Assessment of heavy metals in some edible fish species of the Komadugu-Yobe River, Gashua, Yobe State, North-East Nigeria: Threat to public health

Abstract

Contamination of Heavy metals in the aquatic environment has been a major challenge across the globe, due to the persistence of these metals and the tendency to accumulate in living organisms especially, fish species, which are important source of protein for most humans ‘consumption. In this study, the bio-accummulation of six metals (As, Cd, Cu, Ni, Pb and Zn) were analysed in three edible fish species (Oreochromis niloticus, Clariasgariepinus and Synodontisschall) sampled from the Komadugu-Yobe Riverusing Atomic Adsorption Spectrophotometry. The potential health threats for consumers were also assessed using standard indicators. Results showed that the mean concentration of heavy metals in the three fish species was in the following rank order: 22.23> 11.23 > 0.45> 2.56 >0.48> 2.33 > 0.05 for Zn >Ni >Cu >Pb >As >Cd, respectively. Zn recorded the highest concentration in both the gills and muscles of all the fishes at 11.28 mg/kg and 15.23 mg/kg, while 4 metals (Zn, Cd, Ni and Cu) out of 6 measured their highest concentrations in O. niloticus species. The remaining 2 metals (As and Pb) measured their highest levels in C. gareipinus. Furthermore, the highest concentrations of studied metals in the whole fish samples were lower than the maximum acceptable limits compared in this study. The potential human health indices associated with ingesting heavy metal indicated that HI (Hazard intake) and THQ (Target hazard quotient) values were below 1 implying that they pose no health threat, whereas EDI (Estimated Daily Intake) values of each metal were higher than the TDI (Tolerable daily intake) values indicating harmful effect on human health in daily consumption. Thus, constant monitoring and sustainable management of the Komadugu-Yobe River at Gashua is required to reduce the amount of contaminant entering the river which may pose a health threat to the inhabitants that feed on the contaminated fishes.