Levels of heavy metals in water and Nile tilapia fish (<i>Oreochromis niloticus</i>) of Eleyele Lake in Ibadan, Nigeria

Abstract

Surface waters are susceptible to hazardous pollution which may migrate with devastating health challenges through the food chain to humans. This study evaluates the levels of heavy metals in water and Nile tilapia of Lake Eleyele. The physicochemical properties of water samples were determined using standardized methods, while heavy metals in both water and fish samples were determined using atomic absorption spectrophotometer (AAS). Water pH, electrical conductivity, total dissolved solids, total suspended solids, and dissolved oxygen were within WHO and USEPA limits for potable water. Cu (0.028 – 0.112 mgL^-1), Pb (0.002 – 0.009 mgL^-1), and Zn (1.46 – 3.79 mgL^-1) were below the maximum permissible limits by both WHO and USEPA, while cadmium, chromium, and nickel were not detected in the water samples. Cu (2.56 -3.54 mg/kg), Zn (22.93 – 32.13 mg/kg), and Ni (0.39 – 0.48 mg/kg), are within acceptable levels, while Cd and Cr were also not detected in the fish samples. However, Pb (1.71 – 2.30 mg/kg) was higher in the fish samples than the threshold limit (0.3 mg/kg) by FAO and WHO. In accordance, Pb with bioconcentration factor (BCF: 402) was more highly bio-accumulated in the fishes than Cu (BCF: 54.4) and Ni (BCF: 10.97). The results recommend the river water for utility purposes but raised concerns about the consumption of Nile tilapia fishes in the lake.