Atmospheric Environment 37 (2003) 73–82 SourcecharacterizationofBTEXinindoormicroenvironments in Hong Kong H. Guo a, *, S.C. Lee a ,W.M.Li a ,J.J.Cao b a Department of Civil and Structural Engineering, Research Centre for Urban Environmental Technology and Management, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong b State Key Laboratory of Loess & Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China Received 10 May 2002; accepted 16 August 2002 Abstract Levels of benzene, toluene, ethylbenzene and the xylenes (BTEX) in different indoor microenvironments such as offices, homes, schools, shopping malls and restaurants were investigated in Hong Kong. Different indoor environments including six offices, six homes, six air-conditioned classrooms, six shopping malls and four restaurants were selected in Hong Kong for indoor and outdoor BTEX measurement. This study is aimed to determine qualitatively or semi-quantitatively sources of BTEX. Source identification is possible by determining the indoor/ outdoor (I =O) concentration ratio. An I =O ratio > 1wasconsideredasanindicatorforindoorsources.ForBTEXin different indoor environments except for schools, some of the pollutants were dominated by outdoor sources while othersmainlyoriginatedfromindoorsources.Inschools,however,theBTEXpredominantlyoriginatedfromoutdoor sources. The potential sources of BTEX in indoor environments were also identified by using principal component analysisandnonparametricKruskal–Wallistest.Thenumberofvariableswasreducedtotwoandonenewfactorsfor indoorandoutdoordata,respectively.Thesefactorswererelatedtocertainsourcecharacteristics.Itisshownthatthe typeoflanduse,theuseofprinters,thetrafficcondition,thecookingstyle,thetypeofgasstove,smokingandinternal decoration strongly influence the indoor concentrations of BTEX (po0:05). Significant difference of BTEX concentrations in the five types of indoor environments were also observed (po0:05). r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Indoor air pollution; BTEX; I =O ratios; Statistical analysis; Principal component analysis 1. Introduction Thequalityofindoorairiscausingincreasingconcern in the community. Volatile organic compounds (VOCs) are major indoor air contaminants. Many studies have indicated that indoor air is contaminated to various degrees by a wide variety of hydrocarbons and hydrocarbon derivatives including aliphatics, aromatics, alkylbenzenes, ketones, polycyclic aromatics and chlori- natedhydrocarbons(Godish,1989).Amongthevolatile indoor air pollutants, aromatic hydrocarbons, such as benzene,toluene,ethylbenzene,andtheisomericxylenes (BTEX), are particularly abundant in the indoor environment (Krause et al., 1991; Raaschou-Nielsen et al., 1997; Ilgen et al., 2001a,b). Previous studies demonstrated that vehicular emis- sions and industrial sources are the major sources of ambientVOCs(ScheffandWadden,1993;Pfeffer,1994; Vega et al., 2000; Ho et al., 2002; Chan et al., 2002), while the sources of VOCs are quite numerous within anyindoorenvironment.Thesesourcesincludecombus- tion by-products, cooking, construction materials, fur- nishings, paints, varnishes and solvents, adhesives and caulks, office equipment, and consumer products. AE International – Asia *Corresponding author. Tel.: +852-2766-6017; fax: +852- 2334-6389. E-mail address: ceguohai@polyu.edu.hk (H. Guo). 1352-2310/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S1352-2310(02)00724-0