An integrated risk assessment and intercity comparison model of PAHs in ambient air of six metropolitans in China

An integrated method comprised of Polycyclic Aromatic Hydrocarbons (PAHs) concentration dispersion in ambient air of metropolitans and relative inhabitant risk assessment was utilized with multi-layer uncertainty analysis methods. This paper used a series of multi-layer uncertainty analysis methods, including three layers for uncertainty analysis of variants or parameters. In order to simulate the whole PAHs level in metropolitans, a sampling method of bootstrap was adopted in three layers of an integrated model: (1) bootstrap volume estimation of variance, where a multi-scale sampling test was examined to find a proper sampling volume; (2) bootstrap confidence interval and statistical analysis of a certain metropolitan's ambient air PAHs; (3) bootstrapping data analysis with dependencies of intercity comparisons. Primarily, two variants/parameters were analyzed by bootstrap: (i) ambient PAH concentration level simulation, where bootstrap is utilized as a dispersion function; (ii) Toxic Equivalent Factor (TEF) acquirement and interpolation. Based on the multi-layer uncertainty analysis methods, an integrated model was built to assess the ambient air PAHs' risk to metropolitan's inhabitants. The results were expressed by TEQ (totality of equivalent Benzo(a)pyrene, BaP) and increased risk of cancer for inhabitants. This paper comprised six metropolitans in China: Beijing, Dalian, Tianjin, Shanghai, Macao and Hongkong. The results showed that ambient air PAHs in Beijing, Shanghai and Tianjin are more serious than that of Dalian, Macao and Hongkong. The possibility of increased cancer risk for these cities was evaluated, and a comparison among these cities was executed in an integrated model with directly exporting port.