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Context: Effective management of environmental risks such as food and water contamination requires both high quality scientific information and effective, informed social policy. Not only must health practitioners and policy-makers recognize the complexities of human health as a social phenomenon, they must also negotiate the vagaries of uncertainty, precaution, and ethics in their implementation of public health guidelines and advisories. For example, some health practitioners in Alaska have argued against implementation of US Environmental Protection Agency and World Health Organization's standardized consumption advisories for methylmercury (MeHg) in fish, in favor of place-based approaches to evaluating and communicating risk. They stress the importance of traditional subsistence foods and lifestyles, along with other local environmental, economic, and cultural drivers and determinants of environmental health. Such place-based approaches have been successful in improving health outcomes in Alaska and elsewhere., Issue: Nevertheless, debate continues regarding the validity and ethics of place-based approaches to developing and communicating standards and advice for managing environmental risks. Recent critiques suggest that place-based approaches to environmental health represent an undesirable kind of regional 'exceptionalism': the implication of which is that precaution, in respect to acting on the best available objective science, is undermined by attention to subjective local values. In this article we comment on this debate, a debate rooted in concerns regarding the delineation between science-based and policy-based decision-making., Lessons Learned: Our experience with the social and ecological dimensions of MeHg contamination of fish and game in Alaska and elsewhere offers three considerations regarding the potential benefits available through place-based approaches: (1) they can contribute to the accuracy and systematic characterization of risks and their relationship to multiple direct and indirect health outcomes; (2) they are more likely to inform actual changes in behavior; and (3) they afford greater transparency to the risk management process and therefore facilitate environmental justice. We stress that standardized risk assessments and advisories remain important for providing a precautionary baseline that can inform the management and enforcement of industrial and other polluting activities at the state level. However, the management of environmental health at the regional and local level requires an approach that is cognizant of local circumstances and needs, and addresses health in a systemic and integrative fashion capable of incorporating qualitative social, cultural, and economic drivers and determinants. Thus, we recommend a two-tiered approach that blends state-based and place-based environmental risk management.

Studies of neurodevelopmental outcomes in offspring exposed to MeHg from maternal consumption of fish have primarily measured cognitive abilities. Reported associations have been subtle and in both adverse and beneficial directions. Changes in functional outcomes such as school achievement and behavior in exposed children and adolescents have not been examined. We undertook an assessment of school success of children in the Seychelles Child Development Study (SCDS) main cohort to determine if there were any associations with either prenatal or recent postnatal MeHg exposure. The primary endpoints were Seychelles nationally standardized end-of-year examinations given when the cohort children were 9 and 17 years of age. A subgroup (n=215) from the main cohort was also examined at 9 years of age using a regional achievement test called SACMEQ. Prenatal MeHg exposure was 6.8 ppm in maternal hair; recent postnatal exposure was 6.09 ppm at 9 years and 8.0 ppm at 17 years, measured in child hair. Multiple linear regression analyses showed no pattern of associations between prenatal or postnatal exposure, and either the 9- or 17-year end-of-year examination scores. For the subgroup of 215 subjects who participated in the SACMEQ test, there were significant adverse associations between examination scores and postnatal exposure, but only for males. The average postnatal exposure level in child hair for this subgroup was significantly higher than for the overall cohort. These results are consistent with our earlier studies and support the interpretation that prenatal MeHg exposure at dosages achieved by mothers consuming a diet high in fish are not associated with adverse educational measures of scholastic achievement. The adverse association of educational measures with postnatal exposure in males is intriguing, but will need to be confirmed by further studies examining factors that influence scholastic achievement., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Fish provide nutrition for much of the world's population, and when not contaminated with chemicals, fish is a very good food. A major benefit of fish is that they are high in polyunsaturated fatty acids (PUFAs), low in saturated fat, and they contain other critical nutrients. Much of the benefit of fish consumption derives from their high levels of long chain omega-3 PUFAs, which are produced by aquatic microorganisms and bioconcentrate in the aquatic food supply. The PUFAs are essential, in that humans and other vertebrates are not able to synthesize them and therefore must obtain them from the diet. The PUFAs particularly concentrate in the nervous system, alter immune system function reduce serum triglyceride levels and have been reported to reduce the risk of sudden death after a myocardial infarction. But the problem is that most fish have at least some degree of chemical contamination with methylmercury, (which binds to muscle) and/or with persistent organic pollutants such as dioxins, polychlorinated biphenyls, polybrominated diphenyl ethers, chlorinated pesticides (which concentrate in fish fat). These chemicals have adverse effects on nervous system function, modulate the immune system, and are associated with elevations in risk of cardiovascular disease. Thus the question of benefits and risk from fish consumption is complex but very important.

Mercury is a ubiquitous contaminant in aquatic ecosystems, posing a significant health risk to humans and wildlife that eat fish. Mercury accumulates in aquatic food webs as methylmercury (MeHg), a particularly toxic and persistent organic mercury compound. While mercury in the environment originates largely from anthropogenic activities, MeHg accumulation in freshwater aquatic food webs is not a simple function of local or regional mercury pollution inputs. Studies show that even sites with similar mercury inputs can produce fish with mercury concentrations ranging over an order of magnitude. While much of the foundational work to identify the drivers of variation in mercury accumulation has focused on freshwater lakes, mercury contamination in stream ecosystems is emerging as an important research area. Here, we review recent research on mercury accumulation in stream-dwelling organisms. Taking a hierarchical approach, we identify a suite of characteristics of individual consumers, food webs, streams, watersheds, and regions that are consistently associated with elevated MeHg concentrations in stream fish. We delineate a conceptual, mechanistic basis for explaining the ecological processes that underlie this vulnerability to MeHg. Key factors, including suppressed individual growth of consumers, low rates of primary and secondary production, hydrologic connection to methylation sites (e.g., wetlands), heavily forested catchments, and acidification are frequently associated with increased MeHg concentrations in fish across both streams and lakes. Hence, we propose that these interacting factors define a syndrome of characteristics that drive high MeHg production and bioaccumulation rates across these freshwater aquatic ecosystems. Finally, based on an understanding of the ecological drivers of MeHg accumulation, we identify situations when anthropogenic effects and management practices could significantly exacerbate or ameliorate MeHg accumulation in stream fish.

Objective: To study the toxicity of Cinnabar and Cinnabar-containing traditional medicines (Zhusha Anshenwan) comparable to common mercurials., Method: The toxicity of methylmercury (MeHg), mercuric chloride (HgCl2), Cinnabar and Zhusha Anshenwan was studied in cultured human liver HL-7702 cells and in mice following acute and subacute exposures., Result: The 50% lethal concentrations (LC50) of MeHg, HgCl2, Cinnabar and Zhusha Anshenwan in human liver HL-7702 cells were 4.4, 9.2, 2460, 4050 mg x L(-1), respectively . Oral cinnabar at a dose of 20 g x kg(-1) (clinical dosage 250 times) did not kill mouse, but no mouse could survive MeHg at a dose of 0.1 g x kg(-1) or HgCl2 at a dose of 0. 15 g x kg(-1). Subacute toxicity experiment indicated that HgCl2 retarded body weight gain with significant accumulation of Hg in the liver and kidney. In comparison, mercury accumulation after Cinnabar and Zhusha Anshenwan was insignificant. No apparent hepatic and renal dysfunctions were evident under the experimental conditions, but the metallothionein-2 mRNA levels were much higher in HgCl2 group than in other groups., Conclusion: Cinnabar and Zhusha Anshenwan are much less toxic than MeHg and HgCl2.

Background: Many populations are exposed to multiple species of mercury (Hg), predominantly organic Hg as methylmercury (MeHg) from fish, and inorganic Hg as Hg vapor from dental amalgams. Most of our knowledge of the neurotoxicity of Hg is based on research devoted to studying only one form at a time, mostly MeHg., Objectives: In this study we investigated the effects of prenatal exposure to MeHg and Hg vapor on Hg concentrations in the brain of neonatal rats., Methods: Female Long-Evans hooded rats were exposed to MeHg (0, 3, 6, or 9 ppm as drinking solution), Hg vapor (0, 300, or 1,000 microg/m3 for 2 hr/day), or the combination of both, from 30 days before breeding through gestational day 18. On postnatal day 4, whole brains were taken from one male and one female from each of four litters in each treatment group to assess organic and inorganic Hg in the brain by cold vapor atomic absorption spectrometry., Results: Statistical analysis using linear mixed effects models showed that MeHg dose was the primary determinant of both organic and inorganic brain Hg levels. For both outcomes, we also found significant interactions between MeHg and Hg vapor exposure. These interactions were driven by the fact that among animals not exposed to MeHg, animals exposed to Hg vapor had significantly greater organic and inorganic brain Hg levels than did unexposed animals., Conclusion: This interaction, heretofore not reported, suggests that coexposure to MeHg and Hg vapor at levels relevant to human exposure might elevate neurotoxic risks.

This study estimates mercury and methylmercury levels in fish and fishery products commercialized in the city of Barcelona, Spain, from 2001 to 2007. Combining data of mercury levels in food with the consumption data of 2158 people (as the median of two 24-h recall), the total mercury intake of the Catalonian population was calculated. Mercury was detected in 32.8% of analysed samples. The general population average weekly intake of total mercury in the Catalonian population was 0.783 microg kg(-1) of body weight. This value is clearly lower than the Joint FAO/WHO Expert Committee on Food Additives (JECFA) provisional tolerable weekly intakes (PTWI) of 5 microg kg(-1) of body weight. The fish group was the main contributor to this value, mainly due to predatory species.

This article discusses the seafood consumption worldwide as well as the related nutritional-toxicological conflict. An exposure assessment was performed using seafood consumption data from the Global Environment Monitoring System and nutrient and contaminant concentration data. The data indicated that the region of Japan, Korea, Madagascar and Philippines have the highest seafood consumption, followed by the Nordic-Baltic countries and South-East Asia. In Japan, Korea, Madagascar, Philippines and the Nordic-Baltic countries, pelagic marine fishes are highly consumed compared to fresh water fishes in South-East Asia. Because pelagic fishes are oily fishes, Japan, Korea, Madagascar, Philippines and the Nordic-Baltic countries have high omega-3 fatty acids and vitamin D intake. Iodine intake is influenced by the demersal fish consumption. The current intake of these nutrients via seafood consumption is still below the recommendations. From the toxicological side, the data indicate that none of the seafood groups had a median contaminant concentration above the EU maximum limits. Though, the results show that in some regions the contaminant intake exceeded the international health-based guidance values, mainly focussing on sensitive subpopulations. In contrast, when using less stringent guidance values relevant for non-sensitive subpopulations, the results show that the benefits of increased seafood consumption outweigh the risks.

The main objectives of our study were to estimate the impact of a mercury cell chlor-alkali (MCCA) complex in Rosignano Solvay (Tuscany, Italy) on the local environment and to assess mercury exposure of inhabitants living near the plant. Measurement campaigns of atmospheric Hg near the MCCA plant showed that the impact of the emitted Hg from the industry on the terrestrial environment is restricted to a close surrounding area. Total gaseous mercury concentrations in ambient air of inhabited area around the MCCA plant were in the range of 8.0-8.7 ng/m3 in summer and 2.8-4.2 ng/m3 in winter. Peaks of up to 100 ng/m3 were observed at particular meteorological conditions. Background levels of 2 ng/m3 were reached within a radius of 3 km from the plant. Reactive gaseous mercury emissions from the plant constituted around 4.2% of total gaseous mercury and total particulate mercury emission constituted around 1.0% of total gaseous mercury emitted. Analysis of local vegetables and soil samples showed relatively low concentrations of total mercury (30.1-2919 microgHg/kg DW in the soil; <0.05-111 microgHg/kg DW in vegetables) and methylmercury (0.02-3.88 microgHg/kg DW in the soil; 0.03-1.18 microgHg/kg DW in vegetables). Locally caught marine fish and fresh marine fish from the local market had concentrations of total Hg from 0.049 to 2.48 microgHg/g FW, of which 37-100% were in the form of methylmercury. 19% of analysed fish exceeded 1.0 microgHg/g FW level, which is a limit set by the European Union law on Hg concentrations in edible marine species for tuna, swordfish and shark, while 39% of analysed fish exceeded the limit of 0.5 microgHg/g FW set for all other edible marine species. Risk assessment performed by calculating ratio of probable daily intake (PDI) and provisional tolerable daily intake (PTDI) for mercury species for various exposure pathways showed no risks to human health for elemental and inorganic mercury, except for some individuals with higher number of amalgam fillings, while PDI/PTDI ratio for methylmercury and total mercury exceeded the toxicologically tolerable value due to the potential consumption of contaminated marine fish.

Selenium (Se) is absolutely required for activity of 25-30 genetically unique enzymes (selenoenzymes). All forms of life that have nervous systems possess selenoenzymes to protect their brains from oxidative damage. Homeostatic mechanisms normally maintain optimal selenoenzyme activities in brain tissues, but high methylmercury (MeHg) exposures sequester Se and irreversibly inhibit selenoenzyme activities. However, nutritionally relevant amounts of Se can replace the Se sequestered by MeHg and maintain normal selenoenzyme activities, thus preventing oxidative brain damage and other adverse consequences of MeHg toxicity. Findings of studies that seem contradictory from MeHg exposure perspectives are entirely consistent from MeHg:Se molar ratio perspectives. Studies that have reported dose-dependent consequences of maternal MeHg exposures on child development uniformly involved seafoods that contained much more Hg than Se. Meanwhile more typical varieties of ocean fish contain much more Se than Hg. This may explain why maternal MeHg exposure from eating ocean fish is associated with major IQ benefits in children instead of harm. Therefore, instead of being avoided, ocean fish consumption should be encouraged during pregnancy. However, the safety of freshwater fish consumption is less certain. In freshwater fish, MeHg bioaccumulation and toxicity are both inversely related to Se bioavailability. Their Se can be far lower than their MeHg contents, potentially making them more dangerous than pilot whale meats. Therefore, to provide accurate and appropriate regulatory advice regarding maternal consumption of seafoods and freshwater fish, Hg:Se molar ratios need to be incorporated in food safety criteria.

Mercury is a well-known environmental toxicant, particularly in its most common organic form, methylmercury. Consumption of fish and shellfish that contain methylmercury is a dominant source of mercury exposure in humans and piscivorous wildlife. Considerable efforts have focused on assessment of mercury and its attendant risks in the environment and food sources, including the studies reported in this issue. However, studies of mercury intoxication have frequently failed to consider the protective effects of the essential trace element, selenium. Mercury binds to selenium with extraordinarily high affinity, and high maternal exposures inhibit selenium-dependent enzyme activities in fetal brains. However, increased maternal dietary selenium intakes preserve these enzyme activities, thereby preventing the pathological effects that would otherwise arise in their absence. Recent evidence indicates that assessments of mercury exposure and tissue levels need to consider selenium intakes and tissue distributions in order to provide meaningful risk evaluations.

The variance of variables associated with neurodevelopment at 180 days, pre-natal variables (Hg in placenta, blood and hair) and post-natal Hg exposure (including Thimerosal-containing vaccines, TCV) were examined in 82 exclusively breastfed infants using principal component analysis (PCA). This multivariate method was applied to identify hierarchy and sets of interrelated variables. The PCA yielded a two-factor solution, explaining 92% of variance and summarizing most of the relevant information in the dataset matrix: the first component represented birth weight and vaccine (first doses of Hepatitis B and DTP) variability and explained 57% of variance; the second component represented a gradient of neurodevelopment (Gesell scores) and explained 35% of variance. The third component explained only 3% of the remaining 8% variance. Beside CNS priming by breastfeeding, infant development (birth weight) and time of immunization with TCV should be considered in epidemiological studies. PCA can classify sets of variables related to vaccination and neuromotor development schedules, clearly discriminating between earlier and later TCV exposures of exclusively breastfed infants. In conclusion, the incommensurable concept of the chance of toxic risk caused by TCV-EtHg exposure against the proven benefit of immunization is in no way disputed here. However, infant neurodevelopmental (ND) disorders linked to Thimerosal-Hg stands in need of proof, but PCA points to the possibility of identifying exposure risk variables associated with ND schedules.

Information exchanges, debates, and negotiations through community social networks are essential to ensure the sustainability of the development process initiated in participatory research. The authors analyze the structural properties and robustness of a discussion network about mercury issues in a community in the Brazilian Amazon involved in a participatory research aimed at reducing exposure to the pollutant. Most of the villagers are connected in a large network and are separated from other individuals by few intermediaries. The structure of the discussion network displays resilience to the random elimination of villagers but shows vulnerability to the removal of one villager who has been a long-term collaborator of the project. Although the network exhibits a structure likely to favor an efficient flow of information, results show that specific actions should be taken to stimulate the emergence of a pool of opinion leaders and increase the redundancy of discussion channels.

Evidence supports the benefits of fish consumption during pregnancy, primarily because of the effects of n-3 polyunsaturated fatty acids on the neurodevelopment of the fetus. Many fish may also be potent sources of methylmercury and polychlorinated biphenol exposure, which have been shown to have severe negative impacts on both the mother and fetus. Therefore, all women of childbearing age should be informed of both the benefits and risks of fish consumption.

The classical statistical paradigm emphasizes the development and application of methods to account for sampling variability. Many modern day applications, however, require consideration of other sources of uncertainty that are not so easy to quantify. This paper presents a case study involving an assessment of the impact of in-utero methylmercury exposure on the Intelligence Quotient (IQ) of young children. We illustrate how familiar techniques such as hierarchical modeling, Bayesian methods and sensitivity analysis can be used to aid decision making in settings that involve substantial uncertainty.

The controversy regarding the once widely used mercury-containing preservative thimerosal in childhood vaccines has raised many historical questions that have not been adequately explored. Why was this preservative incorporated in the first place? Was there any real evidence that it caused harm? And how did thimerosal become linked in the public mind to the "autism epidemic"? I examine the origins of the thimerosal controversy and their legacy for the debate that has followed. More specifically, I explore the parallel histories of three factors that converged to create the crisis: vaccine preservatives, mercury poisoning, and autism. An understanding of this history provides important lessons for physicians and policymakers seeking to preserve the public's trust in the nation's vaccine system.

The benefits of fish consumption have been known to be the prevention of certain heart disease, neurological disorders and a very important role in fetal brain development. However there has been, in the past, certain doubts on whether fish should be classified as a beneficial meat source as part of a pregnant woman's diet as it has been documented that fish contains harmful substances that could effect a child's cognitive and neuro development. Methylmercury (MeHg), in particular, has been singled out. As it turned-out, with the use of numerous literature reviews, MeHg is not as dangerous as we have been led to believe. It has been suggested that even during neonatal exposure to MeHg as a result of maternal fish consumption one can reverse the harmful effects of MeHg if, after birth, the child is exposed to a favorable environment and a nutritious diet. The role of antioxidants is also important as they can help in reducing the harmful effects of MeHg if administered in sufficient amounts during pregnancy. There are also many fish types that should be avoided during pregnancy, particularly predatory and dark-meat fish as they are associated with high amounts of MeHg. This review shows that the benefits of maternal fish consumption during pregnancy can outweigh the harmful effects of neonatal MeHg exposure.

Studies of the association between prenatal methylmercury exposure from maternal fish consumption during pregnancy and neurodevelopmental test scores in the Seychelles Child Development Study have found no consistent pattern of associations through age 9 years. The analyses for the most recent 9-year data examined the population effects of prenatal exposure, but did not address the possibility of non-homogeneous susceptibility. This paper presents a regression tree approach: covariate effects are treated non-linearly and non-additively and non-homogeneous effects of prenatal methylmercury exposure are permitted among the covariate clusters identified by the regression tree. The approach allows us to address whether children in the lower or higher ends of the developmental spectrum differ in susceptibility to subtle exposure effects. Of 21 endpoints available at age 9 years, we chose the Weschler Full Scale IQ and its associated covariates to construct the regression tree. The prenatal mercury effect in each of the nine resulting clusters was assessed linearly and non-homogeneously. In addition we reanalyzed five other 9-year endpoints that in the linear analysis had a two-tailed p-value <0.2 for the effect of prenatal exposure. In this analysis, motor proficiency and activity level improved significantly with increasing MeHg for 53% of the children who had an average home environment. Motor proficiency significantly decreased with increasing prenatal MeHg exposure in 7% of the children whose home environment was below average. The regression tree results support previous analyses of outcomes in this cohort. However, this analysis raises the intriguing possibility that an effect may be non-homogeneous among children with different backgrounds and IQ levels.

Fish provide a healthful source of dietary protein and are high in nutrients such as omega-3 fatty acids. There is evidence of beneficial effects of fish consumption in coronary heart disease, stroke, age-related macular degeneration, and growth and development. Yet, benefits may be offset by the presence of contaminants, such as methylmercury (MeHg), dioxins, polychlorinated biphenyls (PCBs) and several other halogenated persistent organic pollutants. MeHg is a known developmental neurotoxicant, as evidenced by several animal studies and episodes of human intoxication in Japan and Iraq. Fish represent the main source of exposure to MeHg for the general population, and large predatory fish (swordfish, tuna) have the highest levels of MeHg contamination. Provisional tolerable weekly intakes of 0.7 microg kg(-1) to 1.6 microg kg(-1) have been set by regulatory agencies. Concern for contamination of fish with dioxins and dioxin-like PCBs stems from their reported carcinogenicity, immunotoxicity, and reproductive and developmental toxicities. Farmed and wild-caught fish appear to have similar levels of contaminants. Advisories are in place that recommend limited consumption of certain fish in children, pregnant women and women of childbearing age. Careful risk-benefit considerations should foster fish consumption while minimizing exposure to toxic contaminants.

Recent studies have shown an association between myocardial infarction and the intake of MeHg from fish in amounts near the current reference dose (RfD). Biochemical studies support the association. This article considers the results of recent epidemiological studies in relation to an evaluation of RfD and food guidelines. MeHg levels in certain Danish fish are close to harmful levels if the food guidelines are followed. Revised food guidelines should be based on assessments of the MeHg amount in each fish species.

The small-scale gold mining activities using mercury began in the late 1980s in Sibutad, Western Mindanao. It is located very near the Murcielagos Bay with tailing ponds directly discharging into bodies of water. This cross-sectional study aimed to determine the health and environmental effects of gold mining activities on the community. Residents were randomly selected and classified into two groups, namely, the directly exposed and indirectly exposed populations using a set inclusion criteria. Complete medical and laboratory examinations were performed. Environmental and biologic samples were collected for total mercury and methylmercury determinations. The results showed that the directly exposed group had significantly higher mean blood total mercury and methylmercury levels in comparison with the indirectly exposed population. Although there were no significant differences between hair total mercury and methylmercury levels, there was a trend for higher levels of these biomarkers among the directly exposed residents as compared with the unexposed group. The absence of statistically significant differences may be attributable to the small sample size. Ambient air quality monitoring for mercury exceeded the allowable levels. However, levels of mercury in drinking water and sediments were within allowable limits. Frequency of gastrointestinal complaints was significantly associated with elevated hair methylmercury levels (p=0.02). Also, there appears to be a trend towards higher blood total mercury levels and frequency of gastrointestinal complaints (p=0.09). An interesting finding in this study was the increasing incidence of elevated diastolic blood pressure with elevated hair total mercury levels (p=0.07). Mercury storage at home is a risk factor.

The aim of the present study was to investigate the potential deleterious effects of dietary contaminants such as polychlorinated biphenyls (PCBs) and methylmercury (MeHg) on different molecules sensitive to oxidative stress, namely, plasma oxidized low-density lipoproteins (OxLDLs), plasma homocysteine (Hcy), blood glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione (GSH). We also planned to assess the potential beneficial effects of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) and selenium (Se) that are also present in the traditional Inuit diet. A total of 99 participants were studied. Plasma levels of PCBs, blood levels of Se and MeHg, plasma lipids (triacylglycerols, total, LDL-, and high-density lipoprotein cholesterol [LDL-C and HDL-C, respectively], apolipoprotein B-LDL), erythrocyte n-3 PUFAs, OxLDL, Hcy, blood GPx, GSH, and GR have been determined. Mean concentrations of MeHg, Se, and PCBs were respectively 10- to 14-fold, 8- to 15-fold, and 16- to 18-fold higher than reported in white population consuming little or no fish. Multivariate analyses show that variance in plasma OxLDL concentrations was predicted by LDL-C (P = .007), HDL-C (P = .005), and PCBs (P = .006). The level of LDL oxidation, represented as the ratio OxLDL/apolipoprotein B-LDL, was predicted by LDL-C (P = .0002), HDL-C (P = .002), and GSH (P = .005). Concentration of plasma Hcy was positively predicted by age (P = .02) but negatively by body mass index (P = .04) and Se (P = .005). Glutathione was predicted by the smoking status (P = .004) and the level of LDL oxidation (P = .005), whereas GR was only predicted by the smoking status (P = .0009). The variance of GPx was not predicted by any contaminant or other physiological parameter. Dietary MeHg showed no association with the examined oxidative biomarkers, whereas PCB level was a predictor of the plasma concentration of OxLDL, although this concentration remained very low. The level of GPx activity in Inuit was higher than levels previously reported to be protective in whites. Homocysteine was negatively predicted by Se, suggesting a possible beneficial effect of Se. Moreover, n-3 PUFAs were highly correlated with dietary contaminants, but had no relationships with oxidative biomarkers. This study suggests that, in adult Inuit, contaminated traditional diet seems to have no direct oxidative effects on molecules involved in oxidative stress.

Until the Clean Air Mercury Rule was signed in March 2005, coal-fired electric utilities were the only remaining, unregulated major source of industrial mercury emissions in the United States. Proponents of coal-burning power plants assert that methylmercury is not a hazard at the current environmental levels, that current technologies for limiting emissions are unreliable, and that reducing mercury emissions from power plants in the United States will have little impact on environmental levels. Opponents of coal-burning plants assert that current methylmercury exposures from fish are damaging to the developing nervous system of infants, children, and the fetus; that current technology can significantly limit emissions; and that reducing emissions will reduce exposure and risk. One concern is that local mercury emissions from power plants may contribute to higher local exposure levels, or "hot spots." The impact of the Mercury Rule on potential hot spots is uncertain due to the highly site-specific nature of the relationship between plant emissions and local fish methylmercury levels. The impact on the primary source of exposure in the United States, ocean fish, is likely to be negligible due to the contribution of natural sources and industrial sources outside the United States. Another debate centers on the toxic potency of methylmercury, with the scientific basis of the US Environmental Protection Agency's (EPA's) recommended exposure limit questioned by some and defended by others. It is likely that the EPA's exposure limit may be appropriate for combined exposure to methylmercury and polychlorinated biphenyls (PCBs), but may be lower than the available data suggest is necessary to protect children from methylmercury alone. Mercury emissions from power plants are a global problem. Without a global approach to developing and implementing clean coal technologies, limiting US power plant emissions alone will have little impact.

Although a rich source of n-3 polyunsaturated fatty acids (PUFAs) that may confer multiple health benefits, some fish also contain methyl mercury (MeHg), which may harm the developing fetus. U.S. government recommendations for women of childbearing age are to modify consumption of high MeHg fish to reduce MeHg exposure, while recommendations encourage fish consumption among the general population because of the nutritional benefits. The Harvard Center for Risk Analysis convened an expert panel (see acknowledgements) to quantify the net impact of resulting hypothetical changes in fish consumption across the population. This paper quantifies the impact of prenatal MeHg exposure on cognitive development. Other papers quantify the beneficial impact of prenatal intake of n-3 PUFAs on cognitive function and the extent to which fish consumption protects against coronary heart disease mortality and stroke in adults. This analysis aggregates results from three major prospective epidemiology studies to quantify the association between prenatal MeHg exposure and cognitive development as measured by intelligence quotient (IQ). It finds that prenatal MeHg exposure sufficient to increase the concentration of mercury in maternal hair at parturition by 1 microg/g decreases IQ by 0.7 points. This paper identifies important sources of uncertainty influencing this estimate, concluding that the plausible range of values for this loss is 0 to 1.5 IQ points.

Recent and powerful epidemiological studies have been used as a basis for revising international and domestic guidelines for human exposure to mercury. Long-range transport of mercury into the Arctic makes some Arctic peoples consuming traditional marine foods, especially newborns, children and pregnant women, very vulnerable to harmful exposures. The WHO, the USEPA and Health Canada have all recently revised their mercury intake guidelines as a result of neurological effects reported in children exposed in utero and adults. Guidance values are equivalent to 0.23 microg/kg-bw/d, 0.1 microg/kg-bw/d and 0.2 microg/kg-bw/d respectively. Differences between the numbers represent slight differences in the uncertainty factors applied, rather than in toxicological interpretation. More recent findings suggest that mercury may also be a factor in ischemic heart disease, which could lower guidance values in the future. Considering the benefits of marine fatty acids (n-3 fatty acids) and guidance that populations consume 300-400g fish/week, consumers face a reality that most open ocean and relatively 'unpolluted' fish species contain levels of mercury that would lead to exposures at current guidance levels. Clearly, there is no more room for further mercury pollution and there is an urgent need for international action to reduce mercury emissions. Concomitantly, while there may be a need for public health authorities to provide consumption advisories to some highly exposed populations, such as in the Arctic, there remains a need to better understand the interactions and benefits associated with marine foods that may reduce health risks associated with low-level mercury exposure.

National fish consumption advisories that are based solely on assessment of risk of exposure to contaminants without consideration of consumption benefits result in overly restrictive advice that discourages eating fish even in areas where such advice is unwarranted. In fact, generic fish advisories may have adverse public health consequences because of decreased fish consumption and substitution of foods that are less healthy. Public health is on the threshold of a new era for determining actual exposures to environmental contaminants, owing to technological advances in analytical chemistry. It is now possible to target fish consumption advice to specific at-risk populations by evaluating individual contaminant exposures and health risk factors. Because of the current epidemic of nutritionally linked disease, such as obesity, diabetes, and cardiovascular disease, general recommendations for limiting fish consumption are ill conceived and potentially dangerous.

Unlabelled: Methylmercury is a neurotoxicant that bio-accumulates in the aquatic food chain and is present in all fish. Little is known about the effects of long-term low-dose exposure to methylmercury in adults. The aim of this study was to determine whether a dose-response relationship exists between long-term methylmercury exposure and neurological abnormalities in aboriginal Quebec Cree adults for whom fish is a dietary staple. We re-analysed data from a 1977 cross-sectional study conducted by Kofman and collaborators on a group of Quebec Cree individuals claiming ill health from local fish consumption. In the original 1977 study, 306 adult participants aged 18-82 years were assessed for methylmercury exposure. Tremor and other neurologic outcomes were assessed with a clinical examination. The investigators did not find clinical evidence of methylmercury intoxication based on an analysis of covariance. We used ordinal regression to obtain odds ratios for the relationship between total hair mercury levels and neurologic abnormalities. Hair mercury concentrations ranged from 0.5 to 46 ppm (parts per million). A 6 ppm increase in hair mercury was associated with increasing levels of tremor (OR, 2.22; 95% CI, 1.15-4.26) in adults under 40 years of age. There was no association with nine other outcomes considered, nor with tremor among older persons. Odds ratios were not influenced by gender, smoking, alcohol use, or co-morbidity., Conclusion: : Dose-dependent effects of methylmercury on tremor may occur below the commonly accepted 50 ppm threshold, particularly in young adults. These effects may be detectable by clinical examination. However, the results should be interpreted with caution given that alcohol use was probably under-reported and that multiple outcomes were studied.

Consumption of at least two servings of fish per week is recommended by the American Heart Association (AHA) to achieve cardio-protective effects. However, some fish are contaminated with methylmercury, which may counteract the positive effect of the omega-3 fatty acids, and numerous governments have issued advisories for certain fish species. These mixed messages may be a source of confusion to the consumer and to the health professional. This paper reviews whether it is possible to follow the AHA recommendation for fish consumption while avoiding the risks associated with consuming mercury in amounts in excess of government thresholds.

There is significant public concern about the potential health effects of exposure to mercury vapour (Hg(0)) released from dental amalgam restorations. The purpose of this article is to provide information about the toxicokinetics of Hg(0), evaluate the findings from the recent scientific and medical literature, and identify research gaps that when filled may definitively support or refute the hypothesis that dental amalgam causes adverse health effects. Dental amalgam is a widely used restorative dental material that was introduced over 150 years ago. Most standard dental amalgam formulations contain approximately 50% elemental mercury. Experimental evidence consistently demonstrates that Hg(0) is released from dental amalgam restorations and is absorbed by the human body. Numerous studies report positive correlations between the number of dental amalgam restorations or surfaces and urine mercury concentrations in non-occupationally exposed individuals. Although of public concern, it is currently unclear what adverse health effects are caused by the levels of Hg(0) released from this restoration material. Historically, studies of occupationally exposed individuals have provided consistent information about the relationship between exposure to Hg(0) and adverse effects reflecting both nervous system and renal dysfunction. Workers are usually exposed to substantially higher Hg(0) levels than individuals with dental amalgam restorations and are typically exposed 8 hours per day for 20-30 years, whereas persons with dental amalgam restorations are exposed 24 hours per day over some portion of a lifetime. This review has uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.

A previously developed exposure model was used [Risk Anal. 22 (2002) 689] to assess the effectiveness of various advisory scenarios on minimizing mercury (Hg) blood levels via the consumption of commercial seafood, both finfish and shellfish. This exposure model was developed to predict levels of Hg in blood in women of child-bearing age in the US based on the frequency of seafood consumption, the amount of seafood consumed per serving, and the types of seafood consumed. Steady-state relationships that employed descriptive statistics to account for toxicokinetic variation were used to predict levels of Hg in blood. The model incorporates an uncertainty dimension that is intended to represent the range of plausible interpretations of the data. The predictability of the model was confirmed via the use of National Health and Nutrition Examination Survey (NHANES) blood Hg data. In the present analysis, the model was used to predict the impact of limitations in the amount or types of seafood consumed on blood Hg levels. Specifically, simulations for various advisory scenarios were developed on the basis of limitations on total consumption of seafood, elimination of the consumption of certain species altogether, and/or a combination of both. In the baseline model, the median (uncertainty) estimates for the 50th, 95th, and 99th per capita population percentiles were 1.25, 8.2, and 16.1 ppb blood Hg, respectively. After restriction of seafood consumption to no more than 12 oz/week, the median (uncertainty) estimates for the 50th, 95th, and 99th per capita population percentiles were 1.22, 6.8, and 10.6 ppb blood Hg, respectively. Elimination of MeHg species, with average concentrations above 0.6 ppm, resulted in very modest decrements in Hg blood levels, in comparison to either the baseline or the reduced consumption scenarios. These results suggest that strategies to reduce MeHg exposure by reducing the amount of fish consumed (e.g., 12 oz/week) are more effective at eliminating the high end of the exposure distribution than are strategies intended to change the types of fish consumed.

The objective of the present article was to present the most important data generated by a multicentric study carried out by Brazilian researchers who, with the support of national and international institutions, worked during the 1990s to describe human exposure to mercury in gold mining areas in the Brazilian Amazon. Three sets of procedures were followed with residents of the Tocantins and Xingu river basins: (1) clinical examination, based on a standardized protocol and performed by a single researcher, in order to identify five basic levels of contamination; (2) determination of mercury levels in blood, hair, and urine, using atomic absorption spectrophotometry (Xingu Project); and (3) investigation of genotoxicity by using four cytogenetic indicators. During the first stage, 41 individuals were studied. Mercury was found in miners and their family members. Contamination was significantly associated with occupation and showed a differential correlation with genotoxicity indicators. After that, the Xingu project, which encompassed 625 individuals, focused on 417 Kayapó natives from the Gorotire and Djudjetiktire villages; 142 miners; and 66 riverine individuals (ribeirinhos). The highest levels of methylmercury in hair and total mercury in blood and urine were found among the Indian population. Contamination with inorganic forms of mercury was also observed in the blood, hair, and urine of Indians. Following a specific recommendation from the World Health Organization, special attention was given to pregnant Gorotire and Djudjetiktire women, who, although not directly exposed to mercury vapors, showed considerable levels of mercury intoxication. Despite this worrisome scenario, a number of social achievements in the 1990s point to new standards of dignity in health care and of social ethics in Brazil that could benefit everyone, including the victims of environmental injury.

Perinatal exposure to methylmercury is known to result in severe neurological effects on the developing fetus and infant, including cerebral palsy, mental retardation, and seizures. Males are more susceptible than females to neurological damage from perinatal methylmercury exposures. Preliminary analyses of data and statistics for the hospitalization rates of males for cerebral palsy in the 17 Canadian Areas of Concern in the Great Lakes basin indicate a possible geographic association with locations with elevated mercury from natural or industrial sources.