Hg Molar Ratios Research Articles

Ethnic variations in mercury exposure from seafood consumption and the risk of Kawasaki disease in young children

Kawasaki disease (KD) is an acute febrile illness predominately affecting children <5 years that can result in serious cardiovascular complications such as coronary artery lesion formation. The cause of KD remains unknown 50 years after Kawasaki first described the illness in Japan, while KD has since replaced rheumatic fever as the leading cause of acquired heart disease for children in the developed world. KD has become the most commonly diagnosed pediatric vasculitis with the highest incidence rates of KD reported from East Asian countries such as Japan, Korea, and Taiwan. Even when residing in Western nations, East Asian children still have 10 to 20 times the risk of developing KD than children of other ethnicities. Speculation that genetic differences between ethnic groups account for the ethnic disparity in KD rates led to the discovery and confirmation of numerous susceptibility loci, although these risk alleles only appear to confer risk passively to the currently unknown environmental triggers of KD. Previously, we described how ITPKC susceptibility in KD patients would render these individuals vulnerable to mercury (Hg)‐induced autoimmunity through the induction of intracellular calcium release with downstream effects upon cell signaling, immune proliferation, and gene expression via the Ca2+/NFAT pathway. This led us to hypothesize that the ethnic disparities in KD risk may be accounted for by variations in Hg exposure rates, particularly from significant differences in total methylmercury (MeHg) intake from seafood. We examined two separate cohorts that were nationally representative of either KD hospitalization rates or toxic metal concentrations in the blood in our initial investigations. Our results demonstrated that increasing ethnic KD risk between Caucasian, Hispanic, Black, and Asian children was significantly associated with average blood levels and detection rates of Hg or cadmium (Cd) but not lead (Pb), manganese (Mn), or selenium (Se). In our most recent investigations using the same two datasets, we observed that ethnic KD risk was significantly associated with increasing consumption of total fish and seafood but not shellfish. Further examinations by Hg type demonstrated that MeHg from seafood is the primary source of blood Hg in children, while average blood MeHg levels but not inorganic or ethylmercury were significantly associated with increasing ethnic KD risk. Lastly, ethnic KD risk was significantly associated with molar ratios of Hg and Se in the blood that are indicative of seafood consumption. We conclude that Hg exposure particularly from seafood consumption may increase susceptibility for the development of KD in young children or trigger the disease, itself. However, our hypothesis requires determinations of blood Hg levels and cumulative Hg exposure such as from dietary seafood intake in KD patients, which are currently lacking and that we are presently examining.Support or Funding InformationNone

The importance of the age when evaluating mercury pollution in fishes: the case of <em>Diplodus sargus</em> (Pisces, Sparidae) in the NW Mediterranean

The aim of this study was to analyse the concentration of mercury (Hg) in the muscle of a common littoral, omnivorous fish such as the white seabream, <em>Diplodus sargus</em>, and to evaluate its relationship with the age and size of the specimens. Large, older predatory fishes have typically been the main target species for risk assessment of Hg intake in humans. The white seabream is neither a big fish nor a predator, but all sizes of NW Mediterranean specimens of this species showed high levels of Hg, with clear increases in older specimens. In addition, although the Se:Hg molar ratio was high and could reduce the impact of high concentrations of Hg in smaller fishes, it could not in the older specimens of <em>D. sargus</em> analysed because it decreased with age. This is not a major concern for human health because the white seabream is not a widely consumed species. However, in special situations involving toddlers, children and women of childbearing age, problems might arise if the white seabream or similar species are consumed in place of those that current recommendations advise against eating. In these cases it is very important to consider the species of fish consumed in each country and carefully assess the risk of Hg intake.

Muscle mercury and selenium in fishes and semiaquatic mammals from a selenium-deficient area

The aim of this study was to investigate and compare total mercury (Hg), selenium (Se), and Se:Hg molar ratios in fish muscles (phytophages n=3; benthophages n=32; predators n=5) and semiaquatic carnivores, including piscivores (the European otter n=8, the feral American mink n=7) and the omnivorous raccoon (n=37) from a riverine European ecosystem in a Se-deficient area. The Hg concentration in fish reached 0.337μg/g dry weight, dw (0.084μg/g wet weight, ww). We found significant differences among Hg levels in tested vertebrate groups (predators vs benthophages: 0.893 vs 0.281μg/g; piscivores vs omnivores: 6.085 vs 0.566μg/g dw). Fish groups did not differ in Se concentrations, with a mean value of 0.653μg/g dw. Significant differences were revealed between Se levels in piscivorous and omnivorous carnivores (0.360 vs 0.786μg/g dw, respectively). Fish Se:Hg molar ratio values were >2.2. Benthophages had higher the ratio than predators but similar to phytophages. Among carnivores, piscivores had much lower the ratio than raccoon (0.14 vs 3.75) but raccoon and fish medians did not significantly differ. We found almost two times higher Se levels in fish and raccoons compared to piscivores, possibly resulting from lower fish Se digestibility by piscivores in contrast to higher absorption of plant Se by many fish and omnivorous raccoons. Considering that a tissue Se:Hg molar ratio <1 may be connected with a Hg toxicity potential increase, we assume that piscivores in Se-deficient area are in worse situation and more exposed to Hg than fish and omnivores.

Mercury and selenium concentrations in marine shrimps of NW Mexico: health risk assessment.

We determined total Hg and Se contents of hepatopancreas, exoskeleton, and muscle, and the Se:Hg molar ratios in the muscle of shrimps Farfantepenaeus californiensis and Litopenaeus stylirostris caught in NE Pacific Mexican waters. Total Hg mean values in muscle, hepatopancreas, and exoskeleton were 0.31±0.26, 0.28±0.29, and 0.24±0.06μgg-1, and 0.46±0.46, 0.41±.034, and 0.24±0.06μgg-1 for F. californiensis and L. stylirostris, respectively. In all tissues, the mean concentrations of Se tended to be close to one order of magnitude higher than the respective Hg values. In F. californiensis, the hepatopancreas of the larger commercial size had significantly (p<0.05) higher Hg content than smaller sizes, but correlations size-Hg concentration calculated for each tissue of either species were not significant. The Hg content of the muscle of all commercial sizes of both species was lower than the permissible limit and their Se:Hg ratios in all sizes were higher than 1, indicating low risk for human consumption.

Mercury and selenium interactions in human blood in the Wanshan mercury mining area, China

Human blood mercury (Hg), selenium (Se) and other trace element levels were investigated in the Wanshan mercury mining area. Residents living near the mine waste heaps had significantly elevated blood Hg, Se and arsenic (As) levels, which indicates the impact from Hg mining and smelting activities. Rice samples showed high Se levels, as 72.6% of total Se intake comes from rice consumption. The means of the Se:total Hg (THg) and Se:methyl Hg (MeHg) molar ratios were 60.7±27.1 and 110±53.6 respectively. Blood Se:Hg molar ratios were negatively correlated with blood Hg levels. 80.2% of the study population had blood THg levels that exceeded the 5.8μg/L regulation level set by the USEPA, which indicated the risk of Hg exposure. On the other hand, the blood Se levels were within a safe-level range, and dietary Se intake protected local residents who suffered from Hg exposure.

Effect of Intestinal Tapeworm Clestobothrium crassiceps on Concentrations of Toxic Elements and Selenium in European Hake Merluccius merluccius from the Gulf of Lion (Northwestern Mediterranean Sea).

The capacity for heavy metal bioaccumulation by some fish parasites has been demonstrated, and their contribution to decreasing metal concentrations in tissues of parasitized fish has been hypothesized. The present study evaluated the effect of the cestode Clestobothrium crassiceps on the accumulation of trace elements in 30 European hake, Merluccius merluccius, in Spain (half of them infested by C. crassiceps). Tissue samples from all M. merluccius and specimens of C. crassiceps from the infected hakes were collected and stored until element analysis by inductively coupled plasma mass spectrometry (ICP-MS). Arsenic, mercury, and selenium were generally present in lower levels in the cestode than in all hake tissues. The mean value of the muscular Se:Hg molar ratio in the infested subsample was higher than that in hakes without cestodes. Values indicate that the edible part of infested hakes presents a lower amount of Cd and Pb in relation to noninfested hakes.

A survey of trace element distribution in tissues of the dwarf sperm whale (Kogia sima) stranded along the South Carolina coast from 1990–2011

Few studies report trace elements in dwarf sperm whale (Kogia sima). As high trophic level predators, marine mammals are exposed through diet to environmental contaminants including metals from anthropogenic sources. Inputs of Hg, Pb, and Cd are of particular concern due to toxicity and potential for atmospheric dispersion and subsequent biomagnification. Liver and kidney tissues of stranded K. sima from coastal South Carolina, USA, were analyzed for 22 trace elements. Age-related correlations with tissue concentrations were found for some metals. Mean molar ratio of Hg:Se varied with age with higher ratios found in adult males. Maximum concentrations of Cd and Hg in both tissues exceeded historical FDA levels of concern, but none exceeded the minimum 100μg/g Hg threshold for hepatic damage. Tissue concentrations of some metals associated with contamination were low, suggesting that anthropogenic input may not be a significant source of some metals for these pelagic marine mammals.

Mercury and Selenium in Muscle and Target Organs of Scalloped Hammerhead Sharks Sphyrna lewini of the SE Gulf of California: Dietary Intake, Molar Ratios, Loads, and Human Health Risks.

Selenium and mercury were evaluated in muscle, liver, kidney, brain, and the stomach contents of juvenile scalloped hammerhead shark Sphyrna lewini. Se:Hg molar ratios were calculated. The average Hg levels in muscle ranged from 0.12 to 1.17μg/g (wet weight); Hg was <0.39μg/g in liver and kidneys and <0.19μg/g in brain. The lowest value of Se was found in muscle (0.4μg/g) and the highest in kidney (26.7μg/g). An excess of Se over Hg was found, with Se:Hg molar ratios >1. Correlations were found for Hg in muscle with size, age, and weight, and also for Hg in liver with size, age, and weight. Hg in muscle was significantly positive correlated to Hg in brain as well as Hg in liver was correlated to Hg in kidney. The highest Hg in preys was for carangid fishes; scombrid and carangid fishes contributed with the highest Se levels. Results suggest that more than 98% of the total Hg and 62% of Se end up in muscle and might be affected by factors, such as geographical area, age, size, and feeding habits. The muscle of S. lewini should be consumed by people cautiously so as not to exceed the recommended intake per week.

Mercury and selenium concentrations in skeletal muscle, liver, and regions of the heart and kidney in bearded seals from Alaska, USA.

Mean concentrations of total mercury ([THg]) and selenium ([TSe]) (mass and molar-based) were determined for 5 regions of the heart and 2 regions of the kidney of bearded seals (Erignathus barbatus) harvested in Alaska, USA, in 2010 and 2011. Mean [THg] and [TSe] of bearded seal liver and skeletal muscle tissues were used for intertissular comparison. The Se:Hg molar ratios were used to investigate elemental associations and potential antioxidant protection against Hg toxicosis. Age was an important factor in [THg] and Se:Hg molar ratios in heart and kidney. Small but statistically significant differences in mean [THg] occurred among some of the 5 heart regions (p < 0.05). Mean [THg] was highest in liver, 3.057 µg/g, and lowest in heart left ventricle, 0.017 µg/g. Mean [THg] ranked: liver > kidney cortex > kidney medulla > skeletal muscle > heart left ventricle (p < 0.001). Mean [TSe] was highest in liver, 3.848 µg/g, and lowest in heart left ventricle, 0.632 µg/g. Mean [TSe] ranked: liver > kidney cortex > kidney medulla > skeletal muscle > heart left ventricle (p < 0.001). The Se:Hg molar ratios were significantly greater than 1.0 in all tissues (p < 0.001) and represented baselines for normal [TSe] under relatively low [THg]. Mean Se:Hg molar ratios ranked: heart left ventricle > kidney medulla > kidney cortex (p < 0.001).

Analysis of mercury and methylmercury concentrations, and selenium:mercury molar ratios for a toxicological assessment of sperm whales (Physeter macrocephalus) in the most recent stranding event along the Adriatic coast (Southern Italy, Mediterranean Sea)

Mass stranding of sperm whales (Physeter macrocephalus) is a rare event in the Mediterranean Sea. In September 2014, a pod of seven sperm whales became stranded along the Adriatic coast of Southern Italy. This is the seventh occurrence of this type since 1555 in this sea basin.Total concentrations of mercury (T-Hg), methylmercury (MeHg) and selenium (Se) were measured from brain, muscle, liver and kidney of three female sperm whales, which died in this event.Analyses showed considerable, age-dependent variations in Hg and Se concentrations in the different organs. The contamination levels of T-Hg in the liver (up to 200mgkg−1) and brain (up to 21mgkg−1) samples were markedly higher than those in the kidney and muscle samples. The liver and brain also showed the highest Se levels. Se:Hg molar ratios ⩾1 were observed in all the organs of the three sperm whales, suggesting that Se could protect the animals from Hg toxicity. The risk of Hg-associated neurotoxicity was assessed by comparing our values to thresholds set for neurotoxicity in mammals, and the role of Se in the detoxification process of T-Hg/MeHg is discussed herein.

Selenium and mercury molar ratios in commercial fish from the Baltic Sea: Additional risk assessment criterion for mercury exposure

BackgroundMercury content in fish poses risks to the fish and to those who consume them. The aim of the current study was to verify the protective role of selenium against toxic mercury in Baltic fish. The assessment criteria were the Se:Hg molar ratio, its variability depending on species and tissue, and correlations among Se:Hg ratios, mercury concentration, and specimen length. Assays were performed in muscle and liver tissues of Baltic Sea commercial fish species, i.e., cod, herring, sprat, plaice, and turbot. ResultsMercury concentrations in fish from the Baltic Sea are at low level. The values of the Se:Hg molar ratio were higher than 1 (with the exception of a few cod specimens), with ranges in muscle tissues as follows: cod 0.75–28.2; herring 2.0–50.3; sprat 14.2–56.2; flatfish 1.5–35.1; and in livers as follows: cod 10.9–268.2; herring 10.7–87.1; flatfish 10.2–232. The values of the Se:Hg ratio in muscle and liver tissues were negatively correlated with mercury content and specimen length. ConclusionMercury concentrations in commercial fish from the Baltic Sea are low and do not pose risks to consumers. The high values of the Se:Hg molar ratio confirm that mercury levels are safe, and also that selenium might offer protection against methylmercury toxicity, which could increase the safety of fish consumption. The values of the Se:Hg molar ratio could be an additional criterion, in addition to measuring Hg concentrations, for evaluating the risk of mercury exposure in fish from the Baltic Sea.

Effect of eutrophication on mercury, selenium, and essential fatty acids in Bighead Carp (Hypophthalmichthys nobilis) from reservoirs of eastern China

Analyses of the risks and benefits of consuming fish assess the content of beneficial fatty acids found in fish relative to harmful pollutants such as methylmercury (MeHg). Quantifying the effect of eutrophication on mercury (Hg), selenium (Se) and essential fatty acids (EFAs) in fish is necessary to determine how measures of risk vary with productivity. Total Hg and MeHg, Se and fatty acids, including the EFA eicosapentaenoic acid (EPA, 20:5n−3) and docosahexaenoic acid (DHA, 22:6n−3), were analyzed in Bighead Carp (Hypophthalmichthys nobilis) dorsal muscle tissue from seven subtropical reservoirs of eastern China. Individual elements and fatty acids, as well as derived measures of risk (Se:Hg and hazard quotient, HQEFA) were regressed against indicators of eutrophication, including total phosphorous (TP), chlorophyll-a (chl-a) and phytoplankton species composition. We found low MeHg concentrations (range=0.018–0.13μg/g ww) and Se concentrations (range=0.12–0.28μg/g ww), and Se:Hg molar ratios that were well above 1.0, indicating a low risk of Hg toxicity. Bighead Carp had a high content of total polyunsaturated fatty acids (∑PUFAs=44.2–53.6%), which included both EPA (6.9–12.5%) and DHA (16.1–23.2%). However, fish had significantly lower Se:Hg molar ratios in reservoirs with high TP, and lower EPA content with increasing plankton density (i.e. higher chl-a). Phytoplankton species composition predicted Se concentrations, but not Hg concentrations or EFA content. Overall, Hg concentrations in Bighead Carp were very low relative to consumption guidelines, and Se concentrations were adequate to confer protective benefits against MeHg toxicity. Our findings suggest that changes to plankton species composition and density with eutrophication may result in fish of lower nutritional value and thus increase risks to fish consumers by changing the availability of Se and EPA relative to MeHg.

Assessment of neurotoxic effects of mercury in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) from the Canadian Arctic

Marine mammals are indicator species of the Arctic ecosystem and an integral component of the traditional Inuit diet. The potential neurotoxic effects of increased mercury (Hg) in beluga whales (Delphinapterus leucas), ringed seals (Pusa hispida), and polar bears (Ursus maritimus) are not clear. We assessed the risk of Hg-associated neurotoxicity to these species by comparing their brain Hg concentrations with threshold concentrations for toxic endpoints detected in laboratory animals and field observations: clinical symptoms (>6.75mg/kg wet weight (ww)), neuropathological signs (>4mg/kg ww), neurochemical changes (>0.4mg/kg ww), and neurobehavioral changes (>0.1mg/kg ww). The total Hg (THg) concentrations in the cerebellum and frontal lobe of ringed seals and polar bears were <0.5mg/kg ww, whereas the average concentration in beluga whale brain was >3mg/kg ww. Our results suggest that brain THg levels in polar bears are below levels that induce neurobehavioral effects as reported in the literature, while THg concentrations in ringed seals are within the range that elicit neurobehavioral effects and individual ringed seals exceed the threshold for neurochemical changes. The relatively high THg concentration in beluga whales exceeds all of the neurotoxicity thresholds assessed. High brain selenium (Se):Hg molar ratios were observed in all three species, suggesting that Se could protect the animals from Hg-associated neurotoxicity. This assessment was limited by several factors that influence neurotoxic effects in animals, including: animal species; form of Hg in the brain; and interactions with modifiers of Hg-associated toxicity, such as Se. Comparing brain Hg concentrations in wildlife with concentrations of appropriate laboratory studies can be used as a tool for risk characterization of the neurotoxic effects of Hg in Arctic marine mammals.

Mercury and selenium in tropical marine plankton and their trophic successors

Selenium (Se), mercury (Hg) and methylmercury (MeHg) were determined in microplankton (⩾25μm), crustacean muscle tissue, in the muscle and liver of two fish species and tissues of a dolphin from a bay in the Brazilian Southeast coast. Differences were found between the fish and dolphin muscle and hepatic concentrations. Liver showed the highest concentrations of Se and Hg. Positive biotransference of MeHg from source to consumer was observed for all interactions, demonstrating that MeHg biomagnified along the food web. The pelagic food chain has the highest biomagnification potential when compared to the benthic system. A large excess of Se in relation to Hg was observed in all tissues. The muscle and liver of the predator species, the dolphin and the carnivorous fish, presented similar MeHg. The predator species presented similar MeHg to Hg (% MeHg) ratios in muscle tissues (∼100%), whereas dolphin showed lower hepatic% MeHg (18) than the carnivorous fish (69%). Iliophagous fish presented the lowest % MeHg in tissues. Fish showed a positive relationship between hepatic MeHg and Se, whereas % MeHg did not change with increasing Se:Hg molar ratios in liver. Dolphins showed a significant inverse relationship between hepatic MeHg and Se and the % MeHg and Se:Hg ratios. This suggests a strong antagonistic effect of Se on MeHg assimilation and accumulation in this species. Probably, the differences observed among Hg as MeHg and Se and on the effect of Se on MeHg assimilation and accumulation in all marine species are related to the physiological differences between dolphins and fish.

Assessment of mercury and selenium tissular concentrations and total mercury body burden in 6 Steller sea lion pups from the Aleutian Islands

Concentrations of total mercury ([THg]) and selenium ([TSe]) were measured in several tissue compartments in Steller sea lion (Eumetopias jubatus) pups; in addition we determined specific compartment and body burdens of THg. Compartmental and body burdens were calculated by multiplying specific compartment fresh weight by the [THg] (summing compartment burdens equals body burden). In all 6 pup tissue sets (1) highest [THg] was in hair, (2) lowest [THg] was in bone, and (3) pelt, muscle and liver burdens contributed the top three highest percentages of THg body burden. In 5 of 6 pups the Se:Hg molar ratios among compartments ranged from 0.9 to 43.0. The pup with the highest hair [THg] had Se:Hg molar ratios in 9 of 14 compartments that were ⩽0.7 potentially indicating an inadequate [TSe] relative to [THg].

Relations between total mercury, methylmercury and selenium in five tissues of Sepia officinalis captured in the south Portuguese coast

Mercury, methylmercury and selenium were determined in digestive gland, branchial hearts, mantle, kidney and gills of Sepia officinalis from two areas of the south Portuguese coast. To the best of our knowledge these are the first data on Hg, MeHg and Se in branchial hearts, kidney and gills of cuttlefish. Digestive gland, branchial hearts and kidney presented higher levels of Hg and Se than mantle and gills. Methylmercury was significantly higher in digestive gland, branchial hearts and mantle. The enhanced levels of Hg in digestive gland and branchial heart reinforce the elevated storage capacity of these two tissues. The percentage of MeHg varied from 6.1% in gills to 92% in mantle. Linear and positive MeHg–Hg relations were obtained for the five tissues, being the better relation and higher slope observed for mantle, followed by branchial hearts, digestive gland, kidney and gills. The Se:Hg molar ratios showed a surplus of Se in all tissues. Calculations based on the equimolarity of Se:Hg point that 95–99% of Se are not linked to Hg (Se free). The negligible quantity of Se associated with Hg suggests that the mechanism of MeHg demethylation was not triggered in none of the tissues, presumably because the threshold for MeHg toxicity was not achieved.

Differential trends in mercury concentrations in double-crested cormorant populations of the Canadian Prairies

Mercury and selenium concentrations were measured in double-crested cormorants (Phalacrocorax auritus), piscivorous fish, and common prey items in five lakes in two ecoregions in Saskatchewan, Canada. Hg and Se concentrations in cormorants were within the natural ranges of birds living in un-impacted sites. Site explained a significant proportion of the variation in total Hg (THg) and methylmercury (MeHg) concentrations in both cormorant breast muscle and livers. Birds nesting on more northern lakes in the Boreal Plain ecoregion (THg range0.11-1.06 and 0.26-9.27μgg(-1) wet weight, for breast and liver respectively) had lower THg concentrations compared to those from lakes in the Prairie ecoregion (THg range0.60-4.26μgg(-1) ww and 1.59-25.11μgg(-1), for breast and liver respectively). Concentrations of MeHg in livers was also lower in birds from northern sites (0.06-1.15μgg(-1) ww) compared to those from prairie sites (0.22-4.06μgg(-1) ww). We documented a wide range of %MeHg in livers (4.5-52%), indicative of detoxifying MeHg via demethylation to inorganic Hg. Our data suggest that the threshold value where demethylation rates increase substantially appears to be ~10μgg(-1) ww MeHg, similar to thresholds in other wildlife. Molar ratios of Hg:Se suggests that some birds from highly saline Reed Lake in the prairie region had insufficient Se available to bind to Hg, thereby removing Se binding as a mitigative strategy for high Hg levels for these birds.

Total mercury and selenium concentrations in Sarpa salpa and Balistes capriscus and in their respective Digenean endoparasites Robphildollfusium fractum and Neoapocreadium chabaudi from Tunisia.

The present study reports the levels of mercury and selenium in Sarpa salpa and Balistes capriscus collected along the coast of Mahdia and Sfax (Tunisia). The systems constituted by S. salpa and Robphildollfusium fractum and by B. capriscus and Neoapocreadium chabaudi were tested as potential bioindicators to monitor environmental Hg pollution in marine ecosystems. Mercury and selenium concentrations were assessed in kidney, liver and muscle of 51 S. salpa and of 45 B. capriscus as well as in their respective endoparasites R. fractum and N. chabaudi. The Se:Hg molar ratios were evaluated for both species across the study areas. Surprisingly, the Se:Hg molar ratio in B. capriscus muscle from Mahdia is significantly lower than in Sfax. Our results indicate that some parasites may also be implicated in the amount of Se and Hg available in tissues and therefore contribute to oscillations of the Se:Hg molar ratios. In the model involving the carnivorous species (B. capriscus), the 5.1-times higher levels of mercury in N. chabaudi than in B. capriscus muscle in Sfax enable this fluke to be a sensitive biomonitoring tool for Hg pollution. The present results confirm that the habitual consumption of S. salpa should not suppose any potential health risk for Tunisian people. On the other hand, the consumption of B. capriscus may be of concern and further monitoring is advisable, since the Hg average concentration in Mahdia was above the maximum allowed Hg concentration in the edible portion of fish fixed by the European Union.

Selenium and mercury in widely consumed seafood from South Atlantic Ocean

The growing ingestion of predatory fish by humans has increased their exposure to toxic chemicals. Mercury (Hg) is an exogenous and harmful trace-element that accumulates in all marine organisms. Selenium (Se) is nutritionally important as a micronutrient, but is potentially harmful at intakes above 1mg per day. Se:Hg molar ratios in excess of 1:1 are thought to counteract the adverse effects of Hg, protecting against Hg toxicity. Evaluation of the health risk posed by Hg exposure from seafood consumption requires concurrent consideration of Se content in the same individuals. This study evaluated the Se and Hg concentrations in the edible tissues of 652 individual samples of commonly consumed varieties of carnivorous and planktivorous fish, squid, mussel, shrimp and crab collected from south-eastern Brazil. The Se:Hg molar ratios showed significant variation among and within tropical seafood. All organisms presented Se concentration in muscle of less than 2.0µgg−1, the maximum allowed selenium concentrations. Only seven individuals of a carnivorous fish species presented Hg in muscle above the maximum permissible limit of 0.5µgg−1 established by WHO and Brazilian legislation for human consumption of most aquatic species. These same individuals also showed Se:Hg molar ratio of less than 1:1. Se:Hg molar ratios were found to decline with increasing fish length, potentially reducing Se-dependent protection. As a result of their rich Se, low Hg contents and Se:Hg molar ratios exceeding 1:1, nearly all species included in this study provide benefits for human consumption. Two popular seafoods in the region, the carnivorous fish Centropomus undecimalis (common snook) and Micropogonias furnieri (Atlantic croaker), had the most favorable Se:Hg molar ratio values of 33 and 21, respectively. Among the invertebrates, Xiphopenaeus kroyeri (seabob shrimp) and Loligo sanpaulensis (squid) had the most favorable Se:Hg molar ratio values, higher than 20. A selenium health benefit value based on the absolute amounts and relative proportions of Se and Hg in seafood was proposed as a more comprehensive seafood safety criterion.

Element levels in cultured and wild sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) from the Adriatic Sea and potential risk assessment

In this study, the role of aquaculture activity as a source of selected metals was analyzed. Significant differences in element content between cultured (Dicentrarchus labrax, Sparus aurata) and wild fishes as well as between fish muscle and their feed were detected. Higher concentrations of trace elements (i.e., As, Cu, Hg, Se) in wild fish tissues in comparison with cultured ones indicate additional sources of metals beside fish feed as natural and/or anthropogenic sources. Generally, mean Cd, Cu, Pb, Se, and Zn concentrations in cultured (0.016, 1.79, 0.14, 0.87, and 34.32μg/g, respectively) and wild (0.011, 1.97, 0.10, 1.78, and 23,54μg/g, respectively) fish samples were below the permissible levels, while mean As (2.57μg/g in cultured, 4.77μg/g in wild) and Cr (5.25μg/g in cultured, 2.92μg/g in wild) values exceeded those limits. Hg values were lower in cultured (0.17μg/g) and higher in wild (1.04μg/g) fish specimens. The highest elemental concentrations were observed in almost all fish samples from Korčula sampling site. The smallest cultured sea basses showed As (4.01μg/g), Cr (49.10μg/g), Pb (0.65μg/g), and Zn (136μg/g) concentrations above the recommended limits; however, values decreased as fish size increased. Therefore, the majority of metal concentrations in commercial fishes showed no problems for human consumption. Also calculated Se:Hg molar ratios (all >1) and selenium health benefit values (Se-HBVs) (all positive) showed that consumption of all observed fishes in human nutrition is not risk.