Reduction in population exposure to PM2.5 and cancer risk due to PM2.5-bound PAHs exposure in Beijing, China during the APEC meeting.

Radical measures for controlling ambient air pollution sources were employed by the Chinese government during the Asia-Pacific Economic Cooperation (APEC) meeting in 2014, providing a unique case to evaluate the health effect benefits from such measures. To examine the cancer risk reduction from the source control measures during the APEC meeting, we estimated the reduction in population exposure to PM2.5 and PAHs and the reduction in PAHs-associated cancer risk if the control measures were sustained over time. We determined the population exposure to PM2.5 and PM2.5-bound PAHs for the 21.52 million Beijing residents using a Land Use Regression model to determine the spatial distribution of PM2.5 and a Monte Carlo approach to revise indoor/outdoor infiltration factor and time activity patterns. Into the model and approach, we incorporated the spatial variance and indoor/outdoor differences in the PM2.5 and PM2.5-bound PAHs concentrations, based on measurements. We then estimated lung cancer risk using the population attributable fraction (PAF), assuming the control measures were sustained over time. The mean PM2.5 exposure concentration decreased from 37.5 μg/m3 (CI:17.1-74.9 μg/m3) to 24.0 μg/m3 (CI:10.2-47.7 μg/m3), whereas the mean PM2.5-bound equivalent benzo[a]pyrene (BaPeq) exposure concentration decreased from 7.1 ng/m3 (CI:3.3-14.2 ng/m3) to 4.2 ng/m3 (CI:1.8-7.7 ng/m3), resulting in a reduction in the lung cancer PAF from 0.75% to 0.45%, if the measures were sustained over time.