Occurrence, Sources and Exposure Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in Street Dusts from the Nigerian Megacity, Lagos

Abstract

This study presents the results for the determination of the concentrations and distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in urban street dusts from the Nigerian megacity, Lagos, in order to provide information on their sources, and the potential environmental and human health risks arising from exposure to PAH contaminated dust. Gas chromatography-mass spectrometry was used for the quantification of the levels of PAHs in the dust samples after they were extracted with n-hexane/dichloromethane by ultrasonication. The PAH concentrations in the urban street dusts ranged from 545 to 10785 μg kg−1, 289 to 17943 μg kg−1 and 616 to 13174 μg kg−1 for industrial, commercial, and residential areas, respectively. The risk quotient (RQ) values indicated a moderate to high ecosystem risk for organisms in contact with PAHs in dust from these functional areas. The BaPTEQ and BaPMEQ values indicated potential carcinogenic and mutagenic risks to residents of the megacity. The hazard index (HI) values signify that there is a substantial non-carcinogenic risk relating to exposure of children to PAHs in dusts from the commercial areas, while the lifetime cancer risk factors indicate a considerable cancer risk for human exposure to PAHs via oral ingestion and dermal contact with the dust particles. The source diagnosis, determined from PAH isomeric ratios and multivariate analysis, showed that PAHs in the urban street dust originated from vehicular traffic emissions, burning of biomass, volatilization of petroleum products, and domestic cooking gas.