Mercury-selenium species ratio in representative fish samples and their bioaccessibility by an in vitro digestion method

P. Oliveira MB, Prieto MA. Health benefits of bluefin tuna consumption: (Thunnus thynnus) as a case study

Consumers are increasingly interested in food products with high nutritional value and health benefits. For instance, fish consumption is linked with diverse positive health benefits and the prevention of certain widespread disorders, such as obesity, metabolic syndrome, or cardiovascular diseases. These benefits have been attributed to its excellent nutritional value (large amounts of high-quality fatty acids, proteins, vitamins, and minerals) and bioactive compounds, while being relatively low-caloric. Atlantic bluefin tuna (Thunnus tynnus) is one of the most consumed species worldwide, motivated by its good nutritional and organoleptic characteristics. Recently, some organizations have proposed limitations on its consumption due to the presence of contaminants, mainly heavy metals such as mercury. However, several studies have reported that most specimens hold lower levels of contaminants than the established limits and that their richness in selenium effectively limits the contaminants' bioaccessibility in the human body. Considering this situation, this study aims to provide baseline data about the nutritional composition and the latest evidence regarding the beneficial effects of Atlantic bluefin tuna consumption. A review of the risk-benefit ratio was also conducted to evaluate the safety of its consumption, considering the current suggested limitations to this species' consumption.

Selenium Health Benefit Values and Hg and Se speciation studies for elucidating the quality and safety of highly consumed fish species and fish-derived products

Nowadays, there has been an increase in the consumption of fish-derived products that constitute alternative ways of introducing fish into the diet, such as fish roe and products made from fish (crab sticks andsurimi-derived products). However, there is no data available considering selenium and mercury total contents along with speciation studies in these kinds of samples, which are mandatory for a proper safety and quality assessment. In this study,Selenium Health Benefit Values (HBVSe) in fish and fish-derived products were evaluated, resulting inpositivein all cases. Selenium speciation studies performed by HPLC-ICP-MS and confirmed by HPLC-ESI-MS/MS revealed that SeMet and SeMeSeCys are present in fish and fish-derived products. Finally, Hg speciation studiesshow that the percentage of Hg2+ increases in fishes lower in the food chain as well as in fish-derived products.

Bioaccumulation and sources of metal(loid)s in fish species from a subtropical river in Bangladesh: a public health concern

Toxic metals and freshwater fish's metalloid contamination are significant environmental concerns for overall public health. However, the bioaccumulation and sources of metal(loids) in freshwater fishes from Bangladesh still remain unknown. Thus, the As, Pb, Cd, and Cr concentrations in various freshwater fish species from the Rupsha River basin were measured, including Tenualosa ilisha, Gudusia chapra, Otolithoides pama, Setipinna phasa, Mystus vittatus, Glossogobius giuris, and Pseudeutropius atherinoides. An atomic absorption spectrophotometer was used to determine metal concentrations. The mean concentrations of metal(loids) in the fish muscle (mg/kg) were found to be As (1.53) > Pb (1.25) > Cr (0.51) > Cd (0.39) in summer and As (1.72) > Pb (1.51) > Cr (0.65) > Cd (0.49) in winter. The analyzed fish species had considerably different metal(loid) concentrations with seasonal variation, and the distribution of the metals (loids) was consistent with the normal distribution. The demersal species, M. vittatus, displayed the highest bio-accumulative value over the summer. However, in both seasons, none of the species were bio-accumulative. According to multivariate statistical findings, the research area's potential sources of metal(loid) were anthropogenic activities linked to geogenic processes. Estimated daily intake, target hazard quotient (THQ), and carcinogenic risk (CR) were used to assess the influence of the risk on human health. The consumers' THQs values were < 1, indicating that there were no non-carcinogenic concerns for local consumers. Both categories of customers had CRs that fell below the permissible range of 1E - 6 to 1E - 4, meaning they were not at any increased risk of developing cancer. The children's group was more vulnerable to both carcinogenic and non-carcinogenic hazards. Therefore, the entry of metal(loids) must be regulated, and appropriate laws must be used by policymakers.

Health Benefits of Oily Fish: Illustrated with Blue Shark (Prionace glauca), Shortfin Mako Shark (Isurus oxyrinchus), and Swordfish (Xiphias gladius)

Oily fish is a rich source of energy, proteins, essential amino acids, lipids, vitamins, and minerals. Among the macronutrients with the highest contribution are lipids, mainly long-chain omega 3 polyunsaturated fatty acids (ω-3 LC-PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both EPA and DHA play a beneficial role in promoting health and preventing many diseases, including cardiovascular diseases, such as stroke and acute myocardial infarction. They also contribute to the prevention of neurological, metabolic, and immune-system-related diseases, as well as supporting body-weight control. Oily fish consumption is also important at different stages of human life, from conception to old age. For example, DHA plays an important role in brain and retina development during fetal development and in the first two years of life, as it positively influences neurodevelopment, such as visual acuity, and cognitive functions. In contrast with the possible health benefits of the intake of oily fish, the presence of certain chemical pollutants, for example, heavy metals, can be a risk for the health of consumers, mainly in sensitive population groups such as pregnant women and children under 2 years of age. The presence of these pollutants is influenced to a greater extent by fish species, their role in the trophic chain, and their size. However, various studies state that the benefits outweigh the risk of consuming certain species. This review will be focused on the health benefits of the intake of three oily fish species, namely blue shark (Prionace glauca), shortfin mako shark (Isurus oxyrinchus), and swordfish (Xiphias gladius).

Bioavailability-based risk assessment of various heavy metals via multi-exposure routes for children and teenagers in Beijing, China

Assessing the health risks of sensitive population, such as children and teenagers, through multiple exposure routes (MERs) such as ingestion, inhalation, and dermal contact is critical for policy creation that protects or reduces exposure to pollutants for all populations. Heavy metal (HM) contents in food and environmental media in Beijing, capital of China, were collected. Furthermore, on the basis of considering the bioavailability of HMs, we evaluated the multiple environmental routes and health risks to HMs in children and teenagers of eight age groups (2-<3, 3-<4, 4-<5, 5-<6, 6-<9, 9-<12, 12-<15, and 15-<18) in Beijing, China by Monte Carlo simulation approach. The main findings are as follows: lead exposure in children aged 2-<3 years exceeds the exposure dose (0.3 μg·kg-1·d-1) of 0.5 point reduction in intelligence quotient. Moreover, children aged 2-<3 and 6-<9 years have relatively high non-carcinogenic risk (NCR) of 1.32 and 1.30, respectively. The carcinogenic risk (CR) for children aged 6-<9 and 9-<12 years is 2.73×10-6 and 2.39×10-6, respectively. Specifically, the contributions of oral ingestion, dermal contact, and inhalation to the NCR were 69.5%, 18.9%, and 11.6%, respectively. Moreover, the combined NCR contributions of copper, cadmium, mercury, and arsenic (As) were about 69.4%. The contributions of the above three routes to the CR were 93.4%, 4.1%, and 2.5%, in that order, with the largest CR contribution of As being about 92.0%. This study can provide new ideas for accurately assessing the exposure and health risks of HMs in the population, and we believe that it is necessary to update the national standards for food and soil based on the bioavailability of HMs.

Relationship between trace element concentrations and body length in dolphinfish (Coryphaena hippurus) in the northwest Atlantic Ocean

Dolphinfish (Coryphaena hippurus) is a popular seafood choice worldwide, however, except for mercury (Hg) and selenium (Se), little is known about the concentration of other trace elements in dolphinfish muscle tissue, especially in the northwest Atlantic Ocean. This study investigated the relationship between body length (61 to 94 cm fork length) and trace element [silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), Hg, manganese (Mn), nickel (Ni), lead (Pb), Se, and zinc (Zn)] concentrations in muscle tissue of dolphinfish caught off Long Island, New York (n = 16). There was a positive relationship with body length for As and Hg, a negative relationship with body length for Cu and Zn, and no relationship with body length for Cd, Fe, Mn, Pb, and Se. A negative relationship between the Se:Hg molar ratio and body length and Se:Hg molar ratio and Hg concentration was observed. Dolphinfish were low in Hg with only 18.9% (n = 3) of individuals exceeding the U.S. EPA human health criterion of 0.3 µg/g wet weight, making this species a suitable seafood choice to reduce dietary intake of Hg at the investigated body length. All fish had a Se:Hg molar ratio > 1:1 indicating that Se may have a protective effect against Hg toxicity. The selenium health benefit value (HBVSe) for all individuals was > 1, indicating there may be health benefits from consuming dolphinfish.

Mercury and selenium co-ingestion assessment via rice consumption using an in-vitro method: Bioaccessibility and interactions

Mercury (Hg) was reported to accumulate in rice grains, and, together with the selenium (Se) was found in rice, the co-exposure of Hg-Se via rice consumption may present significant health effects to human. This research collected rice samples containing high Hg:high Se and high Se:low Hg concentrations from high Hg and high Se background areas. The physiologically based extraction test (PBET) in vitro digestion model was utilized to obtain bioaccessibility data from samples. The results showed relatively low bioaccessible for Hg (<60%) and Se (<25%) in both rice sample groups, and no statistically significant antagonism was identified. However, the correlations of Hg and Se bioaccessibility showed an inverse pattern for the two sample groups. A negative correlation was detected in the high Se background rice group and a positive correlation in the high Hg background group, suggesting various micro forms of Hg and Se in rice from different planting locations. In addition, when the benefit-risk value (BRV) was calculated, some "fake" positive results showed while Hg and Se concentrations were directly used, which indicated that bioaccessibility should not be neglected in benefit-risk assessment.

Selenium Status: Its Interactions with Dietary Mercury Exposure and Implications in Human Health

Selenium is an essential trace element in humans and animals and its role in selenoprotein and enzyme antioxidant activity is well documented. Food is the principal source of selenium, and it is important that selenium status in the body is adequately maintained for physiological functions. There has been increasing attention on the role of selenium in mitigating the toxic effects of mercury exposure from dietary intake in humans. In contrast, mercury is a neurotoxin, and its continuous exposure can cause adverse health effects in humans. The interactions of selenium and mercury are multi-factorial and involve complex binding mechanisms between these elements at a molecular level. Further insights and understanding in this area may help to evaluate the health implications of dietary mercury exposure and selenium status. This review aims to summarise current information on the interplay of the interactions between selenium and mercury in the body and the protective effect of selenium on at-risk groups in a population who may experience long-term mercury exposure.

Source identification of pollution and health risks to metals in household indoor and outdoor dust: A cross-sectional study in a typical mining town, China

Dust is regarded as an important pathway of heavy metal(loid)s to the human body. Health risks posed by metal(loid)s from household dust are of particular concern. However, the contamination and sources of heavy metal(loid)s in household dust environments, as well as source identification of health risks related to heavy metal(loid)s from household dust for vulnerable populations such as children, have not been thoroughly studied in China, particularly for the areas involved with industrial activities such as ore mining. Thus, a cross-sectional study was conducted in a rural area famous for Pb/Zn ore mining, to assess the pollution sources and health risks of heavy metal(loid)s from household indoor and outdoor dust and to identify the contribution of household dust to the health risks for children. The results indicated that household environment was heavily contaminated by metal(loid)s, which were mainly attributed to mining activity. Meanwhile, the indoor/outdoor ratio and the redundancy analysis indicated that there were other pollution sources in indoor environments such as coal combustion, materials for interior building and decoration. Vapor inhalation was the main exposure pathway for Hg, while ingestion was the predominant pathway for other metal(loid)s. Although the cancer risks were relatively low, the HIt from household indoor and outdoor dust (2.19) was about twice the acceptable limit (1) and was primarily from Pb (64.52%) and As (23.42%). Outdoor dust was a larger contributor to the HI of Sb, As, Cr, Cd, Zn and Pb, which accounted for 51.37%, 58.63%, 52.14%, 59.66%, 52.87% and 64.47%, respectively, and the HIt was mainly from outdoor dust (60.76%). These results indicated that non-cancer health risks were largely from outdoor dust exposure, and strengthened the notion that concern should be given to the potential health risks from metal(loid)s in household dust both originating from mining activity and indoor environmental sources.

Metal concentrations and metallothionein metal detoxification in blue sharks, Prionace glauca L. from the Western North Atlantic Ocean

BACKGROUND

Elasmobranchs are particularly vulnerable to environmental metal contamination, accumulating these contaminants at high rates and excreting them slowly. The blue shark Prionace glauca L. is one of the most heavily fished elasmobranchs, although information regarding metal contamination and detoxification in this species is notably lacking.

METHODS

Blue sharks were sampled in the western North Atlantic Ocean, in offshore waters adjacent to Cape Cod, Massachusetts. Total and metallothionein-bound liver and muscle metal concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS), metallothionein detoxification and oxidative stress endpoints were determined by UV-vis spectrophotometry.

RESULTS

Metallothionein detoxification occurred for As, Cd, Cs, Cu, Hg, Pb, Se, Ti and Zn in liver, and for As, Cd, Cs, Pb, Se, and Zn in muscle, while reduced glutathione defenses seem to be related to Co and Zn exposure.

CONCLUSION

This is the first report for several metals (Ag, Co, non-radioactive Cs, Sb, Ti and V) for this species, which will aid in establishing baseline elemental data for biomonitoring efforts, health metrics, and conservation measures.

Levels of Mercury, Methylmercury and Selenium in Fish: Insights into Children Food Safety

Total mercury (THg), methylmercury (MeHg), and selenium (Se) concentrations were measured in various commercially important fish species. The benefit-risk binomial associated with these chemicals was assessed in children through the probability of exceeding the provisional tolerable weekly intakes (PTWIs) of the contaminants and the Se recommended dietary allowance (RDA). The Se:Hg molar ratios, selenium health benefit values (HBVSe), and monthly consumption rate limits (CRmm) for each species were also calculated. THg and Se were analyzed by atomic absorption spectrophotometer (Shimadzu, Milan, Italy), while MeHg was determined by Trace Ultra gas chromatograph connected with a PolarisQ MS (Thermo Fisher Scientific, Waltham, MA, USA). None of the analyzed fish had Hg levels above the European Community regulatory limits, while most large predators had MeHg levels over the threshold concentration set by US EPA. The estimated weekly intakes of THg and MeHg exceeded in many cases the PTWIs and the Se estimated daily intakes were provided from 0.71% to 2.75% of the RDA. Se:Hg molar ratios above 1 and positive HBVSe index suggested that Se in fish could be enough to alleviate the potential toxic effect of Hg. However, high-risk groups as children should consume fish in moderation because a large consumption pattern, especially of swordfish and tunas, might be of concern for health.

Green tea infusion reduces mercury bioaccessibility and dietary exposure from raw and cooked fish

Human exposure to mercury (Hg) and methylmercury (MeHg) through the ingestion of seafood raises human health-related concerns. In contrast, green tea has health benefits and its consumption potentially reduces bioaccessibility of dietary Hg. The present study aimed to assess the effect of green tea in total mercury (THg) and MeHg bioaccessibility in raw and cooked marine fish species commonly having high Hg levels. Preliminary results demonstrated that significantly higher reductions of bioaccessible THg were attained after the co-ingestion of green tea infusion (1 cup or more) in the oral and intestinal phases. Overall, the present findings clearly show that the co-ingestion of green tea along with seafood grilling strongly reduces THg and MeHg bioaccessibility in all fish species and consequently diminishes the probability of exceeding MeHg provisional tolerable weekly intakes through the consumption of these species with high Hg levels. Such results point out the need to better understand the beneficial/preventive role of green tea infusions and other food processing techniques in bioaccessibility reduction of other chemical contaminants present in food products. Such information is certainly useful to help consumers to wisely select their food, and to enable food safety authorities to integrate such information in risk assessment.

Study of Cd Content Distribution and Its Bioaccessibility in Edible Tissues of Crab Portunus trituberculatus from the Coastal Area of Shandong, China

Bioaccessibility study is of great significance to the health risk assessment of trace elements in the seafood. In this work, the most consumed crab (Portunus trituberculatus) in coastal area of Shandong, China was analyzed to study the distribution and the bioaccessibility of cadmium (Cd) in the edible tissues of crab, and the dietary risk from consumption of crab was also evaluated. Results showed that the content of Cd in the whole edible tissues of 109 crab specimens ranged from 0.052 to 8.89 mg/kg ww (wet weight) with mean of 2.26 mg/kg ww. The Cd content in 85% of the crab samples was higher than the national food safety limits (0.5 mg/kg ww) of China. The gender study indicated that there was no significant difference in Cd content in total edible tissues between the males and females (p > 0.05). Cadmium was highly concentrated in the brown meat with mean value of 4.13 mg/kg ww, which was about 5 times higher than that in the white meat (0.75 mg/kg ww). The bioaccessibility of Cd ranged from 48.1 to 71.0% in the white and brown meat. The risk assessment based on the bioaccessibility of Cd revealed that the consumption of the edible crab brown and white meat for adults should be limited in 0.13 kg and 1.56 kg per week respectively.

Hg and Se composition in demersal deep-sea fish from the North-East Atlantic

It has been emphasized that seafood consumers may have a higher risk of mercury (Hg) exposure. Nevertheless, the co-occurrence of selenium (Se) in organisms may affect the toxicity and bioavailability of Hg. In this work, we aim to demonstrate the possible role of Se as a potential protective element against Hg in muscle and liver tissues of three demersal deep-sea fish species: common mora Mora moro, birdbeak dogfish Deania calcea, and smooth lanternshark Etmopterus pusillus. Comparing species, the birdbeak dogfish D. calcea showed the highest Hg concentrations, the lowest Se levels, the lowest mean Se:Hg molar ratio, a negative HBV-Se index, and no correlation between total length. On the other hand, smooth lanternshark E. pusillus showed the lowest Hg concentrations, the highest Se concentrations, the highest mean Se:Hg molar ratio, a positive HBV-Se index, and a significant positive correlation between total length and Se concentrations in muscle. Comparing tissues, the common mora Mora moro seems to accumulate more Hg and Se in liver than shark species D. calcea and E. pusillus that showed to accumulate Hg and Se preferentially in muscle. Our results indicate that these three species for having Hg concentrations near and above the EU regulatory thresholds and for presenting low Se:Hg ratios, and negative (or low positive) HBV-Se index may pose a real risk of Hg toxicity for the consumer.

Quantificational exposure, sources, and health risks posed by heavy metals in indoor and outdoor household dust in a typical smelting area in China

Contamination of metals in household dust remains a concern for human health. However, few studies to date have been conducted on the contribution of both indoor and outdoor environments to the health risks posed by metals. This study was carried out to assess the potential health risks from both indoor and outdoor household dust and the respective contribution to the health risks for children. The results showed that household dusts were heavily polluted by metal(loid)s, which were up to 30 times higher than the relative background level, and were attributed to smelting activity. However, there are other pollution sources in indoor environments, since the I/O ratio values of Pb, Cd, and As were significantly higher than 1. HI values of Pb and As exceeded the threshold of (1) and accounted for approximately 60% and 24% to the HIt, respectively. The HIts of Zn, Cr, Mn, Hg, and Cu were mainly attributable to indoor dust exposure, particularly for Hg (73.44%), indicating non-carcinogenic health risks could be attributed more to the indoor dust exposure. This study highlights the potential risks of metal contamination in household environment, particularly indoor environment, on the health of children who live in the vicinity of smelting activity.

Selenium and mercury in dolphinfish (Coryphaena hippurus) from the Gulf of California: inter-annual variations and selenium health benefit value

With the aim of determining the benefit from consumption of dolphinfish Coryphaena hippurus from La Paz and Cabo San Lucas in the southern area of the Gulf of California, mercury (Hg) and selenium (Se) were measured in liver and muscle of specimens (n = 362) collected between 2006 and 2013. Mean levels of Hg in muscle (0.61 μg g^-1) and liver (0.42 μg g^-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas; in the case of Se, mean concentrations in liver (1.54 μg g^-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas. Hg levels in muscle were positively and significantly (p < 0.05) correlated with fork length and weight of fish; in liver, Hg and Se were significantly (p < 0.05) correlated with fork length and weight of specimens. Levels of Hg and Se in muscle and liver among years varied significantly (p < 0.05); although there was not a defined pattern of temporal fluctuations for both elements, the lowest Hg levels occurred in 2009 when surface water temperatures were the highest for the sampled years. With respect to the Se health benefit value (HBV_Se), results were positive and above the unit in all cases; it implies that consumption of dolphinfish in the southern Gulf of California is beneficial.

In vivo oral bioavailability of fish mercury and comparison with in vitro bioaccessibility

Fish consumption is considered to be a major human exposure route for mercury (Hg), but assessing the actual Hg bioavailability from consumed fish is challenging. In this study, we conducted both in vivo bioavailability (using a mouse model) and in vitro bioaccessibility (using various gastrointestinal digestion methods) assessments of Hg from consumed fish. Lyophilized fish muscles which already absorbed Hg through natural incorporation were introduced to mice by active feeding. Assimilation efficiency (AE) was measured as a short-term kinetic parameter, while a 7-day accumulation of Hg in mice blood, liver and kidney was determined. The AEs of Hg in mice ranged between 82 and 96% and showed a positive relationship with MeHg in fish independent of the fish species. For long-term bioavailability tests in which the Hg retention in organs was measured after a 7-day exposure, most Hg was found to be accumulated in liver and kidney, resulting in a strong correlation between Hg dosage and accumulation in mice organs. The long-term absolute bioavailability of mice was comparable between the liver and kidney, but much lower in the blood. The calculated absolute total Hg bioavailability ranged between 38% and 99% and decreased as the Hg dosage increased. Results of bioaccessibility tests varied considerably among different methods, illustrating that there were limitations for the in vitro bioaccessibility assay to predict the digestive dynamics of Hg in mammalian gastrointestinal tract. Our study strongly demonstrated the expediency of direct determination of Hg bioavailability, but more bioaccessibility assessments should be explored and optimized as an alternative to traditional animal experimentation.

Mercury, silver, selenium and other trace elements in three cyprinid fish species from the Vaal Dam, South Africa, including implications for fish consumers

The levels of Cr, Cu, Zn, Se, Ag, Cd, Hg, and Pb were determined in muscle and liver samples from 30 specimens of fish belonging to the species Labeobarbus aeneus, Labeobarbus kimberleyensis, and Labeo umbratus from the Vaal Dam. Health risks for human fish consumers were estimated using the target hazard quotient (THQ), the Se:Hg-ratio, and Se health benefit value (Se HBV). This is the first comprehensive report on Hg levels in fish from this lake. Mean concentrations ranging from 0.247-0.481 mg/kg dw in muscle and from 0.170-0.363 mg/kg dw in liver clearly show a contamination with this element. Although levels in muscle did not exceed maximum allowances for human consumption, a calculated THQ of 0.12 and 0.14 for the two Labeobarbus species, respectively, showed a potential risk due to additive effects. All Se:Hg-ratios as well as Se HBVs clearly suggested positive effects for fish consumers. Levels of Cu were remarkably high in the liver of L. umbratus, calling for further investigation on this species. Cadmium levels were above the maximum allowances for fish consumption in the liver of all three species (means between 0.190 and 0.460 mg/kg dw), but below the LOD in all muscle and intestine samples. This is also the first report of Ag in fish from South Africa. Levels were below the LOD in muscle, but well detectable in liver; they varied significantly between the two Labeobarbus species (0.054 ± 0.030 and 0.037 ± 0.016 mg/kg dw) compared to L. umbratus (1.92 ± 0.83 mg/kg dw) and showed a positive correlation with Cu levels (63.7 ± 17.0; 70.3 ± 9.0 and 1300 ± 823 mg/kg dw), possibly due to similar chemical affinities to metallothioneins. The detected Ag levels can serve as a basis to monitor the development of this new pollutant in aquatic environments in South Africa and worldwide.

Determination of Hg in Farmed and Wild Atlantic Bluefin Tuna (Thunnus thynnus L.) Muscle

Mercury (Hg) is a well-known toxic element, diffused in the environment, especially in the Mediterranean Sea which is rich in cinnabar deposits. Mercury bioaccumulation in fish is of great concern, especially for top-level aquatic predators (e.g., shark, tuna, swordfish) and above all for species of large human consumption and high nutritional value. This work aimed to determine Hg concentrations in farmed and wild Atlantic Bluefin tuna (Thunnus thynnus) caught in the Mediterranean area in order to evaluate the level of Hg bioaccumulation. selenium (Se) content was also determined, since this element is an antagonist of mercury toxicity. Mercury and Se were analysed by atomic absorption spectrometry after microwave digestion of the samples. Hg content in farmed tuna was below the legal limit (1 mg/kg, wet weight, w.w.) for all specimens (0.6 ± 0.2 mg/kg), whereas the wild ones had a content over the limit (1.7 ± 0.6 mg/kg); Se concentration was higher in farmed specimens (1.1 ± 0.9 mg/kg) compared to wild ones (0.6 ± 0.3 mg/kg). A safe seafood could show a Se/Hg ratio >1 and a health benefit value (HBV_Se) > 0: farmed tuna had higher values than the wild specimens (Se/Hg 5.48 vs. 1.32; HBV_Se 11.16 vs. 0.29). These results demonstrate that for Hg, there is a better risk/benefit ratio in farmed T. thynnus. making it safer than wild tuna.

Selenium, total mercury and methylmercury in sardine: Study of molar ratio and protective effect on the diet

The purpose of this work was to evaluate the risk-benefit associated with canned sardine consumption, considering the selenium, the mercury and the methylmercury contents and the Se:Hg molar ratio and the Se-health benefit value (HBV) index. In this study, 63 canned sardine samples were purchased worldwide and for the determination of selenium and mercury species, the inductively coupled plasma optical emission spectrometry and thermal decomposition and amalgamation atomic absorption spectrometry were employed. The mean results obtained for the Brazilian samples varied between 12.6 and 65.5 μg kg^-1 for Hg; <3.7 and 45.4 μg kg^-1 for methylmercury; 310 and 1370 μg kg^-1 for Se. The MeHg/Hg ratio showed that the most toxic forms of Hg (MeHg) is predominant in 52 and 39% of the Brazilian samples conserved in tomato sauce and in oil, respectively. Nevertheless, the Se-HBV index and the Hg:Se and Se:Hg molar ratios indicated that the selenium content in canned sardine samples is enough to provide a protective effect on the Hg species.

Diet composition and serum levels of selenium species: A cross-sectional study

Selenium is a trace element of both nutritional and toxicological interest, depending on its dose and chemical form. Diet is the primary source of exposure for most individuals. We sought to investigate the influence of food intake on serum levels of selenium species. Among fifty subjects randomly selected from a Northern Italian population, we assessed dietary habits using a validated semi-quantitative food frequency questionnaire. We also measured circulating levels of selenium species in serum using high pressure liquid chromatography associated with inductively-coupled plasma dynamic reaction cell mass spectrometer. Circulating levels of inorganic selenium, the most toxic selenium species, were positively associated with intake of fish, legumes and dry fruits, and inversely associated with intake of dairy products and mushrooms. Concerning the organic selenium species, selenoproteinP-bound selenium was inversely associated with intake of fish, fresh fruits, vegetables, and legumes, while selenocysteine-bound selenium positively associated with intake of fresh fruit, potato, legume and mushroom. In the present study, intakes of different foods were correlated with different types of selenium species. These results have important public health implications when assessing the nutritional and toxicological potential of diet composition with reference to selenium exposure.

Cooking and co-ingested polyphenols reduce in vitro methylmercury bioaccessibility from fish and may alter exposure in humans

Fish consumption is a major pathway for mercury exposure in humans. Current guidelines and risk assessments assume that 100% of methylmercury (MeHg) in fish is absorbed by the human body after ingestion. However, a growing body of literature suggests that this absorption rate may be overestimated. We used an in vitro digestion method to measure MeHg bioaccessibility in commercially-purchased fish, and investigated the effects of dietary practices on MeHg bioaccessibility. Cooking had the greatest effect, decreasing bioaccessibility on average to 12.5±5.6%. Polyphenol-rich beverages also significantly reduced bioaccessibility to 22.7±3.8% and 28.6±13.9%, for green and black tea respectively. We confirmed the suspected role of polyphenols in tea as being a driver of MeHg's reduced bioaccessibility, and found that epicatechin, epigallocatechin gallate, rutin and cafeic acid could individually decrease MeHg bioaccessibility by up to 55%. When both cooking and polyphenol-rich beverage treatments were combined, only 1% of MeHg remained bioaccessible. These results call for in vivo validation, and suggest that dietary practices should be considered when setting consumer guidelines for MeHg. More realistic risk assessments could promote consumption of fish as a source of fatty acids, which can play a protective role against cardiovascular disease.

Developmental selenium exposure and health risk in daily foodstuffs: A systematic review and meta-analysis

Selenium (Se) is a trace mineral and an essential nutrient of vital importance to human health in trace amounts. It acts as an antioxidant in both humans and animals, immunomodulator and also involved in the control of specific endocrine pathways. The aim of this work is to provide a brief knowledge on selenium content in daily used various foodstuffs, nutritional requirement and its various health consequences. In general, fruits and vegetables contain low content of selenium, with some exceptions. Selenium level in meat, eggs, poultry and seafood is usually high. For most countries, cereals, legumes, and derivatives are the major donors to the dietary selenium intake. Low level of selenium has been related with higher mortality risk, dysfunction of an immune system, and mental failure. Selenium supplementation or higher selenium content has antiviral outcomes and is necessary for effective reproduction of male and female, also decreases the threat of chronic disease (autoimmune thyroid). Generally, some advantages of higher content of selenium have been shown in various potential studies regarding lung, colorectal, prostate and bladder cancers risk, nevertheless results depicted from different trials have been diverse, which perhaps indicates the evidence that supplementation will merely grant advantage if the intakes of a nutrient is deficient. In conclusion, the over-all people should be advised against the usage of Se supplements for prevention of cardiovascular, hepatopathies, or cancer diseases, as advantages of Se supplements are still ambiguous, and their haphazard usage could result in an increased Se toxicity risk. The associations among Se intake/status and health, or disease risk, are complicated and need exposition to notify medical practice, to improve dietary recommendations, and to develop adequate communal health guidelines.

In vitro evaluation of dietary compounds to reduce mercury bioavailability

Mercury in foods, in inorganic form [Hg(II)] or as methylmercury (CH₃Hg), can have adverse effects. Its elimination from foods is not technologically viable. To reduce human exposure, possible alternatives might be based on reducing its intestinal absorption. This study evaluates the ability of 23 dietary components to reduce the amount of mercury that is absorbed and reaches the bloodstream (bioavailability). We determined their effect on uptake of mercury in Caco-2 cells, a model of intestinal epithelium, exposed to Hg(II) and CH₃Hg standards and to swordfish bioaccessible fractions. Cysteine, homocysteine, glutathione, quercetin, albumin and tannic reduce bioavailability of both mercury species. Fe(II), lipoic acid, pectin, epigallocatechin and thiamine are also effective for Hg(II). Some of these strategies also reduce Hg bioavailability in swordfish (glutathione, cysteine, homocysteine). Moreover, extracts and supplements rich in these compounds are also effective. This knowledge may help to define dietary strategies to reduce in vivo mercury bioavailability.

Oral bioaccessibility of toxic and essential elements in raw and cooked commercial seafood species available in European markets

The oral bioaccessibility of several essential and toxic elements was investigated in raw and cooked commercially available seafood species from European markets. Bioaccessibility varied between seafood species and elements. Methylmercury bioaccessibility varied between 10 (octopus) and 60% (monkfish). Arsenic (>64%) was the toxic element showing the highest bioaccessibility. Concerning essential elements bioaccessibility in raw seafood, selenium (73%) and iodine (71%) revealed the highest percentages. The bioaccessibility of elements in steamed products increased or decreased according to species. For example, methylmercury bioaccessibility decreased significantly after steaming in all species, while zinc bioaccessibility increased in fish (tuna and plaice) but decreased in molluscs (mussel and octopus). Together with human exposure assessment and risk characterization, this study could contribute to the establishment of new maximum permissible concentrations for toxic elements in seafood by the European food safety authorities, as well as recommended intakes for essential elements.

Use of Saccharomyces cerevisiae To Reduce the Bioaccessibility of Mercury from Food

Food is the main pathway of exposure to inorganic mercury [Hg(II)] and methylmercury (CH₃Hg). Intestinal absorption of these mercury species is influenced by their chemical form, the luminal pH, and the composition of the diet. In this regard, strategies have been proposed for reducing mercury absorption using dietary components. This study evaluates the capacity of Saccharomyces cerevisiae to reduce the amount of mercury solubilized after gastrointestinal digestion that is available for intestinal absorption (bioaccessibility). The results show that S. cerevisiae strains reduce mercury bioaccessibility from aqueous solutions of Hg(II) (89 ± 6%) and CH₃Hg (83 ± 4%), and from mushrooms (19-77%), but not from seafood. The formation of mercury-cysteine or mercury-polypeptide complexes in the bioaccessible fraction may contribute to the reduced effect of yeasts on mercury bioaccessibility from seafood. Our study indicates that budding yeasts could be useful for reducing the extent of intestinal absorption of mercury present in water and some food matrices.

Methylmercury in fish from the southern Baltic Sea and coastal lagoons as a function of species, size, and region

Background:

Methylmercury (MeHg) is a highly toxic compound that traverses the blood–brain barrier with deleterious effects to the central nervous system. Exposure is generally through the ingestion of contaminated fish. Fish are a main source of MeHg.

Goals and methods:

The aim of this study was to determine the dependence of MeHg concentrations on fish species and age, the percentage of MeHg in total mercury (THg) and risk assessment depending on the size of fish. Assays of THg and MeHg were performed on the muscle tissues of 18 species of fish.

Results:

The investigations indicated there were differences in the mercury concentrations depending on fish size. THg and MeHg concentrations in the muscles of fish species that have a wide length distribution were strongly, positively correlated with fish length. However, concentrations of MeHg were strongly, positively correlated with those of THg in all the fish species investigated. Variation in the percentage share of MeHg in THg in the muscles of fish of large sizes was also noted within species, but this correlation was not noted in small-sized fish. The dose of MeHg in small-sized fish species was estimated and the risk posed to consumer health was assessed using mean MeHg concentrations determined for different fish species.

Conclusions:

For species of fish that occur within a wide length distribution, the dose of MeHg should be assessed separately in different length classes. Fish consumption of small-sized species poses no health risk.

Bioaccessibility and bioavailability of methylmercury from seafood commonly consumed in North America: In vitro and epidemiological studies

Methylmercury (MeHg) is a global contaminant of concern and human exposures are largely realized via seafood consumption. While it is assumed that 95-100% of the ingested MeHg from seafood reaches systemic circulation, recent in vitro studies have yielded results to suggest otherwise. Of the published studies to have characterized the bioaccessibility or bioavailability of MeHg from seafood, only a handful of seafood species have been characterized, there exists tremendous variability in data within and across species, few species of relevance to North America have been studied, and none of the in vitro studies have adapted results to an epidemiology study. The objective of the current study was two-fold: (a) to characterize in vitro MeHg bioaccessibility and bioavailability from ten commonly consumed types of seafood in North America; and (b) to apply the bioaccessibility and bioavailability data from the in vitro study to an existing human MeHg exposure assessment study. Raw seafood samples (cod, crab, halibut, salmon, scallop, shrimp, tilapia, and three tuna types: canned light, canned white, fresh) were purchased in Montreal and their MeHg concentrations generally overlapped with values reported elsewhere. The bioaccessibility of MeHg from these samples ranged from 50.1±19.2 (canned white tuna) to 100% (shrimp and scallop) of the amount measured in the raw undigested sample. The bioavailability of MeHg from these samples ranged from 29.3±10.4 (crab) to 67.4±9.7% (salmon) of the value measured in the raw undigested sample. There were significant correlations between the initial MeHg concentration in seafood with the percent of that Hg that was bioaccessible (r=-0.476) and bioavailable (r=-0.294). When the in vitro data were applied to an existing MeHg exposure assessment study, the estimated amount of MeHg absorbed into systemic circulation decreased by 25% and 42% when considering bioaccessibility and bioavailability, respectively. When the in vitro data were integrated into a regression model relating dietary MeHg intake from seafood with hair and blood Hg biomarkers, there were no differences in key model parameters when comparing the default model (that assumes 100% bioavailability) with models adjusted for the in vitro bioaccessibility and bioavailability data. In conclusion this work adds to a growing number of studies that together suggest that MeHg bioavailability from seafood may be less than 100%, but also documents the challenges when integrating such in vitro data into human exposure and risk assessments.

Food wastes as fish feeds for polyculture of low-trophic-level fish: bioaccumulation and health risk assessments of heavy metals in the cultured fish

The major purpose of this study was to use different types of food wastes which serve as the major sources of protein to replace the fish meal used in fish feeds to produce quality fish. Two types of food waste-based feed pellets FW A (with cereals) and FW B (with cereals and meat products) and the commercial feed Jinfeng® were used to culture fingerlings of three low-trophic-level fish species: bighead carp, grass carp, and mud carp (in the ratio of 1:3:1) for 1 year period in the Sha Tau Kok Organic Farm in Hong Kong. Heavy metal concentrations in all of the fish species fed with food waste pellets and commercial pellets in Sha Tau Kok fish ponds were all below the local and international maximum permissible levels in food. Health risk assessments indicated that human consumption of the fish fed with food waste feed pellets was safe for the Hong Kong residents. The present results revealed that recycling of food waste for cultivating low-trophic-level fish (mainly herbivores and detritus feeders) is feasible, and at the same time will ease the disposal pressure of food waste, a common problem of densely populated cities like Hong Kong.

Influence of metal(loid) bioaccumulation and maternal transfer on embryo-larval development in fish exposed to a major coal ash spill

In December 2008, an earthen retaining wall at the Tennessee Valley Authority (TVA) Kingston Fossil Fuel Plant failed and released 4.1 millionm(3) of coal ash to rivers flowing into Watts Bar Reservoir in east Tennessee, United States (U.S.). As part of a comprehensive effort to evaluate the risks to aquatic resources from this spill - the largest in U.S. history - we compared bioaccumulation and maternal transfer of selenium (Se), arsenic (As), and mercury (Hg) in adult redear sunfish (Lepomis macrolophus), collected two years after the spill from both coal-ash exposed and non-exposed areas of the Emory and Clinch Rivers, with the success of embryo-larval development in their offspring. Whole body and ovary concentrations of Se in female sunfish at three study sites downstream of the spill were significantly elevated (site means=4.9-5.3 and 6.7-9.0mg/kg d.w. whole body and ovary concentrations, respectively) compared with concentrations in fish from reference sites upstream of the spill site (2.2-3.2mg/kg d.w. for whole bodies and 3.6-4.8mg/kg d.w. for ovaries). However, Se concentrations in coal ash-exposed areas remain below proposed U.S. Environmental Protection Agency (USEPA) criteria for the protection of aquatic life. Site-to-site variation in fish concentrations of As and Hg were not well-correlated with ash-exposure, reflecting the multiple sources of these metal(loid)s in the affected watersheds. In 7-day laboratory tests of embryos and larvae derived from in vitro crosses of eggs and sperm from these field-collected sunfish, fertilization success, hatching success, embryo-larval survival, and incidences of developmental abnormalities did not differ significantly between ash-exposed and non-exposed fish. Furthermore, these developmental endpoints were not correlated with whole body or ovary concentrations of Se, As, or Hg in the maternal fish, or with fish size, ovary weight, or gonadal-somatic indices. Results from this and related studies associated with the Kingston coal ash spill are consistent with proposed USEPA fish-based water quality criteria for Se, and to date continue to suggest that long-term exposures to sediment containing residual ash may not present a significant chronic risk to fish populations exposed to this major coal ash release.

Influence of Physiological Gastrointestinal Parameters on the Bioaccessibility of Mercury and Selenium from Swordfish

Swordfish tend to accumulate mercury (Hg), but they are rich in selenium (Se), an element that can counteract the toxic effects of Hg. The aim of the present study was to evaluate the concentrations and bioaccessibility of Hg and Se in cooked swordfish and to identify the digestion parameters (pH, residence time, and enzyme concentrations) that may influence their bioaccessibility. The Hg concentrations ranged between 0.17 and 2.82 mg/kg wet weight (ww) and the bioaccessibility between 14 and 92%. The range for Se concentrations was narrower (0.29-1.17 mg/kg ww), with a bioaccessibility that was generally greater than that of Hg (59-103%). Most of the solubilization took place in the gastric step, where acidic pH and the increase in the pepsin concentration led to greater bioaccessibility, especially for Hg. In the intestinal stage, the most notable effect was the decrease in the bioaccessibility of Hg in the presence of bile salts.

Does boiling affect the bioaccessibility of selenium from cabbage?

The bioaccessible selenium species from cabbage were studied using an in vitro physiologically-based extraction test (PBET) which establishes conditions that simulate the gastric and gastrointestinal phases of human digestion. Samples of cabbage (Brassica oleracea) grown in peat fortified with different concentrations of Se(IV) and Se(VI) were analysed, and several enzymes (pepsin, pancreatin and amylase) were used in the PBET. The effect of boiling before extraction was also assayed. Selenium speciation in the PBET extracts was determined using anionic exchange and LC-ICP/MS. The selenocompounds in the extracts were Se(IV), SeMet and, mostly, Se(VI) species. The results show that the activity of the enzymes increased the concentration of the selenocompounds slightly, although the use of amylase had no effect on the results. The PBET showed the concentration of inorganic selenium in the extracts from boiled cabbage decreased as much as 4-fold while the release of SeMet and its concentration increased (up to 6-fold), with respect to raw cabbage.

Environmental mercury concentrations in cultured low-trophic-level fish using food waste-based diets

In this study, different types of food wastes were used as the major source of protein to replace the fish meal in fish feeds to produce quality fish (polyculture of different freshwater fish). During October 2011-April 2012, the concentrations of Hg in water, suspended particulate matter, and sediment of the three experimental fish ponds located in Sha Tau Kok Organic Farm were monitored, and the results were similar to or lower than those detected in commercial fish ponds around the Pearl River Delta (PRD) region (by comparing data of previous and present studies). Health risk assessments indicated that human consumption of grass carp (Ctenopharyngodon idellus), a herbivore which fed food waste feed pellets would be safer than other fish species: mud carp (Cirrhina molitorella), bighead carp (Hypophthalmichthys nobilis), and largemouth bass (Lepomis macrochirus). Due to the lower species diversity and substantially shorter food chains of the polyculture system consisting of only three fish species, the extent of Hg biomagnification was significantly lower than other polyculture ponds around PRD. Furthermore, the use of food waste instead of fish meal (mainly consisted of contaminated trash fish) further reduced the mercury accumulation in the cultured fish.

Interspecific and locational differences in metal levels in edible fish tissue from Saudi Arabia

Metal levels in fish have been extensively studied, but little data currently exists for the Middle East. We examined the levels of metals and metalloids (aluminum, arsenic, copper, manganese, selenium, zinc, and mercury) in the flesh of 13 fish species collected from three fishing sites and a local fish market in Jeddah, Saudi Arabia. We tested the following null hypotheses: (1) there are no interspecific differences in metal levels, (2) there are no differences in metal levels in fishes between market and fishing sites, (3) there are no size-related differences in metal levels, and (4) there are no differences in selenium:mercury molar ratio among different fish species. There were significant interspecific differences in concentrations for all metals. There was an order of magnitude difference in the levels of aluminum, arsenic, mercury, manganese, and selenium, indicating wide variation in potential effects on the fish themselves and on their predators. Fishes from Area II, close to a large commercial port, had the highest levels of arsenic, mercury, and selenium, followed by market fishes. Mercury was positively correlated with body size in 6 of the 13 fish species examined. Mercury was correlated positively with arsenic and selenium, but negatively with aluminum, cobalt, copper, manganese, and zinc. Selenium:mercury molar ratios varied significantly among species, with Carangoides bajad, Cephalopholis argus, Variola louti, and Ephinephelus tauvina having ratios below 10:1. These findings can be used in risk assessments, design of mercury reduction plans, development of fish advisories to protect public health, and future management decision-making.

Selenium:mercury molar ratios in bullfrog and leopard frog tadpoles from the northeastern United States

Vertebrates experience adverse effects from methylmercury, largely obtained through their food. Selenium has the potential to reduce the toxic effects of methylmercury (and vice versa). In this paper, we examine the selenium:mercury molar ratios in tadpoles (Lithobates sphenocephalus, Lithobates catesbeianus (formerly Rana), and a newly documented leopard frog species currently referred to as R. sp. nov.) and fully formed leopard frog metamorphs. There were no significant differences in metal levels between the two leopard frog species, and data were therefore combined. Selenium:mercury molar ratios varied from 19 to 38 for bullfrog tadpoles, from 16 to 330 for leopard frog tadpoles, and from 7 to 17 for leopard frog metamorphs. Leopard frog tadpoles with less than 45 days exposure to field conditions had significantly higher molar ratios than other tadpoles and leopard frog metamorphs. There were significant locational differences for the molar ratios of bullfrogs, and leopard frog tadpoles with more than 45 days of field exposure. At the sites where we were able to sample both leopard frog tadpoles and leopard frog metamorphs, there were significant differences between the two distinct life stages. Most of the variation in the ratio was accounted for by selenium levels, field sites, and exposure period.

Novel oral detoxification of mercury, cadmium, and lead with thiol-modified nanoporous silica

We have developed a thiol-modified nanoporous silica material (SH-SAMMS) as an oral therapy for the prevention and treatment of heavy metal poisoning. SH-SAMMS has been reported to be highly efficient at capturing heavy metals in biological fluids and water. Herein, SH-SAMMS was examined for efficacy and safety in both in vitro and in vivo animal models for the oral detoxification of heavy metals. In simulated gastrointestinal fluids, SH-SAMMS had a very high affinity (Kd) for methyl mercury (MeHg(I)), inorganic mercury (Hg(II)), lead (Pb(II)), and cadmium (Cd(II)) and was superior to other SAMMS with carboxylic acid or phosphonic acid ligands or commercially available metal chelating sorbents. SH-SAMMS also effectively removed Hg from biologically digested fish tissue with no effect on most nutritional minerals found in fish. SH-SAMMS could hold Hg(II) and MeHg(I) tightly inside the nanosize pores, thus preventing bacteria from converting them to more absorbable forms. Rats fed a diet containing MeHg(I), Cd(II), and Pb(II) and SH-SAMMS for 2 weeks had blood Hg levels significantly lower than rats fed the metal-rich diet only. Upon cessation of the metal-rich diet, continued administration of SH-SAMMS for 2 weeks facilitated faster and more extensive clearance of Hg than in animals not continued on oral SH-SAMMS. Rats receiving SH-SAMMS also suffered less weight loss as a result of the metal exposure. Retention of Hg and Cd in major organs was lowest in rats fed with SH-SAMMS throughout the entire four weeks. The reduction of blood Pb by SH-SAMMS was significant. SH-SAMMS was safe to intestinal epithelium model (Caco-2) and common intestinal bacteria (Escherichia coli). Altogether, it has great potential as a new oral drug for the treatment of heavy metal poisoning. This new application is enabled by the installation of tailored interfacial chemistry upon nontoxic nanoporous materials.

Heavy metal (As, Cd, Hg, Pb, Cu, Zn, Se) concentrations in muscle and bone of four commercial fish caught in the central Adriatic Sea, Italy

Heavy metal (As, Cd, Cu, Pb, Zn, Hg and Se) concentrations in the muscle and bone of four fish species (Mullus barbatus, Merluccius merluccius, Micromesistius poutassou, and Scomber scombrus) from the central Adriatic Sea were measured and the relationships between fish size (length and weight) and metal concentrations in the tissues were investigated. Samples were analyzed by inductively coupled plasma-atomic emission spectrophotometry with automatic dual viewing. In the muscle, results of linear regression analysis showed that, except for mercury, significant relationships between metal concentrations and fish size were negative. Only mercury levels were positively correlated with Atlantic mackerel size (p < 0.05). No significant variations of heavy metal concentrations were observed in muscles of the examined species, but a significant difference (p < 0.01) was found for As, Cd, Pb, and Se concentrations in bone. All the investigated metals showed higher values in the muscle than in bone, except for lead and zinc. Regarding cadmium, lead, and mercury maximum levels, set for the edible portion by European legislation, several samples exceeded these values, confirming the heavy metal presence in species caught near the Jabuka Pit.

Contamination of different portions of raw and boiled specimens of Norway lobster by mercury and selenium

The aim of this study was to evaluate mercury and selenium distribution in different portions (exoskeleton, white meat and brown meat) of Norway lobster (Nephrops norvegicus). Some samples were also analysed as whole specimens. The same portions were also examined after boiling, in order to observe if this cooking practice could affect mercury and selenium concentrations. The highest mercury concentrations were detected in white meat, exceeding in all cases the maximum levels established by European legislation. The brown meat reported the highest selenium concentrations. In all boiled samples, mercury levels showed a statistically significant increase compared to raw portions. On the contrary, selenium concentrations detected in boiled samples of white meat, brown meat and whole specimen showed a statistically significant decrease compared to the corresponding raw samples. These results indicate that boiling modifies mercury and selenium concentrations. The high mercury levels detected represent a possible risk for consumers, and the publication and diffusion of specific advisories concerning seafood consumption is recommended.

Selenium and mercury molar ratios in commercial fish from New Jersey and Illinois: variation within species and relevance to risk communication

There is an emerging consensus that people consuming large amounts of fish with selenium:mercury ratios below 1 are at higher risk from mercury toxicity. As the relative amount of selenium increases compared to mercury, risk may be lowered, but it is unclear how much excess selenium is required. It would be useful if the selenium:mercury ratio was relatively consistent within a species, but this has not been the case in our studies of wild-caught fish. Since most people in developed countries and urban areas obtain their fish and other seafood commercially, we examined selenium:mercury molar ratios in commercial fish purchased in stores and fish markets in central New Jersey and Chicago. There was substantial interspecific and intraspecific variation in molar ratios. Across species the selenium:mercury molar ratio decreased with increasing mean mercury levels, but selenium variation also contributed to the ratio. Few samples had selenium:mercury molar ratios below 1, but there was a wide range in ratios, complicating the interpretation for use in risk management and communication. Before ratios can be used in risk management, more information is needed on mercury:selenium interactions and mutual bioavailability, and on the relationship between molar ratios and health outcomes. Further, people who are selenium deficient may be more at risk from mercury toxicity than others.