Polychlorinated biphenyls in soils around a poorly-managed dumpsite in SE Nigeria: contamination status, exposure risks, source identification and pathways for environmental sustainability
Victor Chukwuemeka Eze, Tochukwu O. Maduka, Callistus Izunna Iheme, Aralu Chukwuemeka Chiedozie, Hillary Onyeka Abugu, Johnbosco C. Egbueri, Solomon I. Ogbuefi, Miracle Muogbo, Sani I. Abba
Abstract
Polychlorinated biphenyls (PCBs) pose significant environmental and health risks globally, especially in developing nations with poor waste management practices. Despite extensive research on PCB contamination in various matrices, there is a critical gap in understanding the PCB levels and risks in soils around poorly-managed dumpsites in Nigeria. This study contributes to addressing this gap by examining the contamination status, exposure risks, source identification, and environmental pathways of PCBs in soils surrounding the Ugwuaji waste dumpsite in Enugu State, southeastern Nigeria. Topsoil samples were taken from five distinct locations around the dumpsite. Ten sub-samples at each location were taken, which were then tested utilising gas chromatography-mass spectrometry to quantify 28 congeners. This provided a detailed profile of PCB contamination, revealing substantial contamination across all sampling locations, with the concentration sums found between 1912.68 and 2737.71 ng g−1. PCB-118 was the predominant congener, while PCB-8 was the least abundant. Higher-chlorinated PCBs were more prevalent due to their increased hydrophobicity, persistence, and reduced volatility. PCB toxicity was evaluated. The Toxic Equivalency (TEQ) approach yielded TEQ values from 6.99E + 00 to 11.07E + 00 ng TEQ g−1, with PCB-126 and PCB-169 posing significant risks. Health risk assessments showed hazard index values for both adults and children exceeding 1, indicating potential chronic risks, while total cancer risk remained within acceptable thresholds. Hierarchical clustering, correlation matrix, and principal component analysis suggested that the PCB contamination originated from similar anthropogenic sources related to the dumpsite. Strong interactions between PCB congeners were noted, indicating similar environmental fate and behaviour patterns. The research findings call for improved waste management practices, regular and systematic monitoring of PCB levels around the dumpsite, cost-effective remediation techniques, and environmental health protection; providing valuable insights for similar regions in Nigeria and beyond.