Balancing fish consumption benefits with mercury exposure

Climate-Driven Deoxygenation of Lakes Alters the Nutrient-Toxin Profile of a Food Fish

Climate change is rapidly altering fisheries supporting aquatic ecosystems. The implications for food security depend not only on harvest biomass but also concentrations of nutrients and toxins in fish. Using brook trout from Adirondack lakes (New York, USA), we tested whether ongoing lake deoxygenation trends will affect fish muscle omega-3 fatty acids, selenium, and mercury concentrations. Across space (16 lakes: 1 year) and time (6 years: 1 lake), anoxia decreased selenium and was associated with elevated fish mercury, with no effect on omega-3 content. Because selenium may mitigate some end points of mercury toxicity, highly variable Se:Hg molar ratios (0.70-35.79) in neighboring lakes may have health risk implications. For fish consumers, ongoing lake deoxygenation under climate change could potentially reduce selenium intake while enhancing mercury exposure. Simultaneous alteration of beneficial compounds and toxins by environmental change complicates the development of fish consumption advisories to safeguard public health in a warming world.

Exposure, spatial distribution, and health risks of perfluoroalkyl acids in commercial fish species in the Beibu Gulf

The global distribution, persistence, bioaccumulation, and toxicity of per- and polyfluoroalkyl substances (PFAS) have received significant attention. We determined the contents of major perfluoroalkyl acids (PFAAs) in various commercial fish species from different regions of the Beibu Gulf. We detected 14 out of 17 PFAAs across all species, with PFOS (Perfluorooctanesulphonate) showing the highest detection rate, followed by PFHxS (Perfluorohexanesulfonic acid), PFPeA (Perfluorovaleric acid), and PFTrDA (Perfluorotetradecanoic acid). The concentrations of ∑PFAAs ranged from 0.22 to 7.43 ng/g (ww). Additionally, PFCAs dominated the PFAA profile (70 %) in the southern Beibu Gulf in comparison with the northern (53 %) and central Beibu Gulf (48 %). PFOS was the most abundant compound, accounting for 41 % of total PFAAs, followed by PFUdA (Perfluoroundecanoic Acid) (14 %) and PFOA (Perfluorooctanoic Acid) (12 %). The estimated daily intakes and hazard ratios of PFOS and PFOS indicate that there is no significant health risk from people consuming these fish.

Health Risk Assessment Attributed to Consumption of Fish Contaminated with Mercury in the Rio Branco Basin, Roraima, Amazon, Brazil

The aim of this study was to assess the health risk attributable to the consumption of mercury-contaminated fish for the urban and non-urban populations living in the Roraima state, Amazon, Brazil. Seventy-five fish specimens distributed across twenty different species, comprising four trophic levels (i.e., herbivore, omnivore, detritivore, and carnivore), were collected at four locations in the Branco River Basin. The fish samples were sent to the Toxicology Laboratory at Evandro Chagas Institute to determine the total-Hg levels by using the cold vapor atomic system (CVAAS). The total-Hg levels ranged from 0 to 3.159 µg/g. The average concentration in non-carnivorous species (n = 32) was 0.116 µg/g, and among carnivorous fish (n = 43), it was 0.869 µg/g. The weighted average of contamination levels for all samples was 0.545 µg/g. The health risk assessment was conducted according to the methodology proposed by the World Health Organization and different scenarios of human exposure were considered, based on three levels of fish consumption (low: 50 g/day; moderate: 100 g/day and high: 200 g/day). Women of childbearing age ingest 5 to 21 times more mercury than the dose considered safe by the U.S. EPA and intake a dose from 2 to 9 times higher than the safe dose proposed by FAO/WHO. Children under 5 years of age ingest from 18 to 75 times the dose proposed by the U.S. EPA and from 8 to 32 more mercury than the limit proposed by FAO/WHO. In summary, regardless of the level of fish consumption, type of residency (urban or non-urban), and the subset of the population analyzed, anyone who consumes fish from the locations sampled is at high risk attributable to mercury ingestion, with the only exception of adult men, who consume an average of 50 g of fish per day.

Selenium and mercury balance in sea bream obtained from different living environments in Turkey: a risk assessment for the consumer health

The selenium health benefit value (Se-HBV) is the criterion developed for revealing nutritional values or the risks related to mercury (Hg) toxicity which can emerge in relation to consumption of fish. In this study, the conditions of Se and Hg elements in the muscular tissues of sea bream (Sparus aurata) living in different environments in Mugla province were examined. In addition, a benefit/risk assessment was performed in terms of consumer health with the calculation of Se-HBV. In this context, muscular tissues of sea bream obtained from wild species (WS), offshore marine cages species (OS), and soil ponds species (SS) were dissolved with microwave wet digestion and the concentrations of Se and Hg (mg/kg wet weight) were determined by using inductively coupled plasma mass spectroscopy (ICP-MS). According to the obtained results, the highest mean Se level was determined in SS (0.43 ± 0.02 mg/kg) followed by WS (0.35 ± 0.03 mg/kg) and OS (0.34 ± 0.02 mg/kg). The highest mean Hg concentration was detected in WS (0.09 ± 0.02 mg/kg) followed by OS and SS as 0.05 ± 0.01 mg/kg respectively. As a result of risk assessment conducted with Se-HBV, positive values were determined for each one of three sea bream groups.

Using a geographic information system to assess local scale methylmercury exposure from fish in nine communities of the Eeyou Istchee territory (James Bay, Quebec, Canada)

Exposure to methylmercury is a concern for those who rely on fish as a traditional food in the Eeyou Istchee territory of James Bay, Quebec, Canada, because industrial land uses overlap with community water bodies where fish are harvested. Consequently, this study assessed if traditional practices, particularly fishing, increased the risk of exposure to methylmercury from the consumption of locally harvested fish. We designed a geographic information system (GIS) that included land use and fish methylmercury tissue concentrations to assess clustering of potential hot spots. We also used generalized linear models to assess the association of fish consumption to blood organic-mercury concentrations, and logistic regression models to assess the probability of fish exceeding the safety threshold for methylmercury tissue concentrations in areas of high intensity land use. The GIS demonstrated significant clustered hot spots around regions of hydroelectric and mining land use. Our results also revealed that adult consumption of pike, lake trout and/or walleye, and child consumption of pike or walleye were significantly associated with blood organic-mercury concentrations. Further, large fish harvested in a community with high intensity land use yielded a 77% probability that the fish exceeded the safety threshold. From a human exposure perspective, our study highlights the need for further research on children who consume fish from this region.

Human mercury exposure levels and fish consumption at the French Riviera

Humans are exposed to methylmercury (MeHg), a bioaccumulative neurotoxin, mainly through the consumption of marine fish. Several studies showed that high MeHg exposure can lead to neurological damage. This is particularly relevant for pregnant women, because MeHg exposure negatively impacts foetal development. Populations living near the sea are generally at increased exposure risk due to higher consumption of fish and seafood. Here, we present the first study of MeHg exposure levels of the population living at the French Riviera, using mercury (Hg) concentrations in hair as a proxy for MeHg exposure. We found that older people that consume more fish presented the highest hair Hg concentrations. Compared to other Mediterranean bordering countries and other European countries, the southern France population is among those with high MeHg exposure (median for women of childbearing age is 0.56 μg g^-1). A global implementation of the Minamata Convention is necessary to lower MeHg exposure of the population.

Subsistence fishing in the Eeyou Istchee (James Bay, Quebec, Canada): A regional investigation of fish consumption as a route of exposure to methylmercury

Fishing is part of the traditional activities of Indigenous people in Canada. However, it is also a route of exposure to methylmercury, a known neurotoxicant, and this is a concern for those who rely on fish as part of their diet. The probable weekly intake (PWI) of methylmercury from six species of fish was calculated for Indigenous community members (N = 1406), grouped by age and sex, and compared to Canadian and international provisional reference doses to assess exposure. Mixed-effects regression models were also used to estimate the input of methylmercury into the blood, and Hazard Quotients (HQ) were used to assess potential effects. Of the species of fish in our study, walleye and lake trout contributed the most to methylmercury intake. There was a positive association between the consumption of walleye and the total blood mercury concentrations of mercury in women and men (R²_A = 0.40 and 0.47, respectively), and to a lesser extent, children. Similar results were observed for the consumption of lake trout. The 95th-percentile HQ for girls (3.16) and boys (3.18) from the consumption of lake trout was relatively high, and to a lesser extent, so was the HQ for walleye and pike. The consumption of some species of fish increases the exposure to methylmercury, however, taking a balanced approach, there are health benefits associated with the consumption of fish that must be considered. To mitigate future exposure to methylmercury, we recommend follow-up blood monitoring and local-geospatial-based assessments.

Using carbon and nitrogen stable isotope modelling to assess dietary mercury exposure for pregnant women in Baja California Sur, Mexico

INTRODUCTION

Previous studies of mercury (Hg) in pregnant women in the area of La Paz, Baja California Sur (BCS), Mexico found a proportion of individuals had concentrations of total Hg ([THg]) above some thresholds of concern set by health agencies. The [THg] were associated with fish and seafood consumption as well as other factors; although it was unclear which marine diet items could potentially be contributing to the concentrations observed.

METHOD

We examined [THg] and monomethylmercury concentration ([MeHg⁺]) in the archived hair of 70 pregnant women from BCS as well as in diet items including fish, shellfish, and staple items (rice, beans, corn, and flour). We measured stable isotopes of carbon and nitrogen and employed a Bayesian stable isotope mixing model to investigate the proportion of fish and seafood in the isotopic profiles of archived hair samples.

RESULTS

Concentrations of Hg species were low in staple foods and ranged from below detection limit to 5.71 parts per billion (ppb) wet weight. In hair, geometric mean [THg] was 658 ppb and [MeHg⁺] was 395 ppb, which were lower than previous reports. Percent MeHg⁺ was positively correlated with higher δ¹⁵N values.

CONCLUSIONS

The largest carbon contributors to the diet of the study participants were corn and rice, and our analysis of fish contribution to diet varyingly agreed with the self-reported fish consumption. This report highlights the ability to discriminate potential sources of Hg from a diverse diet and the limitations of dietary recall studies.

Sustainable Seafood and Vegetable Production: Aquaponics as a Potential Opportunity in Urban Areas

Global population growth will increase pressures on current food systems in order to supply adequate protein and produce to the increasingly urban world population. The environmental impact of food production is a critical area of study as it influences water and air quality, ecosystem functions, and energy consumption. Aquaponics (in which seafood and vegetables are grown in a closed-loop system) has the potential to reduce the environmental impact of food production. A review of the current environmental and economic considerations is provided in order to identify current research gaps. Research gaps exist with respect to 1) diversity of aquatic and plant species studied; 2) inconsistent bounds, scope, and lifetime across studies; 3) diverse allocation of the environmental and economic impacts to the coproducts; 4) scale of systems considered; 5) transportation of produced food; and 6) presence of heavy metals, pests, and pathogens with human health implications. These aspects require increased attention to close the existing gaps prior to widescale deployment of these systems for increased sustainable food production toward satisficing human needs. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

The three 'B' of fish mercury in China: Bioaccumulation, biodynamics and biotransformation

Mercury (Hg) is a global toxic pollutant and has raised the world's attention for decades. In this study, we reviewed the fish mercury levels in China (both marine and freshwater, as well as wild and farmed) documented over the past decade and their controlling environmental and biological factors. China is the largest contributor of global Hg cycling and the largest nation for the consumption and export of fish and fish product, thus Hg level in fish becomes a critical issue for food safety and public health. In China, Hg in fish is generally accumulated at a low level, but significant geographical differences were evident and formed the "hot spots" from the north to the south. For marine fish, the east (median: 70 ng g^-1 ww, range: 5.0-330 ng g^-1 ww) and southeast (median: 72 ng g^-1 ww, range: 0.3-329 ng g^-1 ww) of China have higher total Hg concentrations than the other coastal areas. For freshwater fish, Tibetan Plateau exhibited the highest total Hg levels (median: 104 ng g^-1 ww, range: 5.0-868 ng g^-1 ww). Risk assessment of the exposure of low-Hg-level fish to China's population deserves more attention and detailed fish consumption advisories to specific populations are urgently needed. The biokinetic model is a useful tool to characterize the underlying processes involved in Hg accumulation by fish. The diet (Hg concentration, speciation, food quality and quantity) and growth appear to be the important factors affecting the Hg levels of fish in China. The Hg biotransformation can also make contributions to Hg speciation and overall accumulation in fish. The intestinal microbes play an important role in Hg biotransformation and the potential for minimizing Hg contamination in fish deserves further investigation.

Trophodynamics and mercury bioaccumulation in reef and open-ocean fishes from The Bahamas with a focus on two teleost predators

Identifying prey resource pools supporting fish biomass can elucidate trophic pathways of pollutant bioaccumulation. We used multiple chemical tracers (carbon [δ¹³C] and nitrogen [δ¹⁵N] stable isotopes and total mercury [THg]) to identify trophic pathways and measure contaminant loading in upper trophic level fishes residing at a reef and open-ocean interface near Eleuthera in the Exuma Sound, The Bahamas. We focused predominantly on the trophic pathways of mercury bioaccumulation in dolphinfish Coryphaena hippurus and wahoo Acanthocybium solandri, 2 commonly consumed pelagic sportfish in the region. Despite residing within close proximity to productive and extensive coral reefs, both dolphinfish and wahoo relied almost exclusively on open-ocean prey over both short and long temporal durations. A larger isotopic niche of dolphinfish suggested a broader diet and some potential prey differentiation between the 2 species. THg concentrations in dolphinfish (0.2 ± 0.1 ppm) and wahoo (0.3 ± 0.3 ppm) were mostly below recommended guidelines for humans (US Environmental Protection Agency (EPA) = 0.3 ppm, US Food and Drug Administration (FDA)= 1.0 ppm) and were within ranges previously reported for these species. However, high THg concentrations were observed in muscle and liver tissue of commonly consumed reef-associated fishes, identifying a previously unrecognized route of potentially toxic Hg exposure for human consumers on Eleuthera and neighboring islands.

Fish for Dinner? Balancing Risks, Benefits, and Values in Formulating Food Consumption Advice

Many and complex factors underlie seemingly simple decisions about what to eat. This is particularly so for foods such as fish, which present consumers with both risks and benefits. Advice about what type of and how much fish to consume is abundant, but that advice is often confusing or contradictory, reflecting the differing mandates and orientations of those advising. We survey a range of issues that can and should be incorporated into dietary advice, and offer tools for health agencies tasked with providing it. We argue that risks and benefits should not be limited to direct physical health. Rather, socioeconomic and community factors, unintended or indirect effects, and nonhuman-health outcomes such as animal welfare and planetary health should also be considered and weighed. We provide examples of existing fish consumption guidance to highlight the conflicting messages that emerge when different sources of advice with singular aims of avoiding risk, gaining nutritional benefit, or sustaining fish populations are juxtaposed. We then offer tools borrowed from health and other fields to guide health agencies toward developing more comprehensive advice and targeting that advice for specific populations.

In Vivo Mercury Demethylation in a Marine Fish (Acanthopagrus schlegeli)

Mercury (Hg) in fish has attracted public attention for decades, and methylmercury (MeHg) is the predominant form in fish. However, the in vivo MeHg demethylation and its influence on Hg level in fish have not been well-addressed. The present study investigated the in vivo demethylation process in a marine fish (black seabream, Acanthopagrus schlegeli) under dietary MeHg exposure and depuration and quantified the biotransformation and interorgan transportation of MeHg by developing a physiologically based pharmacokinetic (PBPK) model. After exposure, we observed a 2-fold increase of the whole-body inorganic Hg (IHg), indicating the existence of an in vivo demethylation process. The results strongly suggested that the intestine played a predominant role in MeHg demethylation with a significant rate (6.6 ± 1.7 day^-1) during exposure, whereas the hepatic demethylation appeared to be an extremely slow (0.011 ± 0.001 day^-1) process and could hardly affect the whole-fish Hg level. Moreover, demethylation in the intestine served as an important pathway for MeHg detoxification. Our study also pointed out that in vivo MeHg demethylation could influence Hg level and speciation in fish although food is the major pathway for Hg accumulation. Enhancing in vivo MeHg biotransformation (especially in the intestine) could be a potential key solution in minimizing Hg contamination in fish. The related factors involved in intestinal demethylation deserve more attention in the future.

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.

Fish consumption recommendations to conform to current advice in regard to mercury intake

This article reviews fish consumption data, mercury tolerable intake values, and mercury (Hg) content in fish, based on several reports from the Food and Agriculture Organization and European Union. The study assumptions are valid based on the current established USEPA reference dose (RfD). Combining the number of meals (per week), amount of fish ingested (by meal), and levels of MeHg in fish, this study calculates and presents isocurves indicating the maximum number of fishmeal per week without exceeding the USEPA RfD for methylmercury (MeHg). RfD are assumed to be the "exposure dose that is likely to be without deleterious effect even if continued exposure occurs over a lifetime." The study points out that even considering a single 50-g fish meal per week, the USEPA RfD would be exceeded, triggered by values above 0.84 μg g(-1) of MeHg in fish, and this despite being allowed levels up to 1.0 μg g(-1) of MeHg in fish consumption!-Have we a health risk? Fish consumption is expected to be relatively stable, while anthropogenic mercury emissions are expected to stabilize or even to increase beyond current values. How many meals of fish per week can we have, combining the number of fish meals per week, amount of fish ingested by meal, and levels of MeHg in fish?

Ultrasensitive and highly selective detection of bioaccumulation of methyl-mercury in fish samples via Ag⁰/Hg⁰ amalgamation

Methylmercury (CH3Hg(+)), the common organic source of mercury, is well-known as one of the most toxic compounds that is more toxic than inorganic or elemental mercury. In seabeds, the deposited Hg(2+) ions are converted into CH3Hg(+) by bacteria, where they are subsequently consumed and bioaccumulated in the tissue of fish, and finally, to enter the human diet, causing severe health problems. Therefore, sensitive and selective detection of bioaccumulation of CH3Hg(+) in fish samples is desirable. However, selective assay of CH3Hg(+) in the mercury-containing samples has been seriously hampered by the difficulty to distinguish CH3Hg(+) from ionic mercury. We report here that metal amalgamation, a natural phenomenon occurring between mercury atoms and certain metal atoms, combining with DNA-protected silver nanoparticles, can be used to detect CH3Hg(+) with high sensitivity and superior selectivity over Hg(2+) and other heavy metals. In our proposed approach, discrimination between CH3Hg(+) and Hg(2+) ions was realized by forming Ag/Hg amalgam with a CH3Hg(+)-specific scaffold. We have found that Ag/Hg amalgam can be formed on a CH3Hg(+)-specific DNA template between silver atoms and mercury atoms but cannot between silver atoms and CH3Hg(+). With a dye-labeled DNA strand, the sensor can detect CH3Hg(+) down to the picomolar level, which is >125-fold sensitive over Hg(2+). Moreover, the presence of 50-fold Hg(2+) and 10(6)-fold other metal ions do not interfere with the CH3Hg(+) detection. The results shown herein have important implications for the fast, easy, and selective detection and monitoring of CH3Hg(+) in environmental and biological samples.

Mercury toxicity and the protective role of selenium in eel, Anguilla anguilla

The aim of the study was to determine the impact trace metals, mainly toxic ones, on the condition of eel (Anguilla anguilla) inhabiting four regions of Poland. Metal concentrations in eel muscle tissues were studied as functions of size, region, and season 2011-2012. The levels of metals were also used for risk assessment on consumer health. Copper and zinc occurred at concentrations that could only have positive impacts on eel condition. Low levels of cadmium and lead did not impair the condition of the fish. However, mercury occurred at high levels and increased with fish length and season. The mercury levels in eels were compared with the threshold of toxicity (500-1,200 μg kg(-1)), which can cause changes in biochemical processes and impair fish reproduction. The concentration of mercury was 1,010 μg kg(-1) in one specimen of the 120 samples examined, and in 16 specimens, it exceeded 500 μg kg(-1). The toxic effects of the mercury could have been attenuated by the selenium in the muscles of the eel, especially in the muscles of smaller specimens in which the Se/Hg molar ratio was higher than 1 with a positive correlation between these two elements. In larger specimens measuring in excess of 70 cm, this coefficient was below 1, and the mercury to selenium correlation was negative, which meant that the protective effects of selenium were weaker. The mercury in the muscles of large specimens at levels exceeding 500 μg kg(-1) could have weakened eel condition and also posed a threat to consumer health. The cadmium and lead in the muscles of the eel did not affect the condition of the fish. Mercury weakened the condition of large eel, A. anguilla. Selenium protected small- and medium-sized eel against the toxic effects of mercury.

Cooking fish is not effective in reducing exposure to perfluoroalkyl and polyfluoroalkyl substances

Consumption of fish is considered a part of a healthy diet; however, health risks from fish consumption exist due to potential exposure to various contaminants accumulated in fish. Cooking fish can reduce exposure to many organic chemicals in fish. Similar results have been presented for low levels of perfluoroalkyl and polyfluoroalkyl substances (PFASs), a class of contaminants of emerging concern, in grocery store fish. We examined the effectiveness of three cooking methods (i.e., baking, broiling, and frying) on reducing PFAS levels in four sport fish species. Samples of Chinook salmon, common carp, lake trout and walleye were collected from four rivers in Ontario, Canada and skin-off fillets were analyzed for regular groups of PFASs such as perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs), as well as perfluoroalkyl phosphonic acids (PFPAs), perfluoroalkyl phosphinic acids (PFPIAs) and polyfluoroalkyl phosphoric acid diesters (diPAPs), which are PFASs of emerging concern. Perfluorooctane sulfonate (PFOS) was the dominant PFAS detected and the concentrations were more than an order of magnitude higher than those reported for fish from grocery stores in Canada, Spain, and China. Although concentrations of PFOS in fish fillets generally increase after cooking, amounts of PFOS largely remain unchanged. Relatively minor differences in changes in the fish PFAS amounts after cooking depended on fish species and cooking method used. We conclude that cooking sport fish is generally not an effective approach to reduce dietary exposure to PFASs, especially PFOS.

Heavy metals in fish from the Aleutians: interspecific and locational differences

The objectives of this study were to examine levels of arsenic, cadmium, lead, mercury and selenium in edible tissue of seven species of marine fish collected from several Aleutian islands (in 2004) to determine: (1) interspecific differences, (2) locational differences (among Aleutian Islands), (3) size-related differences in any metal levels within a species, and (4) potential risk to the fish or to predators on the fish, including humans. We also compared metals levels to those of three other fish species previously examined in detail, as well as examining metals in the edible tissue of octopus (Octopus dofleini). Octopus did not have the highest levels of any metal. There were significant interspecific differences in all metal levels among the fish species, although the differences were less than an order of magnitude, except for arsenic (mean of 19,500 ppb in Flathead sole, Hippoglossoides elassodon). Significant intraisland variation occurred among the four sites on Amchitka, but there was not a consistent pattern. There were significant interisland differences for some metals and species. Mercury levels increased significantly with size for several species; lead increased significantly for only one fish species; and cadmium and selenium decreased significantly with size for halibut (Hippoglossus stenolepis). The Alaskan Department of Health and Social Services supports unrestricted consumption of most Alaskan fish species for all people, including pregnant women. Most mean metal concentrations were well below the levels known to adversely affect the fish themselves, or predators that consume them (including humans), except for mercury in three fish species (mean levels just below 0.3 ppm), and arsenic in two fish species. However, even at low mercury levels, people who consume fish almost daily will exceed guideline values from the Centers for Disease Control and the Environmental Protection Agency.

Children's health risk and benefits of fish consumption: risk indices based on a diet diary follow-up of two weeks

Several epidemiological studies indicate that fish intake is associated with neurocognitive development and visual outcomes in children attributed to long-chain polyunsaturated fatty acids (PUFA). However, methylmercury (MeHg) represents the most toxic and abundant form of environmental mercury (Hg) exposure to humans and exposure occurs primarily through fish consumption. The objective of the study was to describe fish consumption during childhood in Portugal, estimating the intake of Hg from fish and calculating the indices of risk. The group consisted of 233 infants and students aged 7-11 yr and attending 5 primary schools in Lisbon, Amadora, and Sesimbra. Information regarding food consumption habits was collected through a food diary during 2 weeks, completed under the supervision of teachers and parents, where participants registered what was ingested for lunch and dinner during that period. The exposure assessment and indices of risk were calculated for each participant. Individuals were classified according to weekly intake and indices of risk determined per group. In addition, the methods used to collect information on fish intake habits, a food frequency questionnaire and diet diary, are described in relation to quality of information provided. The mean value of fish meals per week was approximately 5. The calculated indices of risk reached values above 1 in more than 50% of the studied population, demonstrating the presence of risk in subsets of the population. While Portuguese children represent an important group of fish consumers, this does not manifest as appreciable benefit with respect to omega-3 ingestion, as children ingest half or less of the recommended value (200 mg/d of omega-3), which is equivalent to being exposed to risk for Hg intoxication. The choice of fish species shows lack of knowledge of fish characteristics. Therefore, risk communication and population education need to be established to prevent consumption of predatory fish species that contribute to the increase in risk toxicity and to encourage ingestion of prey fish, which represent significant levels of high-value nutrients such as PUFA.

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.

Direct absorption of methyl mercury by lymph

Methyl mercury is contained in fish and seafood products and is taken up into the body in food. While the central nervous system is known as a target organ, methyl mercury also induces autoimmunity and acts as a potent immunosuppressor. The aim of the present study is to know whether methyl mercury is directly absorbed by lymph. Conscious rats were infused with methyl mercury (4 mg/kg) via duodenal tubing as a single pulse infusion, followed by the continuous infusion of saline, and lymphatic fluids were continuously collected from the thoracic lymph duct every 30 min until 360 min after infusion. Mercury was detected immediately after infusion, and total mercury contents in lymph gradually increased until 90-120 min, remained steady, and then gradually decreased until 360 min; however, the amount of mercury collected during 330-360 min was about twofold higher than during 0-30 min. The amount of cumulative mercury in lymph at 360 min was 1.4 μg. In contrast, blood mercury concentration was 2.4 μg/ml 5 min after infusion, with the value at 360 min being 12.6 times higher than at 5 min. Plasma mercury concentration was 56 ng/ml at 5 min, with hundreds of nanograms per milliliter of mercury detected until 360 min. From the present study, it is concluded that some methyl mercury is directly absorbed by lymph and remains steady 6 h after infusion.

Quantification of total mercury in liver and heart tissue of Harbor Seals (Phoca vitulina) from Alaska USA

This study quantified the Hg levels in the liver (n=98) and heart (n=43) tissues of Harbor Seals (Phoca vitulina) (n=102) harvested from Prince William Sound and Kodiak Island Alaska. Mercury tissue dry weight (dw) concentrations in the liver ranged from 1.7 to 393 ppm dw, and in the heart from 0.19 to 4.99 ppm dw. Results of this study indicate liver and heart tissues' Hg ppm dw concentrations significantly increase with age. Male Harbor Seals bioaccumulated Hg in both their liver and heart tissues at a significantly faster rate than females. The liver Hg bioaccumulation rates between the harvest locations Kodiak Island and Prince William Sound were not found to be significantly different. On adsorption Hg is transported throughout the Harbor Seal's body with the partition coefficient higher for the liver than the heart. No significant differences in the bio-distribution (liver:heart Hg ppm dw ratios (n=38)) values were found with respect to either age, sex or geographic harvest location. In this study the age at which Hg liver and heart bioaccumulation levels become significantly distinct in male and female Harbor Seals were identified through a Tukey's analysis. Of notably concern to human health was a male Harbor Seal's liver tissue harvested from Kodiak Island region. Mercury accumulation in this sample tissue was determined through a Q-test to be an outlier, having far higher Hg concentrarion (liver 392Hgppmdw) than the general population sampled.

Assessing risk of mercury exposure and nutritional benefits of consumption of caribou (Rangifer tarandus) in the Vuntut Gwitchin First Nation community of Old Crow, Yukon, Canada

The contamination of traditional foods with chemical pollutants is a challenge to the food security of Aboriginal Peoples. Mercury levels are generally low in terrestrial animals; however renal mercury levels have been shown to change over time in the Porcupine Caribou Herd, the principal food source for the Vuntut Gwitchin First Nation of Old Crow in Yukon, Canada. Seventy-five Porcupine Caribou muscle, sixty-three kidney and three liver samples were analyzed for total mercury. Average concentrations were 0.003, 0.360 and 0.120mg/kg wet weight total mercury for muscle, kidney and liver, respectively. Consumption data of caribou muscle, kidney and liver were collected from twenty-six adults in Vuntut Gwitchin households. Women of child-bearing age (n=5) consumed a median of 71.5g/person/day of caribou muscle and 0.0g/person/day kidney but consumed no liver; median consumptions for all other adults (women aged 40+ and all men, n=21) were 75.8, 3.2 and 2.5g/person/day for meat, kidney and liver, respectively. Median dietary exposures to total mercury from caribou tissues were estimated to be 0.138μg/kg body weight for women of child-bearing age and 0.223μg/kg body weight for other adults. Caribou tissues were found to contribute high levels of important nutrients to the diet and pose minimal health risk from mercury exposure.

Mercury and selenium levels in 19 species of saltwater fish from New Jersey as a function of species, size, and season

There are few data on risks to biota and humans from mercury levels in saltwater fish. This paper examines mercury and selenium levels in muscle of 19 species of fish caught by recreational fisherfolk off the New Jersey shore, as a function of species of fish, size, and season, and risk of mercury to consumers. Average mercury levels ranged from 0.01 ppm (wet weight) (Menhaden Brevoortia tyrannus) to 1.83 ppm (Mako Shark Isurus oxyrinchus). There were four categories of mercury levels: very high (only Mako), high (averaging 0.3-0.5 ppm, 3 species), medium (0.14-0.20 ppm, 10 species), and low (below 0.13 ppm, 5 species). Average selenium levels for the fish species ranged from 0.18 ppm to 0.58 ppm, and had lower variability than mercury (coefficient of variation=38.3 vs 69.1%), consistent with homeostatic regulation of this essential element. The correlation between mercury and selenium was significantly positive for five and negative for two species. Mercury levels showed significant positive correlations with fish size for ten species. Size was the best predictor of mercury levels. Selenium showed no consistent relationship to fish length. Over half of the fish species had some individual fish with mercury levels over 0.3 ppm, and a third had fish with levels over 0.5 ppm, levels that pose a human health risk for high end consumers. Conversely several fish species had no individuals above 0.5 ppm, and few above 0.3 ppm, suggesting that people who eat fish frequently, can reduce their risk from mercury by selecting which species (and which size) to consume. Overall, with the exception of shark, Bluefin Tuna (Thunnus thynnus), Bluefish (Pomatomus saltatrix) and Striped Bass (Morone saxatilis), the species sampled are generally medium to low in mercury concentration. Selenium:mercury molar ratios were generally above 1:1, except for the Mako shark.

State calculations of cultural survival in environmental risk assessment: consequences for Alaska Natives

In 2007, the Alaska Division of Public Health issued their first-ever fish consumption advisory to reduce exposure to methylmercury. Interestingly, they utilized a toxicity level in their calculations of risk that is four times higher than the U.S. Environmental Protection Agency's (EPA) level, arguing that the EPA's calculation is "inappropriately restrictive" for Alaskans. This article explores the institutional reasoning and scientific calculations behind the state's fish consumption advice, with special attention paid to the consequences for Alaska Natives. I argue that a discourse of "Alaskan exceptionalism" is utilized by the health department to justify their assessment of risk. Although this exceptionalist discourse is intended to accommodate the unique lifestyles of Alaskan citizens, it may actually serve to undermine the very lifeways and traditions that it presumes to preserve. This article contributes insights into the ways that states can influence the social and material reproduction of communities through the deployment of "cultural difference" during the risk-assessment process.

Mercury hair concentrations and dietary exposure among Inuit preschool children in Nunavut, Canada

There is concern that the traditional diet is a source of mercury exposure among Inuit in the Canadian Arctic. Mercury exposure in utero and in early childhood presents a risk to neurodevelopment. The objectives of the present study were to assess the dietary mercury exposure from traditional food among Inuit children 3 to 5 years of age in Nunavut, and evaluate the association between estimated dietary mercury intake and body burden. A cross-sectional Nunavut Inuit Child Health Survey was conducted in 2007 and 2008 which included assessment of dietary habits and children's hair mercury (Hg) levels. Further, an Inuit Adult Health Survey was conducted in the same years which included assessment of dietary habits and whole blood mercury concentrations. Traditional food samples were collected during this study and previously from the Canadian Arctic. Daily mercury intake from traditional food was calculated. Body mercury burden was determined using the hair mercury concentration. The geometric mean of children's hair Hg was 0.66 μg/g and varied by region. Nearly 25% of children had hair Hg concentrations equal to or higher than 2 μg/g (WHO reference level). There was a significant correlation between mercury levels in children's hair and that of the adults in the same household. For children, beluga muktuk, narwhal muktuk, ringed seal liver, fish, caribou meat and ringed seal meat were the major dietary sources of mercury. These food items together accounted for over 95% of total daily dietary mercury intake. A positive linear regression relationship between children's hair mercury levels and estimated dietary mercury intake was observed. Estimated intake in Baffin decreased by 30% compared to 20 years ago. Some traditional food items were significant sources of mercury to Inuit children in Nunavut. Although a reduction in the consumption of these diet items may be a way to reduce mercury intake, the nutritional, social and cultural benefits of traditional food and countervailing risks must be taken into account in risk mitigation.

A risk-benefit analysis of wild fish consumption for various species in Alaska reveals shortcomings in data and monitoring needs

Northern peoples face a difficult decision of whether or not to consume wild fish, which may contain dangerous levels of contaminants such as methylmercury (MeHg), but which also offer a number of positive health benefits, and play an important role in rural household economies. Here, new methods for developing consumption advice are applied to an existing data-set for methylmercury (MeHg) levels in Alaskan fish. We apply a quantitative risk-benefit analysis for eight freshwater, saltwater and anadromous fish species, using dose-response relationships to weigh the risks of MeHg bioaccumulation against the benefits of omega-3 fatty acids (EPA and DHA) toward cardiovascular and neurodevelopmental health endpoints. Findings suggests that consumption of many of the fish species reviewed here, including northern pike, Pacific Halibut, and arctic grayling, may lead to increased risk of coronary heart disease and declines in infant visual recognition memory. However, we also identify significant variation among regions, among studies within the same region, and also within studies, which make it difficult to craft consistent consumption advice. Whereas salmon consistently shows a net-benefit, for instance, data for arctic grayling, pike, sablefish, and some halibut are all too imprecise to provide consistent recommendations. We argue for more detailed local-scale monitoring, and identification of possible thresholds for increased risk in the future. We caution that MeHg and omega-3 FA are just two variables in a complicated calculus for weighing the risks and benefits of locally-available and culturally-significant foods, and argue for future work that takes both a place-based and plate-based approach to diet and contamination.

Mercury advisories and household health trade-offs

The conventional economic wisdom is that improving consumer information will enhance welfare. Yet, some scientists speculate that the Food and Drug Administration's prominent mercury in fish advisory may have harmed public health. Lower mercury intakes reduce neurological toxicity risks. However, since seafood is the predominant dietary source of healthful omega-3 fatty acids, reduced fish consumption may have significant offsetting health impacts. We explore this risk trade-off using a rich panel of household-level seafood consumption data. To control for confounding factors, we use a non-parametric changes-in-changes approach. We find strong evidence that while the advisory reduced mercury loadings, it did so at the expense of substantial reductions in healthful omega-3s. We find this response pattern even for consumers with low fish consumption. Using advisory response patterns as inputs into a prominent risk assessment model, the central estimate is that net benefits from the advisory were negative.

Essential (Cu) and nonessential (Cd and Pb) metals in ichthyofauna from the coasts of Sinaloa state (SE Gulf of California)

With the aim of giving an overview on concentration and distribution of Cd, Cu, and Pb in fish from the coasts of Sinaloa state (SE Gulf of California), specimens with different feeding habits were collected in five locations. Sampling occurred between June 2003 and March 2004. Metal analyses on fish tissues were made by graphite furnace (Cd, Pb) and flame (Cu) atomic absorption spectrophotometry. Metal concentrations in tissues of carnivorous fish were grouped together and compared with corresponding concentrations in non-carnivorous fish; Cu and Pb levels were significantly (p < 0.05) higher in liver of non-carnivorous species. Though no samples exceeded the maximum level set in international legislation for fish, from the perspective of the public health and considering the legal limits of fishery products for human consumption, Cu concentrations were exceeded (in tissues different from muscle) in four carnivorous and five non-carnivorous species according to the Australian legislation. In the case of Cd, two carnivorous species (Pomadasys leuciscus and Caulolatilus princeps) and one non-carnivorous species (Mugil cephalus), showed concentrations over the maximum level of 2 microg g(-1) dry weight considered in the Mexican legislation. Considering average amounts of fish consumption in Mexico, daily mineral intake (DMI) values for Cu and percentage weekly intake (PWI) of Cd and Pb were estimated; none of the analyzed metals in edible portion of analyzed fish could be detrimental to humans.

An evaluation of mercury concentrations in three brands of canned tuna

There is widespread concern over the presence of Hg in fish consumed by humans. While studies have been focused on determining the Hg concentration in sport fish and some commercial fish, little attention has been directed to canned tuna; it is widely held that concentrations are low. In the present study, the amount of Hg present in canned tuna purchased in Las Vegas, Nevada, USA, was examined, and the brand, temporal variation, type, and packaging medium impacts on Hg concentrations in tuna were explored. A significant (p < 0.001) brand difference was noted: Brand 3 contained higher Hg concentrations ($\bar x$ standard deviation (SD) (0.777 +/- 0.320 ppm) than Brands 1 (0.541 +/- 0.114 ppm) and 2 (0.550 +/- 0.199 ppm). Chunk white tuna (0.619 +/- 0.212 ppm) and solid white tuna (0.576 +/- 0.178 ppm) were both significantly (p < 0.001) higher in mean Hg than chunk light tuna (0.137 +/- 0.063 ppm). No significant temporal variation was noted, and packaging had no significant effect on Hg concentration. In total, 55% of all tuna examined was above the U.S. Environmental Protection Agency's (U.S. EPA) safety level for human consumption (0.5 ppm), and 5% of the tuna exceeded the action level established by the U.S. Food and Drug Administration (U.S. FDA) (1.0 ppm). These results indicate that stricter regulation of the canned tuna industry is necessary to ensure the safety of sensitive populations such as pregnant women, infants, and children. According to the U.S. EPA reference dose of 0.1 microg/kg body weight per day and a mean Hg value of 0.619 ppm, a 25-kg child may consume a meal (75 g) of canned chunk white tuna only once every 18.6 d. Continued monitoring of the industry and efforts to reduce Hg concentrations in canned tuna are recommended. Environ.

Risk to consumers from mercury in bluefish (Pomatomus saltatrix) from New Jersey: Size, season and geographical effects

Relatively little attention has been devoted to the risks from mercury in saltwater fish, that were caught by recreational fisherfolk. Although the US Food and Drug Administration has issued advisories based on mercury for four saltwater species or groups of fish, there are few data on how mercury levels vary by size, season, or location. This paper examines total mercury levels in muscle of bluefish (Pomatomus saltatrix) collected from coastal New Jersey, mainly by recreational fishermen. Of primary interest was whether there were differences in mercury levels as a function of location, weight and length of the fish, and season, and in what risk mercury posed to the food chain, including people. Selenium was also measured because of its reported protective effects against mercury. Mercury levels averaged 0.35+/-0.02 (mean and standard error)ppm, and selenium levels averaged 0.37+/-0.01ppm (N=206). In this study, 41% of the fish had mercury levels above 0.3ppm, 20% had levels above 0.5ppm, and 4% had levels above 1ppm. Size was highly correlated with mercury levels, but not with selenium. While selenium levels did not vary at all with season, mercury levels decreased significantly. This relationship was not due to differences in the size of fish, since the fish collected in the summer were the smallest, but had intermediate mercury levels. Mercury levels declined from early June until November, particularly for the smaller-sized fish. While there were significant locational differences in mercury levels (but not selenium), these differences could be a result of size. The levels of mercury in bluefish are not sufficiently high to cause problems for the bluefish themselves, based on known adverse health effects levels, but are high enough to cause potential adverse health effects in sensitive birds and mammals that eat them, and to provide a potential health risk to humans who consume them. Fish larger than 50cm fork length averaged levels above 0.3ppm, suggesting that eating them should be avoided by pregnant women, children, and others who are at risk.

Methylmercury and nutrition: adult effects of fetal exposure in experimental models

Human exposure to the life-span developmental neurotoxicant, methylmercury (MeHg), is primarily via the consumption of fish or marine mammals. Fish are also excellent sources of important nutrients, including selenium and n-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA). Laboratory models of developmental MeHg exposure can be employed to assess the roles of nutrients and MeHg and to identify potential mechanisms of action if the appropriate exposure measures are used. When maternal exposure is protracted, relationships between daily intake and brain mercury are consistent and orderly across species, even when large differences in blood:brain ratios exist. It is well established that low-level developmental MeHg produces sensory deficits. Recent studies also show that perseveration in reversal-learning tasks occurs after gestational exposures that produce low micromolar concentrations in the brain. A no-effect level has not been identified for this effect. These exposures do not affect the acquisition or performance of discrimination learning, set shifting (extradimensional shift), or memory. Reversal-learning deficits may be related to enhanced impact of reinforcers as measured using progressive ratio reinforcement schedules, an effect that could result in perseveration. Also reported is enhanced sensitivity to dopamine reuptake inhibitors and diminished sensitivity to pentobarbital, a GABA(A) agonist. Diets rich in PUFAs or selenium do not protect against MeHg's effects on reversal learning but, by themselves, may diminish variability in performance, enhance attention or psychomotor function and may confer some protection against age-related deficits in these areas. It is hypothesized that altered reward processing, dopamine and GABAergic neurotransmitter systems, and cortical regions associated with choice and perseveration are especially sensitive to developmental MeHg at low exposure levels. Human testing for MeHg's neurotoxicity should emphasize these behavioral domains.

High-fish consumption and risk prevention: assessment of exposure to methylmercury in Portugal

The aim of this study was to evaluate the exposure to methylmercury (MeHg) of potential populations at risk living in Portugal. To ascertain youth exposure, a questionnaire was distributed to 300 students of a middle secondary school in Sesimbra and to 429 students studying in Canecas, selected as the control population. The average number of fish meals consumed by person was 4.1 and 3 per week in Sesimbra and Canecas, respectively. The subpopulations of high intake (PHI) corresponding to those ingesting 7 or more fish meals per week were also analyzed separately, with 17% of the students belonging to the PHI of Sesimbra versus 6.1% in Canecas. Socioeconomic aspects such as relative's professional involvement with fisheries correlated with the higher intakes in Sesimbra. Fish samples were collected in the dock of Sesimbra and total mercury (Hg) was determined by flow injection cold vapor atomic fluorescence spectroscopy (FI-CV-AFS). The mean value found for nonpredators was 0.035 microg/g. Dogfish specimens surpassed the legislated limit for predator species and increased the predators mean to 1 microg/g. The cross-sectional data were integrated with the fish analysis results to estimate the population exposure to MeHg. The indices of risk calculated for youth reached values of 4.5, demonstrating the existence of risk to a part of the population exceeding the provisional tolerable weekly intake (PTWI) level mandated by WHO (1.6 microg/kg bw). The results indicate that monitoring of Hg levels in fish is mandatory and counseling should be provided to populations at risk, encouraging them to prevent the risk.

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

The potential toxicity of mercury (Hg) content in fish has been widely evaluated by the scientific community, with Methylmercury (MeHg) being the only legislated species (1 mg kg-1, maximum concentration allowed in predatory fish). On the other hand, selenium (Se) is recognized to decrease its toxicity when both elements are simultaneously administrated. In the present paper, the total content of Se and Hg and their species in fish of high consumption, such as tuna, swordfish, and sardine, have been evaluated. The percentage of MeHg is higher than 90% of total Hg content. The results show that, for all of them, the Se/Hg ratio is significantly higher than one, being the maximum ratio for sardine. As only studying the bioaccessible fraction the extent of a toxic effect caused by an element can be predicted, the bioaccessibility of both analytes through an in vitro digestion method has been carried out. The results show that MeHg in all fishes is very low bioaccessible in both gastric and intestinal digestion. Because the MeHg bioaccessible fraction might be correlated to the Se content, the potential toxicity cannot be only related to the total Hg content but also to Se/Hg ratio.

Epidemiologic confirmation that fruit consumption influences mercury exposure in riparian communities in the Brazilian Amazon

Since deforestation has recently been associated with increased mercury load in the Amazon, the problem of mercury exposure is now much more widespread than initially thought. A previous exploratory study suggested that fruit consumption may reduce mercury exposure. The objectives of the study were to determine the effects of fruit consumption on the relation between fish consumption and bioindicators of mercury (Hg) exposure in Amazonian fish-eating communities. A cross-sectional dietary survey based on a 7-day recall of fish and fruit consumption frequency was conducted within 13 riparian communities from the Tapajós River, Brazilian Amazon. Hair samples were collected from 449 persons, and blood samples were collected from a subset of 225, for total and inorganic mercury determination by atomic absorption spectrometry. On average, participants consumed 6.6 fish meals/week and ate 11 fruits/week. The average blood Hg (BHg) was 57.1 +/- 36.3 microg/L (median: 55.1 microg/L), and the average hair-Hg (HHg) was 16.8 +/- 10.3 microg/g (median: 15.7 microg/g). There was a positive relation between fish consumption and BHg (r = 0.48; P<0.0001), as well as HHg (r =0.34; P<0.0001). Both fish and fruit consumption entered significantly in multivariate models explaining BHg (fish: beta = 5.6, P<0.0001; fruit: beta = -0.5, P = 0.0011; adjusted model R2 = 36.0%) and HHg levels (fish: beta = 1.2, P<0.0001; fruit: beta = -0.2, P = 0.0002; adjusted model R2 = 21.0%). ANCOVA models showed that for the same number of fish meals, persons consuming fruits more frequently had significantly lower blood and HHg concentrations. For low fruit consumers, each fish meal contributed 9.8 microg/L Hg increase in blood compared to only 3.3 microg/L Hg increase for the high fruit consumers. In conclusion, fruit consumption may provide a protective effect for Hg exposure in Amazonian riparians. Prevention strategies that seek to maintain fish consumption while reducing Hg exposure in fish-eating communities should be pursued.

Mercury levels and potential risk from subsistence foods from the Aleutians

Considerable attention has been devoted to contaminants (mainly PCBs and mercury) in subsistence foods (particularly fish) from various parts of the world. However, relatively little attention has been devoted to examining mercury levels in a full range of subsistence foods from a particular region. While managers and scientists compute risk based on site-specific data on contaminant levels and consumption rates, a first step in making risk decisions by subsistence peoples is knowledge about the relative levels of mercury in the foods they eat. This study examined levels of mercury in subsistence foods (edible components) from several islands in the western Aleutians of Alaska, including algae (4 species), invertebrates (9 species), fish (15 species) and birds (5 species). Samples were gathered by both subsistence hunters/fishers and by scientists using the same equipment. Another objective was to determine if there were differences in mercury levels in subsistence foods gathered from different Aleutian islands. We tested the null hypotheses that there were no interspecific and interisland differences in mercury levels. Because of variation in distribution and the nature of subsistence hunting and fishing, not all organisms were collected from each of the islands. There were significant and important differences in mercury levels among species, but the locational differences were rather small. There was an order of magnitude difference between algae/some invertebrates and fish/birds. Even within fish, there were significant differences. The highest mean mercury levels were in flathead sole (Hippoglossoides elassodon, 0.277 ppm), yellow irish lord (Hemilepidotus jardani, 0.281 ppm), great sculpin (Myoxocephalus polyacanthocephalus, 0.366 ppm), glaucous-winged gull (Larus glaucescens, 0.329 ppm) and its eggs (0.364 ppm), and pigeon guillemot (Cepphus columba, 0.494 ppm). Mercury levels increased with increasing weight of the organisms for limpets (Tectura scutum), and for 11 of the 15 fish species examined. Nine of the 15 fish species had some samples over the 0.3 ppm level, and 7 of 15 fish had some samples over 0.5 ppm. For birds, 95% of the pigeon guillemot muscle samples were above the 0.3 ppm, and 43% were above 0.5 ppm. While health professionals may argue about the risk and benefits of eating fish, and of eating alternative protein sources, the public should be provided with enough information for them to make informed decisions. This is particularly true for subsistence people who consume large quantities of self-caught foods, particularly for sensitive sub-populations, such as pregnant women. We argue that rather than giving people blanket statements about the health benefits or risks from eating fish, information on mean and maximum mercury levels should also be provided on a wide range of subsistence foods, allowing informed decisions, especially by those most at risk.

Risk to consumers from mercury in Pacific cod (Gadus macrocephalus) from the Aleutians: fish age and size effects

While there has been considerable attention devoted to the risks to high level consumers from mercury in freshwater fish, relatively little attention has been devoted to saltwater fish. Although the U.S. Food and Drug Administration has issued advisories based on mercury for four saltwater species or groups of fish, there are few data on mercury levels generally, or on the risk these levels pose to the fish themselves or to consumers of marine fish. We examined total mercury levels in liver and muscle of Pacific cod (Gadus macrocephalus) collected from the northern Pacific and Bering Sea waters around Nikolski, Amchitka, and Kiska Islands in the Aleutian Chain (Alaska). We were interested in whether there were differences in mercury levels as a function of location, weight, length, and age of the fish, and what risk mercury posed to the food chain, including people. Fish were aged by examining otoliths, and we measured selenium because of its reported protective effects against mercury. Regression models indicated that 27% of the variation in levels of mercury was due to tissue examined and age, while 67% of the variation in levels of selenium was due to tissue, length, and age. Mercury levels were significantly higher in the muscle than the liver, and the reverse was true for selenium. Mercury levels were negatively correlated with selenium levels, and positively correlated with length, weight, and age. There were no gender differences in mercury or selenium levels. The mean levels of mercury in muscle (0.17 ppm wet weight) are within the range known to cause adverse effects in sensitive birds and mammals. Only 4% of the Pacific cod samples had mercury levels above 0.5 ppm, the action level promulgated by many states and countries, and none were above the 1 ppm action level of the U.S. FDA.

Role of Docosahexaenoic Acid in Modulating Methylmercury-Induced Neurotoxicity

The effect of docosahexaenoic acid (DHA) in modulating methylmercury (MeHg)-induced neurotoxicity was investigated in C6-glial and B35-neuronal cell lines. Gas chromatography measurements indicated increased DHA content in both the cell lines after 24 h supplementation. Mitochondrial activity evaluated by 3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide (MTT) reduction indicated that 10 microM MeHg treatment for 50 min led to a significant (p < 0.001) and similar decrease in MTT activity in both the cell lines. However, DHA pretreatment led to more pronounced depletion (p < 0.05) in the MTT activity in C6 cells as compared to B35 cells. The depletion of glutathione (GSH) content measured with the fluorescent indicator monochlorobimane was more apparent (p < 0.001) in C6 cells treated with DHA and MeHg. The amount of reactive oxygen species (ROS) detected with the fluorescent indicator -- chloromethyl derivative of dichloro dihydro fluorescein diacetate (CMH(2)DCFDA) -- indicated a fourfold increase in C6 cells (p < 0.001) as compared to twofold increase in B35 cells (p < 0.001) upon DHA and MeHg exposure. However, the cell-associated MeHg measurement using (14)C-labeled MeHg indicated a decrease (p < 0.05) in MeHg accumulation upon DHA exposure in both the cell lines. These findings provide experimental evidence that although pretreatment with DHA reduces cell-associated MeHg, it causes an increased ROS (p < 0.001) and GSH depletion (p < 0.05) in C6 cells.

Spatial and visual discrimination reversals in adult and geriatric rats exposed during gestation to methylmercury and n-3 polyunsaturated fatty acids

Fish contain essential long chain polyunsaturated fatty acids (PUFAs), particularly docosahexaenoic acid (DHA), an omega-3 (or n-3) PUFA, but are also the main source of exposure to methylmercury (MeHg), a potent developmental neurotoxicant. Since n-3 PUFAs support neural development and function, benefits deriving from a diet rich in n-3s have been hypothesized to protect against deleterious effects of gestational MeHg exposure. To determine whether protection occurs at the behavioral level, female Long-Evans rats were exposed, in utero, to 0, 0.5, or 5ppm of Hg as MeHg via drinking water, approximating exposures of 0, 40, and 400 microgHg/kg/day and producing 0, 0.29, and 5.50ppm of total Hg in the brains of siblings at birth. They also received pre- and postnatal exposure to one of two diets, both based on the AIN-93 semipurified formulation. A "fish-oil" diet was high in, and a "coconut-oil" diet was devoid of, DHA. Diets were approximately equal in alpha-linolenic acid and n-6 PUFAs. As adults, the rats were first assessed with a spatial discrimination reversal (SDR) procedure and later with a visual (nonspatial) discrimination reversal (VDR) procedure. MeHg increased the number of errors to criterion for both SDR and VDR during the first reversal, but effects were smaller or non-existent on the original discrimination and on later reversals. No such MeHg-related deficits were seen when the rats were retested on SDR after 2 years of age. These results are consistent with previous reports and hypotheses that gestational MeHg exposure produces perseverative responding. No interactions between diet and MeHg were found, suggesting that n-3 PUFAs do not guard against these behavioral effects. Brain Hg concentrations did not differ between the diets, either. In geriatric rats, failures to respond were less common and response latencies were shorter for rats fed the fish-oil diet, suggesting that exposure to a diet rich in n-3s may lessen the impact of age-related declines in response initiation.

Gender differences in the disposition and toxicity of metals

There is increasing evidence that health effects of toxic metals differ in prevalence or are manifested differently in men and women. However, the database is small. The present work aims at evaluating gender differences in the health effects of cadmium, nickel, lead, mercury and arsenic. There is a markedly higher prevalence of nickel-induced allergy and hand eczema in women compared to men, mainly due to differences in exposure. Cadmium retention is generally higher in women than in men, and the severe cadmium-induced Itai-itai disease was mainly a woman's disease. Gender differences in susceptibility at lower exposure are uncertain, but recent data indicate that cadmium has estrogenic effects and affect female offspring. Men generally have higher blood lead levels than women. Lead accumulates in bone and increased endogenous lead exposure has been demonstrated during periods of increased bone turnover, particularly in women in pregnancy and menopause. Lead and mercury, in the form of mercury vapor and methylmercury, are easily transferred from the pregnant women to the fetus. Recent data indicate that boys are more susceptible to neurotoxic effects of lead and methylmercury following exposure early in life, while experimental data suggest that females are more susceptible to immunotoxic effects of lead. Certain gender differences in the biotransformation of arsenic by methylation have been reported, and men seem to be more affected by arsenic-related skin effect than women. Experimental studies indicate major gender differences in arsenic-induced cancer. Obviously, research on gender-related differences in health effects caused by metals needs considerable more focus in the future.

Mercury in seafood: mechanisms of accumulation and consequences for consumer health

Mercury is a largely uncontrollable heavy metal contaminant in that it is globally ubiquitous, and environmentally persistent. The element has the potential for global mobilization following liberation from environmental stores, which can occur as a consequence of either anthropogenic activities or natural processes. Furthermore, organic forms like methylmercury accumulate in biological tissues with an exceptionally long biological half-life, facilitating the magnification of this toxin along trophic food chains. Bioaccumulation is particularly evident in aquatic environments, in which long-lived piscivorous fishes and marine mammals are reported with a mercury burden one-million times that of the surrounding water body, typically attaining mercury burdens exceeding 1 microg g(-1). Mercury levels in other seafood, however, are typically reported in the range of 0.1 to 0.2 microg g(-1) and usually less then 0.5 microg g(-1). The primary source of human exposure to environmental mercury is through seafood consumption. The dangers associated with the consumption of large amounts of methylmercury accumulated in seafood are well recognized from past poisoning incidents, in which fish with mercury burdens in the range of 9 to 24 microg g(-1) were consumed. Nevertheless, the toxicological consequence of chronic low-level mercury exposure from habitual seafood consumption is an area of contention. This review discusses the mechanisms of mercury accumulation and distribution in fish tissues and the toxicological consequences of mercury exposure from seafood consumption with regard to international safety guidelines.

Biomarkers of exposure and effect as indicators of the interference of selenomethionine on methylmercury toxicity

The present study was conducted to clarify the interference of selenomethionine (SeMet) on methylmercury (MeHg) toxicity through the evaluation of changes in biomarkers of exposure and effect in rats exposed to MeHg and co-exposed to MeHg and SeMet. Male Wistar rats received two intraperitoneally (i.p.) administrations, either MeHg (1.5mg/kg body weight), SeMet alone (1mg/kg body weight) or combined MeHg and SeMet, followed by 3 weeks of rat urine collection and neurobehavioural assays. The effects of different administrations were investigated by the quantification of total mercury in kidney and brain, analysis of urinary porphyrins, determination of hepatic GSH and evaluation of motor activity functions (rearing and ambulation). MeHg exposure resulted in a significant increase of urinary porphyrins during the 3 weeks of rat urine collection, where as it caused a significant decrease in motor activity only at the first day after cessation of rat exposure. Additionally, SeMet co-exposure was able to normalize the porphyrins excretion, and a tendency to restore rat motor activity was observed, on the first day after cessation of exposure. Brain and kidney mercury levels increased significantly in rats exposed to MeHg; however, in co-exposed rats to SeMet no significant changes in Hg levels were found as compared to rats exposed to MeHg alone. Hence, the present study shows that urinary porphyrins are sensitive and persistent indicators of MeHg toxicity and demonstrates for the first time that SeMet reduces its formation. Finally, these results confirm that the mechanism of interaction between SeMet and MeHg cannot be explained by the reduction of Hg levels in target organs and suggestions are made to clarify the interference of SeMet on MeHg toxicity.

Socioeconomic consequences of mercury use and pollution

In the past, human activities often resulted in mercury releases to the biosphere with little consideration of undesirable consequences for the health of humans and wildlife. This paper outlines the pathways through which humans and wildlife are exposed to mercury. Fish consumption is the major route of exposure to methylmercury. Humans can also receive toxic doses of mercury through inhalation of elevated concentrations of gaseous elemental mercury. We propose that any effective strategy for reducing mercury exposures requires an examination of the complete life cycle of mercury. This paper examines the life cycle of mercury from a global perspective and then identifies several approaches to measuring the benefits of reducing mercury exposure, policy options for reducing Hg emissions, possible exposure reduction mechanisms, and issues associated with mercury risk assessment and communication for different populations.

Metal levels in flathead sole (Hippoglossoides elassodon) and great sculpin (Myoxocephalus polyacanthocephalus) from Adak Island, Alaska: potential risk to predators and fishermen

Increasingly there is a need to assess the contaminant levels in fish as indicators of the health and well-being of both the fish and their consumers, including humans. This paper examines the levels of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the kidney, liver, and muscle of great sculpin and flathead sole from Adak Island in the Aleutian Islands, Alaska. Both species are consumed by the local Aleuts and others. There were significant differences in the levels of heavy metals as a function of tissue for both fish species; the liver of sculpin and sole generally had the highest levels of most metals, except for arsenic, lead, and selenium. Sole had significantly higher mean levels of arsenic in kidney (32,384 vs. 531 ppb, wet weight), liver (18,954 vs. 2532 ppb), and muscle (19,452 vs. 1343 ppb) than did sculpin. Sole also had higher mean levels of cadmium (230 vs. 63 ppb), lead (1236 vs. 48 ppb), mercury (150 vs. 107 ppb), and selenium (5215 vs. 1861 ppb) in kidney than did sculpin. There were significant correlations among weight and length measurements for both species. However, except for mercury, there were few significant correlations among tissue types for most metals. Only mercury and manganese levels were significantly correlated with size for sculpin (but not for sole). Levels of arsenic, lead, and mercury may pose a risk to predators that consume them, and arsenic and mercury may pose a risk to human consumers.

Mercury content of hair in different populations relative to fish consumption

Hair has been used in many studies as a bioindicator of mercury exposure for human populations. At the time of hair formation, mercury from the blood capillaries penetrates into the hair follicles. As hair grows approximately 1 cm each month, mercury exposure over time is recapitulated in hair strands. Mercury levels in hair closest to the scalp reflect the most recent exposure, while those farthest from the scalp are representative of previous blood concentrations. Sequential analyses of hair mercury have been useful for identifying seasonal variations over time in hair mercury content, which may be the result of seasonal differences in bioavailability of fish and differential consumption of piscivorous and herbivorous fish species. Knowledge of the relation between fish-eating practices and hair mercury levels is particularly important for adequate mitigation strategies. Methyl mercury is well absorbed, and because the biological half-life is long, the body burden in humans may reach high levels. People who frequently eat contaminated seafood can acquire mercury concentrations that are potentially dangerous to the fetus in pregnant women. The dose-response relationships have been extensively studied, and the safe levels of exposure have tended to decline. Individual methyl mercury exposure is usually determined by analysis of mercury in blood and hair. The objective of the present review was to examine variations in hair mercury levels from different populations with respect to fish-eating practices.

Effects of polychlorinated biphenyls, hexachlorocyclohexanes, and mercury on human neutrophil apoptosis, actin cytoskelton, and oxidative state

Apoptosis, or programmed cell death, has been proposed as a biomarker for environmental contaminant effects. In this work, we test the hypothesis that in vitro assays of apoptosis are sensitive indicators of immunological effects of polychlorinated biphenyls, hexachlorocyclohexanes, and mercury on human neutrophils. Apoptosis, necrosis, and viability as well as the related indicators F-actin levels, and active thiol state were measured in purified human neutrophils after treatment with contaminants. Effective concentrations observed were 0.3μM (60μg/L) mercury, 750μg/L Aroclor 1254, and 50μM (14,500μg/L) hexachlorocylcohexanes. Concentrations of contaminants that induced apoptosis also decreased cellular F-actin levels. Active thiols were altered by mercury, but not organochlorines. Comparison of these data with levels of contaminants reported to be threats to human health indicate neutrophil apoptosis is a sensitive indicator of mercury toxicity.