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

Robert B Suami,Dhafer Mohammed M Al Salah,César D Kabala,J.-P Otamonga,Crispin K Mulaji,Pius T Mpiana,John W Poté

doi:10.1016/j.heliyon.2019.e03049

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 (Egeria congica) and shrimp (Macrobrachium spp., Parapenaeus spp., Penaeus 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 Egeria congica; Cu in Macrobrachium spp., and Hg and Sb in Parapenaeus spp. Cu levels in 33.3% of Macrobrachium spp. and 16.7% of Egeria congica samples exceeded the FAO permissible limit of 30 mg kg−1 (wet weight (ww)). The concentration of Pb in one of six analyzed Egeria congica 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.

Highlights

In marine environments, heavy metals contamination has been of great concern due to inherent toxicity of living organisms, potential ecological effects, vast sources, persistence, non-degradability, bioaccumulation, long biological half-lives, and public food safety (Besada et al, 2011; Wang et al, 2013; Le et al, 2016; Jonathan et al, 2017; Ross et al, 2017)
The main objectives of this study were (i) to evaluate the concentration of metals including Hg, Cr,Ni, Cu, Zn, Se, Cd, Sb, Pb, Mn, Co, and Fe in oyster tissues (Egeria congica) and in three shrimp (Macrobrachium spp., Parapenaeus spp., Penaeus spp.) from the Atlantic Coast of the Democratic Republic of the Congo (DRC) in the territory of Muanda, (ii) to compare the metal concentrations in investigated seafood species with international regulations set for human consumption
This research was performed in the Atlantic Coast of DRC in the territory of Muanda, located in the West of the Democratic Republic of the Congo, province of Kongo Central, district of Boma, Muanda territory (Figure 1)

Summary

Introduction

Heavy metals contamination has been of great concern due to inherent toxicity of living organisms, potential ecological effects, vast sources, persistence, non-degradability, bioaccumulation, long biological half-lives, and public food safety (Besada et al, 2011; Wang et al, 2013; Le et al, 2016; Jonathan et al, 2017; Ross et al, 2017). The World Health Organization (WHO) recommends the control of heavy metals in food sources in order to assure public safety (Heidarieh et al, 2013; Olgunoglu et al, 2015). The extent of heavy metal accumulation within an organism is affected by internal and external factors. External factors include total amount of each metal bioavailability in the environmental medium, route of uptake, dissolved metals, dissolved oxygen, interactions between metals, sediment, food, seasonal effects and geographical differences (Chapman et al, 1996; Gokoglu et al, 2008; Chiarelli and Roccheri, 2014; Olgunoglu et al, 2015)

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