Characteristics of particle matter and associated polycyclic aromatic hydrocarbons in indoor and outdoor air in two cities in Shizuoka, Japan

Indoor and outdoor concentrations of particle matter (PM) and associated polycyclic aromatic hydrocarbons (PAHs) in summer and winter in two industrial cities in Shizuoka, Japan, were determined. Fine particles (PM2.5) accounted for 44–56% of the total suspended PM. Most (>80%) of the PAHs associated with the particles were in the PM2.5 fraction. The concentration of PAHs, but not particles, was elevated in winter. A strong correlation (p < 0.01) between indoor and outdoor air was found for almost PAHs measured, but not for particles. Ratios of indoor to outdoor PAH concentrations showed that the indoor PAHs were mostly from outdoor sources, and the trends were especially noticeable in winter. In spite of the high contribution of PAHs to PM2.5, no significant correlation was found between the concentration of PM2.5 and the associated PAH concentration either indoors or outdoors. Outdoors, individual relative PAH concentrations (normalized to benzo[e]pyrene concentration) were greater in winter than in summer for light molecular PAHs ( 4 rings), as well as for benzo[a]pyrene (BaP), whereas the seasonal differences for other heavy molecular PAHs (except BaP) were negligible. This suggested that the contributions of decay reactions such as photodegradation were relatively small for the heavy molecular PAHs. Carcinogenic risks associated with the inhalation of indoor PAHs were assessed, and BaP showed the greatest contribution (51–64%) to the total carcinogenic risk.