Assessment of heavy metals bioaccumulation and health risk in crops grown in farmlands around mining sites in Gwana, Alkaleri lga, Bauchi state, Nigeria

Analysis was carried out on farm crops (Guinea corn, Millet and Beans) collected from adjourning farmlands around mining area of Gwana in Alkaleri Local Government Area, Bauchi State. Their heavy metal concentrations were determined and quantified using Atomic Absorption Spectroscopy (AAS). The heavy metal characterization revealed the presences copper, iron, lead, manganese, nickel and zinc in the farm crops. The mean values of the elements that where obtain for copper, iron, lead, manganese, nickel, silver and zinc by AAS are 33.90, 12.00, 71.43, 12.56, 4.40, 0.60 and 101.96 mg/kg, respectively. From the Analysis of variance (ANOVA) used to compare these levels of heavy metals in the crops, it showed that there was a significant difference in their concentration. Exposure assessment and risk characterization of the heavy metals present in the farm crops showed that the mean values of the bioaccumulation coefficient for the elements of copper, iron, lead, manganese, nickel, silver and zinc are1.24, 0.03, 1.68, 0.80,1.64, 0.89 and 1.21 respectively. The estimated daily intake rate for the elements of copper, iron, lead, manganese, nickel and zinc are 1.17 to 1.28 mg/kg, 0.03 to 0.04 mg/kg, 0.06 to 0.011 mg/kg, 1.39 to 1.96 mg/kg, 1.92 to 3.14 mg/kg and 1.18 to 1.26 mg/kg respectively. The hazard quotient for the elements of copper, iron, lead, manganese, nickel and zinc are 0.57–1.31, 0.01–0.02, 22.95–32.50, 0.07–0.12, 0.02–0.26 and 0.32–0.40 respectively. The carcinogenic risk for the elements of lead and nickel are 0.0003–0.0011 and 0.0006–0.0089 respectively. It is hereby recommended that the farm crop samples from within the catchment areas understudy should be subjected to clinical trials to evaluate the extent of the damage it can cause on body tissues.