II) Paramount Scientific Documents
The amalgam has two fundamental health flaws:
1) it has a sustained release of mercury and other toxic metals into the body, and
2) galvanic action produces electricity that flows through the body. Since pathophysiologic effects that toxicity has on the body can be objectively measured, scientific research pertaining to the amalgam’s fundamental health flaws have been focused on the sustained mercury release.
II a) Review
Lorscheider, F.L., Vimy, M.J., and Summers, A.O. “Mercury Exposure from Silver Tooth Fillings: Emerging Evidence Questions a Traditional Dental Paradigm.” FASEB Journal (April 1995).
SUMMARY: This document reviews results of animal and human studies of pathophysiologic effects related to mercury leaking from amalgam restorations. Some pertinent points presented include:
II b) Dental Mercury Impairs Kidney Function
Boyd, N.D., H. Benediktsson, M.J. Vimy, D.E. Hooper, and F.L. Lorscheider, “Mercury From Dental “Silver” Tooth Fillings Impairs Sheep Kidney Function”, Am.J. Physiol. 261, Regulatory Integrative Comp. Physiol. 30: R1010-R1014, (1991).
ABSTRACT: In humans Hg vapor is released from “silver” amalgam fillings that contain 50% Hg by weight. Previous studies show that when 12 such fillings are placed in sheep teeth, the kidneys will concentrate amalgam Hg at levels ranging from 5 to 10 ug Hg/g renal tissue 4 to 20 weeks after placement. In the present study 12 occlusal fillings were placed in each of six adult female sheep under general anesthesia, using standard dental procedures. Glass ionomer occlusal fillings (12) were inserted in two control sheep. At several days before dental surgery, and at 30 and 60 days after placement of fillings, renal function was evaluated by plasma clearance of inulin and by plasma and urine electrolytes, urea, and proteins. An average plasma inulin clearance rate of 69.5 +/- 7.2 ml/min before amalgam placement was reduced to 32.3 +/- 8.1 ml/min by 30 days and remained low at 27.9 +/- 8.7 ml/min after 60 days. Inulin clearance did not change in controls. After amalgam placement urine concentration of albumin decreased from 93.0 +/- 20.5 to 30.1 +/- 15.3 mg/l and urine Na concentrations increased steadily from 24.8 +/- 7.7 to 82.2 +/- 20.3 mmol/l at 60 days. Concentrations of K, urea, Y-glutamyl transpeptidase, alkaline phosphatase, and total protein did not change significantly form 0 to 60 days in urine. Plasma levels of Na, K, urea, and albumin remained unchanged form 0 to 60 days after amalgam. Renal histology remained normal in amalgam-treated animals. It is concluded that amalgam Hg levels in kidney are sufficient to significantly reduce the rate of inulin clearance by non defined mechanisms and that electrolyte patterns in urine are consistent with impaired renal tubular reabsorption.
II c) Dental Mercury Provokes an Increase in Oral and Intestinal Floras
Summers, A.O., J.Wireman, M.J. Vimy, F.L. Lorscheider, B. Marshall, S.B. Levy, S. Bennett, and L. Billard, “Mercury Released form Dental “Silver” Fillings Provokes an Increase in Mercury- and Antibiotic-Resistant Bacteria in Oral and Intestinal Floras of Primates”, Antimicrobial Agents and Chemotherapy, (April 1993), pages 825 – 834.
ABSTRACT: In a survey of 640 human subjects, a subgroup of 356 persons without recent exposure to antibiotics demonstrated that those with a high prevalence of Hg resistance in their intestinal floras were significantly more likely to also have resistance to two or more antibiotics. This observation led us to consider the possibility that mercury released from amalgam (“silver”) dental restorations might be a selective agent for both mercury- and antibiotic-resistant bacteria in the oral and intestinal floras of primates. Resistances to mercury and the several antibiotics were examined in the oral and intestinal floras of six adult monkeys prior the the installation of amalgam fillings, during the time they were in place, and after replacement of the amalgam fillings with glass ionomer fillings (in four of the monkeys). The monkeys were fed an antibiotic-free diet, and fecal mercury concentrations were monitored. There was a statistically significant increase in the incidence of mercury-resistant bacteria during the 5 weeks following installation of the amalgam fillings and during the 5 weeks immediately following their replacement with glass ionomer fillings. These peaks in incidence of mercury-resistant bacteria correlated with peaks of Hg elimination (as high as 1mM in the feces) immediately following amalgam placement and immediately after replacement of the amalgam fillings. Representative mercury-resistant isolates of three selected bacterial families (oral streptococci, members of the family Enterobacteriaceae, and enterocaocci) were also resistant to one or more antibiotics, including ampicillin, tetracycline, streptomycin, kanamycin, and chloramphenicol. While such mercury- and antibiotic-resistant isolates among the staphylococci, the enterococci, and members of the family Enterobacteriaceae, have been described, this is the first report of mercury resistance in the oral streptococci. Many of the enterobacterial strains were able to transfer mercury and antibiotic resistances together to laboratory bacterial recipients, suggesting that the loci for these resistances are genetically linked. Our findings indicate that mercury released from amalgam fillings can cause an enrichment of mercury resistance plasmids in the normal bacterial floras of primates. Many of these plasmids also carry antibiotic resistance, implicating the exposure to mercury from dental amalgams in an increased incidence of multiple antibiotic resistance plasmids in the normal floras of nonmedicated subjects.
II d) Dental Amalgam Mercury in the Human Population
II d1) Dental Mercury is Source of Two-Thirds of Mercury in Population
Aposhian, H.V., D.C. Bruce, W. Alter, R.C. Dart, K.M. Hurlbut, M.M. Aposhian, “Urinary Mercury after Administration of 2, 3-dimercaptopropane-1-sulfonic acid: Correlation with Dental Amalgam Score” FASEB J. 6: 2472-2476; (1992).
ABSTRACT: There is a considerable controversy as to whether dental amalgams may cause systemic health effects in humans because they liberate elemental mercury. Most such amalgams contain as much as 50% metallic mercury. To determine the influence of dental amalgams on the mercury body burden of humans, we have given volunteers, with and without amalgams in their mouth, the sodium salt of 2, 3-dimercaptopropane-1-sulfonic acid (DMPS), a chelating agent safely used in the Soviet Union and West Germany for a number of years. The diameters of dental amalgams of the subjects were determined to obtain the amalgam score. Administration of 300 mg DMPS by mouth increased the mean urinary mercury excretion of the amalgam group from 0.70 to 17.2 ug and that of the non amalgam group from 0.27 to 5.1 ug over a 9 hour period. Two-thirds of the mercury excreted in the urine of those with dental amalgams appears to be derived originally from the mercury vapor released from their amalgams. Linear regression analysis indicated a highly significant positive correlation between the mercury excreted in the urine 2 hours after DMPS administration and the dental amalgam scores. DMPS can be used to increase the urinary excretion of mercury and thus increase the significance and reliability of this measure of mercury exposure or burden, especially in cases of micromercurialism.
II d2) Neurological Behavaioral Effects from Exposure to Dental Amalgam Mercury (focuses on dental personnel)
D. Echeverria, H.V. Aposhian, J.S. Woods, N.J. Heyer, M.M. Aposhian, A.C. Bittner Jr., R.K. Mahurn, and M. Cianciola, “Neurobehavioral effects from exposure to dental amalgam Hg: new distinctions between recent exposure and Hg body burden,” FASEB Journal 12, 971-980 (1998).
ABSTRACT: Potential toxicity from exposure to mercury vapor (Hg) from dental amalgam fillings is the subject of current public health debate in many countries. We evaluated potential central nervous system (CNS) toxicity associated with handling Hg-containing amalgam materials among dental personnel with very low levels of Hg exposure (i.e., urinary Hg < 4 ug/l), applying a neurobehavioral test battery to evaluate CNS functions in relation to both recent exposure and Hg body burden. New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent exposure. The pattern of results, comparable to findings previously reported among subjects with urinary Hg > 50 ug/l, presents convincing new evidence of adverse behavioral effects associated with low Hg exposures within the range of that received by the general population.
II d3) Mobilization of Mercury and Arsenic in Humans by DMPS (including dental personnel)
H.V. Aposhian, “Mobilization of Mercury and Arsenic in Humans by Sodium 2, 3-dimercaptopropane-1-sulfonate (DMPS),” Environmental Health Perspectives Vol 106, Supplement 4, (August 1998).
Sodium 2, 3-dimercaptopropane-1-sulfonate (DMPS, Dimaval) is a water-soluble chelating agent that can be given by mouth or systemically and has been used to treat metal intoxication since the 1960’s in the former Soviet Union and since 1978 in Germany. To better approximate the body burdens of Hg and As in humans, DMPS-Hg and DMPS-AS challenge tests have been developed. The tests involve collecting an overnight urine, administering 300 mg DMPS at zero time, collecting the urine from 0 to 6 hours, and determining the urinary Hg before and after DMPS is given. The challenge test, when applied to normal college student volunteers with and without amalgam restorations in their mouths, indicated that two-thirds of the Hg excreted in the urine after DMPS administration originated in their dental amalgams. In addition, there was a positive linear correlation between the amalgam score (a measure of amalgam surface) and urinary Hg after the challenge test. When the DMPS-Hg challenge test was used to study dental personnel occupationally exposed to Hg, the urinary excretion of Hg was 88, 49, and 35 times greater after DMPS administration than before administration in 10 dental technicians, 5 dentists, and 13 nondental personnel, respectively. DMPS also was used to measure the body burden of humans with a history of drinking water containing 600 ug As/liter. DMPS administration resulted in a tripling of the monomethylarsonic acid percentage and a halving of the dimethylarsinic acid percentage as related to total urinary As. Because South American animals studied were deficient in arsenite methytransferase, a hypothesis is presented that arsenite and arsenite methyltransferase may have had a role in the evolution of some South American animals.
II e) Mercury Exposure via Breast Milk
Vimy, M.J., Hooper, D.E., King, W.W., Lorscheider, F.L., “Mercury from Maternal “Silver” Tooth Fillings in Sheep and Human Breast Milk: A Source of Neonatal Exposure” Biological Trace Element Research, 56:143-52, (1997).
ABSTRACT: Neonatal uptake of Hg from milk was examined in a pregnant sheep model, where radioactive mercury (Hg203)/silver tooth fillings (amalgam) were newly placed. A crossover experimental design was used in which lactating ewes nursed foster lambs. In a parallel study, the relationship between dental history and breast milk concentration of Hg was also examined.
Results from the animal studies showed that, during pregnancy, a primary fetal site of amalgam, Hg concentration is in the liver, and after delivery the neonatal lamb kidney receives additional amalgam Hg from mother’s milk. In lactating women with aged amalgam fillings, increased Hg excretion in breast milk and urine correlated with the number of fillings or Hg vapor concentration levels in mouth air.
It was concluded that Hg originating from maternal amalgam tooth fillings transfers across the placenta to the fetus, across the mammary gland into milk ingested by the newborn and ultimately into neonatal body tissues. Comparisons are made to the U.S. minimal risk level recently established for adult Hg exposure. These findings suggest the placement and removal of “silver” tooth filings in pregnant and lactating humans will subject the fetus and neonate to unnecessary risk of Hg exposure.
II f) Infertility
Gerhard, I., Monga, B., Waldbrenner, A., Runnebaum, B., “Heavy Metals and Fertility” Journal of Toxicology and Environmental Health, Part, A, 54:593-611, (1998).
Heavy metals have been identified as factors affecting human fertility. This study was designed to investigate whether the urinary heavy metal excretion is associated with different factors of infertility. The urinary heavy metal excretion was determined in 501 infertile women after oral administration of the chelating agent 2,3-dimercaptopropane-1-sulfonic acid (DMPS). Furthermore, the influence of trace element and vitamin administration on metal excretion was investigated. Significant correlations were found between different heavy metals and clinical parameters (age, body mass index, nationality) as well as gynecological conditions (uterine fibroids, miscarriages, hormonal disorders). Diagnosis and reduction of an increased heavy metal body load improved the spontaneous conception chances of infertile women. The DMPS test was a useful and complementary diagnostic method. Adequate treatment provides successful alternatives to conventional hormonal therapy.
IIg) Mercury Associated with Cardiac Dysfunction
Frustaci A, Magnavita N, Chimenti C, Caldarulo M, Sabbioni E, Pietra R, Cellini C, Possati GF, Maseri A. Department of Cardiology, Catholic University, Rome, Italy. “Marked elevation of myocardial trace elements in idiopathic dilated cardiomyopathy compared with secondary cardiac dysfunction.” From: J Am Coll Cardiol 1999 May;33(6):1578-83
OBJECTIVES: We sought to investigate the possible pathogenetic role of myocardial trace elements (TE) in patients with various forms of cardiac failure.
BACKGROUND: Both myocardial TE accumulation and deficiency have been associated with the development of heart failure indistinguishable from an idiopathic dilated cardiomyopathy. METHODS: Myocardial and muscular content of 32 TE has been assessed in biopsy samples of 13 patients (pts) with clinical, hemodynamic and histologic diagnosis of idiopathic dilated cardiomyopathy (IDCM), all without past or current exposure to TE. One muscular and one left ventricular (LV) endomyocardial specimen from each patient, drawn with metal contamination-free technique, were analyzed by neutron activation analysis and compared with 1) similar surgical samples from patients with valvular (12 pts)and ischemic (13 pts) heart disease comparable for age and degree of LV dysfunction; 2) papillary and skeletal muscle surgical biopsies from 10 pts with mitral stenosis and normal LV function, and 3) LV endomyocardial biopsies from four normal subjects.
RESULTS: A large increase (>10,000 times for mercury and antimony) of TE concentration has been observed in myocardial but not in muscular samples in all pts with IDCM. Patients with secondary cardiac dysfunction had mild increase (< or = 5 times) of myocardial TE and normal muscular TE. In particular, in pts with IDCM mean mercury concentration was 22,000 times (178,400 ng/g vs. 8 ng/g), antimony 12,000 times (19,260 ng/g vs. 1.5 ng/g), gold 11 times (26 ng/g vs. 2.3 ng/g), chromium 13 times (2,300 ng/g vs. 177 ng/g) and cobalt 4 times (86,5 ng/g vs. 20 ng/g) higher than in control subjects.
CONCLUSIONS: A large, significant increase of myocardial TE is present in IDCM but not in secondary cardiac dysfunction. The increased concentration of TE in pts with IDCM may adversely affect mitochondrial activity and myocardial metabolism and worsen cellular function.
III) Fetal Malformations
James Paget Lancet 2:1017, 1882
We ought not to set them aside with idle thoughts or idle words about “curiosities” or “chances.” Not one of them is without meaning; not one that might not become the beginning of excellent knowledge, if only we could answer the question – why is it rare or being rare, why did it in this instance happen?
McKeown T., “Human Malformations: Introduction” British Medical Bulletin Vol. 32 Number 1 (January 1976).
“…it is a sobering thought that after several decades of research, a number of international conferences and many other meetings, seminars and symposia, the problem of human malformations remains essentially unchanged.” “…at least in the immediate future, it seems likely that the problem of human malformations will continue at about the present level (27 per every 1000 births).”
Weiss, B; Landrigan, PJ. “The Developing Brain and the Environment, An Introduction.” Environmental Health Perspective, 108(3):373-4, June 2000.
EXCERPTS: We have come to understand that chemicals in the environment can cause a wide range of develpmental disabilities in children, and that anatomic malformations are only the most obvious. Current concerns especially focus on the concept that certain chemicals can cause clinical and subclinical deficits in neurobehavioral development through injury to the fetal brain. The implications of small shifts in intelligence quotient score and a slighlty increased tendency to aggression are not so easilly conveyed or grasped as a picture of deformed limbs. However, recognition of the importance of such changes is gathering momentum and is documented in this monograph.
A prime motivating force is the realization that we know the cause of fewer than 25% of neurodevelopmental disabilities. These disabilities including dyslexia, attention deficit hyperactivity disorder (ADHD), intellectual retardation, and autism, affect an estimated 3 to 8% of the 4 million babies born each year in the United States.
For most neurodevelopmental disabilities, the cause remains unknown. A diverse assortment of toxic chemicals in the environment is capable of causing neurodevelopmental disabilities. Organic mercury compounds are among the most potent developmental neurotoxicants. In the words of pediatrician Herbert L. Needleman: “We are conductiong a vast toxicologic experiment in our society in which our children and our children’s children are the experimental subjects.”
The American Academy of Pediatrics has just publiched its Handbook of Pediatric Environmental Health, the “Green Book,” which is available to pediatricians throughout the Americas. Children’s environmental health has climbed to a critical position as we launch the new millennium. This monograph marks a significant milestone in the evolution of this emerging discipline.
When dental mercury crosses over the placenta into the tissue of the developing fetus, does it cause fetal malformations? These studies answer that question.
III a) Sheep Study
Vimy, M.J., Y. Takahashi, and F.L. Lorscheider “Maternal-fetal distribution of mercury (203Hg) released from dental amalgam fillings.” Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol. 27): R939-R945 (1990).
ABSTRACT: In humans, the continuous release of Hg vapor from dental amalgam tooth restorations is markedly increased for prolonged periods after chewing. The present study establishes a time-course distribution for amalgam, Hg in body tissues of adult and fetal sheep. Under general anesthesia, five pregnant ewes had twelve occlusal amalgam fillings containing radioactive 203Hg placed in teeth at 112 days gestation. Blood, amniotic fluid, feces, and urine specimens were collected at 1- to 3-day intervals for 16 days. From days 16-140 after amalgam placement (16-41 days for fetal lambs), tissue specimens were analyzed for radioactivity, and total Hg concentrations were calculated. Results demonstrate that Hg from dental amalgam will appear in maternal and fetal blood and amniotic fluid within 2 days after placement of amalgam tooth restorations. Excretion of some of this Hg will also commence within 2 days. All tissues examined displayed Hg accumulation. Highest concentrations of Hg from amalgam in the adult occurred in kidney and liver, whereas in the fetus the highest amalgam Hg concentrations appeared in the liver and pituitary glands. The placenta progressively concentrated Hg as gestation advanced to term, and milk concentration of amalgam Hg postpartum provides a potential source of Hg exposure to the newborn. It is concluded that accumulation of amalgam Hg progresses in maternal and fetal tissues to a steady state with advancing gestation and is maintained.
III b) Rat Studies
Fredriksson, A., Dencker, L., Archer, T., Danielsson, B.R. “Prenatal Coexposure to Metallic Mercury Vapor and Methyl Mercury Produce Interactive Behavioral Changes in Adult Rats.” Neurotoxicol Teratol., 18(2): 129-34, (1996).
ABSTRACT: Pregnant rats were either 1) administered methyl mercury (MeHg) by gavage, 2 mg/kg/day during days 6-9 of gestation, 2) exposed by inhalation to metallic mercury (Hg) vapor (1.8 mg/m3 air for 1.5 hours per day) during gestation days 14-19, 3) exposed to both MeHg by gavage and Hg vapor by inhalation (MeHg + Hg), or 4) were given combined vehicle administration for each of the two treatments (control). The inhalation regimen corresponded to an approximate dose of 0.1 mg Hg/kg/day.
Clinical observations and developmental markers up to weaning showed no differences between any of the groups. Testing of behavioral functions was performed between 4 and 5 months of age and included spontaneous motor activity, spatial learning in a circular path, and instrumental maze learning for food reward.
Offspring of dams exposed to Hg vapor showed hyperactivity in the motor activity test chambers over all three parameters: locomotion, rearing and total activity; this effect was potentiated in the animals of the MeHg + Hg group. In the swim maze test, the MeHg + Hg and Hg groups evidenced longer latencies to reach a submerged platform, which they had learned to mount the day before, compared to either the control or MeHg group. In the modified, enclosed radial arm maze, both the MeHg + Hg and Hg groups showed more ambulations and rearings in the activity test prior to the learning test. During the learning trial, the same groups (i.e., MeHg + Hg and Hg) showed longer latencies and made more errors in acquiring all eight pellets.
Generally, the results indicate that prenatal exposure to Hg causes alterations to both spontaneous and learned behaviors, suggesting some deficit in adaptive functions. Coexposure to MeHg, which by itself did not alter their functions at the dose given in this study, served to significantly aggravate the change.
S. Soderstrom, A Fredriksson, L. Dencker, T. Ebendal, “The effect of mercury vapour on cholinergic neurons in the fetal brain: studies on the expression of nerve growth factor and its low- and high-affinity receptors,” Developmental Brain Research 85, 96-108 (1995)
ABSTRACT: The effects of mercury vapour on the production of nerve growth factor during development have been examined. Pregnant rats were exposed to two different concentrations of mercury vapour during either embryonic days E6-E11 (early) or E13-E18 (late) in pregnancy, increasing the postnatal concentration of mercury in the brain from 1 ng/g tissue to 4 ng/g tissue (low-dose group) or 11 ng/g (high-dose group). The effect of this exposure in offspring was determined by looking at the NGF concentration at postnatal days 21 and 60 and comparing these levels to age-matched controls from sham-treated mothers. Changes in the expression of mRNA encoding NGF, the low- and high-affinity receptors for NGF (p75 and p140 trk. respectively) and choline acetyltransferase (ChAT) were also determined. When rats were exposed to high levels of mercury vapour during early embryonic development there was a significant (62%) increase in hippocampal NGF levels at P21 accompanied by a 50% decrease of NGF in the basal forebrain. The expression of NGF mRA was found to be unaltered in the dentate gyrus. The expression of p75 mRNA was significantly decreased to 39% of control levels in the diagonal band of Broca (DB) and to approximately 50% in the medial septal nucleus (MS) whereas no alterations in the level of trk mRNA expression were detectable in the basal forebrain. ChAT mRNA was slightly decreased in the DB and MS, significantly in the striatum. These findings suggest that low levels of prenatal mercury vapour exposure can alter the levels of the NGF and its receptors, indicating neuronal damage and disturbed trophic regulations during development.
Aschner M, Lorscheider FL, Cowan KS, Conklin DR, Vimy MJ, Lash LH “Metallothionein induction in fetal rat brain and neonatal primary astrocyte cultures by in utero exposure to elemental mercury vapor (Hg0).” Brain Res 1997 Dec 5;778(1):222-32
ABSTRACT: Brain metallothionein (MT) protein and mRNA levels were determined in the fetal rat following in utero (gestational days 7-21) exposure to elemental mercury vapor (Hg0; 300 microg Hg/m3; 4 h/day). Total RNA was probed on Northern blots with [alpha-32P]dCTP-labeled synthetic cDNA probes specific for rat MT isoform mRNAs. The probes for MT-I and MT-II mRNA hybridized to a single band of approximately 550 and 450 nucleotides, respectively. Expression of whole brain MT-I mRNA in full-term fetal rats (day 21) was significantly increased (P < 0.03) by in utero exposure to Hg0 compared to nonexposed controls. This corresponded to a 14-fold increase (P < 0.001) in fetal brain Hg concentration after in utero Hg0 exposure. In addition, astrocytes from both control and in utero Hg0-exposed fetuses were isolated, and neonatal primary astrocyte cultures were established and maintained in vitro for up to 3 weeks without additional experimental intervention. Astrocyte monolayers derived from in utero Hg0-exposed fetuses consistently expressed increased abundance of MT-I mRNA transcripts after 1, 2, and 3 weeks in culture (P < 0.03, P < 0.01, and P < 0.03, respectively) compared with controls. The abundance of astrocyte MT-II mRNA was unchanged at 1 and 2 weeks in culture, but was significantly increased at 3 weeks in cultures derived from brains of Hg0-exposed fetuses (P < 0.04). Consistent with the increase in MT mRNA, an increase in astrocytic levels of MT proteins was noted by Western blot analysis and MT-immunoreactivity. These studies suggest that in utero exposure to Hg0 induces brain MT gene expression, and that MT mRNAs and their respective proteins are useful quantitative biochemical markers of intrauterine exposure to Hg0, a potentially cytotoxic challenge to astrocytes in the developing brain. It is concluded that induction of MT by fetal/neonatal astrocytes represents an attempt by these glial cells to protect against Hg cytotoxicity in maintaining cerebral homeostasis.
III c) Human Study
Drasch et. al. “Mercury Burden of Human Fetal and Infant Tissues” European Journal of Pediatrics (August 1994).
ABSTRACT: The total mercury concentrations in the liver (Hg-L), the kidney cortex (Hg-K) and the cerebral cortex (Hg-C) of 108 children aged 1 day- 5 years, and the Hg-K and Hg-L of 46 fetuses were determined. As far as possible, the mothers were interviewed and their dental status was recorded. The results were compared to mercury concentrations in the tissues of adults for the same geographical area. The Hg-K (n=38) and Hg-L (n=40) of fetuses and Hg-K (n=35) and Hg-C (n=35) of older infants (11-50 weeks of life) correlated significantly with the number of dental amalgam fillings of the mother. The toxicological relevance of the unexpected high Hg-K of older infants from mother with higher numbers of dental amalgam fillings is discussed. Conclusion: Future discussion on the pros and cons of dental amalgam should not be limited to adults or children with their own amalgam fillings, but also include fetal exposure. The unrestricted application of amalgam for dental restorations in women before and during the child-bearing age should be reconsidered. Abbreviations: Hg-C total mercury concentration in the cerebral cortex (ng/g wet weight). Hg-K total mercury concentration in the renal cortex (ng/g wet weight). Hg-L total mercury concentration in the liver (ng/g wet weight).
Kenny S. Crump, Tord Kjellstrom, Annette M. Shipp, Abraham Silvers, Alistair Stewart “Influence of Prenatal Mercury Exposure Upon Scholastic and Psycholgical Test Performance: Benchmeark Analysis of a New Zealand Cohort” Risk Analysis, Vol.18, No. 6, 1998.
This paper presents benchmark (BMD) calculations and additional regression analyses of data from a study in which scores from 26 scholastic and psychological tests administered to 237 6- and 7- year old New Zealand children were correlated with the mercury concentration in their mothers’ hair during pregnancy. The original analyses of five test scores found an association between high prenatal mercury exposure and decreased test performance, using category variables for mercury exposure. Our regression analyses, which utilized the actural hair mercury level did not find significant associations between mercury and children’s test scores. However, this finding was highly influenced by a single child whose mother’s mercury hair level (86 mg/kg) was more thatn four times that of any other mother. When that child was ommited, results were more indicative of a mercury effect and scores on six tests were significantly associated with the mothers’ hair mercury level. BMDs calculated from five tests ranged from 32 to 73 mg/kg hair mercury, and corresponding BMDs (95% lower limits on BMDs) ranged form 17 to 24 mg/kg. When the child with the highest mercury level was omitted, BMDs ranged from 13 to 21 mg/kg, and corresponding BMDLs ranged from 7.4 to 10 mg/kg.
IV) Alzheimer’s Disease Studies
Many on-going studies have linked many aspects of amalgam mercury to brain tissue damage found in patients with Alzheimer’s Disease. Abstracts from these on-going studies are presented below.
IV a) Trace Elements in Alzheimer’s Disease Brains
Wenstrup, D., Ehmann, W.D., and Markesbery W.R., “Trace Element Imbalances in Isolated Subcellular Fractions of Alzheimer’s Disease Brains” Brain Research, 533 125-131 Elsevier Science Publishers (1990).
ABSTRACT: Concentrations of 13 trace elements (Ag, Br, Co, Cr, Cs, Fe, Hg, K, Na, Rb, Sc, Se, Zn) in isolated subcellular fractions (whole brain, nuclei, mitochondria, microsomes) of temporal lobe from autopsied Alzheimer’s disease (AD) patients and normal controls were determined utilizing instrumental neutron activation analysis. Comparison of AD and controls revealed elevated Br (whole brain) and Hg (microsomes) and diminished Rb (whole brain, nuclear and microsomes), Se (microsomes) and Zn (nuclear) in AD. The elevated Br and Hg and diminished Rb are consistent with our previous studies in AD bulk brain specimens. Comparison of element ratios revealed increased Hg/Se, Hg/Zn and Zn/Se mass ratios in AD. Se and Zn play a protective role against Hg toxicity and our data suggest that they are utilized to detoxify Hg in the AD brain. Overall our studies suggest that Hg could be and important toxic element in AD. Whether Hg deposition in AD is a primary or secondary event remains to be determined.
Basun H, Forssell LG, Wetterberg L, Winblad B. “Metals and trace elements in plasma and cerebrospinal fluid in normal aging and Alzheimer’s disease.” J Neural Transm Park Dis Dement Sect 1991;3(4):231-58
ABSTRACT: Cerebro-spinal fluid (CSF) and blood levels of aluminum, cadmium, calcium, copper, lead, magnesium, and mercury were studied in 24 subjects with dementia of the Alzheimer type (DAT) and in 28 healthy volunteers. Furthermore, arsenic, bromine, chrome, iron, manganese, nickel, rubidium, selenium, strontium, and zinc were measured only in blood. There were significant changes in the DAT group when compared to the controls. The plasma levels of aluminum, cadmium, mercury and selenium were increased and the contents of iron and manganese were lower in the DAT group as compared to control subjects. In CSF there were low levels of cadmium and calcium and increased content of copper in DAT cases. Iron and zinc levels in blood and calcium in both blood and CSF of DAT patients correlated with memory and cognitive functions. Iron, manganese and strontium levels of DAT sufferers in blood and aluminum in CSF were related with changes in behavior.
C.R. Cornett, W.R. Markesbery, and W.D. Ehmann, “Imbalances of Trace Elements Related to Oxidative Damage in Alzheimer’s Disease Brain” NeuroToxicology 19(3): 339-346 (1998).
ABSTRACT: Four elements that have been implicated in free radical induced oxidative stress in Alzheimer’s Disease (AD) were measured by instrumental neutron activation analysis (INAA) in seven brain regions from 58 AD patients and 21 control subjects. A statistically significant elevation of iron and zinc was observed in multiple regions of AD brain, compared with controls. Mercury was elevated in AD in most regions studied, but the high variability of mercury levels in both AD and control subjects prevented the AD-control difference from reaching significance. Selenium, a protective agent against mercury toxicity, was significantly elevated only in AD amygdala. The elevation of iron and zinc in AD brain has the potential of augmenting neuron degeneration through free radical processes.
IV b) Mercury Vapor Inhalation Inhibits Tubulin in Rat Brain
James C. Pendergrass, Boyd E. Haley, Murray J. Vimy, Stewart A. Winfield and Fritz L. Lorscheider, “Mercury Vapor Inhalation Inhibits Binding of GTP to Tubulin in Rat Brain: Similarity to a Molecular Lesion in Human Alzheimer Brain.” NeuroToxicology 18(2): 315-324, 1997.
ABSTRACT: Mercury (Hg) interacts with brain tubulin and disassembles microtubules that maintain neurite structure. Since it is well known that Hg vapor is continuously released from “silver” amalgam tooth fillings and is absorbed into brain, rats were exposed to Hg 4 hr/day for 0, 2, 7, 14, and 28 days at 250 or 300 mcg Hg/m3 air, concentrations present in mouth air of some humans with many amalgam fillings. Average rat brain Hg concentrations increased significantly (11-47 fold) with duration of Hg exposure. By 14 days of Hg exposure, photoaffinity labeling of the B-subunit of the tubulin dimer with (a32P)8N3GTP in brain hamogenates was decreased 41-74% , upon analysis of SDS-PAGE autoradiograms. The identical neurochemical lesion of similar or greater magnitude is evident in Alzheimer brain homogenates from approximately 80% of patients, when compared to human age-matched controls. Since the rate of tubulin polymerization is dependent upon binding of GTP to tubulin dimers, we conclude that chronic inhalation of low-level Hg can inhibit polymerization of tubulin essential for formation of microtubules.
IV c) HgEDTA Complex Inhibits Tubulin
E.F. Duhr, J.C. Pendergrass, J.T. Slevin, and B.E. Haley, “HgEDTA Complex Inhibits GTP Interactions with the E-Site of Brain B-Tubulin,” Toxicology and Applied Pharmacology 122, 273-280 (1993).
We have found that EDTA and EGTA complexes of Hg2+, which conventional wisdom has assumed are biologically inert, are potentially injurious to the neuronal cytoskeleton. Tubulin, a major protein component of the neuronal cytoskeleton, is the target of multiple toxicants, including many heavy metal ions. Among the mercurials, inorganic mercuric ion (HG2+) is one of the most potent inhibitors of microtubule polymerization both in vivo and in vitro. In contrast to other heavy metals, the capacity of Hg2+ to inhibit microtubule polymerization or disrupt formed microtubules cannot be prevented by the addition of EDTA and EGTA, both of which bind Hg2+ with very high affinity. To the contrary, the addition of these two chelating agents potentiates Hg2+ inhibitiion of tubulin polymerization. Results herein show that HgEDTA and HgEGTA inhibit tubulin polymerization by disrupting the interaction of GTP with the E-site of brain B-tubulin, an obligatory step in the polymerization of tubulin. Both HgEDTA and HgEGTA, but not free Hg2+, prevented binding of (32P)8N3GTP, a photoaffinity nucleotide analog of GTP, to the E-site and displaced bound (32P)8N3GTP at low micromolar concentrations. This complete inhibition of photoinsertion into the E-site occured in a concentration and time dependent fashion and was specific for Hg2+ complexes of EDTA and EGTA, among the chelating agents tested. Given the ubiquity of Hg2+ in the environment and the widespread use of EDTA in foodstuffs and medicine, these mercury complexes may pose a potentially serious threat to human health and play a role in diseases of the neuronal cytoskeleton.
IV d) Increased Blood Mercury Levels in Patients with Alzheimer’s Disease
C. Hock, G. Drasch, S. Golombowski, F. Muller-Spahn, B. Willershausen-Zonnchen, P. Schwarz, U. Hock, J.H. Growdon, R.M. Nitsch “Increased Blood Mercury Levels in Patients with Alzheimer’s Disease” Journal of Neural Transmission, 105: (1998).
SUMMARY: Alzheimer’s disease (AD) is a common neurodegenerative disorder that leads to dementia and death. In addition to several genetic parameters, various environmental factors may influence the risk of getting AD. In order to test whether blood levels of the heavy metal mercury are increased in AD, we measured blood mercury concentrations in AD patients (n=33), and compared them to age-matched control patients with major depression (MD) (n=45), as well as to an additional control group of patients with various non psychiatric disorders (n=65). Blood mercury levels were more than two fold higher in AD patients as compared to both control groups (p=0.0005, and p=0.0000, respectively). In early onset AD patients (n=13), blood mercury levels were almost three fold higher as compared to controls (p=0.0002, and p=0.0000, respectively). These increases were unrelated to the patients’ dental status. Linear regression analysis of blood mercury concentrations and CSF levels of amyloid B-peptide (AB) revealed a significant correlation of these measures in AD patients (n=15, r=0.7440, p=0.0015, Pearson type of correlation). These results demonstrate elevated blood levels of mercury in AD, and they suggest that this increase of mercury levels is associated with high CSF levels of AB, whereas tau levels were unrelated. Possible explanations of increased blood mercury levels in AD include yet unidentified enviromental sources or release from brain tissue with the advance in neuronal death.
IVe) Mercury Induces Cell Cytotoxicity and Oxidative Stress and Increases ÃŸ-Amyloid Secretion and Tau Phosphorylation in SHSY5Y Neuroblastoma Cells
G. Olivieri, Ch. Brack,, F. MÃ¼ller-Spahn, H. B. StÃ¤helin, M. Herrmann, P. Renard, M. Brockhaus and C. Hock. “Mercury Induces Cell Cytotoxicity and Oxidative Stress and Increases ÃŸ-Amyloid Secretion and Tau Phosphorylation in SHSY5Y Neuroblastoma Cells.” Journal of Neurochemistry, Vol. 74, No. 1, 2000 231-236.
ABSTRACT: Concentrations of heavy metals, including mercury, have been shown to be altered in the brain and body fluids of Alzheimer’s disease (AD) patients. To explore potential pathophysiological mechanisms we used an in vitro model system (SHSY5Y neuroblastoma cells) and investigated the effects of inorganic mercury (HgCl2) on oxidative stress, cell cytotoxicity, ÃŸ-amyloid production, and tau phosphorylation. We demonstrated that exposure of cells to 50 Âµg/L (180 nM) HgCl2 for 30 min induces a 30% reduction in cellular glutathione (GSH) levels (n = 13, p < 0.001). Preincubation of cells for 30 min with 1 ÂµM melatonin or premixing melatonin and HgCl2 appeared to protect cells from the mercury-induced GSH loss. Similarly, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assays revealed that 50 Âµg/L HgCl2 for 24 h produced a 50% inhibition of MTT reduction (n = 9, p < 0.001). Again, melatonin preincubation protected cells from the deleterious effects of mercury, resulting in MTT reduction equaling control levels. The release of ÃŸ-amyloid peptide (AÃŸ) 1-40 and 1-42 into cell culture supernatants after exposure to HgCl2 was shown to be different: AÃŸ 1-40 showed maximal (15.3 ng/ml) release after 4 h, whereas AÃŸ 1-42 showed maximal (9.3 ng/ml) release after 6 h of exposure to mercury compared with untreated controls (n = 9, p < 0.001). Preincubation of cells with melatonin resulted in an attenuation of AÃŸ 1-40 and AÃŸ 1-42 release. Tau phosphorylation was significantly increased in the presence of mercury (n = 9, p < 0.001), whereas melatonin preincubation reduced the phosphorylation to control values. These results indicate that mercury may play a role in pathophysiological mechanisms of AD.
IV f) Retrograde degeneration of neurite membrane structural integrity of nerve growth cones following in vitro exposure to mercury.
Christopher C. W. Leong, Naweed I. Syed, Fritz L. Lorscheider. “Retrograde degeneration of neurite membrane structural integrity of nerve growth cones following in vitro exposure to mercury.” NeuroReport 12 (4) pg 733-737, March 2001.
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 Lymnaea stagnalis were cultured for 48 h in 2 ml brain conditioned medium (CM). Following neurite outgrowth, metal chloride solution (2 ml) of Hg, Al, Pb, Cd, or Mn (10â€”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.