Polychlorinated Biphenyls Contamination in Nigeria Soils: A Risk Assessment Study in South-West and South-South, Regions

Transformer leakage, industrial air deposition, open burning of electrical and electronic equipment, and biomass combustion using incinerators are the main sources of PCBs in Nigerian soils. PCBs' strong adsorptive qualities allow them to stick to soil particles for long periods of time. Because of their near proximity, PCBs can be ingested, inhaled, or come into touch with skin. PCB exposure has been linked to a wide range of deleterious health effects, including neurotoxicity, mutagenicity, and carcinogenicity. This study in South-West and South-Southern Nigeria examined the levels of polychlorinated biphenyls (PCBs) and potential health concerns in urban and rural soils. Soil samples were collected and analysed using Gas Chromatography-Mass Spectrometry (GC-MS) at six locations in Nigeria's south and southwest. The study then evaluated the risk associated with human interaction with the soil using health indices such as the Hazard Quotient (HQ), Hazard Index (HI), and Incremental Life Cancer Risk (ILCR) from human unconscious ingestion, inhalation, and skin contact with contaminated soil. Each soil sample contained 17 PCBs, including one dioxin-like congener. The PCB concentrations in the soil samples ranged from 5.87 to 46.12 ng/g, following this pattern: Apata > Apete > Bomadi > Ozoro > Ayeka > Itokin. The toxic equivalent (TEQ) value of PCB-189, the only dioxin-like PCB discovered in the soil sample has a TEQ of 4.2 x 10-6, exceeded the World Health Organization's permissible limit for dioxin-like PCBs (10(-4) -10(-6)). Ingestion, skin contact, and inhalation risks ranged from 1.95 x 10(-6) to 8.73 x 10(-6), 5.55 x 10(-8) to 8.58 x 10(-7), and 2.28 x 10(-17) to 3.93 x 10(-14), respectively. Except for ingestion, these values were below the incremental lifetime cancer risk threshold (10(-6)), indicating that PCBs pose minimal health risks.