Mercury

Background: Amalgam in dental wastewater is receiving increasing scrutiny from regulators because of national, state and local initiatives to reduce or virtually eliminate the discharge of mercury and mercury-containing items into the environment. Amalgam separators are considered to be one means of reducing the amount of amalgam that dental offices discharge into sewers. The purpose of this study was to evaluate the amalgam removal efficiency of commercially available amalgam separators and the total mercury concentration in the effluent from laboratory testing.

Methods: The authors evaluated the amalgam removal efficiency of 12 amalgam separators according to International Organization for Standardization, or ISO, Standard 11143 for Amalgam Separators. Total mercury concentration in the effluent was calculated using the mass of amalgam particles larger than 1.2 micrometers and the volume of effluent, together with U.S. Environmental Protection Agency, or EPA, Method 245.1 for amalgam particles smaller than 1.2 microm. Total dissolved mercury also was determined.

Results: The results show that all 12 amalgam separators exceeded the ISO 11143 requirement of 95 percent amalgam removal efficiency. Statistical differences were found in the efficiencies of the separators. Both the total mercury concentration and total dissolved mercury concentration in the effluent demonstrated large variations.

Conclusions and clinical implications: This laboratory evaluation shows that amalgam separators removed at least 96.09 percent of the amalgam in samples with particle-size distribution as specified in ISO 11143. Total mercury concentration and total dissolved mercury concentration in the effluent varied widely for each amalgam separator. Additional research is needed to develop test methods to evaluate the efficiency of amalgam separators in removing small amalgam particles, colloidal amalgam particles and ionic mercury in solution.

“OBJECTIVES:

The aim of this study was to estimate the amount of mercury released into both air and saliva from fresh and aged, abraded amalgam discs and then investigate neurotoxic effects of inorganic mercury upon sensory neuronal cultures.

METHODS:

An air-tight chamber was constructed to allow the combined estimation of mercury species released from amalgam pellets. The level released into air and saliva from both freshly packed and aged-abraded amalgam pellets was assessed. Dorsal root ganglia cultures from male CBA mice were exposed to 1 and 10 microM mercuric chloride concentrations. The effects of this were assessed by means of morphology, adhesion, size and immunocytochemistry.

RESULTS:

The mercury released into air from dry fresh amalgam was low and less than the recommended industrial exposure limit for mercury. However, covering the discs with saliva reduced air-mercury levels by 46-56% and there was a statistically significant difference in the air-mercury levels recorded (p=0.013-0.048). The mercury released into air from dry abraded amalgam was shown to be above the recommended industrial limit. Coating the abraded amalgam discs with saliva reduced the mercury by 66-72% with the levels recorded being significantly lower (p<0.001). The level of total mercury within the saliva was found to be highly variable. Little change was noted in the neuronal cultures treated with 1 microM mercuric chloride. However, the cultures exposed to high level (10 microM) mercuric chloride showed cells that became rounded and clumped together indicating pathological change.

CONCLUSIONS:

Amalgam placement appears to present minimal mercury exposure risk. To reduce the amount of mercury released into air, however, amalgam should be polished in a moist atmosphere with high volume aspiration. The neurotoxic effect of mercury appears to be related to concentration, as only in the cultures treated with 10 microM mercuric chloride showed striking qualitative and quantitative cellular changes.”

OBJECTIVE:
The intent of this project was to evaluate the efficiency of three commercial amalgam separators based on mercury and particle removal.

METHODS:
Dental wastewater samples were collected from a 54-chair dental clinic and a one chair private dental office. Atomic absorption spectrometry was used to measure mercury, and a laser diffractometer method to determine the particle size distributions.

RESULTS:
The mercury removal efficiency of the three units ranged from 26.5 to 61.8% for the 54-chair clinic and from 80.8 to 94.7% for the one chair office. Following treatment, the particle size range of the effluent was 8.3-19.2 microm for the 54-chair office and 27.5-41.4 microm for the one-chair clinic. For particle samples based on the silver-copper and copper standards, the three amalgam separators had a particle removal efficiency ranging from 92.3 to 99.9%. The initial particle size distributions for these samples were all under 100 microm.

CONCLUSIONS:
The efficiency of the amalgam separators is influenced by the initial concentration of the dental wastewater, the physical setup of the discharge system before the dental wastewater reaches the separators, and the addition of chemicals to the dental wastewater. In addition, it is likely that assessment of efficiency based on particle removal by weight may not be as effective as removal based on concentration.

“OBJECTIVE:

To investigate the release of mercury vapour from a dental aspirator which vented its waste air through its base directly into the surgery environment.

METHODOLOGY:

Mercury vapour in air concentrations were measured at the breathing zone of the dentist during continuous operation of the aspirator. Further series of mercury vapour measurements taken at the aspirator exhaust vent were carried out to determine the sources of mercury vapour from this particular device.

RESULTS:

At the dentist’s breathing zone, mercury vapour concentrations of ten times the current occupational exposure limit of 25 micrograms/m3 were recorded after 20 minutes of continuous aspirator operation. A build up of amalgam contamination within the internal corrugated tubing of the aspirator was found to be the main source of mercury vapour emissions followed by particulate amalgam trapped within the vacuum motor. As the vacuum motor heated up with run time, mercury vapour emissions increased. It was found that the bacterial air exhaust filter (designed to clean the contaminated waste air entering the surgery) offered no protection to mercury vapour. In this case the filter trapped particulate amalgam which contributed to further mercury vapour contamination as high volume air was vented through it.

CONCLUSION:

It is not known how many dental aspirators are in use that vent their waste air directly into the surgery or if this aspirator is representative of others in existence. The safety of dental aspirating systems with regard to mercury vapour exposure requires further investigation.”

“Multiple sclerosis (MS) is aptly named for the many scars it produces in the brain and spinal cord. A sometimes fatal, often debilitating disease, MS features autoimmune inflammatory attack against the myelin insulation of neurons. Thymus derived (T) cells sensitized against myelin self-antigens secrete tumor necrosis factor, cytokines, prostaglandins, and other inflammatory mediators that strip away the myelin and sometimes destroy the axons. Familial and twin inheritance studies indicate MS is mildly heritable. No single MS locus has been identified, but an HLA haplotype has been implicated. Unique geographic distribution of the disease is best attributed to some combination of vitamin D abnormality and dietary patterns. No pharmaceutical or other therapies exist that confer prolonged remission on MS, and obvious interrelationships between toxic, infectious, and dietary factors make a persuasive case for integrative management. The time-proven MS diet meticulously keeps saturated fats low, includes three fish meals per week, and eliminates allergenic foods. Dietary supplementation for MS minimally requires potent vitamin supplementation, along with the thiol antioxidants, the anti-inflammatory omega-3 fatty acids, and adaptogenic phytonutrients. Gut malabsorption and dysbiosis can be corrected using digestive enzymes and probiotics. Long-term hyperbaric oxygen therapy can slow or remit the disease. Transdermal histamine offers promise, and adenosine monophosphate may sometimes benefit. Chronic viruses and other infectious load must be aggressively treated and exercise should maintain muscle tone and balance. Early intervention with integrative modalities has the potential to make MS a truly manageable disease.”

The cytotoxic potentials of the dental composite components triethyleneglycoldimethacrylate (TEGDMA) and 2-hydroxy-ethylmethacrylate (HEMA) as well as mercuric chloride (HgCl2) and methyl mercury chloride (MeHgCl) were investigated. Proliferating A549 and L2 cell monolayers were cultured in the absence or presence of composite components or mercurials. Twenty-four hours later the tetrazolium salt XTT (sodium 3′-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) was added. Formazan formation was quantified using a microtiter plate reader. EC50 values were obtained as half-maximum-effect concentrations from fitted curves. EC50 values were in A549 cells (mean values +/- standard deviation; n = 12; micromol/l); HEMA 8854+/-1882; TEGDMA 1821+/-529; HgCl2 41+/-7 and MeHgCl 27+/-3. EC50 values in L2 cells were: HEMA 191+/-28; TEGDMA 112+/-16; HgCl2 25+/-6 and MeHgCl 8+/-6. All tested substances induced a dose-dependent loss of viability in A549 and L2 cells after 24 h. The EC50 values of both mercurials were significantly (p < 0.05) lower compared to the values of both composite components. TEGDMA was about 5-fold (A549 cells) and about 2-fold (L2 cells) more toxic compared to HEMA. It is to be assumed that the risk of lung cell damage by dental composite components is even more unlikely.

“Inhalation of mercury vapor (Hg0) inhibits binding of GTP to rat brain tubulin, thereby inhibiting tubulin polymerization into microtubules. A similar molecular lesion has also been observed in 80% of brains from patients with Alzheimer disease (AD) compared to age-matched controls. However the precise site and mode of action of Hg ions remain illusive. Therefore, the present study examined whether Hg ions could affect membrane dynamics of neurite growth cone morphology and behavior. Since tubulin is a highly conserved cytoskeletal protein in both vertebrates and invertebrates, we hypothesized that growth cones from animal species could be highly susceptible to Hg ions. To test this possibility, the identified, large Pedal A (PeA) neurons from the central ring ganglia of the snail Lymnoea stagnalis were cultured for 48 h in 2 ml brain conditioned medium (CM). Following neurite outgrowth, metal chloride solution (2 microl) of Hg, Al, Pb, Cd, or Mn (10(-7) M) was pressure applied directly onto individual growth cones. Time-lapse images with inverted microscopy were acquired prior to, during, and after the metal ion exposure. We demonstrate that Hg ions markedly disrupted membrane structure and linear growth rates of imaged neurites in 77% of all nerve growth cones. When growth cones were stained with antibodies specific for both tubulin and actin, it was the tubulin/microtubule structure that disintegrated following Hg exposure. Moreover, some denuded neurites were also observed to form neurofibrillary aggregates. In contrast, growth cone exposure to other metal ions did not effect growth cone morphology, nor was their motility rate compromised. To determine the growth suppressive effects of Hg ions on neuronal sprouting, cells were cultured either in the presence or absence of Hg ions. We found that in the presence of Hg ions, neuronal somata failed to sprout, whereas other metalic ions did not effect growth patterns of cultured PeA cells. We conclude that this visual evidence and previous biochemical data strongly implicate Hg as a potential etiological factor in neurodegeneration.”

“Chelation challenge testing has been used to assess the body burden of various metals. The best-known example is EDTA challenge in lead-exposed individuals. This study assessed diagnostic chelation challenge with dimercaptosuccinic acid (DMSA) as a measure of mercury body burden among mercury-exposed workers. Former employees at a chloralkali plant, for whom detailed exposure histories were available (n = 119), and unexposed controls (n = 101) completed 24-hr urine collections before and after the administration of two doses of DMSA, 10 mg/kg. The urinary response to DMSA was measured as both the absolute change and the relative change in mercury excretion. The average 24-hr mercury excretion was 4.3 microg/24 hr before chelation, and 7.8 microg/24 hr after chelation. There was no association between past occupational mercury exposure and the urinary excretion of mercury either before or after DMSA administration. There was also no association between urinary mercury excretion and the number of dental amalgam surfaces, in contrast to recent published results. We believe the most likely reason that DMSA chelation challenge failed to reflect past mercury exposure was the elapsed time (several years) since the exposure had ended. These results provide normative values for urinary mercury excretion both before and after DMSA challenge, and suggest that DMSA chelation challenge is not useful as a biomarker of past mercury exposure.”

“Micromercurialism (MM) is a term coined by the German chemist Professor A. Stock in the 1920’s and widely used to denote chronic intoxication from long term exposure to low levels of Hg vapor.  He demonstrated (in himself) that MM can be caused by dental amalgams.  Stock stimulated a wave of scientific interest in MM in Germany and Russia.”

“We studied differences in the amounts of organic and inorganic mercury in saliva samples between amalgam and nonamalgam human study groups. The amount of organic and inorganic mercury in whole saliva was measured in 187 adult study subjects. The mercury contents were determined by cold-vapor atomic absorption spectrometry. The amount of organic and inorganic mercury in paraffin-stimulated saliva was significantly higher (p<0.001) in subjects with dental amalgam fillings (n = 88) compared to the nonamalgam study groups (n = 43 and n = 56): log(e) (organic mercury) was linearly related to log(e) (inorganic mercury, r(2) = 0.52). Spearman correlation coefficients of inorganic and organic mercury concentrations with the number of amalgam-filled tooth surfaces were 0.46 and 0.27, respectively. Our results are compatible with the hypothesis that amalgam fillings may be a continuous source of organic mercury, which is more toxic than inorganic mercury, and almost completely absorbed by the human intestine.”