Metal Concentrations in Two Commercial Tuna Species from an Active Volcanic Region in the Mid-Atlantic Ocean

Ecological drivers of mercury accumulation in oceanic apex predators: A human consumption advisory

This article provides a detailed assessment of mercury (Hg) concentrations and stable isotopes (δ15N & δ13C) in sharks and pelagic fishes of high trophic level caught in the Western Equatorial Atlantic Ocean and presents advisories for safe consumption by human populations. We found significant differences in Hg concentrations among species, with highest Hg concentrations in Isurus oxyrinchus (2173.6 ± 1521.5 ng g-1) followed by Xiphias gladius (1600.3 ± 671.9 ng g-1) and Prionace glauca (1293.9 ± 830.8 ng g-1), while lowest Hg concentrations were observed in Thunnus albacares (170.0 ± 42.6 ng g-1) and Coryphaena hippurus (190.7 ± 82.8 ng g-1). Intermediate Hg concentrations were observed in T. alalunga (512.9 ± 145.9 ng g-1), Istiophorus albicans (493.1 ± 348.6 ng g-1) and T. obesus (327.7 ± 343.1 ng g-1). The methylmercury proportion relative to total Hg was higher than 80 % for the species C. hippurus, P. glauca, T. alalunga and X. gladius. The δ15N values corroborate with all species occupying upper trophic levels and ranging from 10.2 ± 0.4 ‰ in T. albacares to 12.4 ± 1.1 ‰ in X. gladius. The highest values were observed in I. oxyrinchus, X. gladius and P. glauca, compared to C. hippurus, I. albicans and T. albacares, which showed the lowest δ15N values. The δ13C values ranged from -18.4 ± 2.6 ‰ in X. gladius to -16.6 ± 0.4 ‰ in C. hippurus, with significant differences between the species. We found significant correlations between Hg concentrations and fish weight for all species, except C. hippurus, I. albicans and I. oxyrinchus, indicating the process of bioaccumulation. The significant and positive correlation between log-transformed Hg concentrations and δ15N indicates biomagnification in the upper trophic levels of this oceanic food-web. The estimated species-specific number of meals that are safe for consumption ranged from 0 to 11 meals per month for adults and children.

Metal variability in small pelagic fish Scomber colias as influenced by volcanic events in the Canary Islands

Offshore volcanic activity occurs when an underwater volcano erupts. These volcanoes can be located underwater or on land and can be very dangerous to marine life. The aim of this study is to examine whether the influence of two volcanoes has an effect on the concentrations of metals and trace elements in the Atlantic mackerel Scomber colias in the Canary Islands. For the study, ten specimens of S. colias were obtained from each sampling area in March 2022. Metal concentrations were determined by inductively coupled plasma optical emission spectrophotometry (ICP-OES). The specimens of Scomber colias from the area affected by the Tajogaite volcano (La Palma) showed higher concentrations of all metals and trace elements analyzed than those from the other study areas. The specimens from the area of influence of the Tagoro Volcano (El Hierro) showed the second highest concentration of the elements studied, although this volcanic process is in a state of degassing.

Impact of natural events on metal bioaccumulation in Anemonia sulcata

Samples of Anemonia sulcata were collected in 2022 from different areas of the Canary Islands affected by different natural contamination sources, such sandstorms, submarine volcanic activity, continuous rainfall, upwelling and dinoflagellate blooms. Significant differences were observed between the zones for the metals and trace elements analyzed (Al, Zn, Cd, Pb, Ni, Co, Fe, B, Cu, Mg and Li). Anemones from volcanic areas showed higher levels of Cd, Pb and Ni. Individuals from sandstorm areas showed elevated levels of Al, Zn and Fe. Samples collected from areas affected by upwelling processes had higher concentrations of Cu, Mg and Li. Finally, the areas affected by dinoflagellates showed lower levels of Zn, Pb, Fe, Mg and Li. The study reveals how natural phenomena dramatically influence metal accumulation in A. sulcata, which is of great value for anticipating and managing potential problems associated with public health.

Lead and cadmium in blood and tissues of Atlantic bluefin tuna (Thunnus thynnus L., 1758)

Cadmium (Cd) and lead (Pb) levels in blood and tissues of Atlantic bluefin tuna were analysed to gather information regarding their distribution, accumulation and inter-relationships, as well as to examine how sex affects them. In the whole population, the concentration range was from below the detection limit (bone) to 8.512 μg g-1 (liver) for Cd, and from below detection limit (bone and gills) to 0.063 μg g-1 (kidney) for Pb. The median concentration in the muscles (0.008 and 0.029 μg g-1 for Cd and Pb, respectively) was 10 times less than the maximum permitted for consumption. Sex was shown to be an important variable affecting concentrations of Cd in both liver and kidneys, so taking into account sex when interpreting results is highly recommended. The importance of Cd and Pb bioaccumulation in fishery by-products, increasingly important in commercial circuits, is also highlighted.

Heavy metals content in fresh tuna and swordfish caught from Hindian and Pacific Oceans: Health risk assessment of dietary exposure

Background and Aim

Yellowfin tuna and swordfish are seafood commodities commonly caught from deep oceans worldwide. Therefore, this study aimed to assess the levels of three heavy metals, namely, cadmium (Cd), lead (Pb), and mercury (Hg) in yellowfin tuna and swordfish. The results are expected to provide consumers with information on the safety of consuming or exporting these fishes caught in the Hindian and Pacific Oceans.

Materials and Methods

Fresh yellowfin and swordfish were obtained from fishermen's catches in FAO Fishing Zone 57 (Indian Ocean) and 71 (Pacific Ocean) and then collected at Benoa Harbor, Bali Province. The comparative method was to evaluate the levels of heavy metals in each fish. Furthermore, heavy metal concentrations, including Pb, Cd, and Hg, were determined using atomic absorption spectroscopy analysis. These results were then used to assess the safety of these fishes by calculating the estimated daily intake (EDI) and target hazard quotients-total target hazard quotients (THQs-TTHQs).

Results

The analysis showed that none of the samples exceeded the threshold levels for the three heavy metals, which was specified by the Indonesian National Standard (SNI) and European Commission Regulation (CR) No. 1881/2006. The EDI and provisional tolerable weekly index (PTWI) obtained in this study were still in the safe range. However, the PTWI values for Pb in yellowfin tuna product from the Indian Ocean were higher (0.0038 mg/kg) compared to the recommended standard for the adult population. The THQ-TTHQ values of fish caught from these oceans were also within the acceptable range specified by the two agencies, indicating that they are safe for consumption by people with various age groups and for export purposes.

Conclusion

The average levels of three heavy metals (Cd, Pb, and Hg) in muscle samples of yellowfin tuna and swordfish caught from the Pacific and Hindian Oceans were within the acceptable range as specified by the SNI and CR No. 1881/2006. Furthermore, the EDI and THQs values indicated that fishes caught from the Pacific and Hindian Oceans were safe for consumption. This research is still limited to assessing two capture fisheries commodities. Further research is needed on the assessment of heavy metal levels in other capture fisheries commodities in this capture zone.

Risk Assessment and Characterization in Tuna Species of the Canary Islands According to Their Metal Content

Bioaccumulation is the process by which living organisms accumulate substances, such as pesticides, heavy metals, and other pollutants, from their environment. These substances can accumulate in the organism’s tissues over time, leading to potential health risks. Bioaccumulation can occur in both aquatic and terrestrial ecosystems, and can have a significant impact on the health of both humans and wildlife. The objective of this study is to find out if the concentrations of metals in the tuna species of the Canary Islands are suitable for human consumption and if they pose a health risk. Fifteen samples of Acanthocybium solandri, Katsuwonus pelamis, Thunnus albacares, Thunnus obesus and Thunnus thynnus present in canaries were analyzed. Ten grams of muscle were taken from each specimen and the metals Al, Cd, Cr, Cu, Fe, Li, Ni, Pb and Zn were determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The tuna species that presented more metals with a higher concentration compared to the others was T. thynnus, reaching up to 100 times more than the other studied species in Fe content with 137.8 ± 100.9 mg/Kg, which may be due to the fact that it is the largest species that reaches ages of more than fifteen years. The species Thunnus thynnus should not be suitable for commercialization according to the current legislation on the concentrations of Cd in blue fish, since 75% of the specimens studied exceeded the concentration legislated for Cd. A total of 40% of the studied specimens of this this species exceeded the legislated values for the concentration of Pb in oily fish meat, so this species must be monitored to ensure that it does not pose a risk to human health.

Mercury in oceanic upper trophic level sharks and bony fishes - A systematic review

Anthropogenic activities contribute to nearly half of current Hg emissions to the atmosphere. In the marine habitat, oceanic predator fishes bioaccumulate Hg throughout their lives, making their consumption the main route of Hg exposure in humans. In this context, several publications, between 1973 and 2022, were selected, analyzed, and duly compiled, with the objective to investigate Hg contamination in nine species of bony fish: Thunnus thynnus (8 publications), Thunnus albacares (19), Thunnus obesus (7), Thunnus atlanticus (5), Thunnus alalunga (4), Katsuwonus pelamis (8), Xiphias gladius (18), Coryphaena hippurus (7) and Euthynnus alletteratus (4), as well as two species of cartilaginous fishes Prionace glauca (13 publications) and Isurus oxyrinchus (8). These studies totaled 5973 individuals. We classified species according to taxonomic groups and region of capture and found a significant difference between sharks and bony fishes, with higher Hg concentrations in sharks. The regions of occurrence were divided into 4 large areas (North Atlantic - NAO, South Atlantic - SAO, Equatorial Atlantic Ocean - EAO, and Mediterranean - MED), but no significant differences were observed when comparing the overall Hg concentrations in fish among regions (including all species). Additionally, a thorough discussion of the risks associated with human consumption of these species was conducted, as nine of the selected species presented individuals with Hg concentration values that exceeded the safety limits (1 ppm) set by health agencies worldwide.

Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador

We examined how dietary factors recorded by C and N influence Hg uptake in 347 individuals of yellowfin tuna (Thunnus albacares), an important subsistence resource from the Galápagos Marine Reserve (Ecuador) and the Ecuadorian mainland coast in 2015-2016. We found no differences in total Hg (THg) measured in red muscle between the two regions and no seasonal differences, likely due to the age of the fish and slow elimination rates of Hg. Our THg concentrations are comparable to those of other studies in the Pacific (0.20-9.60 mg/kg wet wt), but a subset of individuals exhibited the highest Hg concentrations yet reported in yellowfin tuna. Mercury isotope values differed between Δ¹⁹⁹ Hg and δ202Hg in both regions (Δ¹⁹⁹ Hg = 2.86 ± 0.04‰ vs. Δ¹⁹⁹ Hg = 2.33 ± 0.07‰), likely related to shifting food webs and differing photochemical processing of Hg prior to entry into the food web. There were significantly lower values of both δ¹⁵ N and δ¹³ C in tuna from Galápagos Marine Reserve (δ¹⁵ N: 8.5-14.2‰, δ¹³ C: -18.5 to -16.1‰) compared with those from the Ecuadorian mainland coast (δ¹⁵ N: 8.3-14.4‰, δ¹³ C: -19.4 to -11.9‰), of which δ¹³ C values suggest spatially constrained movements of tuna. Results from the pooled analysis, without considering region, indicated that variations in δ¹³ C and δ¹⁵ N values tracked changes of Hg stable isotopes. Our data indicate that the individual tuna we used were resident fish of each region and were heavily influenced by upwellings related to the eastern Pacific oxygen minimum zone and the Humboldt Current System. The isotopes C, N, and Hg reflect foraging behavior mainly on epipelagic prey in shallow waters and that food web shifts drive Hg variations between these populations of tuna. Environ Toxicol Chem 2022;41:2732-2744. © 2022 SETAC.

Trace elements and δ15N values in micronekton of the south-western Indian Ocean

Trace elements and δ¹⁵N values were analysed in micronekton (crustaceans, fishes and squids) sampled in the south-western Indian Ocean. Myctophids were associated with high concentrations of arsenic at La Pérouse and MAD-Ridge seamounts, and with lead and manganese at MAD-Ridge and in the Mozambique Channel. The difference in cadmium, copper and zinc concentrations between micronekton broad categories reflected differing metabolic and storage processes. When significant, negative relationships were found between micronekton body size and trace element concentrations, which can possibly be attributed to differing metabolic activity in young and old individuals, dietary shifts and/or dilution effect of growth. No relationships were found between trace element concentrations and δ¹⁵N values of micronekton (except cobalt which decreased with increasing δ¹⁵N values), since most trace elements are not biomagnified in food webs due to regulation and excretion processes within organisms. All trace element pairs were positively correlated in fishes suggesting regulation processes.

An examination of mercury levels in the coastal environment and fish of Cote d'Ivoire

Artisanal and small-scale gold mining (ASGM), energy production and other industrial inputs are a major source of anthropogenic mercury (Hg) to the aquatic environment globally, and these inputs have led to environmental contamination and human exposure. While studies have documented the effects of Hg inputs to rivers and marine waters of the West African region, estuarine waters of Cote d'Ivoire have been understudied, besides the waters surrounding Abidjan. To fill this gap, and to examine the potential for human exposure to methylmercury (MeHg), we measured the concentrations of total Hg, MeHg, and ancillary parameters in water (dissolved and particulate phases), sediment and fish to determine the extent of environmental impact and the potential for MeHg exposure for people consuming these fish. Levels of Hg and MeHg in sediment were elevated in the vicinity of the urban environment (up to 0.3 ng/g dry weight (dw) MeHg and 623 ng/g dw total Hg) and lowest in the more remote estuarine environments. Measurements of Hg in tuna and other larger pelagic coastal species indicated that levels were elevated but comparable to other North Atlantic regions. However, levels of Hg in fish, even smaller estuarine species, were such that the rural and urban populations are potentially being exposed to unsafe levels of MeHg, primarily as a result of the relatively high fish consumption in Cote d'Ivoire compared to other countries. Overall, both local point sources and the transport of Hg used in interior ASGM activities are the sources for Hg contamination to these coastal waters.

Species-specific heavy metal concentrations of tuna species: the case of Thunnus alalunga and Katsuwonus pelamis in the Western Mediterranean

Albacore Thunnus alalunga and skipjack tuna Katsuwonus pelamis are highly migratory species that are usually caught together in the Western Mediterranean. These species are top predators that are highly affected by the biomagnification process through the trophic chain. Bioaccumulation pattern of the main metal pollutants (mercury, Hg; lead, Pb; and cadmium, Cd) were analyzed in muscle tissues of 52 individuals (26 T. alalunga and 26 K. pelamis) of these highly consumed species in order to address two objectives: (1) compare the species-specific bioaccumulation between these large-pelagic species, and (2) assess the healthy properties of such valuable resources based on the trace metal limits established by the European Commission Regulation (ECR). Both generalized linear mixed models and redundancy analysis indicated a differential bioaccumulation between these two tuna species. While T. alalunga accumulates higher concentrations of Hg (0.1996 ± 0.0602 mg·kg^-1 weight wet-ww), K. pelamis accumulates higher concentrations of Cd (0.0076 ± 0.0049 mg·kg^-1 ww) and Pb (0.0031 ± 0.0017 mg·kg^-1 ww). Size and trophic ecology support the differences detected in the bioaccumulation pattern. Heavy metal concentrations were below the tolerable limits considered by ECR (1, 0.1, and 0.3 mg·kg^-1 ww for Hg, Cd, and Pb, respectively).

Tissue Distribution of Mercury and Its Relationship with Selenium in Atlantic Bluefin Tuna (Thunnus thynnus L.)

Mercury (Hg) is an important heavy metal to consider in marine predators, while selenium (Se) has a natural antagonistic effect on this metal in fish. The Atlantic bluefin tuna (ABFT, Thunnus thynnus) is a pelagic top-level predator of the trophic web and their Hg muscular content is an object of concern in food safety. Nevertheless, little is known about levels of this metal in remaining tissues, which may be important as by-product source, and its relationship with Se. Thus, concentration of both elements in liver, kidney, brain, gill and bone, in addition to muscle, of ABFT were determined. The kidney was the tissue with the highest concentration of Hg (Total-Hg, THg) and Se, and the Se/THg concentration ratio was similar in all tissues, except bone and muscle. The Selenium Health Benefit Value (HBV_Se) was positive in each specimen and tissue, indicating that the Se plays an important role against Hg not only in the muscle.

Mercury and selenium levels in archive samples of wild Atlantic bluefin tuna from the Mediterranean Sea

This study examined total mercury (THg) and selenium (Se) levels in archive samples (white and red muscles, liver, gills) of the wild Atlantic bluefin tuna (ABFT) (Thunnus thynnus) (n = 18) captured in the central Adriatic Sea. The influence of fish size, age, and tissue type on element distribution was examined. There were significant differences in THg and Se levels, and Se:THg molar ratios among tissues. THg levels were highest in liver and lowest in gills (liver > red muscle > white muscle > gills), while Se levels were also highest in liver but lowest in white muscle (liver > red muscle > gills > white muscle). Se:THg molar ratios were highest in gills (22-82), intermediate in liver (11-29) and red muscle (7-36), and lowest in white muscle (1.7-7.6). Concentrations of THg in all tissues and Se in liver and caudal muscle were positively correlated with tuna age and size, while the Se:THg molar ratio in gills and all white muscles was negatively correlated with tuna age and size, indicating that the protective role of Se against THg is reduced in older specimens. The selenium health benefit values (HBV_Se) were above zero in all tissues, indicating a small excess of Se after Hg sequestration. However, since the obtained HBV_Se for edible tissues were near zero (0.01-0.04), and more than 70% of white muscle samples and all red muscle samples exceeded the EU regulatory limit for THg in fish muscle, it would be advisable to limit their intake in adults to one meal per month.

Oceanic karma? Eco-ethical gaps in African EEE metal cycle may hit back through seafood contamination

The increasing global demand for electric and electronic equipment (EEE) such as smartphones, tablets and electric car batteries has resulted in an increase in heavy metal releases to the environment at different steps during its manufacture (e.g. mining, extraction, production and e-waste). Some critical raw materials (CRMs) that supply the worldwide demand of technology are mainly sourced from Africa, but their resulting heavy metal pollution can reach citizens from other regions of the world through seafood caught in African waters, which would act as a vector. In this study, we review heavy metal contents in African fish and, as proof of concept, we analyse heavy metal content in three tuna species (Thunnus alalunga, T. albacares and T. obesus) caught in different regions inside the Sustainable Fisheries Partnership Agreements (SFPAs) by Spanish fleets and commercialised in Spain. Thunnus alalunga and T. albacares from African waters had higher concentrations of heavy metals (especially Hg but also As and Pb) in muscle than samples of the same species caught in other waters. Metal profiles in tunas from African waters were significantly correlated with those of continental and coastal fish from nearby areas impacted by mines and e-waste, as found in the literature review. Based on these results we identify research priorities that should be addressed in order to improve the social and environmental sustainability of EEE metal manufacture in Africa.

Low mercury, cadmium and lead concentrations in tuna products from the eastern Pacific

Tuna species: Skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) are mainly processed into canned products (loins, solid pack, flakes) either in water or oil, and pre-cooked frozen loins. The National Institute of Fisheries of Ecuador (ISO/IEC 17025 certified), which is the official control laboratory, samples and analyses production batches of companies exporting to the European Union in order to ensure the quality control of Ecuadorean tuna product. From 2009 to 2016, 2572 samples have been analysed (by standard methods) for mercury, cadmium, and lead. The averages were 0.24 ± 0.14; 0.03 ± 0.03 and 0.05 ± 0.05 mg kg-1 (wet weight) respectively; which are well below the norms; i.e., total mercury: 1 mg kg-1; Lead: 0.3 mg kg-1 and Cadmium: 0.1 mg kg-1 according to the EU maximum limits. Over time mercury levels in the sample seemed to decrease but for cadmium and lead no clear pattern was observed. Additionally; samples of tuna can products taken at random from local vendor stores gave concentrations of: Mercury: 0.043 ± 0.004 mg kg-1; Cadmium: 0.012 ± 0.002 mg kg-1; Lead: below detection limit (0.01 mg kg-1). There were a few cases (15 out of 2572: 0.58%) of samples with readings near or just over-limit concentrations; of these, 12 corresponded to Cd, two to Pb and one to Hg. Some of them can be considered statistical outliers as well as cross contamination during analytical procedures. Raw tuna samples have given similar or lower concentrations. No significant statistical correlation was found between Hg, Cd and Pb values, this would suggest that the bioaccumulation of each metal is independent of each other. Literature reports that surface dissolved Hg, Cd, and Pb in the eastern Pacific are in the range of 2-18 ng kg-1. Assuming suggested bioaccumulation of 2-6 times, the end concentration in the tuna would be 0.012-0.042; 0.036-0.108 and 0.010-0.027 μg kg-1 of Hg, Cd, and Pb respectively, that would be one order (or more) below the safe consumption limit. Most, if not all the tuna processed in Ecuador is captured in the eastern Pacific and within its EEZ. Ecuadorian canned tuna complies with stringent standards for presence of these metals; therefore, it can be considered safe to be consumed from the point of view of these metal concentrations. However, further studies should assess metal concentrations exclusively from Ecuadorian tuna captured close to coastal and insular areas.

Quality Indicators and Possible Ecological Risks of Heavy Metals in the Sediments of three Semi-closed East Mediterranean Gulfs

Pollution with copper (Cu), lead (Pb), zinc (Zn), chromium (Cr), and nickel (Ni) heavy metals of the surface sediments collected from three semi-closed East Mediterranean Gulfs, namely Kavala, Strymonikos, and Ierissos Gulfs, North Aegean Sea, Greece, was investigated to evaluate potential benthic ecological risks. The mean concentrations of the studied metals decrease according to the order: Zn > Pb > Cr > Ni > Cu (176.50, 166.23, 127.41, 43.12, and 33.64 mg kg⁻¹ dry weight). Quality indicators and possible ecological risks for metals in surface sediments were evaluated at 60 sampling sites of these three gulfs using the contamination factor (CF), the contamination degree (CD), the pollution load index (PLI), the geoaccumulation index (I_geo), the potential risk factor (PRF_i), and the potential ecological risk index (PERI). Based on I_geo, the Ierissos Gulf sampling sites IER 2, 3, 7, and 9 exhibit moderate Pb pollution, whereas the sampling sites IER 6 and 8 show moderate to strong and strong Pb pollution, respectively. Based on the PRFi and PERI, the studied heavy metals did not pose any significant environmental risks for most of the investigated sites except IER 6 and 8 sampling sites, which may pose considerable environmental risk for Pb. To evaluate potential sources for each metal, multivariate techniques including hierarchical cluster analysis and ANOVA were used.

Bioaccumulation Levels and Potential Health Risks of Mercury, Cadmium, and Lead in Albacore (Thunnus alalunga, Bonnaterre, 1788) from The Aegean Sea, Greece

Aegean Sea albacore (T. alalunga), fresh or processed, is marketed locally in Greece or exported, mainly to Japan, Italy, Spain, and France. To provide information for consumers and biomonitoring programs and assess the potential human health risks, concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) were determined in albacore edible muscle samples from two fishing grounds of the Aegean Sea, Greece via graphite furnace atomic absorption spectrometry (GF-AAS). Of the 82 individuals, 28 contained Cd and three contained Pb above the permissible limits set by the European Union (0.1 mg kg⁻¹ wet wt and 0.3 mg kg⁻¹ wet wt, respectively). None of the samples contained mercury above the limit (1.0 mg kg⁻¹ wet wt). Potential health risks to human via dietary intake of albacore were estimated by the total target hazard quotients (TTHQs), which indicated that the consumers could acquire health problems due to consumption of Aegean Sea albacore. Thus consequently, concentrations of toxic heavy metals in albacore, especially mercury, must be monitored regularly and comprehensively with respect to consumer health.

Bioaccumulation of As, Hg, and Se in tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific: tissue distribution and As speciation

With the aim of knowing the distribution of As, Hg, and Se in skipjack (Katsuwonus pelamis, Linnaeus, 1758) and yellowfin tuna (Thunnus albacares, Bonnaterre, 1788) from the Eastern Pacific, elemental concentrations were determined in the muscle and liver; As species were also analyzed in the stomach content. Additionally, health risk for consumers was assessed. For both tunas, levels of As and Se were significantly higher (p < 0.05) in the liver than in the muscle. In K. pelamis, Hg concentrations in the muscle were significantly higher (p < 0.05) than those in the liver. In T. albacares, As, Hg, and Se showed a trend to increase with fish dimensions. Arsenic extractability was better in the muscle than in the liver of both species; in K. pelamis, As species were better extracted than in T. albacares. In both tuna species, the most extractable arsenic was arsenobetaine (AsB) and a minor part was dimethylarsinic acid (DMA). The liver contained mainly AsB with some DMA and arsenocholine (AsC). Hazard indexes (HI) indicated no risk from Hg and Se intake through these tuna species. Considering the individual contribution to the HI, Hg contributed more (80 to 86%) than Se. In the context of health risk, none of the As and Hg values were above the permissible limits; however, two samples of T. albacares (9%) and three samples of K. pelamis (12%) had Se concentrations over the limits. If Hg and Se in the edible portion of tuna are considered under the approach of the HBV_Se, tuna consumption is beneficial.

Arsenic, cadmium and lead in fresh and processed tuna marketed in Galicia (NW Spain): Risk assessment of dietary exposure

Currently, metal bioaccumulation in fish is increasing and is a cause of concern due to toxicity. Total arsenic, cadmium and lead concentrations in fresh and processed tuna (110 samples) marketed in Galicia (NW Spain) were determined by ICP-MS spectrometry. The average concentrations of As and Cd, 3.78 and 0.024 mg kg^-1 w.w., respectively, in fresh tuna were statistically significantly higher than those in processed tuna (p < 0.001). The contents in processed tuna were 0.295-7.85 mg kg^-1 for As and ND-0.045 mg kg^-1 for Cd. The Pb content was negligible in both types of tuna. In canned tuna, decreasing As and Cd concentrations were observed in different preparation-packaging media: olive oil > natural > pickled sauce. Of the two species studied in canned tuna, Thunnus alalunga showed statistically significant higher levels both for As 1.28 mg kg^-1 (p < 0.001) and Pb 0.013 mg kg^-1 (p = 0.0496) than Thunnus albacares. No samples surpassed the limits set by the EU for Cd and Pb. The limit for As in fish has not been established, but the arsenic contents in fresh tuna reported here are important, as they are among the highest reported in the literature. Considering public health in children and adults with respect to the investigated metals, the estimated daily intakes (EDIs) did not exceed the tolerable intakes. No chronic systemic risk was found since all the target hazard quotients (THQs-TTHQs) were far below 1 (critical value), and the carcinogenic risk (CR) for As did not exceed the acceptable value of 10^-5. Thus, tuna consumption in the Galician diet does not pose a risk for different population groups in terms of these studied metals/metalloids.

Arsenic and five metal concentrations in the muscle tissue of bigeye tuna (Thunnus obesus) in the Atlantic and Indian Oceans

White muscle concentrations of As, Cd, Cu, Fe, Se, and Zn were investigated in Atlantic- and Indian-bigeye tuna (BET) (Thunnus obesus) from 6 regions. As and Cd muscle concentrations were significantly higher in the Indian-BET than in the Atlantic-BET, whereas the Indian-BET caught in the waters off South Africa revealed the highest As, Se, and Zn muscle concentrations. Accordingly, multidimensional scaling separated them into two oceanic groups. Positive linear relationships between muscle Cd concentration and fork length (FL) were established in both oceans. For the other elements, only muscle-Fe and FL relationship was found in the Atlantic-BET. 10.3% of BET > 145 cm FL from both oceans possessed muscle Cd concentrations exceeding the food safety limit (0.1 μg g^-1 wet weight) set by the European Commission. Increased Cd, Cu and Zn pollution was found in the Atlantic Ocean compared with previous data, with higher levels found in the Indian Ocean.

Mercury Concentrations in Tuna (Thunnus albacares and Thunnus obesus) from the Brazilian Equatorial Atlantic Ocean

Average total Hg concentrations measured in muscle of two species of tuna (Thunnus obesus and T. albacares) captured in the Brazilian Equatorial Atlantic Ocean varied from 95 to 1748 ng.g^-1 wet weight in T. obesus and 48 to 500 ng.g^-1 wet weight in T. albacares. Higher concentrations in T. obesus are probably related to foraging on deep water carnivorous fish. Smaller individuals of both species showed the lowest concentrations, but a significant positive relationship between fish weight and length and Hg concentrations was found for T. obesus, but not for T. albacares. Largest individuals (>30 kg) of T. obesus showed Hg concentrations ≥1000 ng.g^-1, surpassing the legal limits for human consumption, although the average concentration for this species was much lower (545 ng.g^-1). Concentrations in T. albacares from the Brazilian Equatorial were lower than those found in the African and in the North Atlantic. No comparison could be made for T. obesus due to few studies for this species in the Atlantic Ocean.