Assessment of Trace Metal Levels in Tilapia from Kainji Lake, Niger State

This study assessed the concentrations of trace metals in Oreochromis niloticus (Nile tilapia) from Kainji Lake, Niger State, North Central Nigeria, and evaluated associated risks for human consumers. Kainji Lake, as one of Nigeria's most important freshwater reservoirs, supports substantial artisanal fisheries, yet environmental contamination from surrounding agriculture and irrigation inputs may compromise fish safety. Fish muscle and gill tissue samples were collected from five stations across the lake during both wet and dry seasons. Trace metals analysed included iron (Fe), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), and chromium (Cr) using atomic absorption spectrophotometry. Iron was the most abundant metal in both tissues across all stations, with mean values of 22.4 mg/kg in muscle and 48.6 mg/kg in gill tissue. Lead and cadmium concentrations exceeded WHO and FAO permissible levels in muscle tissue from two stations located near agricultural drainage inflows. Dry season samples recorded higher metal concentrations, attributed to reduced dilution capacity as lake levels drop. No significant sex-based differences in metal accumulation were observed. The human health risk assessment, based on estimated weekly fish intake data for lakeside communities, indicated potential non-carcinogenic risks associated with lead and cadmium ingestion exceeding tolerable weekly intake thresholds. The study recommends strengthened agricultural buffer zones around Kainji Lake, regular biomonitoring, and public health advisories for communities with high fish consumption rates. Keywords: trace metals, Kainji Lake, tilapia, food safety, human health risk