Associations of Time-Weighted Individual Exposure to Ambient Particulate Matter with Carotid Atherosclerosis in Beijing, China

Abstract Background Time-location information, including time spent indoors and outdoors around residential and work places and on commuting, physical activity, infiltrated ambient pollution and traffic transportations, was less considered estimating individual exposure to ambient pollution. Studies investigating the association between individual exposure to particulate matter (PM) with aerodynamic diameter <10 μm (PM10) and <2.5 μm (PM2.5) and carotid atherosclerosis obtained inconsistent results. Moreover, combined effect of mixed pollutants on carotid atherosclerosis was not fully explored because of high collinearity. We aimed to investigate the association between long-term individual time-weighted exposure to PM2.5 and PM10 and the risk of carotid atherosclerosis, and further explore the overall effects of multiple pollutants on carotid atherosclerosis. Methods Daily concentration of ambient pollutants was estimated by land-use regression model at both residential and work addresses, and 1-5 years’ time-weighted individual exposure was calculated by further considering personal activity pattern and infiltrated ambient pollution. We explored the association of PM2.5and PM10 with carotid atherosclerosis and pooled the overall effect of multiple pollutants by quantile g-computation. Results The significant association between time-weighted exposure to PM2.5 and PM10and carotid atherosclerosis was observed. Per interquartile range increase in 2-year exposure to PM2.5 (Hazard ratio (HR): 1.322, 95% confidence interval (CI): 1.219-1.434) and PM10 (HR:1.213, 95% CI: 1.116-1.319) showed the strongest association with carotid atherosclerosis, respectively. Individuals in higher quartiles of pollutants were at higher risk for carotid atherosclerosis. The linear and nonlinear relationships interpreted the upward trend of the risk for carotid atherosclerosis with increasing level of pollutant concentrations. Moreover, the overall adverse effects of multiple pollutants were further demonstrated. Conclusions Individual time-weighted exposure to PM2.5, PM10 and mixed pollutants was associated with carotid atherosclerosis. It is necessary to reduce individual pollutant exposure to inhibit the risk of carotid atherosclerosis and subsequently alleviate disease burdens of atherosclerotic diseases.