Distinguishing urban-rural difference in Chinese population exposure to ambient air pollutants

Using outdoor concentrations as surrogates of human exposure to ambient air pollutants introduces significant errors, as people spend the majority of their lives indoors. The infiltration factor and exposure factor are widely employed to modify outdoor-originated air pollution exposure. However, previous studies of the Chinese population lacked sufficient data on rural residents, limiting the representativeness and accuracy of the results. Here, we modeled the infiltration factor and exposure factor of five ambient air pollutants (NO2, SO2, O3, PM2.5 and PM10) in both rural and urban areas across 31 Chinese provinces and conducted field experiments in Beijing, Yunnan, Guizhou and Sichuan Provinces for 8 months to validate the modeling results. The infiltration factor and exposure factor vary between different air pollutants, with the exposure factor of PM2.5 reaching 70% for rural residents. Additionally, we found significant regional, seasonal, gender, and age differences between the urban and rural modification factors: infiltration and exposure factors in rural areas are generally greater than those in urban areas, especially in Northeast China; and the urban-rural exposure disparity is most pronounced during winter, with a relative difference of up to 28% for SO2. The results are expected to be applied to modify population exposure to ambient air pollutants among Chinese urban and rural residents, promote accurate estimations of population health risks and further contribute to the implementation of targeted interventions.