Polychlorinated biphenyls in dusts and soils from informal trade sites in Nigeria: Implications for sources and risk assessment

Informal trade sites (ITS), such as car dismantling sites (CDS), material recovery sites (MRS) and automobile mechanic workshops, are prevalent in Nigeria due to less stringent environmental regulations. A total of sixty (60) dust and soil samples were collected from thirty (30) informal trade sites and analysed for their polychlorinated biphenyl (PCB) concentrations by gas chromatography-mass spectrometry (GC-MS). The concentrations of Σ28 PCBs in dusts from CDS, MRS and AMW varied from 1.11 to 44.7, 0.91 to 20.6, and 1.71 to 121 ng g -1 , respectively, while those of soils from CDS, MRS and AMW exhibited concentration ranges of 1.23 to 146, 1.00 to 120 and 2.00 to 203 ng g -1 , respectively. The PCB concentrations in dusts and soils from all sites were below the stringent intervention value (1000 ng g⁻¹) and the permissible concentrations for commercial/industrial land use. However, a significant proportion of samples exceeded the more precautionary target value (20 ng g⁻¹). The low chlorinated (LC)-PCBs were more dominant than high chlorinated (HC)-PCBs in dusts and soils from the ITS, except for soils from CDS. The PCB homologue compositions of the matrices mimic those of Aroclor 1254 and 1260. However, the occurrence of deca-PCBs among the top three homologues in dusts and soils from CDS and in dust from AMW, indicates contributions from unintentional sources. Dusts from 50 to 70% of the sites from each category of the ITS had ecological risk index (ERI) values for PCBs in the low ecological risk range, while the ERI values for PCBs in soils from 70 to 80% of the sites from each category of the ITS are in the potential ecological risk range. The hazard index (HI) and carcinogenic risk (CR) values indicated that PCBs in dusts and soils from the ITS may pose significant non-cancer and cancer risks to children and adults.