Estimation of PM2.5 infiltration factors and personal exposure factors in two megacities, China

This study estimates infiltration factors (Finf) and ambient personal exposure factors (Fpex) for fine particulate matter (PM2.5) in two Chinese megacities, and constructs predictive models to explore their determinants. Personal-indoor-outdoor PM2.5 filter samples were collected for five consecutive days from 33 residences (of retired adults) in Nanjing (NJ) and Beijing (BJ), China, in both the non-heating season (NHS) and the heating season (HS). Elemental sulfur in filter deposits was determined by energy-dispersive X-ray fluorescence for PM2.5Finf and Fpex estimations. Season-specific models developed by stepwise multiple linear regression were evaluated using R2 and root mean square error (RMSE). The median [interquartile range (IQR)] of Finf varied from 0.76 (0.15) in the HS to 0.93 (0.11) in the NHS in NJ; and from 0.67 (0.16) to 0.86 (0.12) in BJ. Similarly, Fpex was significantly higher during the NHS [NJ: 0.95 (0.07); BJ: 0.89 (0.14)] than during the HS [NJ: 0.76 (0.17); BJ: 0.67 (0.11); p