Carcinogenicity of dioxin-like polychlorinated biphenyls in transformer soil in vicinity of University of Port Harcourt, Choba, Nigeria

Polychlorinated Biphenyls (PCBs) in soils within the vicinity of transformers in the main campus of university of Port Harcourt, Choba was monitored. Evaluation was done for both total PCBs (Aroclor) and congener’s form using Gas Chromatography at four designated sites; A, B, C, and D with geographical co-ordinates for site A-Donald Ekong Library, latitude 4^o54’, 32’’N and longitude 6^o55:05’’E, site B-Senate building with latitude 4^o54’14’’N and longitude 6^o55’, 23’’N, site C-Transformer close to music department with latitude 4^o54’, 01’’N and longitude 6^o55; 56’’E and finally site D-Gana-Ma Lecturers residential quarters with latitude 4^o54’.23’’ N and longitude 6^o55’, 74’’E. All the sites are polluted with PCBs that exceeds the maximum limit of 2.0 ppm as per United States Toxic Substances Control Act (TSCA). The order of total PCBs was site D site > site A > site B > site C, which also corresponds with the order of sites carcinogenicity of dioxin-like PCBs, calculated as Total toxicity Equivalence concentration (TTEC). The TTEC for site A, B, C and D corresponds to 0.000012, 0.000035, 0.0000185 and 0.00039 (mg/kg), respectively, which exceeded the method B clean up levels for 2, 3, 7, 8-tetrachloro dibenzo-p-dioxin levels of 1.3×10^-5  mg/kg and need of massive cleanup for carcinogenic dioxin-like PCBs.  We also found out there is high loadings of PCBs congeners with little or no biodegradability across the four sites. To mitigate the known human health risks posed by PCBs toxicity, non-PCBs transformers should be replaced with current ones and extensive soil remediation is needed to clean up the PCBs to avoid negative impact.