Characterization of PM2.5 and selected gas-phase compounds at multiple indoor and outdoor sites in Mira Loma, California

Fine particulate matter (PM2.5) and gas-phase carbonyls are categories of atmospheric pollutants that have components known to adversely affect human health. This work describes the chemical characterization of PM2.5 and 13 carbonyl compounds measured inside 20 residences and 7 schoolrooms in Mira Loma, western Riverside County, California. Median PM2.5 concentrations were 32.2 and 13.2 mug m(-3), while median total carbonyl concentrations were 50.8 and 62.9 mug m(-3) inside the residences and schoolrooms, respectively. Organic carbon was typically the largest contributor to indoor PM2.5 concentrations, while formaldehyde, acetaldehyde and acetone were the largest contributors to gas-phase carbonyl concentrations. Indoor/outdoor ratios for PM2.5 were greater for residences than for schoolrooms, while the reverse was true for these ratios for gas-phase carbonyls. These results are likely due to effective PM2.5 removal by filtration on the HVAC and the presence of more significant indoor carbonyl sources within the schoolrooms. Regression analysis of indoor and outdoor pollutant concentrations showed that for PM2.5, sulfate and nitrate were the best- and worst-correlated species, respectively. This suggests that nitrate is a poor tracer for outdoor-to-indoor PM2.5 transfer. In addition, no significant correlations were observed for any of the carbonyl compounds measured. This further suggests the presence of indoor carbonyl sources inside the schoolrooms, and that indoor air quality especially in terms of carbonyl concentrations may be substantially poorer than outdoor air quality. (C) 2004 Elsevier Ltd. All rights reserved.