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“Dentists are exposed to mercury (Hg) during the removal of amalgam fillings. Recent research on dentists and other occupational groups report neurological impairment at Hg exposure levels below the current occupational TLV® (25 µg/m3) and/or the occupational BEI® (35 µg/ Hg/g creatinine in urine). Surveys of Hg° in the general office air of dental offices fail to measure the high levels of Hg-laden respirable amalgam particulate matter sprayed into the dentist’s breathing zone during the removal of old amalgam fillings. This respirable particulate matter represents the vast majority of daily Hg exposure in practicing dentists. Despite this, no research is available on the pharmacokinetic fate of inhaled particulate amalgam Hg in humans. What indirect data does exist demonstrates that absorption from the lung occurs but that fecal excretion may predominate. As a result, urine analysis for Hg may be ineffective as a means of occupational monitoring. Various countries are moving to limit the use of amalgam as a dental restorative material in order to protect dental patients from Hg exposure. However, dentists’ occupational exposure should also be considered as a justification for reduced amalgam use.”

“Mercury is a heavy metal widely used by man. It is considered very toxic causing conditions in the central nervous system, behavior disturbances, and renal and sexual disorders. For a century, mercury has been used in the dental practice for its capacity of joining metals (amalgamate), its low cost and its rapid fixing in dental pieces repair. Currently, there is much controversy about the safety of dental amalgams and it has been demonstrated it poses occupational risks to dental practitioners and their assistants. The objective of this study is review aspects related to metallic mercury toxicity for personnel involved in the dental practice and patients with dental amalgams. Routes of mercury exposure in dentistry, occupational risks and measures to prevent mercury poisoning are presented here. A literature review was conducted mostly on data from Biological Abstracts and the Science Citation Index for the period between 1990 and 2000.”

“Large autism epidemics have recently been reported in the United States and the United Kingdom. Emerging epidemiologic evidence and biologic plausibility suggest an association between autistic spectrum disorders and mercury exposure. This study compares mercury excretion after a three-day treatment with an oral chelating agent, meso-2,3- dimercaptosuccinic acid (DMSA), in children with autistic spectrum disorders and a matched control population. Overall, urinary mercury concentrations were significantly higher in 221 children with autistic spectrum disorders than in 18 normal controls (Relative Increase (RI)=3.15; P < 0.0002). Additionally, vaccinated cases showed a significantly higher urinary mercury concentration than did vaccinated controls (RI=5.94; P < 0.005). Similar urinary mercury concentrations were observed among matched vaccinated and unvaccinated controls, and no association was found between urinary cadmium or lead concentrations and autistic spectrum disorders. The observed urinary concentrations of mercury could plausibly have resulted from thimerosal in childhood vaccines, although other environmental sources and thimerosal in Rh (D) immune globulin administered to mothers may be contributory. Regardless of the mechanism by which children with autistic spectrum disorders have high urinary mercury concentrations, the DMSA treatment described in this study might be useful to diagnose their present burden of mercury.”

“The prevalence of autism in the US has risen from 1 in approximately 2500 in the mid-1980s to 1 in approximately 300 children in the mid-1990s. The purpose of this study was to evaluate whether mercury from thimerosal in childhood vaccines contributed to neurodevelopmental disorders. Neurodevelopmental disorder dose-response curves for increasing mercury doses of thimerosal in childhood vaccines were determined based upon examination of the Vaccine Adverse Events Reporting System (VAERS) database and the 2001 US’ Department of Education Report. The instantaneous dosage of mercury children received in comparison to the Food and Drug Administration (FDA)’s maximum permissible dose for the oral ingestion of methylmercury was also determined. The dose-response curves showed increases in odds ratios of neurodevelopmental disorders from both the VAERS and US Department of Education data closely linearly correlated with increasing doses of mercury from thimerosal-containing childhood vaccines and that for overall odds ratios statistical significance was achieved. Similar slopes and linear regression coefficients for autism odds ratios in VAERS and the US Department of Education data help to mutually validate each other. Controls employed in the VAERS and US Department of Education data showed minimal biases. The evidence presented here shows that the occurrence of neurodevelopmental disorders following thimerosal-containing childhood vaccines does not appear to be coincidental.”

“We studied exposure to methyl mercury (MeHg) in Swedish pregnant women (total mercury [T-Hg] in hair) and their fetuses (MeHg in cord blood) in relation to fish intake. The women were recruited at antenatal care clinics in late pregnancy to participate in an exposure study of environmental pollutants. Fish consumption was evaluated using food frequency questionnaires including detailed questions on fish consumption. In addition, we determined inorganic mercury (I-Hg) and selenium (Se) in cord blood. On average, the women consumed fish (all types) 6.7 times/month (range 0-25 times/month) during the year they became pregnant. They reported less consumption of freshwater fish–species that might contain high concentrations of MeHg–during than before pregnancy. T-Hg in maternal hair (median 0.35 mg/kg; range 0.07-1.5 mg/kg) was significantly associated (R2 = 0.53; p < 0.001) with MeHg in cord blood (median 1.3 microg/L; range 0.10-5.7 microg/L). Both hair T-Hg and cord blood MeHg increased with increasing consumption of seafood (r = 0.41; p < 0.001 and r = 0.46; p < 0.001, respectively). Segmental hair analysis revealed that T-Hg closer to the scalp was lower and more closely correlated with MeHg in cord blood than T-Hg levels in segments corresponding to earlier in pregnancy. We found a weak association between Se (median 86 microg/L; range 43-233 microg/L) and MeHg in cord blood (r = 0.26; p = 0.003), but no association with fish consumption. I-Hg in cord blood (median 0.15 microg/L; range 0.03-0.53 microg/L) increased significantly with increasing number of maternal dental amalgam fillings.”

“Dental amalgam is 50% mercury (Hg) by weight and its continued use as the preferred dental restorative material in Canada constitutes a significant source of Hg to municipal sewers and ultimately to the environment. The Recent CCME Canada Wide Standard on Hg for Dental Amalgam Waste provides a national basis for managing the Hg-containing wastes from dental clinics and ultimately reducing what is currently considered to be the single largest source of Hg to municipal sewers. This paper briefly reviews the background and rationale that lead to the need for and ratification of that Canada Wide Standard.”

“The use of DMPS as a diagnostic tool in patients with symptoms allegedly caused by mercury from dental amalgam fillings is disputed. We have previously shown that the mercury concentrations in urine cannot be used in such a way.In the present study, we wished to evaluate the effect on blood mercury levels (B-Hg) following intravenously injected DMPS in four groups of subjects: 19 controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients with self-reported symptoms from existing dental amalgams; and 20 patients who had removed amalgam fillings.A single dose of DMPS (2 mgykg) was injected.Blood samples were collected prior to the injection and after 15, 30, 120 min, and after 24 h, and mercury was analyzed by cold vapor atomic absorption spectrophotometry.All groups showed an initial drop of 24 to 30% in the blood levels, approaching baseline values (2.5–5.5 mgyl) after 2 h.The subjects with no amalgam experience had the lowest mercury values. There was no significant difference between the three groups with such experience.Ther e were no significant differences between the two groups with amalgam fillings present.Patients with symptoms allegedly caused by amalgam were not different from the control groups.Ther e were indications that part of the urinary mercury excreted during the first 30 min originated from blood.”

“There is a concern on the part of community that adverse health consequences by thimerosal, one of mercurial preservatives, may occur among infants during immunization schedule although it is generally believed that the safety of thimerosal use for humans has been established. Therefore, the effect of thimerosal on K562 human leukemia cells was compared with that of methylmercury. Incubation of K562 cells with thimerosal at micromolar concentrations for 72 hr inhibited the growth and increased the population of shrunken cells in a concentration-dependent manner. Significant changes in growth and population were seen in the case of 3 .MU.M thimerosal. The population of hypodiploidal cells was also greatly increased by 3 .MU.M thimerosal, suggesting that the thimerosal-induced apoptosis of K562 cells. The complete inhibition of growth was observed in the cells incubated with 10 .MU.M thimerosal. The potency of thimerosal to affect K562 cells was similar to that of methylmercury. Therefore, the attention may be paid on the use of thimerosal as a preservative in vaccines for infants.”

“Reported rates of autism have increased sharply in the United States and the United Kingdom. One possible factor underlying these increases is increased exposure to mercury through thimerosal-containing vaccines, but vaccine exposures need to be evaluated in the context of cumulative exposures during gestation and early infancy. Differential rates of postnatal mercury elimination may explain why similar gestational and infant exposures produce variable neurological effects. First baby haircut samples were obtained from 94 children diagnosed with autism using Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV) criteria and 45 age- and gender-matched controls. Information on diet, dental amalgam fillings, vaccine history, Rho D immunoglobulin administration, and autism symptom severity was collected through a maternal survey questionnaire and clinical observation. Hair mercury levels in the autistic group were 0.47 ppm versus 3.63 ppm in controls, a significant difference. The mothers in the autistic group had significantly higher levels of mercury exposure through Rho D immunoglobulin injections and amalgam fillings than control mothers. Within the autistic group, hair mercury levels varied significantly across mildly, moderately, and severely autistic children, with mean group levels of 0.79, 0.46, and 0.21 ppm, respectively. Hair mercury levels among controls were significantly correlated with the number of the mothers’ amalgam fillings and their fish consumption as well as exposure to mercury through childhood vaccines, correlations that were absent in the autistic group. Hair excretion patterns among autistic infants were significantly reduced relative to control. These data cast doubt on the efficacy of traditional hair analysis as a measure of total mercury exposure in a subset of the population. In light of the biological plausibility of mercury’s role in neurodevelopmental disorders, the present study provides further insight into one possible mechanism by which early mercury exposures could increase the risk of autism.”