This review covers the toxicology of mercury and its compounds. Special attention is paid to those forms of mercury of current public health concern. Human exposure to the vapor of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate. Ethylmercury in the form of a preservative, thimerosal, added to certain vaccines, is the most recent form of mercury that has become a public health concern. The review leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an "element of mystery."

The Toxicology of Mercury and Its Chemical Compounds

The paper builds on existing literature, highlighting current understanding and identifying unresolved issues about MeHg exposure, health effects, and risk assessment, and concludes with a consensus statement. Methylmercury is a potent toxin, bioaccumulated and concentrated through the aquatic food chain, placing at risk people, throughout the globe and across the socioeconomic spectrum, who consume predatory fish or for whom fish is a dietary mainstay. Methylmercury developmental neurotoxicity has constituted the basis for risk assessments and public health policies. Despite gaps in our knowledge on new bioindicators of exposure, factors that influence MeHg uptake and toxicity, toxicokinetics, neurologic and cardiovascular effects in adult populations, and the nutritional benefits and risks from the large number of marine and freshwater fish and fish-eating species, the panel concluded that to preserve human health, all efforts need to be made to reduce and eliminate sources of exposure.

Methylmercury exposure and health effects in humans: a worldwide concern.

During the last decade a new pattern of Hg pollution has been discerned, mostly in Scandinavia and North America. Fish from low productive lakes, even in remote areas, have been found to have a high Hg content. This pollution problem cannot be connected to single Hg discharges but is due to more widespread air pollution and long-range transport of pollutants. A large number of waters are affected and the problem is of a regional character. The national limits for Hg in fish are exceeded in a large number of lakes. In Sweden alone, it has been estimated that the total number of lakes exceeding the blacklisting limit of 1 mg Hg kg-1 in 1-kg pike is about 10 000.

Mercury in the Swedish environment — Recent research on causes, consequences and corrective methods

Gender differences in the disposition and toxicity of metals

http://kodaimercury.org/backdoor/wp-content/uploads/2015/01/mercury_article-4.pdf

Mercury exposure in children: a review.

Total mercury concentrations (mean +/- standard deviation) in breast milk, blood, and hair samples collected 6 wk after delivery from 30 women who lived in the north of Sweden were 0.6 +/- 0.4 ng/g (3.0 +/- 2.0 nmol/kg), 2.3 +/- 1.0 ng/g (11.5 +/- 5.0 nmol/kg), and 0.28 +/- 0.16 microg/g (1.40 +/- 0.80 micromol/kg), respectively. In milk, an average of 51% of total mercury was in the form of inorganic mercury, whereas in blood an average of only 26% was present in the inorganic form. Total and inorganic mercury levels in blood (r = .55, p = .003; and r = .46, p = .01 6; respectively) and milk (r = .47, p = .01; and r = .45, p = .018; respectively) were correlated with the number of amalgam fillings. The concentrations of total mercury and organic mercury (calculated by subtraction of inorganic mercury from total mercury) in blood (r = .59, p = .0006, and r = .56, p = .001; respectively) and total mercury in hair (r = .52, p = .006) were correlated with the estimated recent exposure to methylmercury via intake of fish. There was no significant between the milk levels of mercury in any chemical form and the estimated methylmercury intake. A significant correlation was found between levels of total mercury in blood and in milk (r = .66, p = .0001), with milk levels being an average of 27% of the blood levels. There was an association between inorganic mercury in blood and milk (r = .96, p < .0001); the average level of inorganic mercury in milk was 55% of the level of inorganic mercury in blood. No significant correlations were found between the levels of any form of mercury in milk and the levels of organic mercury in blood. The results indicated that there was an efficient transfer of inorganic mercury from blood to milk and that, in this population, mercury from amalgam fillings was the main source of mercury in milk. Exposure of the infant to mercury from breast milk was calculated to range up to 0.3 microg/kg x d, of which approximately one-half was inorganic mercury. This exposure, however, corresponds to approximately one-half the tolerable daily intake for adults recommended by the World Health Organization. We concluded that efforts should be made to decrease mercury burden in fertile women.

Total and inorganic mercury in breast milk in relation to fish consumption and amalgam in lactating women.

Female Sprague-Dawley rats were fed a control standard diet or a selenite (Se) supplemented diet (1.3 p.p.m. Se) for 8 weeks before mating and during gestation and lactation. Blood glutathione peroxidase activity (GSH-Px) was measured as a biomarker of Se in dames. After mating, the females from two dietary groups were divided into three subgroups (6 groups with 10 animals in each) given 0 (vehicle), 2 or 6 mg/kg methyl mercury (MeHg) by gavage on days 6-9 of gestation. Day 2 post parturition all litters were standardized to 6 pups per litter and remaining pups were used for determination of blood and brain total Hg contents. Behavioural testing was performed at two months of age. The results of the study showed that supplementing the diet with Se partly antagonized some adverse effects of the MeHg such as hypoactivity especially in the high MeHg dose group. There were no changes in physical development or body weight except a tendency to decreased body weight in offspring of mothers exposed to 6 mg Hg/kg. The GSH-Px activity was significantly increased in animals fed on Se supplemented diet. The dietary Se supplementation resulted in considerably increased concentrations of mercury in the blood of the offspring despite milder signs of CNS toxicity and no increase in brain concentrations of mercury.

Effects of Maternal Dietary Supplementation with Selenite on the Postnatal Development of Rat Offspring Exposed to Methyl Mercury in Utero

Mercury levels in the hair of pregnant women in a polluted area in Sweden

Mercury concentrations in hair were related to fish‐eating habits in a group of SO people reported to have a high consumption of freshwater fish. Mercury levels in hair ranged from 0.3 to 10.8 mg/kg with a mean ± SD of 3.2 ±2.3 mg/kg. The average mercury level in hair from men was significantly higher than that in hair from women (3.8 ± 2.6 mg/kg versus 2.4 ± 1.8 mg/kg. Seven individuals (14%) had levels above 6 mg/kg. In people with equal fish consumption, significantly higher mercury levels were found in the hair of those eating fish from lakes Malaren and Vattern than in those eating fish from Lake Hjalmaren. It has been reported that fish from the latter lake contains approximately 0.2 mg/kg mercury, whereas fish from the other two lakes contains approximately 0.4 mg/kg. The mean mercury level in hair was higher in the group eating freshwater fish more than three times a week (≥500 g fish flesh/week) than in the group eating less, although the difference was of borderline significance. Within couples ...

B Ohlin

Papers

Total and inorganic mercury in breast milk in relation to fish consumption and amalgam in lactating women.

Effects of Maternal Dietary Supplementation with Selenite on the Postnatal Development of Rat Offspring Exposed to Methyl Mercury in Utero

Mercury levels in the hair of pregnant women in a polluted area in Sweden

Mercury levels in hair from people eating large quantities of Swedish freshwater fish.