Polycyclic aromatic hydrocarbons in dust from rural communities around gas flaring points in the Niger Delta of Nigeria: an exploration of spatial patterns, sources and possible risk

Indoor and outdoor dust from three rural communities (Emu-Ebendo, EME, Otu-Jeremi, OTJ, and Ebedei, EBD) around gas flaring points, and a rural community (Ugono Abraka, UGA) without gas flare points, in the Niger Delta of Nigeria, was analysed for the concentrations and distribution of polycyclic aromatic hydrocarbons (PAHs), their sources, and possible health risk resulting from human exposure to PAHs in dust from these rural communities. The PAHs were extracted from the dust with a mixture of dichloromethane/n-hexane by ultrasonication, and purified on a silica gel/alumina packed column. Gas chromatography-mass spectrometry was employed to determine the identity and concentrations of PAHs in the cleaned extracts. The sigma 16PAH concentrations in the indoor dust ranged from 558 to 167 000, 6580 to 413 000, and 2350-37 500 mu g kg-1 for EME, OTJ and EBD respectively, while those of their outdoor counterparts varied from 347 to 19 700, 15 000 to 130 000, and 1780 to 46 300 mu g kg-1 for EME, OTJ and EBD respectively. On the other hand, the UGA community without gas flare points had sigma 16PAH concentrations in the range of 444-5260 mu g kg-1 for indoor dust, and 154-7000 mu g kg-1 for outdoor dust. The lifetime cancer risk values for PAHs in these matrices surpassed the acceptable limit of 10-6 suggesting a potential carcinogenic risk resulting from human exposure to PAHs in indoor and outdoor dust from these rural communities. Principal component analysis suggested that PAH contamination of dust from these communities arises principally from gas flaring, combustion of wood/biomass, and vehicular emissions. Indoor and outdoor dust from three rural areas around gas flaring points, and a rural area without such points in the Niger Delta of Nigeria, was analysed for the concentrations and distribution of PAHs, their sources, and possible health risk.