Heavy metal contaminants in Malapterurus electricus (Gmeli, 1789), Tilapia zillii (Gervais, 1848) and water from Ikpoba Reservoir, Benin City, Nigeria

Abstract

The study was carried out to evaluate the potential health risk associated with the consumption of fish and water from the Ikpoba Reservoir, with regard to heavy metal contamination. The concentrations of some heavy metals, Manganese (Mn),
Zinc (Zn), Copper (Cu), Cadmium (Cd) and Lead (Pb) were determined in Malpterurus electricus, Tilapia zillii and water by Atomic Absorption Spectrometric Technique. A total of 8 M. electricus sp. (mean wet weight 59.75±2.37g; mean total length 17.50±1.94 cm) and 10 T. zillii sp. (mean wet weight 39.45±2.37g; mean total length 12.35±1.52 cm), were used. The mean concentrations of (Mn, Zn, Cu, Cd and Pb) in mg/kg in M. electricus were 11.4±0.96, 10.13±0.45, 10.03±0.13, 0.323± 0.181 and 0.045±0.003 mg/kg respectively while in T. zillii, the mean concentrations were 10.61±0.33 (Cu), 9.82± 0.18 (Zn), 8.66± 0.74 (Mn), 0.181± 0.001 (Cd) and 0.044± 0.003 (Pb). The mean concentrations (mg/L) of the metals in water were 29.87±0.09 (Mn), 19.01±0.07 (Zn), 23.43±0.03 (Cu), 0.13±0.01 (Cd) and 0.14±0.009 (Pb). The mean concentrations of the heavy metals in water exceeded the World Health Organization (WHO) recommended limits of 0.2 mg/L (Mn), 3.0 mg/L (Zn), 1.0 mg/L (Cu), 0.003 mg/L (Cd) and 0.01 mg/L (Pb), for potable drinking water , while the mean concentrations of Zn, Cu, Cd and Pb in fish fell within the Food and Agriculture Organization (FAO) recommended limits of 30 mg/kg (Zn/Cu/Mn) and 0.05 mg/kg (Cu/Zn) for food fish. The Relative Health Factor (RHF) values for the investigated heavy metals were below unity for the fish species confirming that these fish species were safe for human consumption. The study revealed that, while the fish species might be fit for eating, the water was unsafe for drinking as the WHO limits were exceeded. It was advocated that the reservoir be closely monitored for heavy metal contamination in order to avert serious health hazards.

Keywords: heavy metals, Malapterurus electricus, Tilapia zillii, Relative Health Factor, reservoir