Distribution and toxicological risk assessment of metals in commercial fish species from a lentic ecosystem in Nigeria

Abstract

Background of Study

The increasing exposure of lentic water bodies to pollutants and the ability of aquatic organisms to bioaccumulate heavy metals in its edible body parts has raised concerns on the food safety of aquatic animals harvested from them. This study investigated the distribution of metals in the organs of C. gariepinus and T. zillii from Ikpoba reservoir and evaluated the potential human health risk associated with their consumption.

Methodology

Fish samples of Clarias gariepinus and Tilapia zillii were collected for a period of six months (January 2019 to June 2019) from Ikpoba reservoir using a drag net with the assistance of artisanal fishermen. Fish samples were properly identified and heavy metal content in the gills, liver and muscles were determined using atomic absorption spectrophotometer.

Findings

The results showed that C. gariepinus had higher mean concentration of metals and metalloids than T. zillii in all the organs examined. The order of accumulation of metals in the gills and muscles of C. gariepinus and T. zillii was Fe > Zn > Mg > Cu > Pb > Cd, while order in the liver for both fish species was Fe > Zn > Cu > Mg > Pb > Cd. Human health risk assessment for metals in C. gariepinus and T. zillii indicated no significant health risk to the adults (HI < 1), whereas children were predisposed to health risk of non-carcinogenic effect (HI > 1). Carcinogenic risk values for Pb and Cd in adults and children did not exceed the acceptable carcinogenic risk value for humans. The integrated carcinogenic risk (ICR) values classified the consumption of C. gariepinus and T. zillii as low – medium risk (Grade III).

Conclusion

The study has shown that the consumption of the selected fish species is not safe for children. Also, the consumption of the gills of C. gariepinus along with the head portion of the fish should be discouraged to reduce exposure to heavy metal toxicity. The continuous monitoring of activities within the reservoir watershed to mitigate heavy metal pollution of the reservoir is recommended.