Estimations of infiltration factors of diurnal PM2.5 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.

Keywords: PM2.5; children; heavy metal; indoor air quality; infiltration factor.