Hazard Evaluation and Health Risk Assessment of a Major River in Ondo Nigeria State

Abstract

Regular monitoring of water bodies for pollution is necessary to prevent the depletion of aquatic plants and animals that serve as food to man. This study was carried out in the Ogbese River, situated along the Akure - Owo expressway, Ondo state, Nigeria.  The physicochemical parameters were determined using the standard method while the heavy metal concentration in the river was determined using an Atomic Absorption Spectrophotometer.  The pH, Total Dissolved Solid (TDS) and Electrical Conductivity are within WHO recommended limit. The Dissolved Oxygen (DO) ranged between 2.9 mg/L to 4.2 mg/L with an average value of 3.74 ± 0.04 mg/L, which indicates depletion of Oxygen. The heavy metal concentrations with slightly higher ranges than WHO limits are Ni, and Pb with a range of 0.07 mg/L to 0.12 mg/L, and 0.016 mg/L to 0.042 mg/L respectively. The Average Daily Intake (ADI_i) of metals if the water is consumed and ingested are Cd 6.0 x 10^-4 mg/kg, Ni 2.9 x 10^-3 mg/kg, Pb 8.0 x 10^-4 mg/kg, and Cu 7.9 x10^-3 mg/kg body weight.  The Target Hazard Quotient (dermal) (THQ_d), if used to bathe and shower are Cd 2.4 x 10^-3 mg/kg, Ni 1.16 x 10^-3 mg/kg, Pb 3.2 x 10^-4 mg/kg and Cu 1.1 x10^-1 mg/kg body weight. The Hazard Index (HI) for Cd, Ni, Pb, and Cu are 0.273, 0.146, 0.457, and 0.308 respectively. Ogbese river is polluted with some metals which is due to non-point sources.