Source characterization of BTEX in indoor microenvironments in Hong Kong

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>1 was considered as an indicator for indoor sources. For BTEX in different indoor environments except for schools, some of the pollutants were dominated by outdoor sources while others mainly originated from indoor sources. In schools, however, the BTEX predominantly originated from outdoor sources. The potential sources of BTEX in indoor environments were also identified by using principal component analysis and nonparametric Kruskal–Wallis test. The number of variables was reduced to two and one new factors for indoor and outdoor data, respectively. These factors were related to certain source characteristics. It is shown that the type of land use, the use of printers, the traffic condition, the cooking style, the type of gas stove, smoking and internal decoration strongly influence the indoor concentrations of BTEX (p<0.05). Significant difference of BTEX concentrations in the five types of indoor environments were also observed (p<0.05).

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