QUANTITATIVE AND HEALTH RISKS ASSESSMENTS OF SELECTED HEAVY METALS IN OGBA RIVER, BENIN CITY, NIGERIA

Heavy metal contamination of freshwater bodies poses a significant environmental and public health concern, particularly in urban regions with increasing anthropogenic activities. This study aimed to evaluate the concentrations and health risks of selected heavy metals in the Ogba River, Benin City, Nigeria. Water samples were collected across three locations (upstream, midstream, and downstream) over three months to assess both spatial and temporal variations. The samples were analyzed for copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), manganese (Mn), and cadmium (Cd) using an atomic absorption spectrophotometer. The data were analysed using SPSS version 22, and descriptive statistics and one-way ANOVA were employed to assess variations, with p < 0.05 considered statistically significant. Results revealed that Ogba River water showed elevated levels of Cr, Ni, Pb, Mn, and Cd, often exceeding WHO and, in some cases, NESREA permissible limits, while Cu remained within safe limits. Children had higher Chronic Daily Intake (CDI) values than adults. Hazard Quotient (HQ) indicated low risk for Cu, Ni, and Mn, but potential non-carcinogenic risk from Cr, Cd, and Pb. Combined Hazard Index (HI) exceeded 1 at all stations, with children more vulnerable. Incremental Lifetime Cancer Risk (ILCR) for Cr, Cd, and Pb surpassed USEPA limits, with Cr posing the highest cancer risk. In conclusion, Ogba River is contaminated with heavy metals exceeding safe limits and posing health risks, particularly to children. Immediate monitoring and pollution control are needed to protect human health and the river ecosystem