Quantifying the contribution of activity patterns to PM_2.5 exposure inequity between urban and rural residents by a novel method

PM_2.5 pollution variations in different microenvironments would result in PM_2.5 exposure inequity between rural and urban residents. In this study, the real-time PM_2.5 exposure of urban and rural residents in China was examined based on portable PM_2.5 sensors together with activity patterns derived from questionnaire surveys, with a focus on students and senior citizens who are sensitive to air pollution. The results showed that PM_2.5 exposure varied significantly among different resident groups, with higher PM_2.5 exposure of rural residents than those of urban residents. PM_2.5 exposure peaks mostly occurred during (Accompanied) cooking activities owing to strong emissions. Sleeping and resting were the main activities that affected PM_2.5 exposures of different resident groups, accounting for 60.7%–94.5% of total daily exposures. Furthermore, the long duration of sleeping makes it the predominant activity contributing to PM_2.5 exposure inequity. It is necessary to obtain point-to-point respiratory volume (respiratory rate) data when measuring real-time PM_2.5 exposure data and incorporate respiratory volume (respiratory rate) into the analysis of PM_2.5 exposure. For the first time, this study quantified the PM_2.5 exposure inequality based on a novel method and can provide useful information for further studies on the exposure inequity.