MERCURY - BEAUTIFUL POISON: are amalgam fillings safe?

Controversy about the safety of amalgam fillings continues. Research is conflicting, although there is general consensus that Hg, as a metal is toxic. A group of BCNH tutors, students, graduates and scientists will review and analyse evidence and report on their findings over the next few weeks.

The article below is published on the World Health Organisation site (online) accessed on 20.11.2008 at

http://www.euro.who.int/chemsafety/mercury/20071221_3?PrinterFriendly=1&

Mercury

Mercury and its compounds are highly toxic to humans, ecosystems and wildlife. Even relatively low doses can have serious neurotoxic effects on adults and children. Initially considered as an acute and local problem, they are now understood to be a global challenge with chronic effects. Some studies also show renal and cardiovascular effects. New epidemiological findings indicate that toxic effects may occur at lower exposure levels then previously considered. Methylmercury can cross the placenta, entering the fetus and accumulating in its brain and other tissues. Hence, exposure of women of childbearing age and children is of the greatest concern.

Owing to the transport of mercury through the environment and its bioaccumulation, the principle source of exposure to methylmercury in the general population is diet, in particular fish consumption. Dental amalgams are the main source of mercury exposure for most people in developed countries. Other sources include cosmetics, thiomersal in vaccinnes, thermometers and other medical devices.

Specific concerns are the potential exposures of population living near contaminated sites, waste and dumping sites, and plants producing mercury-containing products. Identifying such sites, assessing health risks from exposure and developing risk management programmes may have immediate positive health effects on the exposed population, and help to prevent the risk of future exposure.

© 2008 World Health Organization

Here are some interesting abstracts downloaded from PubMed. BCNH students can access research papers from BCNH website.

J Expo Sci Environ Epidemiol. 2008 May;18(3):326-31. Epub 2007 Sep 12

Maternal amalgam dental fillings as the source of mercury exposure in developing fetus and newborn.

Palkovicova L, Ursinyova M, Masanova V, Yu Z, Hertz-Picciotto I.

Department of Environmental Medicine, Slovak Medical University, Bratislava, Slovakia.

Dental amalgam is a mercury-based filling containing approximately 50% of metallic mercury (Hg(0)). Human placenta does not represent a real barrier to the transport of Hg(0); hence, fetal exposure occurs as a result of maternal exposure to Hg, with possible subsequent neurodevelopmental disabilities in infants. This study represents a substudy of the international NIH-funded project "Early Childhood Development and polychlorinated biphenyls Exposure in Slovakia". The main aim of this analysis was to assess the relationship between maternal dental amalgam fillings and exposure of the developing fetus to Hg. The study subjects were mother-child pairs (N=99). Questionnaires were administered after delivery, and chemical analyses of Hg were performed in the samples of maternal and cord blood using atomic absorption spectrometry with amalgamation technique. The median values of Hg concentrations were 0.63 microg/l (range 0.14-2.9 microg/l) and 0.80 microg/l (range 0.15-2.54 microg/l) for maternal and cord blood, respectively. None of the cord blood Hg concentrations reached the level considered to be hazardous for neurodevelopmental effects in children exposed to Hg in utero (EPA reference dose for Hg of 5.8 microg/l in cord blood). A strong positive correlation between maternal and cord blood Hg levels was found (rho=0.79; P<0.001). rho="0.46," rho="-0.37,">

Biol Trace Elem Res. 2008 Aug 22. [Epub ahead of print]

Thyroid Hormones and Methylmercury Toxicity

Soldin OP, O'Mara DM, Aschner M.

Departments of Medicine, Oncology and Physiology, Center for Sex Differences, Lombardi Comprehensive Cancer Center, LL, S-166, Georgetown University Medical Center, 3800 Reservoir Road, N.W., Washington, DC, 20057, USA, os35@georgetown.edu.

Thyroid hormones are essential for cellular metabolism, growth, and development. In particular, an adequate supply of thyroid hormones is critical for fetal neurodevelopment. Thyroid hormone tissue activation and inactivation in brain, liver, and other tissues is controlled by the deiodinases through the removal of iodine atoms. Selenium, an essential element critical for deiodinase activity, is sensitive to mercury and, therefore, when its availability is reduced, brain development might be altered. This review addresses the possibility that high exposures to the organometal, methylmercury (MeHg), may perturb neurodevelopmental processes by selectively affecting thyroid hormone homeostasis and function.

Arch Toxicol. 2007 Nov;81(11):759-67. Epub 2007 May 4

Mercuric dichloride induces DNA damage in human salivary gland tissue cells and lymphocytes

Schmid K, Sassen A, Staudenmaier R, Kroemer S, Reichl FX, Harréus U, Hagen R, Kleinsasser N.

University of Regensburg, Regensburg, Germany.

Amalgam is still one of the most frequently used dental filling materials. However, the possible adverse effects especially that of the mercuric component have led to continued controversy. Considering that mercury may be released from amalgam fillings into the oral cavity and also reach the circulating blood after absorption and resorption, it eventually may contribute to tumorigenesis in a variety of target cells. The present investigation focuses on genotoxic effects below a cytotoxic dose level of mercuric dichloride (HgCl(2)) in human samples of salivary glands and lymphocytes to elucidate a possible role in tumor initiation. DNA migration due to single strand breaks, alkali labile sites and incomplete excision repair was quantified with the aid of the single cell microgel electrophoresis (Comet) assay. The concepts of Olive Tail Moment, percentage of DNA in the Tail and Tail Length were used as measures of DNA damage. To control for cytotoxic effects, the trypan blue exclusion test was applied. Human samples of the parotid salivary gland and lymphocytes of ten donors were exposed to HgCl(2)concentrations from 1 to 50 microM. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) served as controls. Increasing dose-dependent DNA migration could be demonstrated after exposure to HgCl(2) in cells of the salivary glands and lymphocytes. In both cell types a significant increase in DNA migration could be shown starting from HgCl(2)concentrations of 5 microM in comparison to the negative control. The viability of the cell systems was not affected except at the highest concentration (50 microM) tested. These data indicate genotoxic effects of mercuric dichloride in human salivary glands and lymphocytes at concentrations not leading to cytotoxic effects or cell death. Consequently, a contributory role in oral salivary gland tumor initiation warrants further investigation.

J Environ Pathol Toxicol Oncol. 2007;26(4):305-22

Need for informed consent for dentists who use mercury amalgam restorative material as well as technical considerations in removal of dental amalgam restorations

Edlich RF, Greene JA, Cochran AA, Kelley AR, Gubler KD, Olson BM, Hudson MA, Woode DR, Long WB 3rd, McGregor W, Yoder C, Hopkins DB, Saepoff JP.

Biomechanical Engineering and Emergency Medicine, DeCamp Burn and Wound Healing Center, University of Virginia Health System, Charlottesville, VA, USA. richardedlichmd@gmail.com

Amalgam restorative material generally contains 50% mercury (Hg) in a complex mixture of copper, tin, silver, and zinc. It has been well documented that this mixture continually emits mercury vapor, which is dramatically increased by chewing, eating, brushing, and drinking hot liquids. Mercury has been demonstrated to have damaging effects on the kidney, central nervous system, and cardiovascular system, and has been implicated in gingival tattoos. While mercury amalgams may result in detrimental exposure to the patient, they can also be a danger in dental practices. In Europe, the federal governments of Norway, Finland, Denmark, and Sweden have enacted legislation requiring that dental patients receive informed consent information about the dental restorative material that will be used. In the United States, a few state governments have enacted informed consent legislation for dental patients receiving dental restorations. These state legislations were enacted by Maine, California, Connecticut, and Vermont. It is a sad tragedy that mercury is causing such health damage to many people. The American Dental Association has said for the past 150 years that the mercury in amalgam is safe and does not leak; however, no clinical studies were ever done and the Food and Drug Administration approved amalgam under a grandfather clause. Subsequent studies have shown this claim of safety not to be true. Over ten years ago, the Federation of American Societies for Experimental Biology Journal published a comprehensive article calling mercury restorative material a major source of mercury exposure to the U.S. population. The authors of this paper recommend that federal and state legislation be passed throughout our country to ensure that consent forms are given to patients receiving silver-mercury amalgam restorative material.

J Long Term Eff Med Implants. 2005;15(6):709-21

Dental amalgam restorations: daily mercury dose and biocompatibility

Mitchell RJ, Osborne PB, Haubenreich JE.

Department of Oral Health Practice, Division of Restorative Dentistry, College of Dentistry, University of Kentucky, Lexington, Kentucky 40536-0027, USA. rjm1@uky.edu

Over the past 150 years, silver-tin-copper amalgam has been the most frequently used dental restorative material. Amalgam may be the single most frequently used implant material. In the early 1980s, researchers discovered that amalgam restorations release mercury vapor during chewing. This review describes the research that has led to an estimate of the daily dose of mercury that will be absorbed by a subject with a large number of amalgam restorations. Along the way, the history and chemistry of dental amalgam are outlined. The routes of absorption of liquid mercury, ionic mercury, organic mercury, and mercury vapor are also briefly described. The daily dose is found to be 14% of the threshold above which observable adverse neurological symptoms are expected. The review concludes with a summary of the research on the adverse effects of dental amalgam. As expected from the low daily dose, few adverse neurological symptoms have been reported. There is also little evidence of an association of amalgam restorations with neurodegenerative diseases, altered renal function, adverse pregnancy outcomes, or autoimmune diseases. There is a lack of data on neurobiological and neurodevelopmental effects on children who may be exposed to mercury from maternal amalgam restorations during gestation. Additional data on the role of amalgam, if any, in Alzheimers disease and multiple sclerosis are needed.

J Nephrol. 2002 Mar-Apr;15(2):171-6

Mercury in dental restoration: is there a risk of nephrotoxicity?

Mortada WL, Sobh MA, El-Defrawy MM, Farahat SE.

Urology and Nephrology Center, Mansoura University, Faculty of Science, Egypt.

BACKGROUND: Concern has been voiced about exposure to mercury (Hg) from dental amalgam fillings, and there is a need to assess whether this leads to signs of nephrotoxicity. METHODS: A total of 101 healthy adults (80 males and 21 females) were included in this study. The population as grouped into those having amalgam fillings (39 males and 10 females) and those without (41 males and 11 females). Hg was determined in blood, urine, hair and nails to assess exposure. Urinary excretion of beta2-microglobulin (beta2M), N-acetyl-beta-D-glucosaminidase (NAG), gamma-glutamyltransferase (gammaGT) and alkaline phosphatase (ALP) were determined as markers of tubular damage. Albuminuria was assayed as an early indicator of glomerular dysfunction. Serum creatinine, beta2M and blood urea nitrogen (BUN) were determined to assess glomerular filtration. RESULTS: Hg levels in blood and urine were significantly higher in persons with dental amalgam than those without; in the dental amalgam group, blood and urine levels of Hg significantly correlated with the number of amalgams. Urinary excretion of NAG, gammaGT and albumin was significantly higher in persons with dental amalgam than those without. In the amalgam group, urinary excretion of NAG and albumin significantly correlated with the number of fillings. Albuminuria significantly correlated with blood and urine Hg. CONCLUSION: From the nephrotoxicity point of view, dental amalgam is an unsuitable filling material, as it may give rise to Hg toxicity. Hg levels in blood and urine are good markers of such toxicity. In these exposure conditions, renal damage is possible and may be assessed by urinary excretions of albumin, NAG, and gamma-GT.

In August 2008 WHO published a 170 page document 'Guidance for Identifying Populations at Risk from Mercury Exposure'. We will objectively review this document and other research and report back our finding. It should be interesting.