Is the concentration of heavy metals in sun-dried Engraulicypris sardella (Günther, 1868) in Malawi, a human health risk?

Abstract

The effects of trophic cascades have made small-size pelagic fish species, such as Engraulicypris sardella, from Lake Malawi an important ecological and food system. However, human-induced activities can potentially pollute Lake Malawi exposing E. sardella to heavy metals contamination. This could pose a food system health risk to the population of Malawians and neighboring countries, which heavily rely on fish as a source of animal protein. Therefore, this study investigated the concentration levels of Lead (Pb), Cadmium (Cd), Zinc (Zn), Copper (Cu), Manganese (Mn), and Iron (Fe) in sun-dried E. sardella and conducted a health risk assessment associated with its consumption. E. sardella samples were collected from Karonga, Nkhata Bay, Nkhotakota, Salima, and Mangochi districts in Malawi between December 2023 and February 2024. The results revealed significant variations in Cd, Zn, Cu, Mn, and Fe concentrations among the sampled sites while Pb contamination was not detected. The concentrations of Zn, Cu, Mn, and Fe in E. sardella were within acceptable consumption limits set by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) in 2012. However, the fish's average Cd levels (0.17 mg kg⁻¹ ww) were slightly above the recommended threshold of 0.1 mg kg⁻¹ ww by FAO/WHO (2012) but remained below the limit of 0.5 mg kg⁻¹ ww set by FAO in 1983. Furthermore, none of the analyzed heavy metals posed a health risk effect to people. Therefore, there is a need for regular monitoring of heavy metal concentrations in E. sardella and other mostly consumed fish species from Lake Malawi, both fresh and processed, for a sustained guarantee of the safety of the fish consumers.