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Lead, Mercury and Cadmium in Fish and Shellfish from the Indian Ocean and Red

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Lead, Mercury and Cadmium in Fish and Shellfish from the Indian Ocean and Red Journal of Marine Science and Engineering Review Lead, Mercury and Cadmium in Fish and Shellfish from the Indian Ocean and Red Sea (African Countries): Public Health Challenges Isidro José Tamele 1,2,3,* and Patricia Vázquez Loureiro 4 1 Department of Chemistry, Faculty of Sciences, Eduardo Mondlane University, Av. Julius Nyerere, n 3453, Campus Principal, Maputo 257, Mozambique 2 Institute of Biomedical Science Abel Salazar, University of Porto, R. Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal 3 CIIMAR/CIMAR—Interdisciplinary Center of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto, Avenida General Norton de Matos, 4450-238 Matosinhos, Portugal 4 Department of Analytical Chemistry, Nutrition and Food Science, Faculty of Pharmacy, University of Santiago de Compostela, Santiago de Compostela, 15782 A Coruña, Spain; [email protected] * Correspondence: [email protected] Received: 20 March 2020; Accepted: 8 May 2020; Published: 12 May 2020 Abstract: The main aim of this review was to assess the incidence of Pb, Hg and Cd in seafood from African countries on the Indian and the Red Sea coasts and the level of their monitoring and control, where the direct consumption of seafood without quality control are frequently due to the poverty in many African countries. Some seafood from African Indian and the Red Sea coasts such as mollusks and fishes have presented Cd, Pb and Hg concentrations higher than permitted limit by FAOUN/EU regulations, indicating a possible threat to public health. Thus, the operationalization of the heavy metals (HM) monitoring and control is strongly recommended since these countries have laboratories with minimal conditions for HM analysis. Keywords: heavy metals; seafood monitoring; Indian Ocean; Red Sea; lead; mercury; cadmium; public health 1. Introduction Seafood (fish and shellfish) is one of the main food and international economic sources in many coastal countries [1,2]. Additionally, it contains an essential nutritional composition which is crucial to human diet such as vitamins D, B12, A and E (for bones fortification [3]; nucleic acids synthesis, red blood cell and neurological function [4]; maintenance of vision and respiratory tract [5]; and for antioxidant defense [5], respectively), minerals [Selenium (for antioxidant defense and thyroid function regulation) [6], calcium (for maintenance of bones and teeth) [7], Zinc (for enzymatic catalysis for human metabolism and immune system functioning) [5], Iron (for oxygen transportation in the blood) [8], proteins (for enzymatic composition) [9], lipids [!-3 polyunsaturated fatty acids, especially eicosapentaenoic acid and docosahexaenoic acid (for prevention the of heart disease due to low cholesterol content) [10]], iodine (for the production and functioning of the thyroid) [8] and others. On the other hand, seafood is one of the vectors of heavy metals (HM) occurring naturally or introduced in the marine environment by different human activities, mainly, port activities, mineral resources extraction in marine and fluvial environments or untreated discharges of chemical industries or domestic wastes [11–25]. Reported HM that are environmentally relevant due to their effects on the species found in the marine environment, including seafood, which constitute a threat for public J. Mar. Sci. Eng. 2020, 8, 344; doi:10.3390/jmse8050344 www.mdpi.com/journal/jmse J. Mar. Sci. Eng. 2020, 8, 344 2 of 32 J. Mar. Sci. Eng.health, 2020, 8, 344 include: lead (Pb), mercury (Hg) and cadmium (Cd) [11–25], due to2 of their 36 involvement in the activation of enzymes and biochemicals, constituting a base for human organism functioning. involvement in theThe activation presence of ofenzymes HM in and seafood biochemicals, is one of constituting the main threats a base for to publichuman health,organism and its monitoring and functioning. control has to be done rigorously in African countries of the Indian Ocean and the Red Sea, where The presence of HM in seafood is one of the main threats to public health, and its monitoring most of the seafood from marine environments are consumed directly without quality control due to and control has to be done rigorously in African countries of the Indian Ocean and the Red Sea, where most of the seafoodpoverty from [20, 26marine,27]. environments Thus, the main are objectiveconsumed of directly this review without was quality to assess control the due incidence to of Pb, Hg and poverty [20,26,27].Cd in seafoodThus, the from main African objective Indian of this and review the Redwas to Sea assess coasts the and incidence the level of Pb, of theirHg and monitoring and control; Cd in seafoodsome from recommendations African Indian and will the also Red be Sea presented. coasts and In the this level review, of their the termmonitoring “HM” and is used to refer to Pb, Hg control; someand recommendations Cd and “seafood” will also to refer be presented. to fish and In this shellfish. review, the term “HM” is used to refer to Pb, Hg and Cd and “seafood” to refer to fish and shellfish. 2. Heavy Metals and Their Effects on Humans 2. Heavy Metals and Their Effects on Humans The occurrence of HM in seafood is one of the main threats to public health since they cause The occurrenceseveral negativeof HM in eseafoodffects in is humans,one of the of ma whichin threats the to most public reported health inducesince they oxidative cause stress [28–36] and several negative effects in humans, of which the most reported induce oxidative stress [28–36] and inactivation of crucial molecules in the human organism, such as sulfhydryl groups [metallothionein inactivation of crucial molecules in the human organism, such as sulfhydryl groups [metallothionein (MT) [37,38] and glutathione (GSH)] [39,40] for Cd, Hg and delta-aminolevulinic acid dehydratase, (MT) [37,38] and glutathione (GSH)] [39,40] for Cd, Hg and delta-aminolevulinic acid dehydratase, delta-aminolevulinicdelta-aminolevulinic acid synthase and acid ferrochelatase synthase and for ferrochelatase Pb [41]. Thus, forthe control Pb [41]. and Thus, monitoring the control and monitoring of HM in seafoodof HM is in most seafood important is most to minimize important associated to minimize seafood associated poisoning. seafood The monitoring poisoning. of The monitoring of HM in seafoodHM requires in seafood active requires organization active because organization there are because a lot of aspects there are that a have lot of to aspects be taken that have to be taken into consideration,into consideration, from the sampling from process the sampling to data processinterpretation. to data HM interpretation. occurs in seafood HM inoccurs the in seafood in the form of differentform species of diff erentdistributed species in a distributed heterogeneous in amanner heterogeneous in different manner seafood in tissues. different Different seafood tissues. Different monitoring monitoringprograms of programsHM (Table of1) specify HM (Table the edibles1) specify tissues the (generally edibles tissues muscle) (generally and seafood muscle) and seafood species to bespecies monitored to be and monitored recommend and the recommend permitted HM the limit permitted for each HM tissue limit and for species each tissue(Table and species (Table1). 1). The analytical methods that are used for HM monitoring, the different human biomarkers and the The analytical methods that are used for HM monitoring, the different human biomarkers and the methods of their detection are described in Table 1. The most reliable HM biomarker is their presence methods of their detection are described in Table1. The most reliable HM biomarker is their presence in essential biological fluids, such as urine and blood, since the biochemical biomarkers seem similar for many HMsin essential[20,26,27,42–44]. biological HM fluids,poisoning such treatmen as urinets consist and blood, generally since of the the biochemicaladministration biomarkers of seem similar chelating agentsfor many that complex HMs [20 the,26 HM,27 ,an42d– 44that]. are HM later poisoning excreted treatmentsin urine. consist generally of the administration of chelating agents that complex the HM and that are later excreted in urine. Table 1. Lead compounds toxicologically relevant. TtEL—tetraethyllead, TEL—trimethyl lead, TML—trimethylTable lead, 1. X -halideLead compounds(Cl). toxicologically relevant. TtEL—tetraethyllead, TEL—trimethyl lead, TML—trimethylStructure R lead,1 X -halideR2 (Cl).R3 R4 Name CH3CH2 CH3CH2 CH3CH2 CH3CH2 TtEL Structure R1 R2 R3 R4 Name X CH3CH2 CH3CH2 CH3CH2 TEL R1 CH3CH2 CH3CH2 CH3CH2 CH3CH2 TtEL R4 Pb R2 X CH3CH2 CH3CH2 CH3CH2 TEL X CH3 CH3 CH3 TML R3 X CH3 CH3 CH3 TML PbSO4 - - - - Lead sulphate Pb3(PO4)2 - - - - Lead phosphate PbSO4 - - - - Lead sulphate Pb3PbS(PO4)2 - -- - - - Lead - phosphate - Lead sulfide PbCOPbS 3 - -- - - - -Lead sulfide - Lead carbonate PbCO3 - - - - Lead carbonate 2.1. Cadmium 2.1. Cadmium 2+ Cadmium usuallyCadmium occurs usually in the environment occurs in the in environmentthe ionic form inCd the2+ (Cadmium ionic form oxide—CdO Cd (Cadmium2, oxide—CdO2, cadmium chloride—CdClcadmium chloride—CdCl2 or cadmium sulfate—CdSO2 or cadmium4 [42]. sulfate—CdSO Cd is considered4 [42]. the Cd seventh is considered most toxic the seventh most toxic nonessentialnonessential heavy metal [44] heavy and metalenters [the44] environm and entersent theby natural environment sources, by such natural as volcanism sources, [45], such as volcanism [45], and anthropogenicand anthropogenic
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