Human health risk assessment to toxic trace elements in groundwater sources in ward 17, Mt Darwin, Zimbabwe

Author

Mamvura, Kudzaishe

Title

Human health risk assessment to toxic trace elements in groundwater sources in ward 17, Mt Darwin, Zimbabwe

Abstract

Background: Access to safe drinking water is a critical public health challenge in many rural communities across Zimbabwe, where reliance on untreated groundwater is common. A general lack of chemical quality data exists for groundwater in the Mt Darwin region, despite the presence of potential geogenic and anthropogenic sources of contamination.Objective: This cross-sectional study was conducted to determine the concentrations of toxic trace elements (As, Cd, Cr, Cu, Pb, Ni, Zn) in different groundwater source types (boreholes, shallow wells, and deep wells) and estimate the associated potential health risks to residents in Ward 17, Mt Darwin district, Zimbabwe.Methods: A total of 60 groundwater samples were collected from 15 sources (8 boreholes, 4 shallow wells, 3 deep wells) across six villages in May 2025. Concentrations of trace elements were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The extent of contamination was assessed using the Heavy Metal Pollution Index (HPI) and Nemerow Pollution Index (NPI). Human health risks (non-carcinogenic and carcinogenic) for adults and children were quantified using the United States Environmental Protection Agency (US EPA) model. Statistical analyses, including one-sample t-tests and one-way ANOVA, were performed using SPSS, with significance set at p < 0.05.Key Findings: The mean concentrations of all analyzed trace elements in all source types were statistically significantly lower than the World Health Organization (WHO) drinking water guidelines (p < 0.001). A one-way ANOVA revealed significant differences between source types, with deep wells showing consistently lower contaminant concentrations than boreholes and shallow wells. Water quality indices confirmed the water is clean and unpolluted (HPI < 40; NPI < 0.7 for all source types). The health risk assessment showed no significant non-carcinogenic risk, with the Hazard Index (HI) for all source types well below the safety threshold of 1 (HI < 0.5 for children, HI < 0.25 for adults). The lifetime cancer risk (LCR) was within acceptable limits.Conclusion: The groundwater in Ward 17, Mt Darwin, is safe for human consumption and does not pose a chemical health threat from the trace elements studied. Deep wells represent the highest quality and safest water source in the region. This study provides crucial baseline data and recommends the prioritization of deep wells for future water supply development and the implementation of a protective monitoring program to safeguard this vital resource.

Date

May 2025

Publisher

BUSE

Keywords

Trace Elements

Health Risk Assessment

Rural Water Supply

Supervisor

Dr A Kanda