Assessment of the Levels and Distribution of Polychlorina Ted Biphenyls in Soils in the Vicinity of Electric Transformers in the Central Region of Ghana

Abstract

Polychlorinated biphenyls (PCBs) in surface soil samples from the Central Region of Ghana were analyzed to assess their distribution, levels and health effects. The soil characteristics were analyzed. Soils samples were digested with a mixture HN03 and HCI04 and the metals analyzed using Varian 235 AAS. The PCBs were extracted with (1:1) hexane:acetone mixture, cleanup with H2S04, 5% KMn04 and copper, and then eluted from a silica gel column with hexane:dichloromethane (97:3% v/v). The PCBs were analyzed using a gas chromatograph equipped with 63Ni electron capture detector (GC - ECD) model CP 3800. The PCBs were dominated by penta and tetra PCBs homologous. The concentration of PCBs for the region was 7.99±0.38 /lg/kg. The levels for the vertical distribution were 9.15± 0.52 /lg/kg for (0-10 cm), 7.55± 0.56 /lg/kg and 7.82 ± 0.55 ug/kg for the 10-20 cm and 20-30 cm subsurface soils. The pH, clay, silts and sand content of the soils correlated positively with the PCB congeners. The effective cation exchange capacity and moisture showed negative correlation. There were no significant correlations between organic matter, exchangeable base, metals and the PCB congeners or LPCB at the 0.05 level. The levels of PCBs were below the soil contact value of 25 mg/kg. The toxicity equivalents of PCB- 118 were all very low. Most of the soils in residential areas had hazard Index greater than one. The estimated lifetime cancer risk to a Reasonable Maximum Exposure (RME) individual via the complete exposure (skin contact) was very low, and ranged between 3.0E-l1 and 3.0E-IO for adult resident and 5.4E-IO to 5.3E-09 for children resident, implying that the levels of exposure to soil PCBs are acceptable.