Bioaccumulation of toxic metals in commercially valuable fish from the western region of ghana

Fish is an important source of protein, however as human impacts on the environment through industrialization, mining and farming among others is resulting in increased concentration of toxic metals in them. The levels of copper (Cu), arsenic (As), zinc (Zn), lead (Pb), cadmium (Cd), mercury (Hg), and selenium (Se) were analysed in fish samples from the southwestern coast of Ghana using acid digestion and atomic absorption spectrophotometer method. A total of 71 fish species were sampled where 35 species were collected in the wet season (October, 2014) whereas 36 species were collected in the dry season (March, 2015). The average levels of heavy metals detected in the wet season were 1.08 mg/kg for Cu, 9.79 mg/kg for Zn, 4.80 mg/kg for Se, 0.06 mg/kg for Pb, 0.03 mg/kg for Hg, 0.02 mg/kg for As, and 0.01 mg/kg for Cd. The average values of heavy metals in fish samples analysed in the dry season were 2.17 mg/kg for Cu, 4.55 mg/kg for Zn, 8.13 mg/kg for Se, 0.06 mg/kg for Pb, 0.03 mg/kg for Hg, 0.09 mg/kg for As, and 0.005 mg/kg for Cd. The results showed that the average levels of toxic metals analysed in the wet season increased in the order of Cd<As<Hg<Pb<Cu<Zn<Se whereas the dry season increased in the order of Cd<Hg<Pb<As<Cu<Zn<Se. The levels of all seven heavy metals were below the FAO/WHO Maximum Permissible Limits (MPL), Australia New Zealand Food Standards, EU, Australian National Health and Medical Research Council (ANHMRC) standards. Hence the consumption of these fish poses no public health concern. The estimated daily intake of the various toxic metals analysed were lower than the daily intake of their respective toxic metals. The non-carcinogenic health risk to adults and children showed that the Total Targeted Hazard Quotients (TTHQ) was less than 1 (<1) hence poses no health risk to humans.