Analysis of Polychlorinated Biphenyls in Transformer Oil from Electrical Substations in Lagos, South West Nigeria

Polychlorinated biphenyls were historically used as dielectric fluids in electrical transformers and capacitors, and their persistent presence in ageing electrical infrastructure poses significant human health and environmental risks requiring systematic monitoring. This study analyses polychlorinated biphenyl congener profiles in transformer oil samples collected from fifteen electrical distribution substations in the Lagos metropolis, South West Nigeria. Oil samples are extracted by the hexane-dichloromethane liquid-liquid partition method and analysed by gas chromatography with electron capture detection, calibrated using certified polychlorinated biphenyl standard mixtures. Total polychlorinated biphenyl concentrations are calculated as the sum of identified congeners and compared against the Stockholm Convention threshold of fifty milligrams per kilogram, above which oils are classified as contaminated waste requiring specialised disposal. The age of each transformer and maintenance history are obtained from the distribution company to assess correlations between equipment age and contamination levels. Results are expected to identify a subset of older transformers installed before the 1980s as containing polychlorinated biphenyl concentrations above regulatory thresholds. Findings directly support the national implementation of the Stockholm Convention on persistent organic pollutants and guide the Lagos State Environmental Protection Agency in developing a prioritised transformer remediation programme. Keywords: polychlorinated biphenyls, transformer oil, persistent organic pollutants, Lagos, electrical substations