Status, source and health risk assessment of polycyclic aromatic hydrocarbons in street dust of an industrial city, NW China.

The status, source and health risk of street-dust-borne polycyclic aromatic hydrocarbons (PAHs) in Lanzhou of Northwest China were investigated. The total level of the 21 PAHs ranged from 1470 to 13,700 µg kg(-1) and that of the 16 priority PAHs from 1240 to 10,700 µg kg(-1). Higher levels of PAHs were mainly distributed in the Chengguan and Qilihe districts at Lanzhou central areas, and the lower levels were in Anning and Xigu districts. The level of seven potential carcinogenic PAHs generally accounted for 35-40 percent of total PAHs, and the PAHs contained two to four rings, mainly phenanthrene, benzo[b]fluoranthene and fluoranthene. The total level of PAHs increased with the decreasing particle size in the street dust. The correlation analysis suggested that the total organic carbon (TOC) was only slightly affected the PAH accumulation in street dust. The isomer ratios and principal component analysis indicated that the dust-borne PAHs in the dust were derived primarily from the combustion of biomass, coal and petroleum emission. The toxic equivalent concentrations (BaP(eq)) of dust-borne PAHs ranged from 115 to 827 µg BaP(eq) kg(-1), with a mean of 300 µg BaP(eq) kg(-1). The 95 percent upper confidence limit of Incremental Lifetime Cancer Risk due to human exposure to urban surface dust-borne PAHs in Lanzhou urban area was 2.031 × 10(-6) for children and 1.935 × 10(-6) for adults.