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Neurotoxic Effects of Mercury Exposure in Dental Personnel
Abstract
Numerous studies have reported neurobehavioural effects in dental personnel occupationally exposed to chronic low levels of mercury (Hg). Mercury exposure from dental work may also induce various chronic conditions such as elevation of amyloid protein expression, deterioration of microtubules, and increase or inhibition of transmitter release at motor nerve terminal endings. Therefore, clinical studies of Hg toxicity in dentistry may provide new knowledge about disturbed metal homeostasis in neurodegenerative diseases like Alzheimer's disease, multiple sclerosis and mood disorders. The purpose of this MiniReview is to evaluate the evidence of possible relevance between Hg exposure in dentistry and idiopathic disturbances in motor functions, cognitive skills and affective reactions, as well as dose‐response relationships.
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... Elemental mercury spills can be still found at home and schools and have been associated with symptoms concordant with mercury vapor exposure (for instance, cough, headache, sore throat, shortness of breath, and visual disturbances) (47,48). The release of mercury from dental k k k k MERCURY 7 amalgam fillings, especially copper amalgam, otherwise is the predominant source of human exposure to elemental mercury in the general population (49,50), and particularly in dental personnel (34,51,52). Increased release occurs in gum-chewers (51). ...
... The release of mercury from dental k k k k MERCURY 7 amalgam fillings, especially copper amalgam, otherwise is the predominant source of human exposure to elemental mercury in the general population (49,50), and particularly in dental personnel (34,51,52). Increased release occurs in gum-chewers (51). ...
... However, after low or moderate chronic levels of exposure, the major functional lesions are found in the central nervous system and kidneys. The neurological effects of Hg 0 can be manifested by behavioral, motor, cognitive and other deficits (51,63,64,81). ...
Mercury is a global pollutant that exists in three oxidation states: Hg ⁰ (metallic), Hg ⁺ (mercurous), and Hg ²⁺ (mercuric) mercury. In organometallic derivatives, such as methylmercury (CH 3 Hg ⁺ ), mercury is covalently bound to carbon. In its elemental form, mercury is a dense, silvery‐white, shiny metal, which is liquid at room temperature and boils at 357°C. At 20°C, the vapor pressure of the metal is 0.17 Pa (0.0013 mmHg), and a saturated atmosphere at this temperature contains a mercury concentration of 14 mg Hg/m ³ , which is more than 200 times the occupational exposure limit. Hg ⁰ residence in the atmosphere can be high (greater than a year). Mercury compounds differ greatly in their solubility, with metallic mercury being very sparingly soluble, and several salts, such as mercuric chloride, being soluble in water. Of relevance for its environmental fate, methylmercury interacts with nucleophilic groups (i.e. thiols) in aquatic organisms (mainly fish), being bioaccumulated and biomagnified in the aquatic food chain, which represents a major source of human exposure. Both Hg ²⁺ and methylmercury have strong affinity for thiol groups, in such a way that in the presence of living cells and dissolved organic matter, they will be found mainly bound to sulfide‐ or thiol‐containing molecules.
... Exposure to some of these metals such as mercury is extremely dangerous in very small amounts and can cause acute and chronic toxicity in humans [5]. Among the heavy metals, mercury has unique physicochemical properties, according to which human exposure to its various compounds has caused a great deal of environmental and health concerns worldwide [6][7][8]. Mercury is known to be the most dangerous element after arsenic and lead [9]; Agency for Toxic Substances and Disease Registry (ATSDR) has classified it as the third element of the highest priority pollutants [10]. Accordingly, mercury effects on health of human have extensively been studied by various authors and international agencies [11][12][13][14][15][16][17][18][19][20][21][22][23]. ...
... In addition, mercury can become one of the most toxic forms in the environment, namely methyl mercury, and via accumulating in the food chain (especially contaminated fish and seafood) and being consumed by humans, it causes serious toxicity and damage to various human organs [29]. Mercury mainly affects the central nervous system [30,31], but can also damage other major organs such as the brain and kidneys [7]. It simply crosses the barriers of blood-brain and is rapidly converted to mineral mercury by the intracellular reaction and remains in the brain for many years [32]. ...
... Blood mercury may reflect inorganic mercury exposure in recent weeks, but this amount is also affected by the consumption of organic mercury in food [82]. So, increased BML can occur after prolonged exposure to inorganic mercury [7]. Although it is difficult to distinguish between occupational and non-occupational exposure to mercury in human biological samples, in the study by Sadeghneiat et al. [66], via removing the effect of seafood consumption, the reason for high levels of mercury in dentists was found to be directly by inhalation of EMVs while working with DA. ...
Exposure to mercury is an important risk to dentists health. The aim of the present study was to assess the pooled mean mercury level (MML) in the urine, blood, nail, and hair of Iranian dentists (IDs) through the meta-analysis technique. Comprehensive and systematic searches were performed in main local databases including SID, Magiran, Iran medex, and ISC as well as internationally available databases including Embase, PubMed and Scopus for all the relevant studies up to 2018. In order to prevent bias in this study and identify eligible studies, various steps of the study was performed independently by two researchers. Out of 13 studies in the meta-analysis process which included 1499 IDs, the mean of the mercury level in the urine, nail, and blood was estimated to be 6.29 (95% CI: 2.61–9.97, I-square: 62.7%, P: 0.006), 3.54 (95% CI: 2.81–4.28, I-square: 0.0%, P: 0.968), 11.20 (95% CI: 2.28–20.13, I-square: 59.9%, P: 0.082), respectively. The mean mercury level (MML) in the biological samples of IDs was higher than the standard of World Health Organization (WHO). So, in accordance with Article 10 of the European Union Regulations (EUR), in the context of the Minamata Convention (MC) on Dental Amalgam (DA), in order to avoid the dangers of mercury exposure in dentists, it is necessary for Iran and other countries to approve laws and to implement a national plan to reduce mercury levels and replace the appropriate materials.
... Contrary to our findings, a study conducted in Pakistan in 2019 found that an overwhelming majority of 216 dentists (90.4%) believed that amalgam poses a health risk to both dental staff and patients [8]. ...
... This is an extremely polluting method. Capsule users are only potentially exposed when they are opened[5] [8].-Placing and removing the amalgam In our study, 82.8% of dentists do not place any amalgam per month and 23.7% do not place any amalgam per month. ...
... As soon as exposure to mercury vapor ceases, mercury level in the blood and urine decreases, but the amount of mercury that accumulates in organs which those in the central nervous system (CNS), may still be high. 15 Demonstrating the effects of microRNA (miRNA) in neurological diseases is not only helpful in understanding the etiology and pathophysiology of these diseases but also in developing more effective diagnosis and treatment methods. Abnormal miRNA functions have been reported to cause neurodegeneration. ...
... 25 Some neurobehavioral symptoms, decreased psychomotor speed, decreased cognitive flexibility, attention deficit, memory loss, fatigue, and sleep disorders have been explained to be related with mercury content in amalgam. 15 Although no toxic cases have been reported, researchers report that dental amalgam may be associated with Alzheimer's Disease and Parkinson's disease with current data. 38 Consistent with the literature, the serum mercury levels of patients with amalgam filling were higher than those of the other groups in the present study. ...
Background: The aim of this study was to investigate the relationship between serum mercury and some plasma microRNA (miRNA) levels associated with neurological diseases in patients with amalgam filling and dentists. Methods: This study included 30 patients with amalgam filling, 30 dentists, and 30 healthy individuals as the control group. Circulating plasma miRNAs (124-3p, 125-5p, and 127-3p) were evaluated using real-time quantitative polymerase chain reaction analysis. The serum mercury levels were measured using inductively coupled plasma-mass spectrometry. ANOVA and Tukey’s multiple comparison tests were used for statistical analyses (α =.05). Results: A significant difference in serum mercury and plasma miRNA levels was found between the groups. Significant positive correlations between serum mercury and plasma miRNA 125-5p and 127-3p levels were detected in the patient group (r: 0.56 and r: 0.39, respectively). Serum mercury and plasma miRNA-125-5p levels showed a positive correlation in the dentist group (r: 0.37). Conclusion: Having amalgam filling caused a significant increase in serum mercury and plasma miRNA levels. The presence of a positive correlation suggests that sensitivity to neurological diseases may increase because of mercury exposure. Alternative restorative materials should be preferred for amalgam filling and amalgam fillings should be replaced with other restorative materials under necessary preventions.
... Mercury has been recognized primarily for its adverse effects on the central nervous system and kidneys in humans (Bjørklund et al., 2019;Bridges and Zalups, 2017;Harari et al., 2012). Other effects related to mercury exposure are damage to the respiratory, cardiovascular, reproductive, and hepatic systems, as well as genotoxicity and immunotoxicity (EPA, 2020; Rice et al., 2014;WHO, 2017). ...
Mercury is a ubiquitous environmental xenobiotic; the primary sources of exposure to this metal are artisanal gold mining and the direct production of mercury. In Mexico, artisanal mercury mining continues to be an important activity in different regions of the country. Exposure to mercury vapors releases can have severe health impacts, including immunotoxic effects such as alterations in cytokine profiling. Therefore, in the present work, we evaluated the inflammatory cytokines profile in the blood serum of miners exposed to mercury. A cross-sectional observational study was performed on 27 mining workers (exposed group) and 20 control subjects (nonexposed group) from central Mexico. The mercury urine concentration (U-Hg) was determined by atomic absorption spectrometry, and IL-2, IL-6, IL-8, IL-10, and TNF-α were measured using a Multiplex Assay. The results showed that the U-Hg in the miners had a median value of 552.70 μg/g creatinine. All cytokines showed a significant increase in the miner group compared with the control group, except for TNF-α. In addition, we observed a positive correlation between U-Hg concentration and cytokine levels. In conclusion, mercury exposure correlated with cytokine levels (considered acute inflammatory marker) in miners; therefore, workers exposed to this metal show an acute systemic inflammation that could lead to alterations in other organs and systems.
... Fish contaminated due to pollution is the primary origin of mercury, mainly in the form of methylmercury. Moreover, in countries that still permit the production of amalgam used for dental fillings, mercury poses a professional risk for dentists [50,53]. ...
Obesity and metabolic syndrome are global health concerns associated with development of different types of diseases and serious health threats in the long term. Their metabolic imbalance can be attributable to inherited and environmental factors. As a considerable environmental agent, heavy metals exposure can predispose individuals to diseases like obesity. This systematic review and meta-analysis aimed to evaluate the association between heavy metals exposure and the risk of obesity.
PubMed/MEDLINE, EMBASE and Web of Science were systematically searched until December 17, 2022. Only observational studies that evaluated heavy metals exposure and obesity were included. Studies were excluded if they assessed maternal or prenatal exposure, the mixture of heavy metals and other chemicals, reported the association with overweight or other diseases, and undesirable study designs. The Joanna Briggs Institute checklist was used for quality assessment. The pooled adjusted odds ratio (aOR) and the pooled standardized mean difference (SMD) with their 95% confidence intervals (CIs) were calculated, respectively. The publication bias was evaluated using Egger's and Begg's tests.
Twenty studies (n = 127755), four case–control and sixteen analytical cross-sectional studies, were included. Lead exposure was significantly associated with a lower risk of obesity (aOR: 0.705, 95% CI: 0.498–0.997), while mercury (aOR: 1.458, 95% CI: 1.048–2.031) and barium (aOR: 1.439, 95% CI: 1.142–1.813) exposure increased the risk of obesity. No significant publication bias was found and the studies had a low risk of bias.
Overall, lead exposure reduced obesity risk, while mercury and barium exposure raised it. Further large-scale observational studies are recommended to determine the roles of heavy metals in obesity.
Study registration ID: CRD42023394865.
... Bjorklund G. и соавт. [35] указывали, что по сравнению с лицами, не подвергавшимися воздействию ртути, специалисты стоматологического профиля во время работы с зубной амальгамой чаще сообщали о нейроповеденческих проблемах, снижении скорости психомоторных реакций, когнитивной гибкости, дефиците внимания, потере памяти, усталости и проблемах со сном. Эти наблюдения, а также широкое применение зубных амальгам во многих странах подтверждают необходимость профилактических мер, направленных на снижение воздействия ртути. ...
The analysis of the data of foreign and domestic literature devoted to the main risk factors for health is carried out and presented, the diseases of medical workers of modern dental practice that are more common at present are studied and described. A distinctive feature of the work of practicing dentists is the influence on their body of a complex of unfavourable factors of the production environment of occupational and non-occupational genesis (biological, chemical, physical and factors of the labour process). It is also common for them to be affected by the intensity of the labour process, which is expressed by significant psycho-emotional stress. Dentists are often at high risk of infection and transmission of dangerous pathogens: viruses (herpes, human immunodeficiency virus, hepatitis B and C, including new coronavirus infection (COVID-19)), bacteria (staphylococcus, tuberculosis), fungi. They have a high prevalence of injuries to the visual organ and upper extremities, allergic reactions. Among dental personnel in countries using amalgam during work, changes in neuropsychiatric reactions, memory loss, and fatigue are described; changes in biochemical parameters of blood, urine analysis are revealed. Physiological and ergonomic loads of dental service specialists and uncomfortable postures associated with work lead to the development of diseases of the musculoskeletal system and the appearance of pain, and affect their quality of life. Despite the harmlessness of the noise level in modern dentistry, the sounds produced by devices at work affect the mental health of dentists. Dental professionals with long work experience are predisposed to the highest risk of hearing loss. Today, dentists continue to show carpal tunnel syndrome and rarely vibration disease from exposure to local vibration. Medical workers of modern dental practice are shown to be affected by a complex of unfavourable factors of the low-intensity production environment and develop diseases associated with their occupational activities.
... However, the properties of the metallic ions (pH, redox potential, and the possible formation of complex metallic compounds) are essential factors in determining the potential toxicity [41]. In addition, other important factors can affect the exposure-response relationship, such as the route and time of exposure, biological factors, skin permeability, and the diet of exposed individuals [42][43][44]. Therefore, dentists, dental students, and dental personnel should evaluate the already reported toxic effects of metal exposure in the dental environment (Table 2) and consider the potential risks of the metallic elements to which they are exposed (Table 3). ...
The dental environment is being polluted with metals from dental materials in many ways, mainly due to aerosol-generating procedures; this could affect the long-term well-being of dentists, dental students, and dental personnel. The current dental pollution incorporates metallic nanoparticles, which are highly reactive and quickly become airborne, especially those particles that become unbound in the bulk composition. In addition, liquid mercury or mercury vapors may be released from dental amalgam, causing concerns in the dental community. In our study, we reviewed the behavior of metallic elements present in dental materials, their routes of exposure, and their potentially toxic effects on the dental team. This review found that skin and lung disorders are the most harmful effects of metallic exposure for dentists, dental students, and dental personnel. Therefore, chronic exposure to low concentrations of metals in the dental environment, especially in nanosized forms, should be further investigated to improve the environmental matrix, material choice, and safety protocols.
... Dünya Sağlık Örgütü tarafından idrarda kabul edilebilir cıva seviyesi <20 µg/L (<100 nmol/L) olarak belirlenmiştir (26). Çeşitli ülkelerde çalışan diş hekimlerinin idrar cıva miktarının araştırıldığı 1988-2017 yılları arasında yayımlanan makaleler incelendiğinde diş hekimlerinin ve diğer diş hekimliği meslek çalışanlarının cıva buharına maruziyet düzeylerinin kontrol gruplarına kıyasla daha yüksek saptandığı ancak idrarda kabul edilebilir cıva düzeyinin aşılmadığı görülmektedir (14,(27)(28)(29). ...
Amaç: Cıva, doğada doğal olarak bulunan, oda sıcaklığında buharlaşabilen ve yüksek toksisite gösteren bir ağır metaldir. Diş hekimliği alanında kullanılan cıvalı materyaller ve amalgam dolgular nedeniyle cıvanın toksikolojik ve ekolojik zararlarından söz edilmektedir. Bu araştırma kapsamında diş hekimlerinin diş hekimliği uygulamaları nedeniyle cıvaya maruziyetleri ve cıvaya maruziyetin önlenmesi için iş sağlığı ve güvenliği, çevre kontrol uygulamaları yolu ile alınacak tedbirlerin ortaya konulması amaçlanmıştır. Yöntem ve Gereç: Çalışma kapsamında gönüllü 41 diş hekiminden alınan idrar örneklerinde indüktif eşleşmiş plazma- kütle spektrometrisi ile cıva analizi yapılmıştır. İdrar cıva analizlerini takiben İstanbul Yeni Yüzyıl Üniversitesi Diş Hekimliği Fakültesi Hastanesi’nde 5 farklı klinikte cıva buharı ölçümü atomik absorpsiyon spektrometre cihazında NIOSH 6009 standardına göre gerçekleştirilmiştir. Bulgular: İdrar cıva analizleri sonucunda en düşük idrar cıva miktarı 0,14 μg/L iken en yüksek idrar cıva miktarı ise 4,12 μg/L olarak bulunmuştur. Dünya Sağlık Örgütü tarafından idrarda kabul edilebilir cıva seviyesi <20 μg/L (<100 nmol/L) olarak belirlenmiş ve idrar örneklerinin tamamında cıva seviyesi bu sınır değerin altında bulunmuştur. İstanbul Yeni Yüzyıl Üniversitesi Diş Hekimliği Fakültesi Hastanesi’nde gerçekleştirilen ölçümlerde en düşük cıva buharı miktarı 0,0021 mg/m3 ve en yüksek cıva buharı miktarı 0,0023 mg/m3 olarak tespit edilmiştir. Bu sonuçlar, iş yeri ortamı için ulusal standardımızda belirlenen 0,02 mg/m3 sınır değerinin ve uluslararası kabul görmüş sınır değerlerin altında kalmaktadır. Sonuç: İş sağlığı ve güvenliği açısından değerlendirildiğinde elde ettiğimiz bulgular, diş hekimleri için amalgam kaynaklı cıva maruziyetinin önemsiz seviyelerde olduğunu ortaya koymuştur. Bu durum, Minamata Sözleşmesi’nin uygulamaya alınması, iş sağlığı ve güvenliği politikalarının ve uygulamalarının yaygınlaşması, gelişen teknoloji ve teknikler gibi etkenler ile ilişkilendirilebilir.
... Accordingly, the contamination of water, soil, and the environment by heavy and transition metal (HTM) ions have aroused global concern for their significant hazardous characteristics, such as extremely harmful effects on human health and the environment (Mishra et al. 2019;Rabiee et al. 2022;Rice et al. 2014;Seidi et al. 2021aSeidi et al. , 2022. Thus, toxic heavy metals with persistent bioaccumulation lead to environmental pollution and injurious effects on the human body because of their high toxicity, stimulus, indestructibility, and accumulation in biological and environmental systems (Bjørklund et al. 2018;Boening 2000;Ding et al. 2007;Scheuhammer et al. 2015). ...
A precise nano-scale biosensor was developed here to detect Hg2+ in aqueous media. Nitrogen-doped carbon nanospheres (NCS) created from the pyrolysis of melamine–formaldehyde resin were characterized by FESEM, XRD, Raman spectra, EDS, PL, UV–vis spectra, and N2 adsorption–desorption, and were used as a highly selective and sensitive probe for detecting Hg2+ in aqueous media. The sensitivity of NCS to Hg2+ was evaluated by photoluminescence intensity fluctuations under fluorescence emission in the vicinity of 390 nm with a λexc of 350 nm. The fluorescence intensity of the NCS probe weakened in the presence of Hg2+ owing to the effective fluorescence quenching by that, which is not corresponding to the special covalent liking between the ligand and the metal. The effects of the fluorescence nanoprobe concentration, pH, and sensing time were monitored to acquire the best conditions for determining Hg2+. Surprisingly, NCS revealed excellent selectivity and sensitivity towards Hg2+ in the samples containing Co2+, Na+, K+, Fe2+, Mn2+, Al3+, Pb2+, Ni2+, Ca2+, Cu2+, Mg2+, Cd2+, Cr3+, Li+, Cs+, and Ba2+. The fluorescence response was linearly proportional to Hg2+ concentration in 0.013–0.046 µM with a limit of detection of 9.58 nM. The in vitro and in vivo toxicological analyses confirmed the completely safe and biocompatible features of NCS, which provides promise for use for water, fruit, vegetable, and/or other forms of natural-connected materials exposed to Hg2+, with no significant toxicity noticed toward different cells/organs/tissues.
... Mercury is a heavy metal known for its toxicity, which depends on the concentration and administration route. Various pathological conditions, including gingivitis, allergic sensitivity, neurological disorders, cardiovascular diseases, and hormonal imbalance have been documented from mercury toxicity [26][27][28]. Further investigation is required to clarify the presence of mercury and its concentration in the clear aligner material. ...
The aim of this study was to evaluate the structural conformations of three clear aligner systems, Eon®, SureSmile®, and Clarity®, and compare them with the most commonly used system, Invisalign®. Clear aligner samples from Invisalign®, Eon®, SureSmile®, and Clarity® were cut into 5 × 5 mm squares and exposed to artificial saliva for 2 weeks. The specimens were then subjected to a Vickers hardness test by applying three separate indentations with a 25 gf load for 15 s. Hardness was calculated using the following formula: Vickers hardness number = 1.854 (F/D2). Fourier transform infrared spectroscopy (FTIR) analysis was performed, with a diamond hemisphere and infrared beam being allowed to pass through each specimen. A mid-infrared range from 4000 to 375 cm−1 was recorded. The samples were also evaluated using scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis spectroscopy at different magnifications. No statistically significant differences were observed between the included systems with regard to hardness. All systems showed a polyurethane-based material, as illustrated by the FTIR analysis. Some structural variations were noted in the Invisalign® system, which had a more homogeneous architecture. Statistically significant differences in the carbon weights were found among the systems. The four systems presented comparable hardness levels. Mild molecular composition differences were found, but all systems had the similarity of being composed of a polyurethane-based material. Carbon and oxygen were the main elements, as they were located in all studied clear aligners. The SEM analysis revealed that Invisalign® had a smoother surface than the other three systems. All included clear aligners had similar characteristics with minimal differences, providing a wide variety of options for clinical orthodontic treatment according to patients’ demands.
... The contamination with mercury occurred mostly through dental treatment, recycling of fluorescent lamps as well as gold mining [91]. ...
Endometriosis is a chronic, estrogen-dependent, inflammatory condition that is defined as the presence of endometrial glands and stroma outside the uterine cavity. Despite the progress in research into the mechanisms leading to the development of endometriosis, its cause has not yet been established. It seems to be possible that the formation of oxidative stress may be one of the main causes of the development of endometriosis. There is much research that studies the potential role of trace elements in the appearance of endometrial-like lesions. Most studies focus on assessing the content of selected trace elements in the blood, urine, or peritoneal fluid in women with endometriosis. Meanwhile, little is known about the content of these elements in endometrial-like implants, which may be helpful in developing the theory of endometriosis. Investigations that are more comprehensive are needed to confirm a hypothesis that some trace elements play a role in the pathomechanism of endometriosis.
... Other common routes of elemental and inorganic Hg exposures are dental amalgam [4,5], dermal contact, exposure through air pollution from Hg released in the air from fossil fuel combustion, mining, and smelting [1], industrial waste, as well as occupational and ritualistic practices [3]. As a neurotoxic agent, several studies have shown associations between high levels of Hg in various human tissues and central nervous system and neurodevelopmental disorders including impairments in vision and hearing, cerebral palsy, intellectual and neurodevelopmental disabilities, hyperactive tendon reflexes and general paralysis [6][7][8][9]. Other studies have reported significant associations between even lower levels of Hg and attention deficits and anxiety, as well as impairments in language, learning, and fine motor and visual-spatial organizational skills [8,[10][11][12]. ...
We investigated interactive roles of three metabolic glutathione S-transferase (GST) genes (GSTP1, GSTT1, and GSTM1) and autism spectrum disorder (ASD) status in relation to blood Hg concentrations (BHC) of Jamaican children. We used data from 266 children (2-8 years) with ASD and their 1:1 age- and sex-matched typically developing (TD) controls. After adjusting General Linear Models for child’s age, socioeconomic status, consumption of leafy vegetables, fried plantain, canned fish, and the interaction between GSTP1 and GSTT1, we found significant interactions between GSTP1 and ASD status in relation to BHC either in a co-dominant or dominant genetic model for GSTP1(P < 0.001, P = 0.007, respectively). In the co-dominant model for the Ile105Val GSTP1 polymorphism, geometric mean (GM) BHC in ASD cases with genotype Ile/Ile were significantly higher than in cases with the Ile/Val genotype (0.73 vs. 0.48 µg/L, P = 0.01). In contrast, in TD controls with the Ile/Val genotype GM BHC were significantly higher than in those with the Ile/Ile genotype (0.72 vs. 0.49 µg/L, P = 0.03) or the Val/Val genotype (0.72 vs. 0.51 µg/L, P = 0.04). Although our findings are consistent with the role of GSTP1 in detoxification of Hg, replication in other populations is warranted.
... Historically, human exposure to this metal has occurred due to contamination of the food chain, especially methyl-mercury contamination of fish products, or in specific work contexts such as mining. More recently, the workplaces that are still potentially involved in this type of exposure are the following: orthodontics and dental activities, due to the use of mercury-based amalgams [63][64][65]; chlorine production plants, in which large quantities of mercury are used (100 tons to produce 50,000 tons of chlorine) [66]; the disposal and recycling of fluorescent lamps [67,68]; and gold mining, especially in developing countries [69]. ...
Endometriosis is a gynecological disorder characterized by the presence of endometrial stroma and glands outside the uterine cavity. A systematic review of the literature was conducted to clarify, starting from environmental exposure data, whether possible occupational risk factors may correlate with the onset of the disease. The guidelines for reporting systematic reviews of the “PRISMA” statement were followed and two databases, Scopus and PubMed, were used. Of the 422 studies selected with specific keywords, 32 publications were eligible, 28 of which referred to chemical agents and 4 related to night work. Conflicting data emerged among these studies. Although some compounds seemed to be more involved than others in the onset of endometriosis. Association with exposure to organochlorine compounds is the most supported by the epidemiological data, while other pesticide exposure did not show any clear correlation. Likewise, the hypothesis of a correlation with perfluoroalkyls exposure is not currently supported by data. The involvement of metals as risk factors has not been confirmed, while the role of night work, in the case of long service, seems to play an etiological role. In order to clarify the potential occupational risk of endometriosis development, well-designed studies are needed to evaluate the potential association between chemical compounds and disease etiology.
... Occupational exposure to elemental inorganic mercury may cause neurological and other adverse effects in exposed workers [4][5][6]. Even if its neurotoxic effects have been known for more than 300 years [7], occupational exposure may still be relevant in certain activities such as mining and metal working [8][9][10], production and waste of fluorescent lamps [11,12] and incinerators [13,14], recycling [15,16], concrete processing [17], battery production [18], thermometer and precision instrument manufacturing [19], dental care [20], and other industrial activities. Chlor-alkali plants have been extensively studied over the past 60 years for being at the origin of the ecological disaster of Minamata [21] and for neurological pathologies in exposed workers [22][23][24][25][26][27][28][29][30][31]. ...
Featured Application: Knowing the effects observed in a worker exposed to mercury can improve the prevention of the risks associated with this toxic metal. Abstract: Chronic exposure to low levels of mercury is involved in the development of motor neuron diseases (MND). Genetic alterations may have a crucial role in the onset and progression. We presented a case of a TANK-binding kinase 1 (TBK1)-mutated 54-year-old male worker who developed a MND due to chronic mercury exposure at work. He was employed in a chlor-alkali plant in Central Italy. After two years of employment he had acute mercury intoxication with suggestive neurological symptoms and a high urinary level of the metal. Through years, many episodes of intoxication occurred, but he continued to perform the same job and be exposed to mercury. After yet another episode of intoxication in 2013, he showed fasciculations of the upper limbs and trunk, and electromyographic activity patterns were consistent with amyotrophic lateral sclerosis (ALS). In 2016, a genetic test revealed a mutation of TBK1, an ALS-related gene. This case highlights the important role of genetics in personalized occupational medicine. Occupational physicians should use genetic tests to identify conditions of individual susceptibility in workers with documented frequent episodes of mercury intoxication recorded during health surveillance programs to customize prevention measures in the workplace and act before damage appears.
... It constitutes an important occupational risk by causing neurological, neuropsychological, cardiovascular, and other adverse effects in exposed workers [2]. This occupational risk has been well known for many centuries [3], and is still relevant for certain categories, such as dental technicians [4], miners [5,6], and other industrial workers [7][8][9][10][11][12][13][14]. Mercury is also an environmental toxicant whose effects on cell membranes have been well documented [15]. ...
Featured Application: Existing studies on the association between certain polymorphisms and the appearance of neurotoxic effects in workers exposed to low doses of elemental mercury can provide physicians in charge of workers' health surveillance with tools to customize exposure monitoring. Abstract: Occupational exposure to elemental mercury still represents a significant risk in the workplace. The sensitivity of the exposed subjects varies considerably. This study aims to summarize the literature on the role of genetic factors in occupationally exposed cohorts. A systematic search of the literature was carried out on PubMed Central (PMC), MEDLINE, and Google Scholar databases in accordance with the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" (PRISMA) guidelines, from 1946 to July 2020. Ten cross-sectional studies were included in the review. All studies referred to the polymorphisms that can favour some neurotoxic effects of the metal in occupational cohorts. Some genetic variants may be associated with an increase in the occupational effects of mercury. Given the limited evidence, genetic screening of all mercury-exposed workers is not recommended. However, a personalized search for polymorphisms could be taken into consideration if exposed workers report early neurotoxic symptoms.
... Several metals in lipophilic forms, e.g., elemental mercury (Hg 0 ) and methylmercury, readily pass through the blood-brain barrier (Lohren et al., 2015;Bjørklund et al., 2017). The toxic effects of metals are mediated through various reactions, including free radical formation, cell membrane disturbance, or enzyme inhibition (Bjørklund et al., 2019b). Some metals also bind to mitochondria, thereby impairing cellular respiration (Belyaeva et al., 2008). ...
It has been demonstrated that metals can induce autoimmunity. However, few studies have attempted to assess and elucidate the underlying mechanisms of action. Recent research has tried to evaluate the possible interactions of the immune system with metal ions, particularly with heavy metals. Research indicates that metals have the potential to induce or promote the development of autoimmunity in humans. Metal-induced inflammation may dysregulate the hypothalamic-pituitary-adrenal (HPA) axis and thus contribute to fatigue and other non-specific symptoms characterizing disorders related to autoimmune diseases. The toxic effects of several metals are also mediated through free radical formation, cell membrane disturbance, or enzyme inhibition. There are worldwide increases in environmental metal pollution. It is therefore critical that studies on the role of metals in autoimmunity, and neuroendocrine disorders, including effects on the developing immune system and brain and the genetic susceptibility are performed. These studies can lead to efficient preventive strategies and improved therapeutic approaches. In this review, we have retrieved and commented on studies that evaluated the effects of metal toxicity on immune and endocrine-related pathways. This review aims to increase awareness of metals as factors in the onset and progression of autoimmune and neuroendocrine disorders.
... Molecules 2019, 24, 3247 ...
The present article reviews the clinical use of thiol-based metal chelators in intoxications and overexposure with mercury (Hg), cadmium (Cd), and lead (Pb). Currently, very few commercially available pharmaceuticals can successfully reduce or prevent the toxicity of these metals. The metal chelator meso-2,3-dimercaptosuccinic acid (DMSA) is considerably less toxic than the classical agent British anti-Lewisite (BAL, 2,3-dimercaptopropanol) and is the recommended agent in poisonings with Pb and organic Hg. Its toxicity is also lower than that of DMPS (dimercaptopropane sulfonate), although DMPS is the recommended agent in acute poisonings with Hg salts. It is suggested that intracellular Cd deposits and cerebral deposits of inorganic Hg, to some extent, can be mobilized by a combination of antidotes, but clinical experience with such combinations are lacking. Alpha-lipoic acid (α-LA) has been suggested for toxic metal detoxification but is not considered a drug of choice in clinical practice. The molecular mechanisms and chemical equilibria of complex formation of the chelators with the metal ions Hg2+, Cd2+, and Pb2+ are reviewed since insight into these reactions can provide a basis for further development of therapeutics.
... Several reports have shown that the serum neuron-specific enolase (NSE-biomarker for the neurotoxic effects of mercury) is associated with the progression of multiple sclerosis [121]. Mercury-containing dental amalgam fillings increased the risk of MS [122] and was linked to neurobehavioral effects in dental personnel exposed to chronic low levels of mercury [123]. Despite these notes, data from patients with neurodegenerative diseases showed inconclusive data about a possible mercury involvement [124]. ...
Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system is common amongst young adults, leading to major personal and socioeconomic burdens. However, it is still considered complex and challenging to understand and treat, in spite of the efforts made to explain its etiopathology. Despite the discovery of many genetic and environmental factors that might be related to its etiology, no clear answer was found about the causes of the illness and neither about the detailed mechanism of these environmental triggers that make individuals susceptible to MS. In this review, we will attempt to explore the major contributors to MS autoimmunity including genetic, epigenetic and ecological factors with a particular focus on toxins, chemicals or drugs that may trigger, modify or prevent MS disease.
... Several reports have shown that the serum neuron-specific enolase (NSE-biomarker for the neurotoxic effects of mercury) is associated with the progression of multiple sclerosis [121]. Mercury-containing dental amalgam fillings increased the risk of MS [122] and was linked to neurobehavioral effects in dental personnel exposed to chronic low levels of mercury [123]. Despite these notes, data from patients with neurodegenerative diseases showed inconclusive data about a possible mercury involvement [124]. ...
Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system is common amongst young adults, leading to major personal and socioeconomic burdens. However, it is still considered complex and challenging to understand and treat, in spite of the efforts made to explain its etiopathology. Despite the discovery of many genetic and environmental factors that might be related to its etiology, no clear answer was found about the causes of the illness and neither about the detailed mechanism of these environmental triggers that make individuals susceptible to MS. In this review, we will attempt to explore the major contributors to MS autoimmunity including genetic, epigenetic and ecological factors with a particular focus on toxins, chemicals or drugs that may trigger, modify or prevent MS disease. Key Contribution: The article is a concise but comprehensive reference for most of the environmental and microbial toxins as well as drugs, organic solvents and heavy metals that can have an impact on the onset and progression of multiple sclerosis.
Dental amalgam is a material used in dentistry for a long time. In its composition there is the presence of metallic mercury, a substance with high volatility at room temperature, whose vapor is colorless, odorless and highly toxic. This work sought to analyze the state of the art of scientific literature on occupational exposure to mercury metal vapor in oral health. To this end, research was carried out in the Web of Science, Scopus and Lilacs databases, research period from January 2000 to March 2023, in English and Portuguese, in addition to search in gray literature, without date limits. After inclusion and exclusion criteria analysis, 86 articles, from 25 countries, were selected for reading. The literature analyzed pointed to the existence of different moments of exposure, possible impacts on health and uncertainties regarding what levels of exposure to mercury vapor can be considered safe. These findings indicate the need to adopt preventive measures whenever there is contact with dental amalgam, always seeking the lowest possible level of exposure. It is concluded that oral health professionals may be exposed to metallic mercury vapor from dental amalgam, and the level of this exposure may vary according to the current working conditions and the preventive measures employed. Seeking to contribute to the promotion of occupational health in this context, an educational material was developed to provide information and awareness among those involved in oral health concerning occupational risks and the indication of some preventive measures regarding exposure to metallic mercury vapor from dental amalgam.
Mercury is a toxic heavy metal that can have significant health impacts on humans and other organisms. Mercury can enter the environment through natural sources such as volcanic activity or through human activities such as industrial pollution. The aim of this chapter is to focus on mercury contamination in water and its impact on public health. Mercury can enter water bodies through various sources such as natural weathering of rocks, atmospheric deposition, runoff from agricultural lands, and industrial effluents. The major sources of mercury pollution in water are mining activities, pulp and paper mills, and coal-fired power plants. Mercury can have significant impacts on public health, especially for vulnerable populations such as pregnant women, infants, and children. Exposure to mercury can cause a range of health problems such as neurological disorders, developmental delays, and cardiovascular disease. Preventing and mitigating mercury contamination in water requires a multi-faceted approach. Industrial sources of mercury pollution must be regulated and monitored to prevent contamination of water bodies. Improving water treatment technologies and practices can also help to remove mercury from contaminated water. Mercury contamination in water is a significant public health issue that can have long-lasting impacts on human health. Preventing and mitigating mercury contamination in water requires a coordinated effort from industry, government, and the public. By taking action to reduce mercury pollution, we can protect public health and preserve the integrity of our water resources.
Mercury poisoning is most frequently associated with multiorgan toxicity involving the brain, lungs, and kidneys. Cardiotoxic effects of mercury are rare and often overlooked. We demonstrate mercury poisoning–induced cardiotoxicity through a case study and then provide a review of the incidence, pathophysiology, and associated management plans. This case illustrates the importance of thorough history-taking to promote early recognition of toxicity.
Background:
Dentists using dental amalgam are chronically exposed to low doses of elemental mercury. The complex toxico-kinetics of this systemic toxicant results in polymorphic and variable clinical phenotypes. In this context, adapted statistical methods are required to highlight potential adverse effects of occupational mercury exposure on dentists' health.
Objective:
The present study aims to analyze the distribution of self-reported subjective symptoms, commonly associated with chronic mercury poisoning, according to occupational mercury exposure in a population of Moroccan liberal dentists.
Methods:
In order to achieve the defined objectives, a three-step latent class regression was fitted. First a latent class analysis was performed to cluster the studied population according to their declared symptoms. Dentists were then classified in the defined latent classes based on their posterior probabilities. Finally, a logistic regression is fitted to identify predictors associated with latent classes' membership.
Results:
The final obtained model showed acceptable calibration and discrimination. Its interpretation revealed that the increase of the frequency of amalgam use was associated with significant higher odds of belonging to the high risk latent class.
Conclusions:
The present study represents an initial step towards the development of diagnosis model that predict clinical profiles according to occupational mercury exposure.
Spent automobile batteries are one of the most significant secondary sources of harmful heavy metals for the environment. After being incorporated into the aquatic ecosystems, these metals disseminate to various plants, microorganisms, and the human body and cause multiple adverse effects. Activated carbons (ACs) have long been used as an effective adsorbent for different heavy metals in wastewater treatment processes. Although numerous research works have been published to date on this topic, they are scattered in the literature. In this review, we have assembled these works and provided an extensive overview of the application of ACs for treating spent car battery heavy metals (CBHMs) from aquatic systems. The preparation of ACs from different precursor materials, their application in the adsorption of CBHMs, the adsorption mechanism, kinetics, adsorption isotherms and various parameters that may affect the adsorption processes have been discussed in detail. A brief comparative analysis of the adsorption performances of ACs prepared from different precursor materials is also provided. Finally, recommendations for future research works are also offered.
Depressive symptoms have a significant impact on the quality-of-life among the oldest old (aged ≥ 80 years) in the population. Current research on the association of blood mercury with depressive symptoms has mainly targeted the general population. However, it is unclear whether this association is present in the oldest old. We used data from the Healthy Aging and Biomarker Cohort Study carried out in 2017–2018, with 1154 participants aged ≥ 80 years eligible for analysis. Inductively coupled plasma mass spectrometry (ICP-MS) was employed to detect blood mercury (Hg) levels, while the CES-D10 depression scale was used to assess depressive symptoms. The association between blood mercury levels and depressive symptoms was investigated using log-binomial and Poisson regression models. We also used restricted cubic splines (RCS) to assess the linear or nonlinear association of blood mercury with depressive symptoms scores. The 1154 participants ranged in age from 80 to 120 years, while the geometric mean of blood mercury concentration was 1.01 μg/L. After adjustment for covariates, log-binomial and Poisson regression analyses revealed a statistically significant, positive association of blood mercury with depressive symptoms. In comparison to the first tertile, the adjusted relative risks of blood mercury and the presence of depressive symptoms in the second and third tertiles were 1.55 (1.20–1.99) and 1.45 (1.11–1.90), respectively. The RCS model showed a linear association between blood mercury level and depressive symptoms scores. In conclusion, among the oldest old, we demonstrated that blood mercury levels were positively associated with depressive symptoms. Further surveys, especially cohort studies and clinical trials are needed to confirm these results.
Background
Mercury (Hg) is a highly toxic substance, and its harmful effects on maternal and infant health have been reported. Yet, the associations of Hg exposure with preeclampsia (PE) and adverse birth outcomes are not well understood. Objective: The aim of this study was to investigate the potential effects of maternal Hg exposure on PE and birth outcomes. Methods: We conducted a case-control study with 84 participants in China. Logistic models were used to estimate odds ratios for PE risk and birth outcomes according to maternal blood Hg levels, adjusting for potential confounding factors. Results: Elevated blood Hg levels were associated with increased risks of mild PE (aOR, 7.03; 95% CI, 1.61, 30.62; P < 0.01) and severe PE (aOR, 47.55; 95% CI, 5.27, 429.05; P < 0.05). We also found that increased blood Hg levels were associated with low birth weight (aOR, 1.12; 95% CI, 1.00, 1.25; P < 0.05) and preterm birth (PTB) (aOR, 1.22; 95% CI, 1.08, 1.38; P < 0.05). Conclusions: Our study provided evidence that elevated blood Hg levels were significantly associated with an increased risk of PE. In addition, our findings support that increased blood Hg levels might be associated with low birth weight and PTB.
Mercury occurs as elemental mercury and as inorganic and organic compounds (mercury vapor, mercury liquid, mercury salts, short-chain alkylmercury compounds, alkoxyalkylmercury compounds, and phenylmercury compounds), all with different toxicological properties. Total mercury can be analyzed in water, air, and biological material by cold vapor atomic absorption methods and by neutron activation analysis and can be detected down to concentrations of a 10th of a nanogram per gram in biological material. Methylmercury (MeHg) can be detected in biological material at levels of a few nanograms by extraction with benzene after strong acidification with hydrochloric acid, followed by gas chromatographic analysis of MeHg chloride. Other analytical methods for speciating inorganic mercury and several of the organomercurial forms have also been published. These methods include isotope dilution mass spectrometry, time-of-flight mass spectrometry, high-performance liquid chromatography inductively coupled plasma (ICP) mass spectrometry, capillary electrophoresis-ICP, gas chromatography-ICP, and X-ray absorption fine structure spectroscopy.
Mercury is circulated naturally in the biosphere, with 5500 metric tons (t) being released into the atmosphere by degassing from the Earth's crust and the oceans. In addition, 2500 t of mercury are released into the environment each year through human activities such as the combustion of fossil fuels and other industrial releases. Approximately 2000 tons of mercury per year is produced for industrial use, a small part of which is used for synthesizing organic mercury compounds. The world production of mercury for commercial uses has been slowly declining over the past 20 years. There is now a ban on the export of mercury from the European Union and the United States.
In nature, MeHg is produced from inorganic mercury as a consequence of microbial activity. In mammals, oxidative demethylation occurs in vivo to produce inorganic mercury. In fish, most mercury is present as MeHg. Factors determining the MeHg concentration in fish are the mercury content in water and bottom sediments, the pH and redox potential of water, and the species, age, and size of the fish.
The toxic properties of mercury vapor are a consequence of mercury accumulation in the brain causing neurological signs involving an unspecific psychasthenic and vegetative syndrome (micromercurialism). At high exposure levels, mercurial tremor is seen, accompanied by severe behavioral and personality changes, increased excitability, loss of memory, and insomnia. Mercurials may also affect other organ systems, such as the kidney. On a group basis, exposure levels are likely to be reflected by mercury concentrations in the blood and urine. Occupational exposure to mercury concentrations in air of >0.1 mg/m³ may produce mercurialism. Micromercurialism has not been reported at concentrations <0.01 mg/m³. Exposure to mercury vapor inhibits brain development in primates and in humans with certain genotypes. The exact dose–response relationship in humans is not known. Inorganic mercury, but not MeHg, has been found to induce and bind to the low molecular weight metal-binding protein, metallothionein.
The acute and long-term actions of mercuric salts, phenylmercury compounds, and alkoxyalkylmercury compounds are likely to be gastrointestinal disturbance and renal damage appearing as tubular dysfunction, with tubular necrosis in severe cases. The lethal dose in humans is approximately 1 g mercuric salt. The mercury load on the kidney is best determined by analysis of renal biopsy. Mercury concentrations in the kidney of between 10 and 70 mg/kg have been reported in poison cases with renal injury. Levels <3 mg/kg may be found in normal cases. Occasionally, mercuric compounds may cause idiosyncratic skin symptoms, which may develop into severe exfoliative dermatitis or cause glomerular nephritis. Animal and clinical observations have shown that mercuric mercury stimulates and MeHg inhibits the immune system. A specific form of idiosyncrasy, called acrodynia or pink disease, is seen in children. Most cases are associated with mercury exposure in which increased levels of mercury in urine are detected.
Hazards involved in the long-term intake of food containing MeHg or ethylmercury (EthylHg) and in occupational exposure to MeHg are a result of the efficient absorption (90%) of alkylmercury in humans and the long retention time (half-life of 70 days for MeHg and shorter for EthylHg) leading to accumulation of alkylmercury in the brain. Chronic poisoning results in degeneration and atrophy of the sensory cerebral cortex, paresthesia, ataxia, hearing, and visual impairment, and an increased risk for cardiovascular diseases such as myocardial infarction and stroke. The latter effects are attenuated by the intake of polyunsaturated fatty acids (PUFAs) through fish consumption. Prenatal exposure causes cerebral palsy and, in less severe cases, psychomotor retardation. MeHg concentration in the blood and hair reflects the body burden and the brain concentration of MeHg. Intake resulting in body burdens of <0.5 mg/kg body weight is not likely to give rise to detectable neurological signs in adults. This intake corresponds to blood values of <200 μg/L and mercury levels in the hair of <50 mg/kg. However, this level of MeHg exposure in pregnant women may result in inhibited brain development of the fetus, with psychomotor retardation of the child. This effect also appears to be reduced by the intake of PUFAs through fish consumption. The highest level of MeHg load in pregnant women that is not associated with inhibition of fetal brain development is not known. Recent epidemiological studies have revealed that genetic polymorphisms can modify mercury metabolism and susceptibility to mercury exposure. Specific genotypes have been associated with increased susceptibility to mercury exposure in humans.
Metals are ubiquitous on the Earth’s crust. Many nonessential metals were not present in high lever in our environment prior to technologic use of them (starting 8,000 years ago) as an anthropic use. The bioaccumulation of metals causes problems because of their toxic effects, particularly when they are neurotoxic. To be able to determine metals, many exposure biomarkers can be use. Dental enamel has the following advantages over some other biomarkers: it is stable over time, the sample collection is easy, the method is noninvasive, and the cost is low. This study aimed at evaluating the concentrations of several metals on the enamel surface of primary teeth collected at different areas of Ribeirao Preto, SP, Brazil. Tooth donation and collection was done based on a large campaign called “Doe Seu Dentinho” (Donate your little tooth) that took place between April 2018 and March 2019. Microbiopsies (a superficial etch with HCl in 70% glycerol) were done on the tooth surface on teeth randomly selected from the 4 districts of the city, with 10 boy- and girl teeth selected from each district (n=4 x 20 primary teeth). Only incisors were used in the process of random selection. Samples were then analyzed by ICP-MS for the presence of Manganese, Zinc, Arsenic, Cadmium, Lead and Mercury. Results were expressed as the amount of metals per gram of dental enamel, since calcium had also been determined. Our results are the first for the presence of some of these metals on the superficial enamel determined by ICP-MS. Results suggest that certain children have high levels of metal that we had not expected to be high, such as Arsenic, Cadmium and Mercury. In comparison to earlier studies of our group in our city 10 years ago and using the same methods, lead levels on superficial enamel were lower. There was a high and statistically significant correlation for the concentration of these metals on the superficial enamel. For all methods, boys always showed higher concentrations than girls (p<0,0001). In conclusion, our results suggest that other toxic metals besides lead and cadmium can be determined on superficial enamel by golden standard analytical techniques, and that the concentrations seem to be high for some of them. Thus, more studies are needed to determine what are the concentrations associated with toxicity and what are the possible sources of exposure in our urban environments.
Alzheimer's disease is the most common neurodegenerative disorder that usually occurs after the age of 65 for which there is currently no cure. The predominant feature of this disease is the appearance of beta amyloid plaques next to the neurons in the brain. Numerous studies have investigated the possible causes of the disease and in particular the role of metals. In the present study, while briefly reviewing the effect of various lifestyle factors on the incidence and prevalence of the disease, by presenting the latest clinical reports and cohort studies regarding the role of metals in the disease, we try to provide a comprehensive overview of this issue to the reader. Some studies have shown changes in the concentration of metals in the brain or body fluids of AD patients, while others have not indicated any change. Therefore, it can be concluded that metals are not causative factor, but they are risk factor in certain conditions.
Introduction:
mercury exposure is recognized as a worldwide public health concern. However, the effect of long-term exposure to low-doses of this heavy metal is still subject to debate. Due to the use of mercury in dental amalgam, dental health care professionals are chronically exposed to low-doses of this metal. In this context, we have conducted a descriptive cross-sectional survey among liberal dentists in two regions of the center of Morocco. In parallel, the global health status of participants was investigated to assess the relevance of a subsequent etiological survey.
Methods:
data were collected through a self-reported questionnaire. Occupational exposure of dentists to mercury was evaluated based on their use of dental amalgam. Moreover, the other common factors increasing the background pollution or inducing exposure peaks were also investigated. On the other hand, smoking, vaccination, fish consumption, and the number of dental amalgam in mouth were considered as non-occupational exposure sources. Finally, the self-reported global health problems of participants were collected.
Results:
192 dentists were included in the present study. Seventy-six percent (76.04%) of them declared using dental amalgam in their practice. Moreover, the presence of dental amalgam in mouth was identified as the main non-occupational source of exposure to mercury (63.45% of participants). Finally, most of participants (46.35%) have expressed neuropsychological complaints.
Conclusion:
altogether, our results revealed a real mercury exposure in the studied population. Thus, effective preventive measures should be promoted to minimize the mercury exposure in dental offices. Moreover, an etiological study will be of great interest to reveal the impact of mercury exposure in this population.
Methylmercury (MeHg) is an extremely important environmental toxicant posing serious health risks to human health and a big source of environmental pollutant. Numerous evidence available showing a link between nervous system toxicity and MeHg exposure. Other forms of mercury are reason of metabolic toxic effects and alteration of DNA in the human body. The sources of exposure could be occupational or other environmental settings. In the present study MeHg was orally gavaged to mice, at doses of 2.5, 5, and 10 mg/kg for 4 weeks. Fasting hyperglycemia, activity of hepatic phoshphoenolpyruvate carboxykinase and glucose 6‐phoshphate were reported high as compared to control group. Inflammatory markers like, tumor necrosis factor α, the actual end product of inflammatory mediators’ cascade pathway was also raised in comparison to control group. Hyperinsulinemia observed in serum showed clear understanding of mercury induced insulin resistance. Moreover, tissue damage due to increased oxidative stress markers like, hepatic lipid peroxidation, 8‐deoxygunosine, reactive oxygen species, and carbonyl groups was significantly higher as compared to control group. MeHg caused a significant reduction in antioxidant markers like ferric reducing antioxidant power and total thiol molecules. The present study highlighted that activity of key enzymes involved in glucose metabolism is changed, owing to MeHg induced toxicity in the liver. Induction of similar toxic effects assumed to be stimulated by the production of high quantity free radicals. Potential toxicity of methylmercury in the liver.
Background and purpose: Dentists are constantly exposed to mercury vapor and its role in the
development of many chronic diseases has been proven. Therefore, this study aims to determine the mean
concentrations of mercury in samples of blood, urine and area air among Iranian dentists. Materials and methods: This study was conducted based on PRISMA guidelines. Two authors
searched Persian and English online databases including Magiran, Iranmedex, SID, Medlib, Scopus,
PubMed, Science Direct, Cochrane, Web of Science and the Google Scholar search engine without time
limit until 2016. To evaluate the heterogeneity of the studies, Cochran's Q test and I2 index were used. Data
were analyzed using Stata 11.1 software based on random effects model. Results: 12 studies with a sample size of 1,276 dentists were reviewed. The mean concentration of mercury in samples of blood, urine and area air was estimated to be 1.21 μg/dl (95% CI [confidence interval]: 0.67 to 1.75), 5.54 μg/l (95% CI: 4.03 to 7.06) and 7.58 μg/m3 (95% CI: 2.56 to 12.60), respectively. The standardized mean difference in the mercury concentration was 1.75 μg/dl (95% CI: -0.05 to 3.55) in blood and 1.79 μg/dl (95% CI: -1.40 to 4.99) in urine between the case and control groups
(P>0.05). Conclusion: The results of this study demonstrated that the 95% CI of the mean concentration of mercury in the urine samples of Iranian dentists is higher than the standard limit. Therefore, Iranian dentists
should be examined annually in terms of urinary mercury concentration.
All types of dental amalgams contain mercury, which partly is emitted as mercury vapor. All types of dental amalgams corrode after being placed in the oral cavity. Modern high copper amalgams exhibit two new traits of increased instability. Firstly, when subjected to wear/polishing, droplets rich in mercury are formed on the surface, showing that mercury is not being strongly bonded to the base or alloy metals. Secondly, high copper amalgams emit substantially larger amounts of mercury vapor than the low copper amalgams used before the 1970s. High copper amalgams has been developed with focus on mechanical strength and corrosion resistance, but has been sub-optimized in other aspects, resulting in increased instability and higher emission of mercury vapor. This has not been presented to policy makers and scientists. Both low and high copper amalgams undergo a transformation process for several years after placement, resulting in a substantial reduction in mercury content, but there exist no limit for maximum allowed emission of mercury from dental amalgams. These modern high copper amalgams are nowadays totally dominating the European, US and other markets, resulting in significant emissions of mercury, not considered when judging their suitability for dental restoration.
Environmental stressors can negatively affect avian cognitive abilities, potentially reducing fitness, for example by altering response to predators, display to mates, or memory of locations of food. We expand on current knowledge by investigating the effects of dietary mercury, a ubiquitous environmental pollutant and known neurotoxin, on avian cognition. Zebra finches Taeniopygia guttata were dosed for their entire lives with sub-lethal levels of mercury, at the environmentally-relevant dose of 1.2 parts per million. In our first study we compared the dosed birds to controls of the same age using tests of three cognitive abilities: spatial memory, inhibitory control, and color association. In the spatial memory assay, birds were tested on their ability to learn and remember the location of hidden food in their cage. The inhibitory control assay measured their ability to ignore visible but inaccessible food in favor of a learned behavior that provided the same reward. Lastly, the color association task tested each bird’s ability to associate a specific color with the presence of hidden food. Dietary mercury negatively affected spatial memory ability but not inhibitory control or color association. Our second study focused on three behavioral assays not tied to a specific skill or problem-solving: activity level, neophobia and social dominance. Zebra finches exposed to dietary mercury throughout their lives were subordinate to, and more active than, control birds. We found no evidence that mercury exposure influenced our metric of neophobia. Together, these results suggest that sub-lethal exposure to environmental mercury selectively harms neurological pathways that control different cognitive abilities, with complex effects on behavior and fitness.
Human exposure to mercury is still a major public health concern. In this context, children have a higher susceptibility to adverse neurological mercury effects, compared to adults with similar exposures. Moreover, there exists a marked variability of personal response to detrimental mercury action, in particular among population groups with significant mercury exposure. New scientific evidence on genetic backgrounds has raised the issue of whether candidate susceptibility genes can make certain individuals more or less vulnerable to mercury toxicity. In this review, the aim is to evaluate a new genetic dimension and its involvement in mercury risk assessment, focusing on the important role played by relevant polymorphisms, located in attractive gene targets for mercury toxicity. Existing original articles on epidemiologic research which report a direct link between the genetic basis of personal vulnerability and different mercury repercussions on human health will be reviewed. Based on this evidence, a careful evaluation of the significant markers of susceptibility will be suggested, in order to obtain a powerful positive “feedback” to improve the quality of life. Large consortia of studies with clear phenotypic assessments will help clarify the “window of susceptibility” in the human health risks due to mercury exposure.
In this study we investigated the additive effect of mercury on the brain mitochondrial
dysfunction in experimental autoimmune encephalomyelitis (EAE) model. Experimental
animals (female C57BL/6 mice) are divided into four groups (n = 8); control, Hg, EAE,
EAE with Hg. EAE model of MS induced by injecting myelin oligodendrocyte glycoprotein
(MOG). Neurobehavioral alterations are recorded and then mice were sacrificed at day 28
and brain mitochondria were isolated and mitochondrial toxicity parameters including
mitochondrial swelling, reactive oxygen species (ROS) formation, collapse of mitochondrial
membrane potential (MMP) and cytochrome c release were measured. Our results showed
that repeated treatment of mercury following induction of EAE in mice significantly increased
the neurobehavioral scores, as well as mitochondrial toxicity through ROS formation,
mitochondrial swelling, collapse of MMP and cytochrome c release. Our findings proved that
repeated exposure with mercury accelerates progression of MS through mitochondrial damage
related to oxidative stress and finally apoptosis.
The objective of this study was to assess the occupational exposure to mercury in dentistry and associated environmental emission in wastewater of Lahore, Pakistan. A total of ninety-eight blood samples were collected comprising 37 dentists, 31 dental assistants, and 30 controls. Results demonstrate that the dentistry personnel contained significantly higher mean concentration of mercury in their blood samples (dentists: 29.835
µ
g/L and dental assistants: 22.798
µ
g/L) compared to that of the controls (3.2769
µ
g/L). The mean concentration of mercury was found maximum in the blood samples of older age group (62.8
µ
g/L) in dentists and (44.3
µ
g/L) in dental assistants. The comparison of mercury concentration among dentists, dental assistants, and controls (pairing based on their ages) revealed that the concentration increased with the age and experience among the dentists and dental assistants. Moreover, the mercury concentration in all the studied dental wastewater samples, collected from twenty-two dental clinics, was found to be exceeding the recommended discharge limit of 0.01 mg/L. Therefore, we recommend that immediate steps must be taken to ensure appropriate preventive measures to avoid mercury vapors in order to prevent potential health hazards to dentistry personnel. Strong regulatory and administrative measures are needed to deal with mercury pollution on emergency basis.
Considerable effort has been made to address the issue of occupational health and environmental exposure to mercury. This review reports on the current literature of mercury exposure and health impacts on dental personnel. Citations were searched using four comprehensive electronic databases for articles published between 2002 and 2015. All original articles that evaluated an association between the use of dental amalgam and occupational mercury exposure in dental personnel were included. Fifteen publications from nine different countries met the selection criteria. The design and quality of the studies showed significant variation, particularly in the choice of biomarkers as an indicator of mercury exposure. In several countries, dental personnel had higher mercury levels in biological fluids and tissues than in control groups, some work practices increased mercury exposure but the exposure levels remained below recommended guidelines. Dental personnel reported more health conditions, often involving the central nervous system, than the control groups. Clinical symptoms reported by dental professionals may be associated with low-level, long-term exposure to occupational mercury, but may also be due to the effects of aging, occupational overuse and stress. It is important that dental personnel, researchers and educators continue to encourage and monitor good work practices by dental professionals.
The purpose of this review is to examine the evidence for a relationship between mercury (Hg) exposure from dental amalgams and certain idiopathic chronic illnesses - chronic fatigue syndrome (CFS), fibromyalgia (FM), depression, anxiety, and suicide. Dental amalgam is a commonly used dental restorative material that contains approximately 50% elemental mercury (Hg0) by weight and releases Hg0 vapor. Studies have shown that chronic Hg exposure from various sources including dental amalgams is associated with numerous health complaints, including fatigue, anxiety, and depression - and these are among the main symptoms that are associated with CFS and FM. In addition, several studies have shown that the removal of amalgams is associated with improvement in these symptoms. Although the issue of amalgam safety is still under debate, the preponderance of evidence suggests that Hg exposure from dental amalgams may cause or contribute to many chronic conditions. Thus, consideration of Hg toxicity may be central to the effective clinical investigation of many chronic illnesses, particularly those involving fatigue and depression.
Over recent years increased MS incidence, primarily in women, has been reported. We recently reported an unexpectedly high MS prevalence of 189/100,000 in Sweden. In the present study we estimated the nationwide age-and gender-specific MS incidence and the sex ratio in Sweden between 2001 and 2008. MS patients were identified by linking two nationwide health data registers, and the Swedish population register. The earliest registered date of MS diagnosis was determined. By logistic regression, the probability of the date of MS diagnosis being within the incidence period, depending on age and time was estimated for a subset of patients and applied to other patients. By Poisson regression, the hazard functions for the incidence of MS diagnosis were estimated. The expected number of MS patients was 7,361.4. The incidence in the average population of 9,054,658 was 10.2 per 100,000 person-years, and 6.2 and 14.0 per 100,000 person-years for men and women, respectively. The crude female to male ratio was 2.26. No increase of incidence or change of sex ratio was observed from 2001 to 2008. In conclusion, the average MS incidence in Sweden from 2001 to 2008 was 10.2 per 100.000, which was considerably higher than previous regional Swedish estimates of 4.3–6.4. No increase of female to male ratio of MS during the study period was observed. We provide supplementary data that can be used as tools for examining excess MS risk in different study materials.
Extracellular accumulation of amyloid beta protein (Aβ) plays a central role in Alzheimer's disease (AD). Some metals, such as copper, lead, and aluminum can affect the Aβ accumulation in the brain. However, the effect of mercury on Aβ accumulation in the brain is not clear. Thus, this study was proposed to estimate whether mercury concentration affects Aβ accumulation in PC12 cells. We treated 10, 100, and 1000 nM HgCl2 (Hg) or CH3HgCl2 (MeHg) for 48 hr in PC12 cells. After treatment, Aβ40 in culture medium increased in a dose- and time-dependent manner. Hg and MeHg increased amyloid precursor protein (APP), which is related to Aβ production. Neprilysin (NEP) levels in PC12 cells were decreased by Hg and MeHg treatment. These results suggested that Hg induced Aβ accumulation through APP overproduction and reduction of NEP.
Abstract Mercury (Hg), also known as quick silver, is an essential constituent of dental amalgam. It is a toxic substance of global concern. Children are more at risk from mercury poisoning which affects their neurological development and brain. In the past, a number of studies at dental sites in many countries have been carried out and reported. The present report briefly describes and discusses our recent investigations carried out at 34 dental sites (teaching institutions, hospitals and private clinics) in Pakistan. It is evident from the data that at many sites the indoor mercury vapor levels exceed far above the permissible limit recommended for safe physical and mental health. At these sites, public in general and the medical, paramedical staff and vulnerable population in particular, are at most serious risk to health resulting from exposure to toxic and hazardous mercury. To minimize such risk, some of the recommendations are, best in-house environmental practices for occupational health and safety, mercury contaminated waste reduction at source, mercury specific legislation and ratification of Minamata convention on mercury by Pakistan and other world governments at the earliest time possible.
The rules governing the use of metallic mercury, a toxic and hazardous chemical, is in most jurisdictions identical to widely accepted standards and practices for handling the same chemical in industry for the protection of humans and their work environment. There cannot be exceptions solely for the practitioner dentists and their patients. Any workplace must be safe for both workers and visitors. The latter being dental patients waiting in the dentist's work environment. We reviewed the literature for toxic health effects of elemental mercury upon humans and present information about the Minimata Convention convened by the United Nations Environment Programme. A study conducted among dentists in Singapore and their personal work environment almost 30 years ago contributed to the workplace standard for elemental mercury, which was reduced, and is still currently enforced as a global standard. We recommend that dentists, with a large alternative battery of restorative materials today, make selection of a restorative material a more seriously considered choice, and not to make use of amalgam without the proper use of personal protective equipment for themselves (members of the dental operating team) and their patients, (amalgam traps and judicious monitoring of their workplace air quality). Mercury is ubiquitous in our presence due to human activities; any reduction in the dentists' workplace contributes to a global reduction.
Ethylmercury (etHg) is derived from the metabolism of thimerosal (o-carboxyphenyl-thio-ethyl-sodium salt), which is the most widely used form of organic mercury. Because of its application as a vaccine preservative, almost every human and animal (domestic and farmed) that has been immunized with thimerosal-containing vaccines has been exposed to etHg. Although methylmercury (meHg) is considered a hazardous substance that is to be avoided even at small levels when consumed in foods such as seafood and rice (in Asia), the World Health Organization considers small doses of thimerosal safe regardless of multiple/repetitive exposures to vaccines that are predominantly taken during pregnancy or infancy. We have reviewed in vitro and in vivo studies that compare the toxicological parameters among etHg and other forms of mercury (predominantly meHg) to assess their relative toxicities and potential to cause cumulative insults. In vitro studies comparing etHg with meHg demonstrate equivalent measured outcomes for cardiovascular, neural and immune cells. However, under in vivo conditions, evidence indicates a distinct toxicokinetic profile between meHg and etHg, favoring a shorter blood half-life, attendant compartment distribution and the elimination of etHg compared with meHg. EtHg's toxicity profile is different from that of meHg, leading to different exposure and toxicity risks. Therefore, in real-life scenarios, a simultaneous exposure to both etHg and meHg might result in enhanced neurotoxic effects in developing mammals. However, our knowledge on this subject is still incomplete, and studies are required to address the predictability of the additive or synergic toxicological effects of etHg and meHg (or other neurotoxicants). Copyright © 2013 John Wiley & Sons, Ltd.
Previous investigations have presented some evidence of late cognitive effects in dental personnel exposed to metallic mercury. We wanted to examine if Norwegian dentists have an increased prevalence of symptoms consistent with neurological and/or cognitive malfunction.
The study group consisted of 406 dentists from central Norway and 217 controls from the general population, all under the age of 70. They had responded to a standardised postal questionnaire (Euroquest) inquiring about seven symptoms in regard to neurology, psychosomatics, memory, concentration, mood, sleep disturbances, and fatigue. A score was calculated for each symptom based on 4 to 15 single questions scored on a scale from 1 (seldom or never) to 4 (very often).
The dentists and controls had a participation rate of 57.2% and 42.9% respectively. The dentists reported no more cognitive symptoms than the controls, with low average symptom scores from 1.16 for neurological symptoms in males to 1.73 for fatigue in females. Corresponding figures for the controls were 1.22 and 1.77. There were a total of 1.2% of the dentists and 1.8% of the controls who reported having three or more of the seven symptoms "often" or more frequently.
Norwegian dentists do not report more cognitive and neurological symptoms than controls from the general population.
Recent studies have suggested that several genes that mediate mercury metabolism are polymorphic in humans.
We hypothesized that single-nucleotide polymorphisms (SNPs) in metallothionein (MT) genes may underlie interindividual differences in mercury biomarker levels. We studied the potential modifying effects of MT SNPs on mercury exposure-biomarker relationships.
We measured total mercury in urine and hair samples of 515 dental professionals. We also surveyed occupational and personal exposures to dental amalgam and dietary fish consumption, from which daily methylmercury (MeHg) intake was estimated. Log-transformed urine and hair levels were modeled in multivariable linear regression separately against respective exposure surrogates, and the effect modification of 13 MT SNPs on exposure was investigated.
The mean mercury levels in urine (1.06 μg/L) and hair (0.51 μg/g) were not significantly different from the U.S. general population (0.95 μg/L and 0.47 μg/g, respectively). The mean estimated daily MeHg intake was 0.084 μg/kg/day (range, 0-0.98 μg/kg/day), with 25% of study population intakes exceeding the current U.S. Environmental Protection Agency reference dose of 0.1 μg/kg/day. Multivariate regression analysis showed that subjects with the MT1M (rs2270836) AA genotype (n = 10) or the MT2A (rs10636) CC genotype (n = 42) had lower urinary mercury levels than did those with the MT1M or MT2A GG genotype (n = 329 and 251, respectively) after controlling for exposure and potential confounders. After controlling for MeHg intake, subjects with MT1A (rs8052394) GA and GG genotypes (n = 24) or the MT1M (rs9936741) TT genotype (n = 459) had lower hair mercury levels than did subjects with MT1A AA (n = 113) or MT1M TC and CC genotypes (n = 15), respectively.
Our findings suggest that some MT genetic polymorphisms may influence mercury biomarker concentrations at levels of exposure relevant to the general population.
Sletvold, H., Svendsen, K., Aas, O., Syversen, T. & Hilt, B. (2012). Neuropsychological function and past exposure to metallic mercury in female dental workers. Scandinavian Journal of Psychology 53, 136–143.
The aim of this study was to see if dental personnel with previous exposure to metallic mercury have later developed disturbances in cognitive function. Ninety‐one female participants who had been selected from a previous health survey of dental personnel were investigated neuropsychologically within the following domains: motor function, short‐term memory, working memory, executive function, mental flexibility, and visual and verbal long‐term memory. The scores were mainly within normal ranges. Relationships between an exposure score, the duration of employment before 1990, and previously measured mercury in urine as independent variables and the neuropsychological findings as dependent variables, were analyzed by multiple linear regression controlling for age, general ability, length of education, alcohol consumption, and previous head injuries. The only relationship that was statistically significant in the hypothesized direction was between the previously measured urine mercury values and visual long‐term memory, where the urine values explained 30% of the variability. As the study had a low statistical power and also some other methodological limitations, the results have to be interpreted with caution. Even so, we think it is right to conclude that neuropsychological findings indicative of subsequent cognitive injuries are difficult to find in groups of otherwise healthy dental personnel with previous occupational exposure to mercury.
To analyse the scientific weight of the studies about reports of suicide rates in dentistry and decide the possible stressors caused by dental clinical activity, their consequences and their treatment.
The previous literature treats the high suicide rate associated with the dental profession in different ways: myth for some, important statistical data which needs further research for others. The possible errors repeated in the literature as a result of not introducing certain indispensable variables are analysed and a report given of the main stressors linked to the profession. The results showed that the absence of treatment of the disorders arising from these stressors by qualified professionals along with the lack of preventative measures developed by universities and clinicians to be one of the main problems.
In the literature we find systematically a suicide rate among dentists higher than those of other occupations. These studies lack the correct scientific weight and new studies are required that introduce the demographic variables, the psiquiatric morbidity previous to the development of the profession, the opportunity factor, the stressors not related to work and the relative emphasis to these are necessary to for the profession to decrease the risk of suicide.
A functional polymorphism in the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) is reported to affect mood and behavior in humans. In this study, the effects of 5-HTTLPR polymorphism on neurobehavioral and mood domains that are known to be affected by elemental mercury (Hg degrees ) exposure in human subjects were examined. The Behavioral Evaluation for Epidemiologic Studies (BEES) test battery was administered concurrently with urine and buccal-cell collections for 164 male dentists (DD) and 101 female dental assistants (DA) with occupational exposure to Hg degrees for an average of 19 and 10 yr, respectively. Geometric mean urinary mercury (Hg) levels in DD and DA were 2.52 (2.22) microg/L and 1.98 (1.98) microg/L, respectively. Corresponding indices of chronic occupational Hg degrees exposure, weighted for historical exposure, were 1212 (1877) and 316 (429). 5-HTTLPR status was 40% and 20% wild type, 40% and 56% single allelic substitution, and 20% and 24% double allelic substitution for the two genders. DD and DA were evaluated separately. Regression analyses controlled for age, premorbid intelligence, frequency of alcohol per week, and education. 5-HTTLPR polymorphism was associated with 5 behavioral measures in DD and with 12 behavioral measures in DA. Mood scores were more consistently associated with the variant in both groups. The strongest evidence for an additive effect for urinary Hg and 5-HTTLPR polymorphism in both groups was for tests of Finger Tap(Alternate) and Hand Steadiness(Factor1). Other significant additive effects that were less consistent across groups were also observed. These results add to the growing evidence of genetic determinants of mood and behavior that potentially increase susceptibility to Hg toxicity in humans.
This article gives a toxicological risk analysis of occupational diseases in dentistry that are related to chronic exposure to inorganic mercury, especially metallic mercury vapour. Studies have indicated that dental work involving mercury may be an occupational hazard with respect to reproductive processes, glioblastoma (brain cancer), renal function changes, allergies and immunotoxicological effects. The correlation of chronic exposure to mercury in dentistry to the health situation of dental workers' health situation needs to be further studied.
A 1989 Occupational Safety and Health Administration standard mandates that workplace air concentrations be held below new permissible exposure limits for 376 substances. As more than 350 of these limits came from the 1987 list of "Threshold Limit Values" (TLVs), the medical basis of the TLVs is of direct importance to the health of millions of workers. However, the TLV development process has been gravely flawed by lack of scientific rigor, inadequate medical input, and lack of attention to financial conflicts of interest. The adoption by the Occupational Safety and Health Administration of many poorly supported values as permissible exposure limits reflects also the underutilization of industrial medicine in identifying health effects of exposures below the TLVs. It is thus the responsibility of the medical profession to act on the presumption that the TLV permissible exposure limits are unsafe limits until a sound underlying body of medical and scientific literature exists for the substances on the list. It is industry's responsibility to commit itself seriously to medical and exposure monitoring and to begin to remedy the knowledge deficit that exists about the less immediate health effects of most industrial materials.
Based on toxicological, clinical, and epidemiological knowledge, the present paper reviews the status regarding possible deleterious health effects from occupational exposure to metallic mercury (Hg) in dental practice. Symptoms from the central nervous system are among the health problems that most often are attributed to Hg exposure in dentists and dental nurses working with amalgam. Uncharacteristic symptoms of chronic low-level Hg vapor exposure including weakness, fatigue, and anorexia have been observed in numerous studies of dental personnel. It is crucial to protect both human health and the environment against negative effects of Hg. In line with this, the use of dental amalgam in industrial countries is about to be phased out. In Norway and Sweden, the use of the filling material is banned.
The neurotoxicity of elemental mercury (Hg⁰) is well-recognized, but it is uncertain whether and for how long neurotoxicity persists; among studies that evaluated previously exposed workers, only one examined workers during and also years after exposure ceased. The aim of this review is to document the type, frequency, and dose-relatedness of objective neurological effects in currently exposed mercury workers and thereby provide first approximations of the effects one would have expected in previously exposed workers evaluated during exposure. We systematically reviewed studies of neurotoxicity in currently exposed mercury workers identified by searching MEDLINE (1950–2015), government reports, textbook chapters, and references cited therein; dental cohorts were not included. Outcomes on physical examination (PE), neurobehavioral (NB) tests, and electrophysiological studies were extracted and evaluated for consistency and dose-relatedness. Forty-five eligible studies were identified, comprising over 3000 workers chronically exposed to a range of Hg⁰ concentrations (0.002–1.7 mg/m³). Effects that demonstrated consistency across studies and increased frequency across urine mercury levels (<50; 50–99; 100–199; ≥200 μg/L) included tremor, impaired coordination, and abnormal reflexes on PE, and reduced performance on NB tests of tremor, manual dexterity and motor speed. The data suggest response thresholds of UHg ≈275 μg/L for PE findings and ≈20 μg/L for NB outcomes. These results indicate that PE is of particular value for assessing workers with UHg >200 μg/L, while NB testing is more appropriate for those with lower UHg levels. They also provide benchmarks to which findings in workers with historical exposure can be compared.
Background and objectives:
Suicide rates among dentists and a perceived elevated risk for suicide have been debated in the academic literature. It has filtered into the public psyche that dentists have the highest suicide rate of any occupation. The present review seeks support for both protagonist and antagonist positions from multidisciplinary perspectives. Contemporary risk factors and strategies for intervention and the prevention of suicide in dentistry are explored.
Methods:
An online database search for articles and reports, with selected target words, was conducted for peer reviewed publications on suicide in the dental profession, and for factors contributing to dentist suicide. Review guidelines from the American Psychological Association were used to clarify concepts, identify where most work was focussed, and to explore the superiority of any approach to the emotive topic over another.
Results:
Findings suggest the dominant belief that dentists have an elevated risk of suicide may be historically, but not currently, accurate. Although dentists' suicide is trending down, diversity in methodology means no current consensus is possible. Factors found to be influencing dentists' suicide ranged from known occupational stressors, to toxins and substance abuse, and untreated mental health problems.
Conclusion:
The contemporary position in New Zealand shows dentists per sé are not more likely than other health professionals to commit suicide although they may have been in the past. Dentists should be aware of individual susceptibility to burnout and mental health problems. Future directions are outlined to address this including peer intervention, and programmes available for dentists to cope better with risks leading to suicide.
Introduction: Dentists are often considered at risk of mercury poisoning due to using amalgam. To investigate the plasma and whole blood mercury levels in dental students, residents and clinical teaching staff, who work with amalgam and have mercury exposure, we performed this study. Materials and Methods: We conducted a historical cohort study on fifty persons of dental group by a census of dentists in restorative department of Tehran Dental School and fifty persons of control group at Des. 2006. Data collection was carried out using questionnaire. Following taking 4cc blood by standard venojects, all samples were sent to a lab by cold box and cold vapor atomic absorption method was performed for determining blood mercury level. Statistical analysis was performed by SPSS program by using t-test, chi square and logistic regression. Results: This study showed mercury blood and plasma levels were significantly more in dental group (P <0.001). Also this study demonstrated all of the persons in exposed group had mercury level under Threshold Level Value (5µg/dl) expect of 2 persons. Conclusion: Although mercury hygiene is good in dental school at present, but close monitoring of environmental mercury and physical and laboratory examination of dental workers is recommended. © 2007 Semnan University of Medical Sciences. All Right Reserved.
Mercury (Hg) exposure, a worldwide public health concern, predominantly takes two forms-methylmercury from fish consumption and elemental Hg from dental amalgam restorations. We recruited 630 dental professionals from an American Dental Association meeting to assess Hg body burden and primary sources of exposure in a dually exposed population. Participants described occupational practices and fish consumption patterns via questionnaire. Hg levels in biomarkers of elemental Hg (urine) and methylmercury (hair and blood) were measured with a Direct Mercury Analyzer-80 and were higher than the general US population. Geometric means (95% CI) were 1.28 (1.19-1.37) μg/l in urine, 0.60 (0.54-0.67) μg/g in hair and 3.67 (3.38-3.98) μg/l in blood. In multivariable linear regression, personal amalgams predicted urine Hg levels along with total years in dentistry, amalgams handled, working hours and sex. Fish consumption patterns predicted hair and blood Hg levels, which were higher among Asians compared with Caucasians. Five species contributed the majority of the estimated Hg intake from fish-swordfish, fresh tuna, white canned tuna, whitefish and king mackerel. When studying populations with occupational exposure to Hg, it is important to assess environmental exposures to both elemental Hg and methylmercury as these constitute a large proportion of total exposure.Journal of Exposure Science and Environmental Epidemiology advance online publication, 2 September 2015; doi:10.1038/jes.2015.52.
Lead (Pb), mercury (Hg) and cadmium (Cd) are environmental pollutants that are wide spread throughout the world. The present study aimed to investigate the level of exposure to Pb, Hg and Cd during the prenatal period, and the possible routes of maternal exposure to these toxic heavy metals.
The study included 123 mothers and their newborns. Umbilical cord blood samples were collected immediately after delivery, and breast milk and newborn hair samples were collected between postpartum d 3 and 10.
Among the 121 cord blood samples that were analyzed, Pb was present in 120 (99.2%) and the mean level was 1.66 ± 1.60 µg dL(-1) (range: <detection limit-12.50 µg dL(-1)), whereas Hg was noted in only 2 (1.7%) (15.74 and 33.20 µgL(-1)) and Cd was detected in 24 (19.8%) (range: < detection limit-6.71 µgL(-1)). The level of Pb in cord blood was ≥2 µg dL(-1) in 29% of the samples. Pb, Hg and Cd were detectable in all the newborn hair samples.
Among the 107 breast milk samples analyzed, 89 (83.2%) had a detectable level of Pb and the mean level was 14.56 ± 12.13 µgL(-1). Detection rate of Cd in breast milk was higher in women who resided near to city waste disposal site. Detection rate of Cd in cord blood was significantly higher in the women who consumed ≥2 servings of fish weekly. Maternal exposure to environmental tobacco smoke (ETS) resulted in elevated levels of Pb and Cd in newborn hair samples.
Most of the study samples had detectable levels of Pb, Hg and Cd, indicating that there was long-term maternal exposure prior to and during pregnancy, and a considerable number of the cord and breast milk samples had levels that exceeded the present accepted safety level.
The effects of stress in dental practice, particularly suicide, continue to pose major health problems warranting urgent attention. To counteract these problems a variety of support networks, referral services and disciplinary bodies have sprung up worldwide. In Australia (Victoria and NSW), the Doctors Health Advisory Service has recently offered its services to the dental profession. Currently, a study utilizing the Dental Health Questionnaire is evaluating the magnitude and types of problems related to healthcare in Australian dentists as well as the accessibility of suitable healthcare. © 1998 John Wiley & Sons, Ltd.
Mercury (Hg) is neurotoxic and children may be particularly susceptible to this effect. A current major challenge is identification of children who may be uniquely susceptible to Hg toxicity because of genetic disposition. This study examined the hypothesis that genetic variants of catechol-O-methyltransferase (COMT) that are reported to alter neurobehavioral functions that are also affected by Hg in adults might modify the adverse neurobehavioral effects of Hg exposure in children. Five hundred and seven children, 8-12 yr of age at baseline, participated in a clinical trial to evaluate the neurobehavioral effects of Hg from dental amalgam tooth fillings. Subjects were evaluated at baseline and at seven subsequent annual intervals for neurobehavioral performance and urinary Hg levels. Following the clinical trial, genotyping assays were performed for single-nucleotide polymorphisms (SNPs) of COMT rs4680, rs4633, rs4818, and rs6269 on biological samples provided by 330 of the trial participants. Regression-modeling strategies were employed to evaluate associations between allelic status, Hg exposure, and neurobehavioral test outcomes. Similar analysis was performed using haplotypes of COMT SNPs. Among girls, few interactions for Hg exposure and COMT variants were found. In contrast, among boys, numerous gene-Hg interactions were observed between individual COMT SNPs, as well as with a common COMT haplotype affecting multiple domains of neurobehavioral function. These findings suggest increased susceptibility to the adverse neurobehavioral effects of Hg among children with common genetic variants of COMT, and may have important implications for strategies aimed at protecting children from the potential health risks associated with Hg exposure.
The risk assessment of mercury (Hg), in both humans and wildlife, is made challenging by great variability in exposure and health effects. Though disease risk arises following complex interactions between genetic ("nature") and environmental ("nurture") factors, a majority of Hg studies thus far have focused solely on environmental factors. In recent years ecogenetic-based studies have emerged and have started to document that genetic and epigenetic factors may indeed influence the toxicokinetics and/or toxicodynamics of Hg. The purpose of this paper is to review these studies, to discuss their utility in terms of Hg risk assessment, management and policy, and to offer our perspectives on fruitful areas of future research. In brief, epidemiological studies on populations exposed to inorganic Hg (e.g., dentists and miners) or methylmercury (e.g., fish consumers) are showing that polymorphisms in a number of environmentally responsive genes can explain variations in Hg biomarker values and health outcomes. Studies on mammals (wildlife, humans, rodents) are showing Hg exposures to be related to epigenetic marks such as DNA methylation. Such findings are beginning to increase our understanding of Hg's mechanisms of actions, and in doing so they may help us identify candidate biomarkers and pinpoint susceptible groups or lifestages. Further, they may help refine uncertainty factors, and thus lead to more accurate risk assessments and improved decision-making. Environ Toxicol Chem © 2013 SETAC.
Methylmercury is among the most potentially toxic species to which human populations are exposed, both at high levels through poisonings and at lower levels through consumption of fish and other seafood. However, the molecular mechanisms of methylmercury toxicity in humans remain poorly understood. We used synchrotron X-ray absorption spectroscopy (XAS) to study mercury chemical forms in human brain tissue. Individuals poisoned with high levels of methylmercury species showed elevated cortical selenium with significant proportions of nanoparticulate mercuric selenide plus some inorganic mercury and methylmercury bound to organic sulfur. Individuals with a lifetime of high fish consumption showed much lower levels of mercuric selenide and methylmercury cysteineate. Mercury exposure did not perturb organic selenium levels. These results elucidate a key detoxification pathway in the central nervous system and provide new insights into the appropriate methods for biological monitoring.
Abstract — Blood samples from a group of 130 dentists and a control group of 40 blood-donors were analyzed by cold vapor atomic absorption spectrophotometry in order to evaluate the extent of mercury exposure. The median blood concentration of mercury was 4.0 (range: 1.2–19.2) μg/1 for dentists and 2.0 (1.1–4.6) μg/1 for controls (2P<0.01). Practice characteristics obtained in a questionnaire showed no statistically significant relationship to blood mercury, but 49 dentists having one or more fish meals per wk, had a median concentration of mercury, which was 47% higher than dentists seldomly consuming fish (2P<0.01). It was concluded that none of the examined dentists had blood concentrations above the level (35 μg Hg/1) associated with the hygienic threshold limit.
A concentrated review on the toxicology of inorganic mercury together with an extensive review on the neurotoxicology of methylmercury is presented. The challenges of using inorganic mercury in dental amalgam are reviewed both regarding the occupational exposure and the possible health problems for the dental patients. The two remaining "mysteries" of methylmercury neurotoxicology are also being reviewed; the cellular selectivity and the delayed onset of symptoms. The relevant literature on these aspects has been discussed and some suggestions towards explaining these observations have been presented.
For many years an amalgam containing metallic mercury, which has been associated with neurological and renal diseases, has been used in dentistry. In this nationwide study we compared hospital admissions due to neurological and renal diseases among dentists and dental assistants to admissions in controls.
This register-based cohort study included all Danish workers employed in dental clinics, general practitioners' clinics or lawyers' offices between 1964 and 2006. We compared dentists with general practitioners and lawyers, and dental assistants with medical secretaries, nurses and legal secretaries. We also compared dentists and dental assistants employed during periods with high occupational mercury exposure with dentists and dental assistants employed during periods with less mercury exposure. We followed all subjects in a nationwide register of hospital admissions. We analysed risk of neurological diseases, Parkinson's disease and renal diseases using a Cox regression model.
The cohort consisted of 122,481 workers including 5371 dentists and 33,858 dental assistants. For neurological diseases, no association was observed for dental assistants, while for dentists an increasing risk for periods with less mercury exposure was observed. Among dental assistants, a negative association between employment length and risk of neurological disease was observed. Admissions for renal disease among dental assistants were increased during periods with less mercury exposure compared with controls. For dentists a non-significant increased risk was observed between employment length and renal disease risk.
Our nationwide study does not indicate that occupational exposure to mercury increases the risk of hospital admissions for neurological, Parkinson's or renal diseases.
The aim of this study is to investigate the effect of elemental mercury exposure on renal function and antioxidative enzymes activity as a possible mechanism of renal affection among dental staff.
This study was performed on a group of dental staff exposed to elemental mercury (N = 32) and matched control group (N = 37). Urinary and blood level of mercury, albumin α1 microgloblin in urine, glutathione peroxidase and superoxide dismutase blood level were measured for the exposed and control group.
Compared to the control group, urinary and blood mercury were significantly higher in the exposed group. Glutathione peroxidase and superoxide dismutase activities in blood were significantly decreased and were negatively correlated with duration of work.
Oxidative stress is an important molecular mechanism for renal dysfunction in mercury exposure, manifested by decreased activities of antioxidant enzymes.
Due to public concern in Scandinavian countries about the health situation of dental nurses, the Norwegian Ministry of Labor and Social Inclusion initiated a project to look at previous exposure to metallic mercury and its possible effects on dental personnel. The aims of this part of the study were to: (i) describe Norwegian dental personnel's exposure to mercury during the last 50 years, (ii) develop a model for scoring that reflects the cumulative exposure on an individual basis, and (iii) relate the calculated score to earlier measured levels of mercury in urine.
We obtained lists of previous and current dental employees in both the private and public sector and mailed them a questionnaire concerning their working conditions. We received a response from 655 dental nurses and 452 dentists. We also obtained urine mercury levels measured between 1970-1990 for 143 (22%) of the dental nurses and 130 (29%) of the dentists.
The results revealed a widespread exposure to mercury in both the individual exposure score and the measured mercury values in urine. For most respondents, however, the level of exposure to mercury seemed to be low. The use of copper amalgam, which is heated before it is applied, is of particular concern as a significant source of mercury exposure in dental personnel.
It seems evident that the exposure to mercury among dental personnel varies substantially; this is important to take into account when making exposure assessments for this group of workers.
Mercury has long been recognised as toxic, principally in relation to its effects on humans following acute or prolonged high-level occupational exposures and, in the latter half of the last century, from a number of environmental incidents. Recognised target organs are the kidneys, central nervous system and thyroid glands. Recently concern has grown about the potential risks to the human population from current background environmental levels, leading bodies such as the World Health Organisation to call for the reduction or, wherever possible, elimination of the use of mercury. This review considers the strength of the epidemiological evidence on the effects of prolonged low-level exposure to the various forms of mercury. The limited research base suggests that several of the potential targets of long-term environmental exposure to mercury are similar to those occurring from occupational exposure including the renal, cardiovascular and immune systems. However, the evidence also suggests that, particularly in the case of organic mercury compounds, the most sensitive endpoint is central nervous system toxicity, especially in relation to exposure during the in utero period and childhood. It also appears that those human populations which have traditionally consumed diets high in seafoods are at greatest risk. While the extent of risk to the general population that may arise from existing environmental exposure levels appears limited, this conclusion is based on an incomplete dataset and therefore the general consensus view that exposure to mercury in its various forms should be minimised where practical, appears to be justified. A number of potential areas of further research are suggested as being pre-requisite to the development of a more rigorous risk assessment.
Previous investigations have presented evidence for an increased prevalence of late cognitive effects in dental personnel exposed to metallic mercury. We wanted to examine if there was a correlation between mercury exposure and cognitive effects in a Norwegian population of dental workers, and if so, to quantify the occurrence. The study group consisted of 608 female dental assistants from central Norway and 425 female controls from the general population, all under the age of 70. They had responded to a standardized postal questionnaire (Euroquest) inquiring about seven symptoms in regard to neurology, psychosomatics, memory, concentration, mood, sleep disturbances, and fatigue. A score was calculated for each symptom based on 4-15 single questions graded on a scale from 1 (seldom or never) to 4 (very often). Dental assistants and controls had a participation rate of 56.4% and 42.9% respectively. Dental assistants reported more cognitive symptoms than the controls, but on average they reported having each of the symptoms "now and then" or less frequently. There were 4.4% of the dental assistants and 2.8% of the controls who reported having three or more of the seven symptoms "often" or more frequently. The corresponding figures for five or more of the seven symptoms were 1.0% and 0.5% respectively. The occurrence of cognitive malfunction may be moderately increased in dental assistants. For dental assistants there was a relative risk of 1.6 of having three or more symptoms "often" or more frequently, and a relative risk of 2.0 of having five or more symptoms as frequently. It can be assumed from our results that the prevalence of possibly work-related cognitive malfunction in dental assistants is between 0.4% and 2.8%, dependent on the applied severity.
The study consisted of 35 male subjects attending an andrology clinic. The subjects all had poor sperm parameters that could not be attributed to any known medical cause. The objective was to evaluate the relation between various seminal characteristics (volume, total sperm count, sperm viability, proportion of progressively motile sperm, and different sperm morphology) and the blood concentrations of lead, cadmium, mercury, copper, and zinc. The mean blood concentrations of lead, mercury, copper, and zinc were within the normal values; cadmium concentration (1.35 micrograms/L) was much higher than the norms. Asthenozoospermic subjects had significantly (p less than .025) higher blood cadmium levels than normozoospermic subjects. No significant differences were noted between the two groups for mean concentration of mercury, zinc, and copper in blood. Significant correlations were observed between blood cadmium levels and volume of semen, midpiece defects, and immature forms of spermatozoa. High blood cadmium levels may have an effect on spermatogenesis. Possible reasons for the high blood cadmium levels among the subjects are discussed.
Neurobehavioural tests were performed by 98 dentists (mean age 32, range 24-49) exposed to elemental mercury vapour and 54 controls (mean age 34, range 23-50) with no history of occupational exposure to mercury. The dentists were exposed to an average personal air concentration time weighted average (TWA) of 0.014 (range 0.0007-0.042) mg/m3 for a mean period of 5.5 (range 0.7-24) years and had a mean blood mercury concentration of 9.8 (range 0.6-57) micrograms/l. In neurobehavioural tests measuring motor speed (finger tapping), visual scanning (trail making), visuomotor coordination and concentration (digit symbol), verbal memory (digit span, logical memory delayed recall), visual memory (visual reproduction, immediate and delayed recall), and visuomotor coordination speed (bender-gestalt time), the performance of the dentists was significantly worse than that of the controls. The dentists scored 3.9 to 38.9% (mean 13.9%) worse in these tests. In trail making, digit span, logical memory delayed recall, visual reproduction delayed recall, and bender-gestalt time test scores were more than 10% poorer. In each of the tests in which significant differences were found and in the block design time, the performance decreased as the exposed dose (product of the TWA of air mercury concentrations and the years of exposure) increased. These results raise the question as to whether the current threshold limit value of 0.050 mg/m3 (TWA) provides adequate protection against adverse effects of mercury.
Samples, mainly from occipital cortex and pituitary gland, but also from rental cortex, olfactory bulbs, thyroid gland and liver were collected from autopsies of 8 dental staff cases and 27 controls. These samples were analysed for total mercury content using radiochemical neutron activation analyses. The results revealed high mercury concentrations (median 815, range 135-4,040 micrograms Hg/kg wet weight) in pituitaries from the dental staff cases compared to controls (N = 23, median 23 range 6-1, 170 micrograms Hg/kg). In occipital cortex, the cases had a median of 17, range of 4-300 micrograms Hg/kg and the controls (N = 20) had a median of 10, range 2-29 micrograms Hg/kg. A few samples from olfactory bulbs show low mercury concentrations for both cases and controls. Renal cortex was analysed from three cases and contained clearly higher concentrations (945, 1,545, 2,110 micrograms Hg/kg) compared to controls (N = 12, median 180, range 21-810 micrograms Hg/kg). There is no control material for the other analysed samples, but one thyroid sample had an extremely high concentration of 28,000 micrograms Hg/kg.
A study of 162 dentists' and their assistants' mercury levels in hair and urine, and of questionnaire items regarding mercury consumption, revealed some striking relations. The mercury concentrations in both hair (Hg-H) and urine (Hg-U) were somewhat higher in the dentists than the assistants. There was no relation between concentrations in hair and urine. The method of condensation of amalgam was positively related to Hg-U; the vibration method was negatively related. Hg-U was also positively related to number of fillings and hours in own practice. The relation of Hg-U to ventilation in the surgery applied only to the dentists.
Blood samples from a group of 130 dentists and a control group of 40 blood-donors were analyzed by cold vapor atomic absorption spectrophotometry in order to evaluate the extent of mercury exposure. The median blood concentration of mercury was 4.0 (range: 1.2-19.2) micrograms/l for dentists and 2.0 (1.1-4.6) micrograms/l for controls (2P less than 0.01). Practice characteristics obtained in a questionnaire showed no statistically significant relationship to blood mercury, but 49 dentists having one or more fish meals per wk, had a median concentration of mercury, which was 47% higher than dentists seldomly consuming fish (2P less than 0.01). It was concluded that none of the examined dentists had blood concentrations above the level (35 micrograms Hg/l) associated with the hygienic threshold limit.
To measure the effects of chronic low-level exposure to inorganic mercury, the neuropsychological performances of 13 female dental auxiliary workers with elevated head mercury levels (as measured by an X-ray fluorescence technique) were compared with 13 workers with no measurable mercury levels. Workers with elevated mercury levels scored significantly less well on the Recurrent Figures, and SCL-90-R, but not on the WAIS, Rey's AVL, PASAT, BGT, Grooved Pegboard, and Finger Tapping tests. Chronic subtoxic levels of inorganic mercury appear to produce mild changes in short-term nonverbal recall and heightened distress generally, and particularly in categories of obsessive compulsion, anxiety and psychoticism, without alterations in general intellectual functioning, attention, verbal recall, and motor skills.