Human Health Risk Assessment of Selected Heavy Metals in Soil Surrounding Tank Farms in Oghareki-Oghara, Delta State, Nigeria

This study investigated the levels of selected heavy metals in the soil surrounding tank farms in the Oghareki community of Delta State, Nigeria. The objectives were to assess the concentrations of volatile organic compounds (VOCs), total petroleum hydrocarbons (TPHs), oil and grease (O and G), selected heavy metals in soil considering variations over distances from the tank farms, and, additionally, human health risks models to estimate the chronic daily intake (CDI), hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) for the local population around the study location. Soil samples were collected at distances ranging from 100 meters to 1 kilometer from the tank farms. Each sample was analyzed for heavy metals using an Atomic Absorption Spectrophotometer (AAS). The data obtained were presented as mean values from triplicate analyses. Results for contaminants in soil, that is, Pb levels, ranged from 9.35–(16.69±1.56) mg/kg; Cd from 9.121±1.050 mg/kg; Fe from 305.08±5.610 to 554.50±7.583 mg/kg; Cu from 5.08±0.520 to 10.919±1.482 mg/kg; and Zn from 2.128±0.610 to 5.118±1.284 mg/kg, based on distance of sampling. The chronic daily intake, hazard quotient and incremental lifetime cancer risk indices were notably high in the soil. Comparisons with control samples indicated that the soil around the tank farms were contaminated with heavy metals, although the results remained within the acceptable limits set by the Nigerian Midstream and Downstream Petroleum Regulatory Authority (NMDPRA) for soil in Nigeria.