CONCENTRATION OF HEAVY METALS IN THE ATLANTIC HORSE MACKEREL

ABSTRACT

Heavy metals are known to accumulate in various environmental compartments and can devastatingly contaminate fish and water which in turn present a risk to humans. The dearth of ecotoxicological data with regard to the heavy metal content in Trachurus trachurus from selected cold room in Benin City, Edo State, Nigeria, warranted this research. The heavy metals assessed were; Cadmium (Cd), Copper (Cu), Zinc (Zn) and Lead (Pb), between September, 2021 to December, 2021. The samples were conveyed in labelled polythene bags to the laboratory, oven-dried and crushed to fine powder. Thereafter, they were digested with 65% nitric acid (HNO₃) and 70% perchloric acid (HClO₄), in the ratio of 3:1, before analysis, which was achieved via Atomic Absorption Spectrometric technique (UNICAM 969 SERIES, BELGIUM). The summary statistics for heavy metals in T. trachurus ranged from 0.0289 mg/kg for Cd to 7.077 mg/kg for Zn while the mean concentrations (mg/kg) of heavy metals in T. trachurus by cold rooms ranged from 0.242 for Cd at Uselu to 52.98 for Zn also at Uselu, with observed significant differences (p<0.05) in the mean concentrations of heavy metals in T. trachurus between cold rooms. The target hazard quotient (THQ) values ranged from 0.0000276 for Cd to 0.0000135 for Zn with a total target hazard quotient(TTHQ) value of 0.0000267, while the estimated annual intake (EAI) and estimated daily intake (EDI) of heavy metals were at a peak for Zn with values of 1.345 mg/person/year and 0.00368 mg/person/day respectively. The total toxicity of mixtures (TTM) value for heavy metals in T. trachurus was 0.845 while the quota for heavy metals in T. trachurus ranged from 0.36% for Cd to 87.80% for Zn. The total heavy metal burden in T. trachurus by cold rooms ranged from 46.95 mg/kg at Oliha to 54.37 mg/kg at Uselu. The research established that T. trachurus from cold room were safe for human consumption with regard to heavy metal levels as International threshold levels for metals in fish were not surpassed. It was proffered that continuous monitoring of the heavy metal status of this fish species is maintained in order to protect the health of potential consumers.