Mercury

“BACKGROUND:

Intraoral metal contact allergy may result in mucositis that mimics lichen planus and the pathogenesis of squamous cell carcinoma.

METHODS:

Clinical records of all patients examined in the departments of dermatology and otorhinolaryngology at a tertiary-care academic medical center between June 1994 and June 2000 who had a diagnosis of intraoral squamous cell carcinoma adjacent to a metal dental restoration and who were patch tested with our metal series were reviewed retrospectively. Eleven patients met the inclusion criteria.

RESULTS:

Ten patients (91%) had positive patch tests to metals. In eight (73%), the oral cancer was adjacent to a dental restoration containing a metal to which the patient was allergic. Prevalence of gold, mercury, silver, and copper allergy among these patients was substantially higher than that reported in the available worldwide patch-test clinic population.

CONCLUSION:

Contact allergy to metal dental restorations may be a risk factor for development of intraoral squamous cell carcinoma.”

“Dental clinics discharge mercury in the form of amalgam, along with some dissolved mercury. This White Paper is meant to help POTWs and other organizations understand some of the technical issues associated with the generation of dental clinic wastewater and specifically to provide some useful, introductory information for those communities considering formal programs requiring the installation of amalgam separators.
This White Paper was prepared by NACW A to assist those communities or states that decide to recommend or require the installation of amalgam separators. This White Paper should not be interpreted as an endorsement for one approach over another. NACW A understands that there are a number of complex issues underlying the decision to begin an amalgam separator installation program and hopes this White Paper will provide some useful information.”

“Since the late 1960s, investigators have assessed the risks associated with exposure to a variety of potentially harmful agents used in dental practice. This paper provides a brief overview of the epidemiologic literature examining the associations between occupational exposures to elemental mercury and anesthetic gases and reproductive outcomes, such as spontaneous abortion, congenital abnormalities and reduced fertility. Most of the epidemiologic evidence points to a significant relationship between exposure to nitrous oxide and both spontaneous abortion and reduced fertility. There is also evidence for an association between exposure to ethylene oxide and spontaneous abortion, but on the basis of the limited research available, this relationship does not appear to be statistically significant. At this time, evidence of a relationship between exposure to elemental mercury and spontaneous abortion, congenital abnormalities and reduced fertility is limited. Good mercury hygiene by dental personnel and the use of scavenging equipment on nitrous oxide systems and exhaust systems on ethylene oxide sterilizers may reduce the risk of adverse reproductive outcomes.”

“CONCLUSIONS: In this study, there were no statistically significant differences in adverse neuropsychological or renal effects observed over the 5-year period in children whose caries were restored using dental amalgam or composite materials. Although it is possible that very small IQ effects cannot be ruled out, these findings suggest that the health effects of amalgam restorations in children need not be the basis of treatment decisions when choosing restorative dental materials.”

“Mercury toxicity and intoxication (poisoning) are realities that every American needs to face. Both the Environmental Protection Agency and National Academy of Science state that between 8 to 10% of American women have mercury levels that would render any child they gave birth to neurological disorders. One of six children in the USA have a neurodevelopmental disorder according to the Centers for Disease Control and Prevention. Yet our dentistry and medicine continue to expose all patients to mercury. This article discusses the obvious sources of mercury exposures that can be easily prevented. It also points out that genetic susceptibility and exposures to other materials that synergistically enhance mercury and ethylmercury toxicity need to be evaluated, and that by their existence prevent the actual determination of a ‘safe level’ of mercury exposure for all. The mercury sources we consider are from dentistry and from drugs, mainly vaccines, that, in today’s world are not only unnecessary sources, but also sources that are being increasingly recognized as being significantly deleterious to the health of many.”

“OBJECTIVE: To investigate whether municipal health clinics in the city of Belo Horizonte, Brazil, comply with the legal requirements for managing dental wastes.

METHOD:

We collected information from 54 of the city’s 105 municipal health clinics that provide dental care. At each clinic we interviewed the clinic manager, one dental assistant, and one general assistant. Based on the requirements outlined in the Belo Horizonte Health Waste Management Manual, we assessed characteristics in the following three areas: (1) technical and operational (waste classification and characterization, minimization, segregation, pretreatment, conditioning, collection and internal and external transportation, and external storage); (2) general and organizational (inspection, amount of clinic space, environmental permits, floor plan showing waste-generating areas, and whether the clinic had a technical specialist responsible for managing the health wastes); and (3) human resources (employee vaccination records and oversight, occupational safety and occupational medicine program, environmental risk prevention program, medical oversight and occupational health program, hospital (clinic) infection control committee, and training in health waste management).

RESULTS:

The clinics produced an average of 270 liters of solid waste per day. None of the clinics surveyed had a plan for managing health wastes. The only requirements with which all the clinics complied were: segregation of needles and mercury, adequately identified cardboard containers used for disposal of cutting and piercing items, and daily internal collection and transportation of wastes.

CONCLUSIONS:

When the risks associated with each class of waste have not been established, all the wastes should be considered potentially dangerous. Further, a law by itself does not guarantee that the public’s health will be protected. Before public agencies impose legal requirements, it is necessary to know if the agencies themselves are capable of enforcing those requirements. Any proposed waste management legislation should be based on scientific research.”

“Potential cognitive and motor effects from exposure to elemental mercury (Hg(0)) were examined in the presence and absence of a polymorphism (Val66Met) in brain-derived neurotrophic factor (BDNF). A group of 194 male dentists (DDs) and 233 female dental assistants (DAs) were occupationally exposed to mercury and had no history of kidney or nervous system disorders. Acute exposure was measured using spot urinary Hg (HgU) concentrations (average 3.32 and 1.98 microg/l, respectively) and indices of chronic occupational exposure (26.3 and 14.9 years, respectively, weighted for historical exposures). The BDNF status was 68% and 66% wild type, 26% and 30% single substitution, and 5% and 4% full mutation for DDs and DAs, respectively. DDs and DAs were evaluated separately. Regression analyses controlled for age, premorbid intelligence, alcohol consumption, and education. Statistically significant adverse associations with HgU (p<.05) were found for nine measures among DDs (Digit Span (Forward), Digit and Spatial Span(Backward), Visual Reproduction, Finger Tapping(Dominant, Alternate, and Alternate Partialed), Hand Steadiness, and Tracking), and eight measures among DAs (Digit Span(Forward), Visual Reproduction, Pattern Discrimination(Rate), Symbol Digit(Rate), Trailmaking B, Finger Tapping(Dominant and Alternate Partialed), and Hand Steadiness). The BDNF status was associated with four measures in DDs and three measures in DAs. Joint effects were found for Finger Tapping(Alternate and Alternate Partialed) in DDs and Hand Steadiness and Trailmaking B in DAs. Joint effects were additive in all cases. Performance on verbal intelligence and reaction time were not associated with either HgU or BDNF status. A test of threshold effect for the association of Hand Steadiness with HgU demonstrated no lower boundary in both DDs and DAs. No associations were observed with estimates of chronic mercury exposure. Our findings are applicable to exposure levels of the general population and identify a potentially vulnerable group with a BDNF polymorphism.”

“Mercury (Hg) is a naturally occurring element and its toxicity, especially in certain forms, has been known for many years. Exposure to Hg can occur in occupational and environmental settings. The toxicity of Hg compounds in dentistry has been an issue of increasing concern. Dental personnel are occupationally exposed to Hg vapor in their working environment and this exposure constitutes a potential risk to people in the dental surgery, mainly from the inhalation of Hg vapor and fine particles of amalgam. In this study, the urinary Hg excretion levels of 20 dentists and nine control subjects, matched for age, were determined by cold-vapor atomic absorption spectrometer (CV-AAS). The levels of Hg in the urine samples of the dentists was about three times higher than the control subjects (6.2 +/- 3.5 and 1.97 +/- 0.9 microg/L, respectively) (P <0.001). Some 90% of dentists wore both gloves and masks. Standards of hygiene (use of mask, glove and gown) may contribute to the degree of exposure. Attention to important hygiene measures, such as the avoidance of spills of Hg, cleaning of floors after such spills, ventilation and the installation of ventilation, depending on technology, should be taken into consideration. Age and smoking habits did not influence the urinary Hg excretion. Our results showed that dentists had significant exposure to Hg vapor compared to control subjects and therefore might be subject to possible adverse effects due to Hg toxicity.”

“BACKGROUND:

Mercury is a ubiquitous and highly toxic environmental pollutant. In this study, we evaluated the relationship between mercury exposure and oxidative stress, serum and urinary mercury concentrations, oxidative DNA damage, and serum redox status in chronically mercury-exposed persons compared with healthy controls.

METHODS:

We measured urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), which we used as a biomarker of oxidative DNA damage in the mercury-exposed persons, by HPLC with electrochemical detection (ECD). We evaluated antioxidant status by measuring the activities of superoxide dismutase and glutathione peroxidase and the concentrations of total reduced glutathione and protein-bound thiols in serum.

RESULTS:

The significant increase in 8-OHdG concentrations in urine indicated that mercury-induced oxidative damage to DNA occurred in vivo. Differences in body mercury burden and antioxidant enzyme activities were statistically significant between the mercury-exposed persons and controls. Serum and urinary mercury concentrations in the mercury-exposed persons were more than 40-fold higher than in controls.

CONCLUSIONS:

Mercury exposure can induce oxidative DNA damage, whereas the antioxidative repair systems can be expected to minimize DNA lesions caused by mercury. Measurement of urinary 8-OHdG could be useful for evaluating in vivo oxidative DNA damage in mercury-exposed populations.”

“Thimerosal is a preservative that has been used in manufacturing vaccines since the 1930s. Reports have indicated that infants can receive ethylmercury (in the form of thimerosal) at or above the U.S. Environmental Protection Agency guidelines for methylmercury exposure, depending on the exact vaccinations, schedule, and size of the infant. In this study we compared the systemic disposition and brain distribution of total and inorganic mercury in infant monkeys after thimerosal exposure with those exposed to MeHg. Monkeys were exposed to MeHg (via oral gavage) or vaccines containing thimerosal (via intramuscular injection) at birth and 1, 2, and 3 weeks of age. Total blood Hg levels were determined 2, 4, and 7 days after each exposure. Total and inorganic brain Hg levels were assessed 2, 4, 7, or 28 days after the last exposure. The initial and terminal half-life of Hg in blood after thimerosal exposure was 2.1 and 8.6 days, respectively, which are significantly shorter than the elimination half-life of Hg after MeHg exposure at 21.5 days. Brain concentrations of total Hg were significantly lower by approximately 3-fold for the thimerosal-exposed monkeys when compared with the MeHg infants, whereas the average brain-to-blood concentration ratio was slightly higher for the thimerosal-exposed monkeys (3.5 +/- 0.5 vs. 2.5 +/- 0.3). A higher percentage of the total Hg in the brain was in the form of inorganic Hg for the thimerosal-exposed monkeys (34% vs. 7%). The results indicate that MeHg is not a suitable reference for risk assessment from exposure to thimerosal-derived Hg. Knowledge of the toxicokinetics and developmental toxicity of thimerosal is needed to afford a meaningful assessment of the developmental effects of thimerosal-containing vaccines.”