Pollution Status and Health Risk Assessment of Heavy Metal in Groundwater Within the Vicinity of Dei-Del in Abuja

Abstract

Access to safe drinking water is essential for protecting human health; however, groundwater contamination by toxic

heavy metals poses significant public health concerns. This study assessed the concentrations of selected heavy metals and their associated human health risks in borehole and dug-well water from Dei-Dei District, Federal Capital Territory (FCT), Nigeria. Twenty groundwater samples comprising ten borehole and ten dug-well water samples were collected from four communities and analyzed for Fe, Zn, Cd, As, Cr, Mn, Pb, and Ni using Atomic Absorption Spectrophotometry (AAS). Mean concentrations (mg/L) in borehole water were Fe (0.225), Zn (0.325), Cd (0.002), As (0.002), Cr (0.023), Mn (0.247), Pb (0.004), and Ni (0.035), whereas dug-well water contained Fe (0.492), Zn (0.225), Cd (0.003), As (0.004), Cr (0.025), Mn (0.273), Pb (0.021), and Ni (0.046). Iron and arsenic in dug-well water exceeded the World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ) guideline values, while manganese and nickel exceeded the NSDWQ limits in borehole water. Estimated Daily Intake (EDI) values were consistently higher for consumers of dug-well water than borehole water, indicating greater exposure to heavy metals. The Hazard Quotient (HQ) values for all individual metals were below unity (HQ < 1), suggesting no significant non-carcinogenic risk from individual metals. However, the mean Hazard Index (HI) was 0.695 for borehole water and 1.110 for dug-well water, with approximately 45% of the dug-well samples exhibiting HI values greater than 1, indicating potential cumulative non-carcinogenic health risks. The mean Incremental Lifetime Cancer Risk (ILCR) values for chromium and nickel in both groundwater sources exceeded the acceptable limit (1 × 10⁻⁴), while arsenic exceeded the permissible carcinogenic risk threshold only in dug-well water. The mean Total Lifetime Cancer Risk (TLCR) was 2.34 × 10⁻³ for borehole water and 3.08 × 10⁻³ for dug-well water, both substantially higher than the acceptable safety threshold. These findings demonstrate that although the groundwater sources pose minimal non-carcinogenic risks from individual heavy metals, prolonged consumption, particularly of dug-well water, presents significant cumulative non-carcinogenic and carcinogenic health risks. Regular groundwater monitoring, effective water treatment, and pollution control measures are therefore recommended to safeguard public health..