Mercury

“The oxidizing thiol reagent, thimerosal, has been shown to activate reversibly the inositol 1,4,5-trisphosphate (InsP(3)) receptor in several cell types. We have studied here the effects of thimerosal by monitoring the [Ca(2+)] inside the endoplasmic reticulum (ER) of intact HeLa cells with targeted aequorin. We show that thimerosal produced little effects on the ER-Ca(2+)-pump and only slightly increased the ER-Ca(2+)-leak in intact cells. Instead, thimerosal increased the sensitivity to histamine of ER-Ca(2+)-release by about two orders of magnitude, made the response much more prolonged at saturating histamine concentrations and enhanced both cytosolic and mitochondrial [Ca(2+)] responses to histamine. Moreover, inhibition of ER-Ca(2+)release by cytosolic [Ca(2+)] microdomains was fully preserved and sensitive to BAPTA-loading, and histamine-induced Ca(2+) release remained quantal in the presence of both thimerosal and intracellular BAPTA. The effects of thimerosal were reversible in the presence of dithiotreitol, suggesting the possible presence of a physiological redox regulatory mechanism. However, in permeabilized cells thimerosal potentiated InsP(3)-induced Ca(2+) release but oxidized glutathione had no effect. In addition, thimerosal increased the [Ca(2+)](ER) steady-state level in permeabilized cells. Thimerosal partially inhibited also plasma membrane Ca(2+)extrusion and increased Ca(2+)(Mn(2+)) entry through the plasma membrane, both phenomena contributing to increase the steady-state cytosolic [Ca(2+)]. Thimerosal-induced Ca(2+) entry was additive to that induced by emptying of the ER, suggesting that store-operated Ca(2+) channels may not be involved. These results provide new insights on the mechanisms of activation and inactivation of InsP(3) receptors.”

“OBJECTIVE:

To determine the blood mercury levels in dental students and clinical teaching staff in a dental school using amalgam as a restorative material.

SETTING:

A dental school in Ege University, Turkey surveyed during one academic year.

SUBJECTS AND METHODS:

Cross-sectional study of groups of dental students (n=92) in years I to V, clinical teachers in restorative dentistry (n=16) and controls (n=14). Mercury concentration was estimated in venous blood samples using a cold vapour atomic absorption method at the commencement and end of the academic year. Daily air mercury levels were determined in clinical and teaching areas by measuring the darkening of palladium chloride discs using spectrophotometry.

RESULTS:

There were statistically significant increases (p<0.001) in plasma mercury concentration between measurements in all groups at the end of the academic year. Red cell mercury levels were also consistently elevated. Although the highest levels of mercury were recorded in persons working with amalgam, increased levels were also found in subjects working in the teaching classrooms but not with amalgam (controls and first year students).

CONCLUSION:

Increased mercury levels appeared to be due to background exposure from spillage of mercury and amalgam residues on floors. Increased mercury hygiene and regular control of working atmosphere should be implemented to prevent mercury exposure in the dental pre-clinical laboratory.”

Mercury and selenium concentrations were determined in scalp hair samples collected postpartum from 82 term pregnancy mothers and their neonates. Maternal mercury and selenium had median concentrations of 0.39 microg/g (range 0.1-2.13 microg/g) and 0.75 microg/g (range 0.1-3.95 microg/g), respectively, and corresponding median neonatal values were 0.24 microg/g (range 0.1-1.93 microg) and 0.52 microg/g (range (0.1-3.0 microg/g). Amalgam-based restorative dental treatment received during pregnancy by 27 mothers (Group I) was associated with significantly higher mercury concentrations in their neonates (p < 0.0001) compared to those born to 55 mothers (Group II) whose most recent history of such dental treatment was dated to periods ranging between 1 and 12 yr prior to pregnancy. In the Group I mother/neonate pairs, amalgam removal and replacement in 10 cases was associated with significantly higher mercury concentrations compared to 17 cases of new amalgam emplacement. Selenium concentrations showed no significant intergroup differences. However, the selenium/mercury molar ratio values were lowest in the Group I neonates, compared to their mothers and to the Group II mother/neonate pairs. This ratio decreased as mercury concentration increased, and this interrelation was statistically significant in both groups of mother/neonate pairs. The data from this preliminary study suggest that amalgam-based dental treatment during pregnancy is associated with higher prenatal exposure to mercury, particularly in cases of amalgam removal and replacement. The ability of a peripheral biological tissue, such as hair, to elicit such marked differences in neonatal mercury concentrations provides supporting evidence of high fetal susceptibility to this form of mercury exposure. The data are discussed in relation to the differences between maternal and fetal mercury metabolisms and to mercury-selenium metabolic intereactions in response to mercury exposure.

“In times like these, there are toxins that we don’t know much about — how to control them, their source, and their impact. But there are toxins that we DO know about — toxins that we know do not belong in our bodies, toxins that we can do something about. My bill addresses that very problem.”

“In this paper we have considered the available literature which demonstrates that sealant restorations perform at least as well as amalgam restorations and are more conservative. Success depends on retention of the overlying sealant and if this is fully retained it is unlikely that any residual caries will progress. The diagnosis of occlusal caries and indications for sealant restorations are discussed and the clinical technique is described. We have concluded that sealant restorations are the optimum restoration in small and discrete occlusal cavities.”

“Mercury is a ubiquitous environmental toxin that causes a wide range of adverse health effects in humans. Three forms of mercury (elemental , inorganic , and organic) exist, and each has its own profile of toxicity. Exposure to mercury typically occurs by inhalation or ingestion. Readily absorbed after its inhalation, mercury can be an indoor air pollutant , for example , after spills of elemental mercury in the home ; however , industry emissions with resulting ambient air pollution remain the most important source of inhaled mercury . Because fresh-water and ocean fish may contain large amounts of mercury, children and pregnant women can have significant exposure if they consume excessive amounts of fish . The developing fetus and young children are thought to be disproportionately affected by mercury exposure , because many aspects of development , particularly brain maturation , can be disturbed by the presence of mercury. Minimizing mercury exposure is, therefore , essential to optimal child health. This review provides pediatricians with current information on mercury, including environmental sources, toxicity, and treatment and prevention of mercury exposure.”

“Dental amalgam fillings containing mercury have been suggested as a possible risk factor for multiple sclerosis (MS). In the context of a wider program of investigation into environmental risk factors and MS, we conducted a case-control comparison to investigate the alleged association between MS, dental caries, and amalgam fillings. We included 132 MS patients with onset during the last 16 years and 423 controls, matched to cases for sex, age and residence. Data were collected by a personal interview conducted by trained doctors. Cases and controls gave informed consent. Although we report a trend toward a higher number of dental fillings in cases than controls, odds ratios for subjects with exposures of different duration and with different numbers of amalgam fillings were not statistically significant. This case-control study failed to demonstrate an association between either the number of dental amalgam fillings or the duration of exposure to mercury amalgam and MS.”

“Autism is a syndrome characterized by impairments in social relatedness and communication, repetitive behaviors, abnormal movements, and sensory dysfunction. Recent epidemiological studies suggest that autism may affect 1 in 150 US children. Exposure to mercury can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to traits defining or associated with autism, and the similarities extend to neuroanatomy, neurotransmitters, and biochemistry. Thimerosal, a preservative added to many vaccines, has become a major source of mercury in children who, within their first two years, may have received a quantity of mercury that exceeds safety guidelines. A review of medical literature and US government data suggests that: (i) many cases of idiopathic autism are induced by early mercury exposure from thimerosal; (ii) this type of autism represents an unrecognized mercurial syndrome; and (iii) genetic and non-genetic factors establish a predisposition whereby thimerosal’s adverse effects occur only in some children.”

“Mercury has long been known to be a potent neurotoxic substance, whether it is inhaled or consumed in the diet as a food contaminant.  Over the past 15 years, medical research laboratories have established that dental amalgam tooth fillings are a major contributor to mercury body burden.  In 1997, a team of research scientists demonstrated that mercury vapour inhalation by animals produced a molecular lesion in brain protein metabolism, which was similar to a lesion seen in 80% of Alzheimer diseased brains. Recently completed experiments by scientists at the University of Calgary’s Faculty of Medicine now reveal with direct visual evidence from brain neuron tissue cultures how mercury ions actually alter the cell membrane structure of developing neurons.”

“Mercury in dentistry has re-emerged as a contentious issue in public health, predominantly because so many people are inadvertently exposed to mercury in order to obtain the benefits of dental amalgam fillings, and the risks remain difficult to interpret. This commentary aims to examine the issues involved in public policy assessment of the continued use of dental amalgam in dentistry. More than 30 per cent of Australian adults are concerned about mercury from dental amalgam fillings but only a small percentage report having their amalgam fillings removed. The placement of dental fillings nearly halved between 1983 and 1997, but many millions of dental amalgam fillings exist in the Australian community. These fillings release mercury (mercury vapour or inorganic ions) at a low level (about 2-5 micrograms/day in an adult). Evidence on the health effect of dental amalgams comes from studies of the association between their presence and signs or symptoms of adverse effects or health changes after removal of dental amalgam fillings. More formal risk assessment studies focus on occupational exposure to mercury and health effects. Numerous methodological issues make their interpretation difficult but new research will continue to challenge policymakers. Policy will also reflect prudent and cautious approaches, encouraging minimization of exposure to mercury in potentially more sensitive population groups. Wider environmental concerns and decreasing tolerance of exposure to other mercury compounds (for example, methylmercury in seafoods) will ensure the use of mercury in dentistry remains an issue, necessitating dentists keep their patients informed of health risks and respect their choices.”