Comparative determination of human health risks associated with consumption of contaminated groundwater with lead in selected areas surrounding the former lead mine in Kabwe and non-mining areas in Lusaka, Zambia.
Human exposure to Lead (Pb) through the ingestion of contaminated groundwater with Pb has been associated with countless health effects. The current study aimed to determine the Pb levels in groundwater and assess the associated human health risks of exposure to Pb through the consumption of groundwater in selected areas surrounding the former lead mine in Kabwe and non-mining areas in Lusaka. A comparative cross-sectional study design was used to determine the levels of Pb and other physicochemical parameters in groundwater of former Pb mining areas in Kabwe and non-mining areas in Lusaka. The human health risk assessment was conducted by estimating the Daily intakes of groundwater in adults and children from mining areas and non-mining areas. A total of 61 groundwater samples were collected from boreholes, that is 34 from mining areas in Kabwe, and 27 samples from non-mining areas in Lusaka. The samples were anlaysed for Pb using Atomic Absorption Spectrometry (AAS). Results showed the Pb levels in groundwater samples from the former Zinc-Lead mining areas in Kabwe (median= 0.131 mg/L) were significantly higher (p< 0.05) than the Pb levels from non-mining areas (median= 0.071mg/L) in Lusaka. Overall, 91% of the groundwater samples from mining and 74% from non-mining areas were above the maximum acceptable limit of 0.010 mg/L of Pb in borehole drinking water (WHO, 2011). The study showed that physicochemical parameters like temperature (median= 23-24.8), Total Dissolved Solids (median= 303-601ppm), and pH (6-7.27) were within the WHO-acceptable levels. However, electricity conductivity from mining areas (585 μS/cm) and non-mining areas (1100 μS/cm) indicated levels that exceeded the WHOs permissible limits of ≤ 400 μS/cm. This could be attributed to the influence of the leachate from the former mining waste in the mining areas. Spearman's rank correlation analysis test showed that the levels of Pb in groundwater were not influenced by the concentration of the other measured physicochemical parameters. The Estimated Daily Intake (EDI) for adults and children from mining areas recorded significantly higher (p< 0.05) values than non-mining areas. The median EDIs for adults (0.004 mg/L) and children (0.013 mg/L) from mining areas as well as children (0.007mg/L) from non-mining areas surpassed the WHOs recommended daily intake of 0.003 mg/L in drinking water. The estimated Target Hazard Quotients (THQs) in children (4.333) and adults (1.333) from mining areas as well as children (2.333) from non-mining areas were > 1. This suggests that health risk complications are likely to accumulate in the future if control measures are not laid in place. Additionally, the estimated cancer risk (CR) was in the range of 5.6 x 10-5 to 1.0 x10-4 which is within the EPAs threshold risk value (1x 10-6) and residual level (1x10-4), therefore, the cancer risk was unlikely. Collectively, drinking groundwater from boreholes in areas surrounding the former Zinc-Lead mine in Kabwe and non-mining areas in Lusaka are a source of exposure to waterbourne Pb in Kabwe and Lusaka. Therefore, ensuring that groundwater sources are monitored for heavy metal levels in accordance with WHO guidelines should be considered. Lastly, investigating the source of Pb contamination of groundwater in non-mining areas of Lusaka is required.
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