Estimations of infiltration factors of diurnal PM _2.5 and heavy metals in children’s bedrooms

Abstract

Children are the sensitive population to fine particulate matter (PM 2.5 ) exposure and spend most of their time in bedroom. Infiltration factor (F inf ) can be used to calculate the fraction of total indoor PM 2.5 with outdoor origin to increase the accuracy of exposure assessment. However, studies have ignored the diurnal variations of PM 2.5 F inf values, and a few studies have estimated F inf values for heavy metals in PM 2.5 in children's bedrooms. To calculate the PM 2.5 F inf , real-time indoor and outdoor PM 2.5 concentrations and occupants' activities were collected in 56 study bedrooms. At 22 of the 56 study bedrooms, PM 2.5 samples were also collected for heavy metals analysis.We noted the PM 2.5 F inf was higher during the daytime (0.70 ± 0.23) than nighttime (0.54 ± 0.27) during the hot season, and the time of air conditioner use was longer at nighttime. The largest F inf value of heavy metal was V (0.88 ± 0.25), followed by Pb (0.85 ± 0.28), Mn (0.72 ± 0.26), Cr (0.69 ± 0.35), and Zn (0.61 ± 0.32), with a larger variation. Our findings suggest that the estimations of diurnal PM 2.5 and heavy metals F inf values are necessary to increase the accuracy of exposure assessment.