title: Chemical characterization and source apportionment of indoor and outdoor fine particulate matter (PM(2.5)) in retirement communities of the Los Angeles Basin.
abstract: Concurrent indoor and outdoor measurements of fine particulate matter (PM2.5) were conducted at three retirement homes in the Los Angeles Basin during two separate phases (cold and warm) between 2005 and 2006. Indoor-to-outdoor relationships of PM2.5 chemical constituents were determined and sources of indoor and outdoor PM2.5 were evaluated using a molecular marker-based chemical mass balance (MM-CMB) model. Indoor levels of elemental carbon (EC) along with metals and trace elements were found to be significantly affected by outdoor sources. EC, in particular, displayed very high indoor-to-outdoor (I/O) mass ratios accompanied by strong I/O correlations, illustrating the significant impact of outdoor sources on indoor levels of EC. Similarly, indoor levels of polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were strongly correlated with their outdoor components and displayed I/O ratios close to unity. On the other hand, concentrations of n-alkanes and organic acids inside the retirement communities were dominated by indoor sources (e.g. food cooking and consumer products), as indicated by their I/O ratios, which exceeded unity. Source apportionment results revealed that vehicular emissions were the major contributor to both indoor and outdoor PM2.5, accounting for 39 and 46% of total mass, respectively. Moreover, the contribution of vehicular sources to indoor levels was generally comparable to its corresponding outdoor estimate. Other water-insoluble organic matter (other WIOM), which accounts for emissions from uncharacterized primary biogenic sources, displayed a wider range of contributions, varying from 2 to 73% of PM2.5, across all sites and phases of the study. Lastly, higher indoor than outdoor contribution of other water-soluble organic matter (other WSOM) was evident at some of the sites, suggesting the production of secondary aerosols as well as direct emissions from primary sources (including cleaning or other consumer products) at the indoor environments.
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors.forename: Sina
authors.initials: S
authors.lastname: Hasheminassab
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Daher
authors.affiliation: University of Wisconsin-Madison, Environmental Chemistry and Technology Program, Madison, WI, USA.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Shafer
authors.affiliation: University of Wisconsin-Madison, Environmental Chemistry and Technology Program, Madison, WI, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Schauer
authors.affiliation: University of California, Department of Epidemiology, School of Medicine, 224 Irvine Hall, Irvine, CA, USA.
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Delfino
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA. Electronic address: sioutas@usc.edu.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Sioutas
mesh_terms: D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis / Q000706:statistics & numerical data; D004784:Environmental Monitoring; D006801:Humans; D015141:Los Angeles; D008670:Metals / Q000032:analysis; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D012179:Retirement; D014131:Trace Elements / Q000032:analysis; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D008670:Metals; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons; D014131:Trace Elements; D001335:Vehicle Emissions
keywords: Indoor air; Indoor–outdoor ratio; Los Angeles Basin; Molecular marker-based chemical mass balance model; PM(2.5); Source apportionment