OCCURRENCE OF MERCURY AND ORGANOHALOGENS (PCBs, OCPs and BFRs) IN MARINE BIOTA OF DARAJANI MARKET.
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Date
2022-12-01
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SUZA
Abstract
Mercury and persistent organic pollutants have received a global concern due to their neurotoxic effect and ubiquitous nature. They can bioaccumulate in edible marine biota to the levels that can pose serious health effects to consumer. The aim of this study is to assess the distribution of mercury and organohalogen along the trophic levels in edible marine biota from Darajani Market and the suitability for human consumption. Fish species belong to different trophic levels, squid and prawns from Darajani Market in Zanzibar were analysed for total mercury and organohalogen contaminants to investigate their distribution and suitability of the biota for human consumption. The analysis revealed presence of both mercury and organohalogen contaminants. The oncentrations of organohalogen increased along the trophic levels indication their ability to biomagnify in marine biota but such magnification trend was not clear for total mercury. The
concentrations of mercury ranged from 0.004 mg/kg w/w in Mackerel to 0.156 mg/kg w/w in Tuna with overall mean of 0.0435±0.016 mg/kg w/w while mean levels of organohalogen contaminants across all species and seasons ranged from belowlimit of detection (LOD) to 129 ng/g lw ΣPCBs; 5.6–336 ng/g lw ΣOCPs; and <LOD –22.1 ng/g lw ΣBDEs. Composition of the measured organochlorines indicated that the contaminates are likely to originate from past wet deposition and terrestrial runoff while BDEs are originated from recent but same sources.
Variations of all contaminants within the marine biota were found to be strongly influenced by species identity while organochlorines (OCPs and PCBs) were also influenced by dietary habit of the biota. BDEs were the only contaminants which showed strong seasonal variations. The measured contaminants were within the lower ranges of the levels reported in the related studies. Comparison with different acceptable standard confirmed that the biota analysed in this study were fit for human consumption with respect to both mercury and organohalogen contamination except tuna which had mercury level slightly above EU standard. As Zanzibar is embarking to blue economy, there is an urgent need to establish regularmonitoring program that will focus in both classical and emerging toxic contaminants
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. The concentrations of organohalogen increased along the trophic levels indication their ability to biomagnify in marine biota but such magnification trend was not clear for total mercury. The
concentrations of mercury ranged from 0.004 mg/kg w/w in Mackerel to 0.156 mg/kg w/w in Tuna with overall mean of 0.0435±0.016 mg/kg w/w while mean levels of organohalogen ontaminants across all species and seasons ranged from belowlimit of detection (LOD) to 129 ng/g lw ΣPCBs; 5.6–336 ng/g lw ΣOCPs; and <LOD –22.1 ng/g lw ΣBDEs