Health effects of PM2.5 emissions from on-road vehicles during weekdays and weekends in Beijing, China

Mobile source emissions have significantly contributed to fine particulate matter (PM2.5) pollution in urban atmospheric environments. Few studies have explored on-road vehicular PM2.5 emissions and the health effects attributed to these emissions under different traffic conditions. Based on driving data obtained from 20000 taxi receipts, a motor vehicle emission simulator (MOVES) model was used to estimate the PM2.5 emission levels of motor vehicles in the urban area within the Sixth Ring Road of Beijing (SRRB) on weekdays and weekends, respectively. Two different PM2.5 exposure scenarios were further simulated using an atmospheric dispersion model. Subsequently, the health effects attributable to traffic-related PM2.5 exposure were quantified by using exposure-response function to calculate the population acute morbidity and premature mortality during different time periods. We found that PM2.5 emission levels of motor vehicles on normal weekdays were overall higher than those on weekends. The median vehicular PM2.5 dispersion concentration in the study area was 2.68 mu g/m(3) on weekdays and 1.82 mu g/m(3) on weekends. Annually, there were 4435 premature deaths attributed to vehicle emissions (95% confidence interval (CI): 3655, 4904) under weekday exposure conditions, and this number sharply decreased to 3462 (95% CI: 3052, 4011) on weekends. Considering the hourly measurements, road traffic emissions have the greatest impact on public health during morning rush hour (8:00 a.m.). Total PM2.5 emissions were closely associated with road traffic conditions and largely determined the magnitude of the health impacts caused by traffic-related PM2.5 exposure. These findings provide information to aid in formulating reasonable public health policies to address vehicular PM2.5 emission-induced health implications.