Occurrence of toxic metals (Hg, Cd and Pb) in fresh and canned tuna: Public health implications
Introduction
An adequate human diet should satisfy the requirements for energy and nutritive components including essential polyunsaturated fatty acids, essential aminoacids, mineral components, vitamins and fat. Fish contains all these substances, but the most important feature of this food is an advantageous fatty acid profile, resulting from the consistent content of essential polyunsaturated fatty acids, such as eicosapentaenoic and docosahexaenoic acid, known to support good health (Usydus et al., 2009). It is estimated that the consumption of one portion of fatty fish, daily, delivers about 900 mg/day of n-3 acids, with consequent reduction of mortality in patients with coronary diseases (Kris-Etherton et al., 2002). However, the indisputable benefits deriving by fish consumption may be offset by the presence in their meat of toxic metals, such as Cd, Pb and especially Hg, which is present in many fish species often at levels exceeding the safety standards established by legislation of the various countries. In relation to this, it is important to remark that with the exception of occupational exposure, the main Hg exposure for human is the ingestion of contaminated fish, especially larger predators. Amongst those species recognised as potentially accumulating elevated metal levels, tuna is one of the most frequently consumed and commercially available groups of fish worldwide (Burger et al., 2005). These pelagic organisms are high performance fish with very high metabolism rates and, thus, high food intake rates, a property that accentuates the exposure to trace elements (Kojadinovic et al., 2007). Consequently, adverse human health effects may occur if this fish is consumed too often or in large enough quantities. In this context it is also of interest to consider canned tuna, which amongst canned fishery products is doubtless the most largely and frequently consumed. Canned tuna is, in fact, well eaten in the developed world, especially in Europe because it is convenient and affordable for most working families. Europe is the world’s largest market for canned tuna with 34% of the global consumption and Italy is, after Spain, the second country in canned tuna consumption (Food Market Exchange, 2003; Glitnir Seafood Team, 2007). Nevertheless, publications on the concentrations of toxic elements in canned tuna and dietary intakes of these elements via these fishery products in Italy are lacking. Also for fresh tuna, information on these topics is rather limited, although the few literature data confirms ability of these large pelagic predators to accumulate substantial levels of toxic metals, especially mercury (Storelli et al., 2002, Licata et al., 2005). In the light of what above reported the objectives of present investigation are the following:
- 1)
to determine the concentration levels of Hg, Pb, Cd either in the edible portion of tuna (thunnus Thynnus) from Mediterranean Sea (Tyrrhenian Sea), or in canned tuna (thunnus albacares) samples purchased from supermarkets located in different Italian cities
- 2)
to ascertain whether the metal concentrations are below the maximum levels established by the European Legislation (Official Journal of the European Union, 2006, EFSA, 2009)
- 3)
to estimated the weekly intake and compared it with the Provisional Tolerable Weekly Intake (PTWI) recommended by the Joint FAO/WHO Expert Committee on Food Additives (WHO, 2006, EFSA, 2009).
Section snippets
Collection of samples
In June–August 2007, 20 specimens of bluefin tuna (T. thynnus) (length: 105–218 cm, average 140.5 ± 27.1 cm; weight: 13–161 kg, average 56.4 ± 34.0 kg) from Tyrrhenian Sea were caught. Approximately 0.1–0.3 kg of muscle tissue was removed from the anterior portion of the carcass by a transverse dissection near the dorsal fin. The tissues were dissected with plastic materials that were washed with HNO3 and rinsed with distilled and deionized water, in order to avoid metal contamination. Concerning canned
Content of toxic metals in fresh tuna
Among the metals analysed, Hg (0.07–1.76, average: 0.61 μg g−1 wet wt) showed the highest concentration, followed by Pb (ND-0.33, average: 0.07 μg g−1 wet wt) and Cd (ND-0.03, average: 0.01 μg g−1 wet wt). Among these toxic metals only Hg was present in all tuna specimens, while Cd and Pb were detected in 95% and 85% of the samples analyzed, respectively. From a more detailed analysis of results it appeared that Cd and Pb levels were rather low and did not exhibit a wide between-specimen variation,
Conclusion
In all tested samples, Hg exhibited the highest concentrations followed by Pb and Cd. The amounts of Cd and Pb were well below the maximum permitted concentrations by EU legislation for the human consumption, whereas 8.9% of the tuna cans and 20% of fresh tuna samples exceeded standard for MeHg. In addition, a general picture of the results concerning the consumer exposure showed that Cd and Pb weekly intakes through either consumption of fresh tuna or canned tuna remained within safety
Conflict of Interest
The authors declare that there are no conflicts of interest.
References (37)
- et al.
Concentrations of trace elements in marine fish and its risk assessment in Malaysia
Mar. Pollut. Bull.
(2005) - et al.
Fishing, consumption, and risk perception in fisherfolk along an East coast estuari
Environ. Res.
(1998) - et al.
Mercury in canned tuna: white versus light and temporal variation
Environ. Res.
(2004) - et al.
High contents of cadmium, lead, zinc and copper in popular fishery products sold in Turkish supermarkets
Food Control
(2007) - et al.
Heavy metals content of canned tuna fish
Food Chem.
(2005) - et al.
Effect of canned tuna fish processing steps on lead and cadmium contents of Iranian tuna fish
Food Chem.
(2010) - et al.
Assessment of trace elements in canned fishes (mackerel, tuna, salmon, sardines and herrings) marketed in Georgia and Alabama (United States of America)
J. Food Comp. Anal.
(2005) - et al.
Bioaccumulation of trace elements in pelagic fish from the Western Indian Ocean
Environ. Pollut.
(2007) - et al.
Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer
Am. J. Med.
(2002) - et al.
Total mercury intake from fish and shellfish by Japanese people
Chemosphere
(1997)
Effects of canning on total mercury, protein, lipid, and moisture content in troll-caught albacore tuna (Thunnus alalunga)
Food Chem.
Heavy metal concentrations in fish, shellfish and fish products from internal markets of India vis-a-vis international stantards
Food Chem.
Potential human health risks from metals (Hg, Cd, and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: Estimation of target hazard quotients (THQs) and toxic equivalents (TEQs)
Food Chem. Toxicol.
Simulation and prediction of anthropogenic lead perturbation in the Mediterranean Sea
Sci. Total Environ.
Determination of trace metals in canned fish marketed in Turkey
Food Chem.
Fish products available in polish market – Assessment of the nutritive value and human exposure to dioxins and other contaminants
Chemosphere
Mercury, cadmium and lead content of canned tuna fish
Food Chem.
Levels of selected heavy metals in tuna fish
Arab. J. Sci. Eng.
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2023, Marine Pollution BulletinCitation Excerpt :Following the EU and US, Latin American countries have the highest annual consumption of canned tuna (FFA, 2011). The consumption of canned tuna is increasing day by day globally (National Fisheries Institute, 2019; Storelli et al., 2010). Tuna accumulates a significant amount of mercury and other toxic metals, especially compared to some other fish species.