BACKGROUND: The study determined the concentrations of lead, arsenic, cadmium, zinc and copper in domestic water samples in four Local Government Areas of Osun State, Nigeria. This was with a view of providing information on the quality and safety of domestic waters from wells and boreholes in the study areas. MATERIALS AND METHODS: Two hundred water samples were collected from wells and boreholes in four Local Government Areas (LGAs) of Osun State (Ife Central, Irewole, Ila Orangun and Ejigbo). Fifty samples were collected from each Local Government Area. The grid location of the sampling points were determined in situ and Cadmium (Cd), Zinc (Zn), Copper (Cu), Lead (Pb) and Arsenic (As) contents were determined using Atomic Absorption Spectrophotometer (AAS). These were determined at the Centre of Energy Research and Development (CERD), Obafemi Awolowo University, Ile-Ife. Data collected were subjected to descriptive statistics and the correlation matrixes were determined. RESULTS: The results showed that the highest physical parameters measured were found in Ife Central LGA. Ila Orangun LGA was found to have the highest mean lead concentration (0.021 ± 0.003 mg/L and 0.060 ± 0.007 mg/L) for borehole and well water samples respectively. The highest mean copper concentration in the borehole and well water samples were also found in Ila Orangun LGA (0.633± 0.031 mg/L and 0.596 ± 0.014 mg/L respectively). Zinc was also highest in Ila Orangun LGA in the well sample while Ejigbo LGA was highest for the borehole sample. Ejigbo LGA was found to have the highest mean arsenic and cadmium (0.028 ± 0.004 mg/L and 0.022 ± 0.001 mg/L for borehole and water samples respectively), (0.173 ± 0.015 mg/L and 0.147 ± 0.006 mg/L for borehole and water samples respectively) for borehole and water samples respectively. Pb and Cu concentration fell within WHO and NESREA standard limits except in Ila Orangun LGA. As and Cd concentrations were low in Ila Orangun LGA and this fell within WHO and NESREA standard but high in the other three LGAs. It was also observed that the concentrations of Zn fell within WHO and NESREA standard limits in all the LGAs. CONCLUSION: The study concluded that the concentration of the heavy metals varied from one location to the other due to anthropogenic and geological factors.

Keywords: domestic water, heavy metals, Osun State (Nigeria), WHO and NESREA water standard