Atmospheric Environment 38 (2004) 2867–2877 Trace elements in fine particulate matter within a community in western Riverside County, CA: focus on residential sites and a local high school Kwangsam Na a , Aniket A. Sawant a,b , David R. Cocker III a,b, * a Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92521, USA b Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA Received 10 September 2003; accepted 20 February 2004 Abstract Measurements of mass concentrations of 35 trace elements (TEs) and of total fine particulate matter (PM 2.5 ) were conductedat20residencesandsixhighschoolroomsinMiraLoma,California,fromSeptember2001toJanuary2002. Sulfur (S) and silicon (Si) were the most abundant TEs measured (excluding a residence with heavy smokers). On average,totalTEconcentrationswerelowerindoorsrelativetooutdoors;theproportionofTEsintotalPM 2.5 wasalso lower indoors relative to outdoors. Among indoor sites, TE concentrations were found to be lower inside the schoolrooms relative to inside the residences. Environmental tobacco smoke (ETS) was found to contribute significantly to elevated levels of total TE inside residences; however, concentrations of carcinogenic TEs were not significantly different between residences with and without smokers. Potassium (K) and chlorine (Cl) were the most abundantspeciesinaresidencewithfrequentindoorsmokers.Combustion-relatedelementsweremoreenrichedinside the residences relative to crustal elements. r 2004 Elsevier Ltd. All rights reserved. Keywords: Trace elements; PM 2.5 ; Environmental tobacco smoke; Indoor air quality; Outdoor-to-indoor ratio 1. Introduction Fine particulate matter with aerodynamic diameter smaller than 2.5 mm (PM 2.5 ) has received considerable attention in recent years as it is easily inhaled and deposited within the lungs, leading to respiratory distress and increased mortality rates (Seaton et al., 1995; Monn et al., 1997). It has been documented that the average person spends approximately 85% of their timeindoors(Jenkinsetal.,1992).Therefore,onemight expectasignificantfractionoftotalpersonalexposureto PM 2.5 to occur within the indoor environment. Indoor particulate matter concentration is influenced byindooremissionsources(e.g.,environmentaltobacco smoke(ETS),cooking,resuspensionbymovement,etc.), outdoor-to-indoor transport (e.g., ventilation and infil- tration) and removal mechanisms (e.g., deposition and filtration during outdoor-to-indoor transport) (Quack- enboss et al., 1989; Thatcher and Laytol, 1995; Moriske et al., 1996). An indoor environment may shield against outdoor pollutants because outdoor air must penetrate the envelope surrounding the indoor environment, offering ample time for filtration and deposition. However, when particles are emitted from indoor sources,particleconcentrationsremainatelevatedlevels in a confined space. Some trace elements (TEs) present in PM 2.5 are human or animal carcinogens including As, Be, Cd, ARTICLE IN PRESS AE International – North America *Corresponding author. Tel.: +1-909-781-5695; fax: +1-909- 781-5790. E-mail address: dcocker@engr.ucr.edu (D.R. Cocker III). 1352-2310/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2004.02.022