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Identifier 000421744
η
Title Study of the contamination of aquaculture and wild fish with Heavy Metals and Organochlorine environmental contaminants. Risk assessment and health implications for humans.
Alternative Title Μελέτη επιμόλυνσης ιχθύων προερχόμενων από ιχθυοκαλλιέργειες και ανοιχτή θάλασσα σε βαρέα μέταλλα και οργανοχλωριωμένους περιβαλλοντικούς μολυντές. Εκτίμηση επιβάρυνσης της διατροφικής αλυσίδας και επιπτώσεις στην ανθρώπινη υγεία.
Author Ρενιέρη, Ελισάβετ-Μαρία
Thesis advisor Τσατσάκης, Αριστείδης
Reviewer Κεντούρη, Μαρουδιώ
Divanach, Pascal
Τζαρδή, Μαρία
Τσακάλωφ, Ανδρέας
Τσιλιγιάννη, Ιωάννα
Ψαρουλάκη, Αννα
Abstract The objective of the thesis was to elucidate aspects of contaminant accumulation and toxicity in the fish as well as to monitor the contaminant load namely: Cd, Pb, Hg and PCBs in commonly consumed fish species from two modes of production, aquaculture and fisheries in Greece. Ultimately, the risk for human health through fish consumption was assessed for the Greek population. For the investigation of metal accumulation and toxicity issues in the fish organism an in vivo study, was planned with aim to investigate zebrafish responses to a range of Cd exposure levels, spanning from environmental to toxic. The hypothesis that there is a linear survival response to exposure levels was examined while further histopathological analysis was conducted, in an attempt to correlate Cd effects with mortality. The results of the study showed that zebrafish accumulated Cd in their tissues in a dose dependant, but not time dependant manner. However, zebrafish manifested deviations from the anticipated linear toxic responses. Documented responses regarding mortality rate were non-linear, supporting the increasingly gaining ground hypothesis of non-monotonic and not linear responses to gradient exposures to toxic stimuli. Histopathological findings also deviated from the anticipated dose dependant responses, revealing more severe effects in lower than the most toxic exposures, while adverse effects occurred even at environmental levels. Moreover, there was a low Cd exposure level with surprisingly high mortality rate for zebrafish, which drew the attention and this level could hold a key to the elucidation of the toxicity coping mechanisms, since modifications of these mechanisms beyond this level are implied by our results. Marine fish, and specifically gilthead seabream (Sparus aurata) and sea bass (Dicentrarchus labrax), are widely farmed and consumed in Greece. Health benefits of fish consumption could be counterbalanced by the intake of contaminants after long term consumption of fish, burdened even in trace levels. In order to assess the contaminant load in the frequently consumed fish species, samples of gilthead seabream and sea bass were collected from aquaculture sites located in the Aegean Sea and the Sea of Crete as well as the fish market of Heraklion, Crete. The heavy metal load (Cd, Pb and Hg) in the edible part the fish was evaluated and the main factors affecting the heavy metal accumulation in the fish muscle tissue were 7 investigated. Moreover, risk assessment for the Greek population from fish consumption was conducted based on the determined heavy metal concentrations. Heavy metal levels in fish were determined at levels far below the safe limits for consumption set by authorities, for each metal individually as well as for their sum. Gilthead seabream and seabass demonstrated significant differences in Hg and Cd levels which can be attributed to a number of reasons such as differences in intrinsic factors between species, different metal behaviour, different aquafeed metal load or a combination of all the above. Hg and Pb seem to be more accumulated in closed seas, which could imply that these metals have a similar distribution pattern in the medium of exposure (water), or that they share the same origin of dispersion, possibly waste disposals from human activity. Metal levels, were clearly affected by seasonality and season dependent variations disclosed a species effect as well, since significant differences in metal accumulation amongst seasons were recorded between species. Differences in metal levels between farmed and wild fish were demonstrated which can be the combined result of different feeding behaviour, growth rate and therefore metabolic rate, aside from the effects of waterborne exposure. The risk evaluation we conducted for Greek consumers based on the metal levels we determined in the most frequently consumed fish, both farmed and wild indicates minimal risk for all metals. Furthermore, the occurrence and burden of the indicator PCBs (ΣPCB-7) in the same fish was determined. Additionally, the association of the ΣPCB-7 accumulation in fish to seasonality, locality, production mode and species was investigated. For the characterization of the hazard of PCB intake through fish consumption for the Greek population, a more elaborate risk assessment method, than those previously used, was developed. Occurrence and levels of the ΣPCB-7 in the muscle tissue of farmed and wild gilthead seabream and seabass reveal that for both species and both modes of production, levels were far below the maximum permissible limits set by the EU (2011). More highly chlorinated congeners such as PCB 138 and PCB 153 were more abundant and more frequently detected in fish tissues, most probably due to higher resistance to degradation and lipophilicity. Wild fish presented higher levels of the ΣPCB-6, while farmed fish accumulated PCB 118 at higher levels. Both ΣPCB-6 and ΣPCB-7 levels are primarily affected by the fish species which is in close relationship to the fact that our results highlighted seasonality, as an important factor affecting PCB accumulation and distribution in fish muscle tissue, as well. Seasonal alterations in PCBs levels seem to be dictated by each species ecology and biological cycle. Distinctions in PCB congeners between open and closed seas were also demonstrated which could be attributed to different types and sources of contamination. The exposure assessment showed that NDL-PCB intake through fish consumption for the Greek adult population is comparable to other European countries. The use of consumption data from the two different sources resulted in slightly divergent exposure results underlying the importance of dietary habits for exposure. 8 Α new food specific HI approach was developed, for which fish contribution to the maximum permitted aggregated dietary exposure was considered, arriving to a lower value for the HI. Risk characterization revealed no risk for Greek consumers. In summary, two major groups of environmental contaminants, heavy metals and PCBs, which can be hazardous to both fish and humans, were determined in fish tissues and investigation revealed that accumulation and toxicity are affected by both abiotic and biotic factors. Secondly, risk assessment conducted for the Greek population regarding fish consumption revealed no risk. Finally, a new risk characterization method was proposed based on food specific HI approach.
Language English
Subject Cadmium
Exposure
Lead
Mercury
Κάδμιο
Μόλυβδος
Πολυχλωρωμένα διφαινύλια( PCBs)
Υδράργυρος
Ψάρια
Issue date 2019-03-27
Collection   Faculty/Department--School of Medicine--Department of Medicine--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/9/1/2/metadata-dlib-1554305207-124110-10638.tkl Bookmark and Share
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