Human risk associated with potential exposure to heavy metals in a gadoid fish species from selected markets in Benin City, Nigeria

Abstract

The study ascertained the levels of Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn) in the Atlantic cod (Gadus morhua) of mean weight 679 ± 16.05 g, from selected markets in Benin city, Nigeria, by Atomic Absorption Spectrometric technique, in order to ascertain their suitability for human consumption. The mean concentrations of heavy metals in G. morhua ranged from 0.03 mg/kg Cd at New Benin market to 52.85 mg/kg for Zn at Ramat market while there was no significant difference (p>0.05) in the mean concentrations of heavy metals in fish between markets. The estimated daily intake (EDI) values for heavy metals ranged from 0.0032 mg/person/day for Cd to 1.70 mg/person/day for Zn while the estimated annual intake (EAI) values for heavy metals ranged from 1.17 mg/person/year for Cd to 620.5 mg/person/year for Zn. The estimated quantity consumed (EQC) values ranged from 0.000064 mg/meal for Cd to 0.034mg/meal for Zn while the theoretical maximum daily intake (TMDI) was 2414 mg/person/day. The margin of exposure (MOE) values for heavy metals ranged from 0.63 for Cd to 4.19 for Cu while the total toxicity of mixtures (TTM) value was 4.82. The toxic/hazard quotient (TQ) values ranged from 0.24 for Cu to 1.60 for Cd while the total heavy metal load in fish by market, ranged from 41.26 mg/kg at New Benin market to 59.27 mg/kg at Ramat market. The mean concentrations of Cd, Pb and Zn in G. morhua exceeded the thresholds established for heavy metals in fish by CODEX Alimentarius, Commission Regulation and Food and Agriculture Organization of the United Nations  (FAO), thus making them the metals of critical ecological concern. The implication is that G. morhuamust be consumed with caution in order to avert health problems associated with excess concentrations of Cd, Pb and Zn.

Keywords: heavy metals, Gadus morhua, toxic/hazard quotient, markets, Nigeria