Heavy Metal Burden and Health Risk Assessment of Fresh, Frozen and Smoked Fish from a Local Market in Southwest Nigeria

Heavy metals load in fish environment and fish products had been an issue of public concern. The burden of some heavy metals in fresh tilapia (Oreochromis niloticus), frozen Herring (Clupea harengus), smoked herring, and associated risk to man was investigated. Atomic absorption spectrometry was used to determine metal concentrations. Standard risk measurement indices [daily metal intake (DMI), hazard quotient (HQ), and health risk index (HRI)] were used. Levels of Mn and Fe were significantly different (p<0.05) among the fish species, while the burden of other metals was low to not detected in the samples. The level of Cu (0.11 +/- 0.04), Zn (2.51 +/- 0.82), and Fe (8.72 +/- 4.41) were recorded in the bones of smoked herrings, while the highest levels of Mg were recorded in fresh tilapia. Gills recorded significantly (p<0.05) high levels of Mg (1.16 +/- 0.02), Fe (14.92 +/- 0.53), Cu (0.10 +/- 0.00), and Zn (1.35 +/- 0.04). The muscle of the frozen herring records the highest burden of these metals. Mn, Fe, Cu, and Cd revealed the highest HRI in all fish samples and age categories, especially for nine years old and below children. In conclusion, health fish indicators revealed that Mn, Fe, Cu, and Cd pose a risk to the populace and, with long time consumption, can do more damage to consumers, especially frozen herring.