Amalgam Fillings Research Articles

Dental amalgam implantation and thyroid autoimmunity

Mercury was heavily studied as a factor in the autoimmune processes. We aimed to observe whether mercury of amalgam is associated with Hashimoto disease. 363 patients with Hashimoto's thyroiditis and 365 control subjects were included in to the study. Amalgam fillings were checked by the physician. 363 (49.9 %) patients and 365 (50.1 %) healthy controls were included into the study. Hashimoto's thyroiditis was diagnosed with thyroid hormones, antithyroid antibody levels, and ultrasonographic findings. Control subjects were selected from patients with no known autoimmune diseases. They were controlled with ultrasonography, as well as antibody titers. None of them had Hashimoto's thyroiditis. Sex distribution of the study population was following: 319 (87.9 %) female, 44 (12.1 %) male in the patient group and 277 (75.9 %) male and 88 (24.1 %) female in healthy control subjects, respectively. Mean free T4 values for Hashimoto's thyroiditis and healthy control group were 15.30±0.76, 17.30±0.96 pmol/L and mean TSH values for Hashimoto's thyroiditis and healthy control group were 9.29±20.79, 1.20±0.32 uIU/ml. Frequency of dental amalgam implantation in patients with Hashimoto's thyroiditis was not statistically significantly different from healthy controls (p=186) (t=-1.324) CONCLUSIONS: Some studies identified mercury of amalgam as responsible for autoimmune thyroiditis. We studied whether amalgam fillings are more frequent in Hashimoto's thyroiditis patients and whether it is a causative factor for Hashimoto's thyroiditis. Statistical analysis revealed that there is no relation of amalgam with Hashimoto's thyroiditis (Tab. 1, Ref. 34).

Blood lead, cadmium and mercury among children from urban, industrial and rural areas of Fez Boulemane Region (Morocco): relevant factors and early renal effects.

To describe blood lead (Pb-B), cadmium (Cd-B) and mercury (Hg-B) levels in children living in urban, industrial and rural areas in Fez city (north of Morocco) and to identify the determinants and some renal effects of exposure. The study was conducted from June 2007 to January 2008 in 209 school children (113 girls, 96 boys), aged 6-12 years, from urban, industrial and rural areas in Fez city. Interview and questionnaires data were obtained. Blood and urinary samples were analyzed. The mean of blood lead levels (Pb-B) in our population was 55.53 μg/l (range: 7.5-231.1 μg/l). Children from the urban area had higher blood lead levels (BLLs) mean (82.36 μg/l) than children from industrial and rural areas (48.23 and 35.99 μg/l, respectively); with no significant difference between boys and girls. BLLs were associated with traffic intensity, passive smoking and infancy in the urban area. The mean of blood cadmium levels (BCLs) was 0.22 μg/l (range: 0.06-0.68 μg/l), with no difference between various areas. Rural boys had higher BCLs mean than rural girls, but no gender influence was noticed in the other areas. BCLs were associated with the number of cigarettes smoked at children's homes. The blood mercury levels (BMLs) mean was 0.49 μg/l (range: 0.01-5.31 μg/l). The BMLs mean was higher in urban and industrial areas than in the rural area with no gender-related difference. BMLs were associated with amalgam fillings and infancy in the urban area. About 8% of the children had BLLs ≥ 100 μg/l particularly in the urban area, microalbuminuria and a decrease in height were noticed in girls from the inner city of Fez and that can be related to high BLLs (89.45 μg/l). There is a need to control and regulate potential sources of contamination by these trace elements in children; particularly for lead.

In Vivo Alteration of Phase II Transformation Enzyme (GST) Levels by Stainless Steel Orthodontic Appliances

Orthodontic appliances includes bands, brackets and wires which are made up of stainless steel with the composition of roughly 8-12% nickel and 17-22% chromium and other trace metals. Corrosion of orthodontic appliances can have a toxic effect on surrounding oral tissues. The main aim of the study is to analyze the Glutathione s transferase activity in saliva and blood samples of patients undergoing Orthodontic treatment. The study group included 40 participants and Samples were taken in different time intervals: Group 1- Collection of samples before the appliances fixed, Group 2- Collection of sample after one week of fixed appliances, Group 3- Collection of sample after three months of fixed appliances each from the Orthodontic Department of A.B Shetty Memorial institute of dental sciences. Glutathione S transferase was estimated using 1-chloro, 2, 4-dinitrobenzene (CDNB) method. In case of Saliva group 3 (211.17±1.84) significantly increased compare to group 1 (87.05±3.86) and group 2 (118.74±2.8). In case of RBC lysate group 2(532.33±3.2) and group 3(512.40±1.16) were increased when compare to group 1(107.12±2.54). The Glutathione s transferase levels of patients increased over a period of time after treatment with orthodontic appliances but other factors like age of the patient, diet rich in antioxidants, light and strenuous physical activity, medication, amalgam fillings and genetic constitution of an individual also influenced the results.

Occupational and Environmental Exposure to Mercury among Iranian Hairdressers

The aim of this study was to describe the mercury concentrations in female hairdressers associated with occupational and environmental exposure through cosmetic products and amalgam fillings. Sixty-two hair and nail samples were collected randomly from Iranian hairdressers. Hg level determination was carried out using a LECO, AMA 254, Advanced Mercury Analyzer according to ASTM, standard No. D-6722. The mean mercury levels were 1.15 ± 1.03 ug/g and 1.82 ± 1.12 μg/g in the hair and nail samples, respectively with a positive correlation among them (r=0.98). A significant relation was also observed between Hg levels and the number of amalgam fillings (p<0.001), use of cosmetics (p<0.001), and use of gloves (p=0.02). The Hg levels in about one-third of the studied samples were higher than the USEPA-recommended 1 ug/g, which represents a serious health risk. Hairdressers with continuous use of cosmetics and a high number of amalgam fillings had significantly elevated mercury concentrations in their hair and nails, suggesting the importance of mercury exposure assessment in hidden, less-explored sources of Hg in the workplace.

Hair mercury and urinary cadmium levels in Belgian children and their mothers within the framework of the COPHES/DEMOCOPHES projects

A harmonized human biomonitoring pilot study was set up within the frame of the European projects DEMOCOPHES and COPHES. In 17 European countries, biomarkers of some environmental pollutants, including urinary cadmium and hair mercury, were measured in children and their mothers in order to obtain European-wide comparison values on these chemicals. The Belgian participant population consisted in 129 school children (6–11years) and their mothers (≤45years) living in urban or rural areas of Belgium.The geometric mean levels for mercury in hair were 0.383μg/g and 0.204μg/g for respectively mothers and children. Cadmium in mother's and children's urine was detected at a geometric mean concentration of respectively 0.21 and 0.04μg/l. For both biomarkers, levels measured in the mothers and their child were correlated. While the urinary cadmium levels increased with age, no trend was found for hair mercury content, except the fact that mothers hold higher levels than children. The hair mercury content increased significantly with the number of dental amalgam fillings, explaining partially the higher levels in the mothers by their higher presence rate of these amalgams compared to children. Fish or seafood consumption was the other main parameter determining the mercury levels in hair. No relationship was found between smoking status and cadmium or mercury levels, but the studied population included very few smokers. Urinary cadmium levels were higher in both mothers and children living in urban areas, while for mercury this difference was only significant for children. Our small population showed urinary cadmium and hair mercury levels lower than the health based guidelines suggested by the WHO or the JECFA (Joint FAO/WHO Expert Committee on Food Additives). Only 1% had cadmium level slightly higher than the German HBM-I value (1μg/l for adults), and 9% exceeded the 1μg mercury/g hair suggested by the US EPA.

The impact of the use of amalgams in the dentition on the appearance of the symptoms of restless legs syndrome developed by older people

Key words: amalgam, lesions to brain cells, restless legs syndrome. The incidence of restless legs syndrome (RLS) increases with advancing age. RLS impairs normal functioning and decreases quality of life in the older population. Many older subjects have amalgam dental fillings containing mercury. Toxic mercury contained in these fillings may injure nervous cells and thus cause the occurrence of restless legs syndrome. We assessed the relationship of RLS symptoms to the use of amalgam in the dentition in 104 older polish immigrants aged 59–97 years living in Penrhos (North West Wales). We applied the diagnostic criteria of the International Restless Legs Syndrome Study Group (IRLSSG) in the form of four questions of internationally used questionnaire in order to determine the appearance of the problem of RLS. In medical anamnesis we tackled the issue of the past and current possession of amalgam in the dentition, and the number of amalgam dental fillings and other metal dental restorative materials was examined. Subjects who answered yes (indicating presence of RLS) to the four consecutive questions had significantly higher number of amalgam dental fillings (2.3 vs 1.0; 2.5 vs 0.9; 2.3 vs 1, 2 and 2.5 vs 1.1; respectively) as compared to the subjects without RLS symptoms (Kruskal–Wallis test p -values were 0.04, 0.01, 0.08 and 0.03, respectively). The number of other metal dental restorative materials had no influence on RLS symptomatology. We conclude that while examining the correlates of the appearance of restless legs syndrome the use of amalgam in the dentition should be taken into account. The authors thank the elderly persons involved for their participation in this project.

Orofacial granulomatosis related to amalgam fillings

This paper reports on a case of Orofacial Granulomatosis (OFG) in which the presence of amalgam fillings appears to have played a part in the aetiology. Once these restorations were removed and replaced with an alternative composite restorative material, all symptoms and signs of OFG resolved completely. This case highlights the necessity to include dental metals in the patch test battery when performing delayed patch testing on patients with OFG.

Human brain mercury levels related to exposure to amalgam fillings

The safety of dental amalgam as the primary material in dental restoration treatments has been debated since its introduction. It is widely accepted that amalgam restorations continuously release elemental mercury (Hg) vapor, which is inhaled and absorbed by the body and distributed to tissues, including the brain. The aim of the present study was to investigate whether the presence of amalgam fillings is correlated with brain Hg level. The Hg levels in the parietal lobes of the brains of 32 cadavers were analyzed with an atomic absorption spectrometer with the mercury hydride system. A total of 32 brain samples were tested; of these, 10 were from cadavers with amalgam fillings, while 22 of them were amalgam free. Hg was detected in 60.0% (6 of 10) of the samples in the amalgam group and in 36.3% (8 of 22) in the amalgam-free group. The average Hg level of the amalgam group was 0.97 ± 0.83 µg/g (minimum: 0.3 µg/g and maximum: 2.34 µg/g), and in the amalgam-free group, it was 1.06 ± 0.57 µg/g (minimum: 0.17 µg/g and maximum: 1.76 µg/g). The results of the present study showed no correlation between the presence of amalgam fillings and brain Hg level.

Amalgam fillings to be phased down

Amalgam fillings to be phased down

Biomonitoring of cadmium, chromium, nickel and arsenic in general population living near mining and active industrial areas in Southern Tunisia

The human health impact of the historic and current mining and industrial activities in Tunisia is not known. This study assessed the exposure to metals in the population of Southern Tunisia, using biomonitoring. The aim of this pilot study was to evaluate metal exposure on 350 participants living near mining and active industrial areas in the South of Tunisia. Blood specimens were analyzed for metals (Cd, Cr, As, and Ni) by Atomic Absorption Spectrometer equipped with Zeeman background correction and AS-800 auto sampler by graphite furnace and graphite tubes with integrated L'vov platform. The sample population was classified according to different age groups, sex, smoking habit, sea food and water drinking consumption, occupational exposure, amalgam fillings and place of residence. The blood As, Cd, Cr and Ni values expressed as mean ± SD were 1.56 ± 2.49, 0.74 ± 1.15, 35.04 ± 26.02 and 30.56 ± 29.96 μg/l, respectively. Blood Cd and Ni levels in smokers were 2 and 1.2 times, respectively, higher than in non-smokers. Blood Cd levels increase significantly with age (p = 0.002). As, Cd and Ni were significantly correlated with gender and age (p < 0.05). Cd level in blood samples of subjects occupationally exposed was 1.3 times higher than that of non-exposed. Blood metals were not significantly affected by amalgam fillings, place of living and sea food and drinking water consumption. This first biomonitoring study of metal exposure in the South of Tunisia reveals a substantial exposure to several metals. The pathways of exposure and health significance of these findings need to be further investigated.

Predictors of mercury (Hg) exposure in breast-fed infants

This study was designed to investigate potential factors that might affect Hg exposure in mothers and their breast-fed infants. Total Hg was measured in the urine and breast milk of 155 mothers (18-42 yrs) and 102 infants (2.5-12.8 mon) living in Riyadh, the Capital of Saudi Arabia. The median (25th-75th) of Hg levels in mother’s urine, breast milk, and infant’s urine were respectively: 0.98 (0.6-1.68?g/g-Cr), 1.08 (0.77-1.40?g/L), and 5.27 (1.97-10.09?g/g-Cr). 48% of mothers and 89% of infants had urinary Hg&gt;1µg/g-Cr (the GerES reference value for adults and children without amalgam fillings). Though Hg in the urine of mother and their infants were correlated (P=0), borderline significant relationship was found between Hg in mother’s urine and breast milk (P=0.077). Bivariate analysis revealed that the use of skin-lightening creams was significantly associated with Hg in mother’s urine (P=0.029) and breast milk (P=0.048). The location of current residence was related to Hg in infant’s urine (P=0.002) and mother’s milk (P=0). Only Hg in infant’s urine was associated with smoking status (P=0.025). Urinary Hg levels were significantly higher in infants who are taking milk formula (P=0.022). No association was seen between the use of dental amalgam fillings or fish consumption and the levels of Hg in the urine or breast milk. Among demographic and socioeconomic factors, only parity (P=0.01), and the number of breast-fed children (P=0.005) had a negative effect on Hg in breast milk. Likewise, there was negative association between infant’s age and their urinary Hg levels (P=0.046). The results of the present study confirm the transfer of Hg from the mother to infants through breast-feeding. Though there might be other sources of Hg exposure that need further investigation, our current findings corroborate our earlier observation linking elevated levels in Hg to the use of skin-lightening creams.

Aggravated neuromuscular symptoms of mercury exposure from dental amalgam fillings

Dental amalgam fillings are widely used all over the world. However, their mercury content can lead to various side effects and clinical problems. Acute or chronic mercury exposure can cause several side effects on the central nerve system, renal and hepatic functions, immune system, fetal development and it can play a role on exacerbation of neuromuscular diseases. In this case, we will present a patient with vacuolar myopathy whose symptoms were started and aggravated with her dental amalgam fillings.

Calle Bengtsson in memoriam

Professor, former Editor-in-Chief, Calle Bengtsson recently passed away. We, his fellow researchers, co-workers and friends, mourn and miss him. During the last 10 years of his life he was very active as professor emeritus at the University of Gothenburg and continued to participate in research in the Population Study of Women in Gothenburg, the population survey he started 40 years ago in 1968 and which is still ongoing. He participated actively in the research group meetings and contributed his extensive expertise both with ideas and also suggestions for new studies on the important facts and details from all the studies that have been generated from the Study of Women. Calle Bengtsson was a farmer's son from a small rural village, where he grew up as number four of five siblings. His teacher at the elementary school strongly supported his ambition for medical training. Internal medicine was his first specialty, and it was at internal medicine at Sahlgrenska hospital in Gothenburg that he was given the task to start the Population Study of Women in Gothenburg. From 1968 Calle Bengtsson devoted much of his time as a researcher to involving 1462 women in periodic surveys to enable studies on many aspects of women's health. His research has been groundbreaking and to some extent unique – there is no population study of women in the world that has gone on for such a long time with such good participation rates and such careful follow-up. Calle Bengtsson's broad medical expertise paired well with a great interest in people and he was a very good colleague and research group leader who constantly supported and supervised numerous graduate students and research colleagues. He was also always very keen that the women who regularly participated in the Study of Women and contributed large amounts of health data would also receive information about their health conditions and be appreciated for their participation. Calle Bengtsson was a specialist in Family Medicine and a great representative of general practice in Sweden and Scandinavia. He was Editor-in-Chief of the Scandinavian Journal of Primary Health Care from 1996 until 2003. During this time, ownership of the journal was changed to the present state, as was the layout, and the publication rate of articles using qualitative methods increased. His great research network also included Iceland's and Finland's medical and primary care researchers and he often visited his colleagues in Reykjavik and Finland and gave – and received – the inspiration for continued research. He was awarded a medal by the President of Iceland, and was awarded honorary doctorates by the University of Tampere. Important achievements have been made by Calle Bengtsson's research concerning women's health. He has clearly shown that women's health is largely determined by different factors than men's health. Specifically, this applies, for example, to cardiovascular disease, in which he demonstrated that risk factors for women's cardiovascular diseases partly differ from those of men; that there is a connection between early menopause and osteoporosis; that the time after menopause is a positive time and there are not more women who have mental health problems after menopause than before; that much amalgam in teeth does not increase the risk of cancer or other diseases later in life; and that it is missing teeth rather than amalgam fillings that increase the risk of ill health. The loss of Calle Bengtsson is great. He held meaning for us as a role model, a research colleague, and a good friend, and he will be deeply missed.

Exposure to mercury among dental health workers in Turkey

To investigate the current status of exposure to mercury (Hg) among dental health workers in Turkey. A total of 115 persons working in the same hospital were included in the study and were divided into three groups. Group 1 consisted of 67 dentists; group 2 consisted of 21 dental personnel who work with amalgam, and group 3 consisted of 27 control subjects who work in the same hospital but are non-dental personnel. The number of amalgam fillings that have been made by the dentists and the number of own fillings of the subjects were recorded. Plasma Hg levels were found to be 3.76 ± 1.84, 3.54 ± 1.83, and 2.69 ± 0.97 µg/L in groups 1, 2, and 3, respectively. Hg concentrations in group 1 were significantly higher than the control group. There was no significant difference between groups 1 and 2. The number of amalgam fillings made by the dentists in the previous year correlated significantly with plasma Hg levels (r = 0.378, p < 0.01). There was no significant correlation between the own amalgam fillings in the teeth of the subjects and Hg levels. Preventive measures for protection from exposure to Hg are necessary for occupational health in dentistry and proper industrial hygiene rules should be emphasized to avoid contamination during work.

German health-related environmental monitoring: Assessing time trends of the general population's exposure to heavy metals

The German system of a health-related environmental monitoring is based upon two instruments: The German Environmental Survey (GerES) and the Environmental Specimen Bank (ESB). The ESB is a tool to describe time trends of human exposure. Each year approx. 500 students from 4 sampling locations are analysed for their heavy metal contents in blood, blood plasma, and urine. GerES is a nationwide representative cross-sectional study that has been conducted four times up to now. Both instruments have been used to measure heavy metals over the last decades and thus provide complementary information. Both instruments are useful to describe time trends. However, combining the two has an added value, which is demonstrated for heavy metals for the first time in this paper. Major results and the changing importance of sources of exposure to heavy metals (Pb, Cd, Hg, Au, Pt, U and Ni) are shown. This leads to the following conclusion about the today's relevance of exposure in Germany. For the study participants of the city of Muenster, lead in whole blood decreased from about 70 μg/l in 1981 to levels below 15 μg/l in 2009. GerES data of young adults confirmed this time trend and GerES IV on children revealed the decreasing relevance of lead in outdoor air and in drinking water. The concentrations of mercury in urine decreased because in Germany it is no longer recommended to use amalgam fillings for children. However, GerES IV and ESB data also demonstrate that despite the decline of these heavy metals exposures to nickel and uranium originating from drinking water are still of importance.

Total and methyl-mercury in hair and milk of mothers living in the city of Porto Velho and in villages along the Rio Madeira, Amazon, Brazil

High fish consumption and extended breastfeeding are hallmarks of traditional lifestyle in Western Amazonia. We studied sources of mercury exposure, fish-methylmercury (meHg) and dental-amalgam filling, in 75 urban and 82 rural lactating mothers. Total mercury was determined in all samples while meHg concentrations were determined in subsamples of milk (45) and hair (27) of urban mothers living in Porto Velho (PV) and in hair (46) and milk (37) of mothers living in traditional communities (TC) of the Rio Madeira. The TC mothers showed significantly higher median hair-Hg concentrations (8.2μgg(-1)) than PV mothers (1.3μgg(-1)). Median total Hg in milk of PV mothers (0.36ngg(-1)) was significantly lower (p=0.0000) than that found in milk of TC mothers (2.30ngg(-1)). The median meHg concentrations in milk of TC mothers were also significantly higher (1.0ngg(-1)) than in milk of PV mothers (0.07ngg(-1)). For urban mothers with low fish consumption rates (and relatively higher dental amalgam fillings) the proportion of inorganic Hg in milk was higher (85%) than in TC (62%). In TC mothers 51% of breast milk Hg concentrations were above 2ngg(-1) (world median concentrations), contrasting with 8% in PV mothers. Despite this, there was no significant correlation between total Hg concentrations in milk and either amalgam filling or daily fish consumption. Socioeconomic changes occurring in Western Amazonia are causing changes in fish-eating habits of urban mothers. However, traditional lifestyle and attendant high fish consumption in riverine populations can still impact total Hg and methylmercury concentrations in mothers' milk and hair.

Human Placenta and Markers of Heavy Metals Exposure: Esteban-Vasallo et al. Respond

We appreciate the interest of Pigatto et al. in our review (Esteban-Vasallo et al. 2012). We understand their concern regarding mercury amalgams; however, the purpose of our review was to summarize the available information on total mercury, cadmium, and lead levels in human placental tissue, obtained from studies that reported original quantitative data. Published evidence suggests a possible association between mercury released from mercury-containing dental amalgam fillings and levels of this metal in diverse fetal tissues (kidney, brain, and cord blood) (Drasch et al. 1994). In contrast, studies focusing on human placenta and amalgams are scarce and their results inconsistent. The only two studies included in our review that assessed a possible relationship between dental fillings and total mercury—a small study in Taiwan (46 women) (Hsu et al. 2007) and another in Jamaica (52 women) (Grant et al. 2010)—found no association. Only Ask et al. (2002) reported higher mercury levels in mothers with a higher number of fillings, but they studied inorganic mercury and not total mercury. None of the studies mentioned by Pigatto et al. in their letter (Clarkson and Magos 2006; Gundacker and Hengstschlager 2012; Richardson et al. 2011) includes original data, although we did identify an additional reference from those articles that might provide more data on this issue, a symposium abstract by Ursinyova et al. (2006). In this abstract, the authors described a significant correlation between the number of amalgams and placental mercury levels in 409 women; however, these findings have not yet been published in a full report that would allow us to better evaluate the results. In addition, Wannag and Skjaerasen (1975) seemed to provide original information, but we were unable to find this paper for our review. In this context, we have to disagree with Pigatto et al.; in our opinion, the association between mercury exposure from dental amalgam fillings and levels of this metal in human placenta cannot yet be considered as well-established.

Cadmium, mercury and lead in the blood of urban women in Croatia, the Czech Republic, Poland, Slovakia, Slovenia, Sweden, China, Ecuador and Morocco

The aim of the study was to make an international comparison of blood levels of cadmium (B-Cd), lead (B-Pb) and mercury (B-Hg) of women in seven European, and three non-European cities, and to identify determinants. About 50 women (age: 46-62) from each city were recruited (totally 480) in 2006-2009. Interview and questionnaire data were obtained. Blood samples were analysed in one laboratory to avoid interlaboratory variation. Between the European cities, the B-Pb and B-Cd results vary little (range of geometric means: 13.5-27.0 μg/l and 0.25-0.65 μg/l, respectively); the variation of B-Hg was larger (0.40-1.38 μg/l). Between the non-European cities the results for B-Pb, B-Cd and B-Hg were 19.2-68.0, 0.39-0.99 and 1.01-2.73 μg/l, respectively. Smoking was a statistically significant determinant for B-Cd, while fish and shellfish intakes contributed to B-Hg and B-Pb, amalgam fillings also contributed to B-Hg. The present results confirm the previous results from children; the exposure to lead and cadmium varies only little between different European cities suggesting that other factors than the living area are more important. The study also confirms the previous findings of higher cadmium and lead levels in some non-European cities. The geographical variation for mercury is significant.

Genetic susceptibility to methylmercury developmental neurotoxicity matters

Epidemiological studies have demon-strated the developmental neurotoxicityassociated with prenatal methylmercuryexposure (Grandjean and Landrigan,2006); However, susceptibility tomethylmercury toxicity may be increasedby genetic factors. This observationraises the question of possible depen-dence of developmental neurotoxicity ongenetic predisposition. A few years ago, aNational Research Council (NRC) eval-uation of the scientific background forrisk assessment concluded that “atten-tion should be directed to vulnerableindividuals and subpopulations thatmay be particularly susceptible or morehighly exposed” (National ResearchCouncil, 2009). The panel also notedthat “variability in susceptibility andvulnerability has received less detailedevaluation in most EPA health effectsassessments.” A previous NRC reviewestimated that, under certain circum-stances, individual susceptibility couldrange up to 50,000-fold, and as muchas 5% of the population could well beat least 25-fold more susceptible thanthe average (National Research Council,2000).In risk assessment, an uncertaintyfactor of 10 is commonly used to takeinto account intraspecies susceptibil-ity. In regard to methylmercury, at therecommendation of the NRC (NationalResearch Council, 2009), EPA used thedefault 10-fold intraspecies uncertaintyfactor. In contrast, the European FoodSafety Authority recently argued that,for methylmercury, a partial uncer-tainty factor of 2 would be sufficientwhen a benchmark dose level (BMDL)hadbeenobtainedfromabirthcohortthat would represent the most vul-nerable population (European FoodSafety Authority, 2012). The magni-tude of the intraspecies uncertaintyfactor therefore appears controversial,and better scientific documentationhas been recommended (Dorne, 2010).Given that gene-environment interac-tion (GxE) may also play a role in regardto disease pathogenesis in a more gen-eral sense, as highlighted by a recentNIH workshop (Bookman et al., 2011),the variability in susceptibility to neu-rotoxicity between population groupsappears to be an important researchpriority.The recent findings on GxE formethylmercury neurotoxicity are sup-ported by several previous studies. Thus,mutations in certain genes seem to conveya greater risk of elemental mercury-associated neurobehavioral deficits orsymptoms in adults working in dentalclinics(Echeverriaetal.,2006,2010;Heyeret al., 2008, 2009). This evidence wasrecently extended to children exposed toinorganic mercury from amalgam fillings(Woodsetal.,2012,2013).Thereasonsforsuch interactions are only partially under-stood, but some gene variants may predictagreaterretentionofmercurycompoundsin the body.Thus, gene mutations seem to affectthe retention of inorganic mercury andmethylmercury in the body, e.g., genesthat affect glutathione (GSH) and metal-lothionein metabolism (Gundacker et al.,2007; Schlawicke Engstrom et al., 2008;Wang et al., 2012). Other studies havealso considered absorption-distribution-metabolism-elimination (ADME) genesthat may be of importance. Thus,methylmercury is eliminated from theliver as GSH conjugates, and the rate-limiting enzyme for GSH synthesis isglutamyl-cysteine ligase (GCL), which iscomposed of a catalytic subunit (GCLC)and a modifier subunit (GCLM). Further,the glutathione-S-transferases (GST) cat-alyze the conjugation of GSH (Gundackeret al., 2007). A recent study in Swedenindicates that a

The association between amalgam dental surfaces and urinary mercury levels in a sample of Albertans, a prevalence study

ObjectiveThe objective of this study was to quantify the relationship between number of dental amalgam surfaces and urinary mercury levels.MethodsThis study uses participant data from a large philanthropic chronic disease prevention program in Calgary, Alberta, Canada. Urine samples were analysed for mercury levels (measured in μg/g-creatinine). T-tests were used to determine if differences in urine mercury were statistically significant between persons with no dental amalgam surfaces and one or more dental amalgam surfaces. Linear regression was used to estimate the change in urinary mercury per amalgam surface.ResultsUrinary mercury levels were statistically significantly higher in participants with amalgam surfaces, with an average difference of 0.55 μg/g-creatinine. Per amalgam surface, we estimated an expected increase of 0.04 μg/g-creatinine. Measured urinary mercury levels were also statistically significantly higher in participants with dental amalgam surfaces following the oral administration of 2,3-dimercaptopropane-l-sulfonate (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) which are used to mobilize mercury from the blood and tissues.DiscussionOur estimates indicate that an individual with seven or more dental amalgam surfaces has 30% to 50% higher urinary mercury levels than an individual without amalgams. This is consistent with past literature that has identified seven amalgam surfaces as an unsafe level of exposure to mercury vapor. Our analysis suggests that continued use of silver amalgam dental fillings for restorative dentistry is a non-negligible, unnecessary source of mercury exposure considering the availability of composite resin alternatives.