Post-epidemic lead exposure to animals following a decontamination exercise in gold mining village of Bagega, Zamfara State, Nigeria

Abstract

This study focused on the evaluation of environmental lead contamination due to artisanal gold mining at a Nigerian village of Bagega one year after a clean-up exercise was carried out. Water samples were collected from earthen dams, faucets and wells, while plant and soil samples from grazing fields, residential areas and sites within the vicinity of the gold mine. The collected samples were digested and analyzed for lead concentration using the atomic absorption spectrophotometer. The recommended safe level of lead in water is 0.01 ppm and all the sources of water analyzed showed elevated lead concentrations. Water from the earthen dam, tap and well had lead concentrations of 31.49±7.1, 5.98±1.5 and 7.14±1.2 ppm, respectively. In the grazing area, the lead concentration was 4.6±7.5 mg/kg, whereas in the residential area and mining vicinity, the concentrations were 46.84±10 and 1153± 165 mg/kg, respectively. Two plants, Alysicarpus vaginalis and Digitaria debilis had a uniquely high bioaccumulation ratio, suggesting their potential as hyperaccumulators of lead. Given that international standards accept lead levels of 420 ppm and below, the residential area and the grazing fields may be safe, but the vicinity of the mine which had a toxic concentration could be unsafe. For animal feed, all plant ingredients analyzed accumulated low levels of lead except for A. vaginalis. This study suggests that soil remediation may be an effective decontaminating procedure. Additionally, grazing plants in the study area are not important sources of lead exposure to animals. However, water bodies may constitute a probable route of lead exposure to both animals and humans. Therefore, there is a need to prevent water contamination by immobilizing lead from the mining site which could be potentially leached into water bodies.