Toxicological Risk of Exposure to Hand-Dug Wells (HDWs): Physicochemical Quality and Elemental Level

Ensuring access to safe drinking water remains a critical challenge in developing regions, particularly in areas reliant on hand-dug wells. This study evaluates the physicochemical characteristics, trace element concentrations, and associated non-carcinogenic health risks of water samples from hand-dug wells (HDWs) in selected Areas in Abeokuta South Local Government Area (LGA), Ogun State, Nigeria. Water samples were collected from seven key areas within the LGA. Physicochemical parameters were analyzed using standard methods, while trace element levels were quantified via Atomic Absorption Spectrophotometry (AAS). The finding showed a range in temperature (24.6 – 25.2 °C), pH (5.8 – 6.8); electrical conductivity (0.852 – 1.36 μS/cm), turbidity (0.4-3.0 NTU), Salinity (0.43 – 0.64 ppm), total dissolved solids (TDS)(76 – 909 mg/L), Total Acidity (20 – 66mg/L), total hardness (112 – 284 mg/L), chloride ion (74 – 134 mg/L), nitrate ion (3.0 – 43.6 mg/L), phosphate ion (0.22 – 4.93 mg/L), sulphate ion ( 22 – 95 mg/L) and dissolved oxygen (DO) (0 – 1.67 mg/L). Total dissolved solid (TDS), TH and Nitrate ions in 71.4, 100 and 85.7% of the HDW respectively were above the WHO standards (<500, 100 and 5.0 mg/L). The Fe, Mn, Ag, Na and Zn levels are 0.89, 0.429, 0.006, 9.63 and 0.365 mg/L respectively. The levels of Cd and Ni were not detected or below the detectable limits across the HDWs. Toxic elements such as Mn and Ag are high in all the hand-dug wells and Kuto respectively compared to the WHO standard. Toxicological risk assessment indicated that the HI <1, suggesting that the people making use of the HDW are at a non-significant non-cancer risk on exposure. In conclusion, the study highlights the urgent need for water treatment interventions to ensure the safety and acceptability of water usage from the hand-dug wells.