ABSTRACT
Lead exposure to human population could occur from different routes such as water, soil and food contamination. Lead mining activities are major sources of the contamination of these media. In this work, the levels of contamination of bitter leaves (Vernonia amygdalina), ora leaves (Pterocarpus mildbraedii), scent leaves (Ocimum gratissimum), okra pods (Abelmoschus esculentus), curry leaves (Murraya koenigii) and garden eggs (Solanum melongena), soil and water , arising from the mining area in Agalegu in Ebonyi State were evaluated. This becomes important as the human population in this area and beyond depend on these plants as sources of food while water is used for different domestic purposes and even drinking. Toxicity of water samples were tested using the “ostracod (Hetrocypris incongruens) toxicity assay kit” and that of soil in earthworms. Also, 40 pupils, each from selected schools in this area were subjected to IQ test while the human risk assessment, as applicable in predictive toxicology (based on estimated daily intake and target hazard quotient) was calculated. Results show that the concentrations the various vegetables, soil and water samples decreased as distances progressed from the mining site. There was no observed mortality of earthworms after 72hours of exposure to the various lead-soil samples. However, 10% mortality of earthworms (after 7 days) and 22.2% mortality (after 14 days) were observed in lead-soil samples collected 0.05km away from the mining site, while 10% mortality was observed (after 14 days) in lead-soil sample collected 2km away from the mining site. Percentage mortality of ostracod crustaceans exposed to lead-water samples decreased as distances progressed from the mining site, but remained constant after distance of 4km. Average intelligent quotient (IQ) scores of the pupils from primary school located 0.05km from the mining site was 89.46 (below average intelligence); primary school located 2km was 95.23 (average intelligence); primary school located 4km was 102.08 (average intelligence) and primary school located 10km was 111.82 (above average intelligence). Both Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) for lead in both adult and children for consumption of all the samples collected around the mining area decreased as distances progressed from the mining site. For some of the samples the EDI values were below the Tolerable Daily intake (TDI) for lead while for others, EDI values were above the TDI in both adult and children. Target Hazard Quotient (THQ) of lead in both adult and children for consumption of the various samples was greater (>) 1 for some of the samples and less (<) 1 for other samples. It is predicted that residents around lead mining sites are prone to health hazard and should, therefore, exercise high degree of caution to reduce the level of exposure to the metal.
