Variations in some heavy metal concentrations and public health risk implications in silver catfish (Chrysichthys nigrodigitatus) and tongue sole (Cynoglossus senegalensis) from the Cross River Estuary

The bioavailability of metals generally differs across species due to species-specific physiological and metabolic differences, changes in behavioral patterns, and habitat preferences. The organ-specific bioaccumulation potential of different heavy metals in organisms is determined by their affinities to these different organs. This study investigated the variations in concentrations of some heavy metals and potential health risk implications in Chrysichthys nigrodigitatus and Cynoglossus senegalensis collected from the Cross River Estuary, Calabar, Nigeria. The fish samples (n=40; 20 per species) were obtained at the Nsidung beach, Calabar, the liver and muscle of the fish samples analyzed for Cr, Cu, Fe, Ni and Zn using atomic absorption spectrophotometer. Higher concentrations of metals were recorded in the liver of both sampled fish species compared with the muscles indicating organ-specific accumulation. Also, C. nigrodigitatus showed a higher accumulation of heavy metals concentrations compared with Cynoglossus senegalensis suggesting a species-specific sensitive accumulation. Our data indicates that C. nigrodigitatus accumulated Cr, Cu, Fe, Zn, while the liver accumulated Cu, Fe. For C. senegalensis , the muscle accumulated Cr, Fe while the liver accumulated Cu, Fe and Zn. The health risk assessment showed that the Estimated Average Daily Intake (EADI) and Hazard Index (HI) of both Chrysichthys nigrodigitatus and Cynoglossus senegalensis were below the World Health Organization (WHO) Reference Dose (RfD), suggesting no potential health risk in to consumers. Given the occurrence and concentrations of heavy metals in aquatic food fish species, the results of this study highlight potential food safety, public health and ecological negative consequences of these groups of chemical contaminants.