LEVELS OF HEAVY METALS, PAHs AND TPHs IN FISHES OF EKPAN RIVER

ABSTRACT

Heavy metals contamination of aquatic environments is of critical concern because of their toxicity and accumulation in aquatic organism such as fish. This study was aimed at assessing the contents of heavy metals, polycyclic aromatic hydrocarbon (PAHs) and total petroleum hydrocarbons (TPHs) in fishes of Ekpan River and evaluate the human health risk associated with their consumption. Fresh fish samples of xenomystis nigri, Tilapia guineensis, leptocypris niloticus and synodontis gambiensis were harvested monthly from Ekpan River with the assistance of local fishermen. The heavy metal content, PAHs and TPHs in the fish species were determined using the Estimated Daily Intake (EDI), the Target Hazard Quoitient (THQ) and the Hazard in Index (HI) parameters. Result showed that the range of mean values for Lead (0.15 – 0.28 mg/Kg), Iron (1.12 – 1.80 mg/Kg), Zinc (0.22 – 0.36 mg/Kg), Copper (0.09 – 0.49 mg/Kg), Nickel (0.20 – 0.44 mg/Kg), Cadmium (0.35 – 1.09 mg/Kg) and Chromium (0.13 – 0.25 mg/Kg) in the fish samples were all below permissible limits except for Cadmium Xenomystis nigri and Synodontis gambiensis which exceeded the FAO/WHO maximum limits of 0.5mg/Kg. Seven (7) types of PAHs were present in the fish species. Of these, Benzo(a)anthracene had the highest concentration of 986µg/kg in Synodontis gambiensis while the lowest value 1.01µg/Kg was detected in Leptocypris niloticus. Twenty nine (29) types of TPHs were present in the fish species. For TPHs, n-dotriacontane had the highest mean value of 20158µg/Kg Tilapia guineensis while n-pentacosane had the lowest mean value of 2.78µg/Kg in Tilapia guineensis. Human health risk assessment of heavy metal content in the fishes indicate non-carcinogenic health risk to consumers as HI values did not exceeded the threshold value of 1, (HI<1). Carcinogenic risk assessment indicate that the fishes portends carcinogenic risk to consumers. There is need for continuous bio-monitoring of the aquatic environment in order to forestall the culmulative effects of these pollutants which may pose threats such as sub-lethal effects to the aquatic fauna and clinical poisoning to the consumers in the future.