Assessment of metal concentrations in oysters and shrimp from Atlantic Coast of the Democratic Republic of the Congo

Abstract

Oysters and shrimp are abundant and commonly consumed seafood by the indigenous population of the Kongo central region of the Democratic Republic of the Congo (DRC). Literature reviews suggest that no data were available for the metal concentrations in these species. Consequently, the purpose of this study is to determine the metal concentrations in tissues of oysters (<i>Egeria congica</i>) and shrimp (<i>Macrobrachium</i> spp., <i>Parapenaeus</i> spp., <i>Penaeus</i> spp.) collected in November 2017 from the Atlantic Ocean Coast of DRC in the territory of Muanda. Metal levels in the seafood species studied here were put into context using international regulation for human consumption set by the Food and Agriculture Organization (FAO), Canadian Food Inspection Agency (CFIA), European Union (EU), and World Health Organization (WHO). Our results demonstrated that the concentration of heavy metals varied considerably between sampling sites and analyzed species (P < 0.05), with the values (in mg kg¹) ranged between 0.05-0.41, 0.03-2.25, <LOD (limit of detection)-1.39, 4.19-60.46, 46.36-319.27, 0.18-3.74, 0.030.35, <LOD-0.01, 0.08-0.64, 1.12-25.76, 0.04-3.40 and 9.73-924.33 for Hg, Cr, Ni, Cu, Zn, Se, Cd, Sb, Pb, Mn, Co, and Fe, respectively. High concentrations of Cr, Mn, Co and Fe were found in <i>Egeria congica</i>; Cu in <i>Macrobrachium</i> spp., and Hg and Sb in <i>Parapenaeus</i> spp. Cu levels in 33.3% of <i>Macrobrachium</i> spp. and 16.7% <i>of Egeria congica</i> samples exceeded the FAO permissible limit of 30 mg kg^-1 (wet weight (ww)). The concentration of Pb in one of six analyzed <i>Egeria congica</i> exceeded the EU permissible limit of 0.5 mg kg^-1 (ww). The average values of Zn in all species exceeded the CFIA permissible limit of 50 mg kg^-1 (ww). Metal pollution can be explained by several activities which include but not limited to oil exploitation, fuel traffic and tanker navigation, and erosion. High metal concentrations in investigated organisms present potential consumer human health risks.