Studio ecotossicologico sull’ aguglia imperiale, Tetrapturus belone (Rafinesque, 1810): esposizione, accumulo ed effetti di contaminanti e considerazioni sul consumo umano

The Mediterranean spearfish, Terapturus belone (Rafinesque, 1810), is a large pelagic fish inhabiting the Mediterranean Sea, poorly known especially from an ecotoxicological point of view. In the present research, the first data regarding the bioaccumulation of trace elements and organochlorine compounds, as well as the levels of biomarkers of exposure and/or effect have been provided for T. belone. Human health implications related to the consumption of the species have been also evaluated. In particular, concentrations of elements of high ecotoxicological relevance such as mercury, cadmium, lead and selenium were determined in muscle and liver providing a first general overview for the species. Trace element levels were generally comparable with those reported for other large fish predators. A higher bioaccumulation of Cd and Se in the liver compared to the muscle was found, while Hg and Pb showed comparable levels in both tissues. A possible detoxification effect of Se on Hg and Cd was also discussed. Human health implications due to the consumption of T. belone were assessed considering Hg and Se concentrations, in comparison with tuna and swordfish. For this purpose, maximum permissible levels were considered and risk/benefit indexes such as the Estimated Weekly Intake (EWI), the Target Hazard Quotient (THQ) and the Selenium Health Benefit Value (HBVSe) were calculated. The assessment was carried out considering also the bioaccessible fractions of the elements, i.e. the fraction actually released from a food as a result of digestive processes, obtained via an in vitro extraction test (Physiologically Based Extraction Test, PBET). The consumption of T. belone represents a lower risk in comparison to tuna and swordfish, however, taking into account only Hg total or bioaccessible concentrations, the species could still raise concern. Nevertheless, taking into account also the levels of Se, which is protective of Hg toxicity, T. belone could be considered healthy for consumption. The investigation of organochlorines (DDTs, PCBs and HCB) concentrations in the liver showed unexpectedly high levels of DDTs and PCBs compared to other large Mediterranean fish. Regarding biomarkers, levels of mixed function monooxygenase (MFO) system and plasma butyrylcholinesterase (BChE) as well as the frequency of erythrocytic nuclear abnormalities (ENA assay) were determined. MFO levels were comparable with those reported for other Mediterranean fish species, but unexpectedly higher in females than in males. BChE activity, lower in comparison to some other fish species, could be likely attributed to specific biological and ecological characteristics of T. belone, as well as the frequencies of erythrocytic abnormalities were probably within natural values. No significant correlations were found between biomarkers and levels of metals (Hg, Cd and Pb) and organochlorines, except for the positive relationship between ENA assay results and op’DDE. This work represents an ecotoxicological baseline for the Mediterranean spearfish by providing a first set of data that could be useful for future monitoring investigations. Moreover, with a view to a possible greater commercialization of T. belone it also offers an initial risk assessment related to the human consumption of the species.