μm (PM(10)) and ≤ 2.5 μm (PM(2.5)) and the absorbance levels of PM(2.5) (PM(2.5)abs), nitrogen dioxide (NO(2)), and nitrogen oxides (NO(x)) in the urban environment. RESULTS: One-year average air pollution exposures were 44.21 ± 4.19 μg/m(3) for PM(10), 27.34 ± 5.12 μg/m(3) for PM(2.5), and (1.97 ± 0.36) × 10(–5)/m for PM(2.5)abs. Multivariate regression analyses showed average percentage increases in maximum left CIMT of 4.23% (95% CI: 0.32, 8.13) per 1.0 × 10(–5)/m increase in PM(2.5)abs; 3.72% (95% CI: 0.32, 7.11) per 10-μg/m(3) increase in PM(10); 2.81% (95% CI: 0.32, 5.31) per 20-μg/m(3) increase in NO(2); and 0.74% (95% CI: 0.08, 1.41) per 10-μg/m(3) increase in NO(x). The associations were not evident for right CIMT, and PM(2.5) mass concentration was not associated with the outcomes. CONCLUSIONS: Long-term exposures to traffic-related air pollution of PM(2.5)abs, PM(10), NO(2), and NO(x) were positively associated with subclinical atherosclerosis in middle-aged adults. CITATION: Su TC, Hwang JJ, Shen YC, Chan CC. 2015. Carotid intima–media thickness and long-term exposure to traffic-related air pollution in middle-aged residents of Taiwan: a cross-sectional study. Environ Health Perspect 123:773–778; http://dx.doi.org/10.1289/ehp.1408553