Characterization and carcinogenic risk assessment of polycyclic aromatic hydrocarbons in the respirable fraction of airborne particles in the Bangkok Metropolitan area

In this study, the characteristics of polycyclic aromatic hydrocarbons (PAHs) in airborne particles equal to or less than 10 mu m (PM10), collected from the Bangkok urban air, were investigated. Sixteen PAHs content in PM10 were simultaneously measured. High molecular weight PAHs (four-, five-, and six-ring) were more abundant in airborne particles (91.7% of total PAHs) than those of low molecular weight PAHs (two-, and three-ring). Further, 71.4% of the total PAHs found in the study sites are potentially carcinogenic PAHs. Benzo[a]pyrene (BaP) was a prominent carcinogenic compound for PAH mixtures found in the area. Correlation analysis revealed that there is a close correlation between the concentration of carcinogenic PAHs and amount of PM10. This is due to their absorptivity property on the surface of the particles. In this study the lifetime lung cancer risk was estimated from the seven carcinogenic PAHs using the toxicity equivalent factor (TEF). The probable number of lung cancer cases in Bangkok Metropolitan was estimated at 27 cases/year. The concentration of carcinogenic PAHs found in Bangkok city in 2002/2003 is comparable to values in many other cities.