Indoor characteristics of polycyclic aromatic hydrocarbons in the urban atmosphere of Taipei

Fifteen polycyclic aromatic hydrocarbons (PAHs) were measured simultaneously in the indoor and outdoor air of 14 homes in the Taipei urban area in both summer and winter seasons. It was indicated that indoor and outdoor geometric mean PAH concentrations were 267 and 209 ng m−3, respectively. In addition, it was observed that indoor PAH concentrations generally exceeded the corresponding outdoor PAH concentrations. Moreover, the median value of indoor/outdoor PAH ratios was observed to be 1.23 which might demonstrate that there was no presence of significant indoor PAH sources in this subtropical region. Concerning PAH seasonal variations, the observed lower winter/summer ratios might be related to the absence of domestic heating in residential environments. With regard to PAH compositions, the most abundant PAH found indoors was naphthalene. Fluorene and phenanthrene were the second and third highest concentrations found indoors and outdoors. In incensed homes, PAHs could be contributed mainly to incense burning as well as background sources might be the largest contributor to PAHs in non-incensed homes