Indoor PM2.5 in Santiago, Chile, spring 2012: Source apportionment and outdoor contributions

Abstract

Indoor and outdoor PM2.5 sampling campaigns were carried out at Santiago, Chile (6 million inhabitants, 33.5°S, 70.6°W) in spring 2012. A pair of samplers was placed inside each household studied and an additional pair of samplers was placed at a fixed outdoor location for measuring trace elements and elemental (EC) and organic carbon (OC) in Teflon and quartz filters, respectively. A total of 47 households in downtown Santiago were included in this study. Mean outdoor and indoor PM2.5 concentrations were 19.2 and 21.6 μg/m3, respectively. Indoor concentrations of PM2.5 were affected by socioeconomic status (p = 0.048) but no such evidence was found for PM2.5 species, except lead (p = 0.046). Estimated species infiltration factors were 0.70 (±0.19), 0.98 (±0.21), 0.80 (±0.12) and 0.80 (±0.03) for PM2.5, OC, EC and sulfur, respectively. Estimated household infiltration factors had a median of 0.75, mean of 0.78, standard deviation of 0.18 and interquartile range (IQR) 0.67–0.86.For the very first time, Positive Matrix Factorization (PMF3) was applied to an indoor PM2.5 chemical composition data set measured at Santiago. Source identification was carried out by inspection of key species and by comparison with published source profiles; six sources were identified. Three of them were outdoor contributions: motor vehicles with 5.6 (±0.7) μg/m3, street dust with 2.9 (±0.5) μg/m3 and secondary sulfates with 3.4 (±0.5) μg/m3. The indoor sources were: indoor dust with 1.6 (±0.3) μg/m3, cleaning and cooking with 2.3 (±0.3) μg/m3 and cooking and environmental tobacco smoke with 6.1 (±0.7) μg/m3. There is potential for further reducing PM2.5 population exposure in the short term —by improving ventilation of indoor air and controlling indoor sources — and in the long term — with filtration of outdoor air and household improvements to reduce air change rates.