Impact of Heavy Metals on the Environment and Human Health: A Comparative Analysis of Two Mining Communities in Niger State, Nigeria.

Abstract

Unregulated mining of precious metals has led to pollution in the environment and food chain, as well as outbreaks of poisoning in affected communities. However, there is limited evidence on the effect of heavy metals on the environment and health of communities in north-central Nigeria. This study investigated the comparative presence and concentration of some heavy metals, namely, arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) in various samples collected from water sources, soils, staple food cultivars, and blood samples of inhabitants around Kataeregi and Kurebe mining communities in Niger State, Nigeria. The samples were collected using standard methods and digested using a tri-acid mixture and concentration of heavy metals was determined using Atomic Absorption Spectrometry (AAS). The analysis revealed the water and soil samples only showed exceeding levels in As, 0.017 mg/L; Hg, 0.014 mg/L; Pb, 0.004 mg/L; and As, 37.2 mg/kg, Cd, 6.7 mg/kg, and Hg, 1.1 mg/kg, respectively, in Kataeregi; and Cd, 0.023 mg/L; Hg, 0.012; and Hg, 0.315 mg/kg, respectively, in Kurebe. Heavy metal concentrations in staple food cultivars consumed at both mining sites were found to be within the permissible levels set by the WHO/FAO, except for As (1.72:1.82 mg/kg), Cd (0.41:0.09 mg/kg), Ni (0.41 mg/kg) and Hg (0.71 mg/kg) in cereals and vegetables from Kataeregi, and As (1.56 mg/kg), Hg (2.09 mg/kg), in legumes and Cd (0.43 mg/kg) in tubers from Kurebe. Also, significant elevations in the blood Pb, 11.2 µg/L; Hg, 11.1 µg/L; urea, 8.43 mmol/L and creatinine, 1.61 mg/dL and a decreased mean hemoglobin (Hb) concentration (67.1%, 9.8±2.3 g/dL, P<0.05) was observed in samples from Kataeregi. Attributing the compromised renal functioning and hematologic impairment to the accumulation of toxic heavy metals, as evident in the clinical manifestation of inhabitants in both mining sites. Alternative safe drinking water sources, continuously monitoring, sensitization and assessment on the potential health risks and profiles are highly advocated for in this community; additionally, nanobioremediation approaches are needed to clean up polluted farmlands and waters to reduce heavy metal contamination in the food chain and the associated health risks.