Mercury vapor exposures in dental offices

Mercury in dental amalgam: Are our health care workers at risk?

Dental amalgam in fillings exposes workers to mercury. The exposure to mercury was investigated among 1871 dental health care workers. The aim of the study was to evaluate the risk of mercury exposure among dental compared to nondental health care workers and to determine other risk factors for mercury exposure. Respondents answered questionnaires to obtain demographic, personal, professional, and workplace information and were examined for their own amalgam fillings. Chronic mercury exposure was assessed through urinary mercury levels. In total, 1409 dental and 462 nondental health care workers participated in the study. Median urine mercury levels for dental and nondental health care workers were 2.75 μg/L (interquartile range [IQR] = 3.0175) and 2.66 μg/L (IQR = 3.04) respectively. For mercury exposure, there were no significant risk factor found among the workers involved within the dental care. The Mann-Whitney test showed that urine mercury levels were significantly different between respondents who eat seafood more than 5 times per week compared to those who eat it less frequently or not at all (p = 0.003). The urinary mercury levels indicated significant difference between dental workers in their practice using squeeze cloths (Mann-Whitney test, p = 0.03). Multiple logistic regression showed that only the usage of cosmetic products that might contain mercury was found to be significantly associated with the urinary mercury levels (odds ratio [OR] = 15.237; CI: 3.612-64.276). Therefore, mean urinary mercury levels of health care workers were low. Exposure to dental amalgam is not associated with high mercury exposure. However, usage of cosmetic products containing mercury and high seafood consumption may lead to the increase of exposure to mercury.

IMPLICATIONS

Exposure to the high levels of mercury from dental amalgam can lead to serious health effects among the dental health care workers. Nationwide chronic mercury exposure among dental personnel was assessed through urinary mercury levels. Findings suggest low urinary mercury levels of these health care workers. Exposure to dental amalgam is not associated with high mercury exposure. However, the usage of cosmetic products containing mercury and high seafood consumption may lead to the increase of exposure to mercury.

Mercury sensitisation: review, relevance and a clinical report

Eczematous eruptions may be produced through topical contact with mercury and by systemic absorption in mercury sensitive individuals. Mercury is considered a weak sensitiser and contact with mercury salts such as chloride or ammonium chloride may cause hypersensitivity leading to contact dermatitis or Coomb's Type IV hypersensitivity reactions. The typical manifestation is an urticarial or erythematous rash, and pruritus on the face and flexural aspects of limbs, followed by progression to dermatitis. True allergy to mercury is rare but is more common in females. Exposure to mercury vapour produced in operating rooms is the main concern for dentists. Every effort should be made to avoid contact with mercury vapour if possible by using barrier techniques, reducing the temperature of the operating room and of the amalgam restoration. Air conditioning and proper ventilation of the operating room, the use of coolant sprays, good suction and proper handling of amalgam waste is recommended. Various reports show the use of MELISA (memory lymphocyte immunostimulation assay) and patch tests in determining mercury sensitivity. Topical application of glucocorticoids and dimethisone is helpful.

Neurological symptoms among dental assistants: a cross-sectional study

Background

Dental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure.

Methods

All dental assistants still at work and born before 1970 registered in the archives of a trade union in Hordaland county of Norway were invited to participate (response rate 68%, n = 41), as well as a similar number of randomly selected assistant nurses (response rate 87%, n = 64) in the same age group. The participants completed a self-administered, mailed questionnaire, with questions about demographic variables, life-style factors, musculoskeletal, neurological and psychosomatic symptoms (Euroquest).

Results

The dental assistants reported significant higher occurrence of neurological symptoms; psychosomatic symptoms, problems with memory, concentration, fatigue and sleep disturbance, but not for mood. This was found by analyses of variance, adjusting for age, education, alcohol consumption, smoking and personality traits. For each specific neurological symptom, adjusted logistic regression analyses were performed, showing that these symptoms were mainly from arms, hands, legs and balance organs.

Conclusion

There is a possibility that the higher occurrence of neurological symptoms among the dental assistants may be related to their previous work exposure to mercury amalgam fillings. This should be studied further to assess the clinical importance of the reported symptoms.

Exposição ocupacional por uso de mercúrio em odontologia: uma revisão bibliográfica

Este trabalho visa apresentar dados referentes ao gerenciamento de resíduos perigosos na área da saúde, com ênfase no uso de mercúrio em odontologia. Foi elaborado com base numa revisão bibliográfica sobre o uso do mercúrio em amálgama dentário e seus potenciais riscos toxicológicos ligados à exposição, tanto de profissionais quanto de pacientes. Os estudos levantados baseiam-se também em recomendações de alguns organismos internacionais e nacionais em relação ao uso do mercúrio e seus limites de exposição ocupacional. Os dados da literatura revelam o potencial tóxico do mercúrio, tanto para o ambiente quanto para a saúde humana. Tendo em vista que o amálgama ainda é muito utilizado na odontologia, considera-se necessário uma tomada de decisão político-administrativa que vise minimizar os riscos relacionados ao uso de amálgama em procedimentos odontológicos, voltados para a segurança ocupacional, dos indivíduos e do ambiente, baseada em diretrizes e orientações técnicas sobre seu uso, descarte e disposição final.

Exposure to mercury vapor and impact on health in the dental profession in Sweden

Possible adverse effects of mercury exposure in dentistry have been discussed in several studies. The objective of the present study was to carry out detailed measurements of mercury exposure in the dental profession in Sweden, and to search for adverse health effects from such exposure. We examined 22 dentists and 22 dental nurses, working in teams, at six Swedish dental clinics. Measurements of air mercury, performed with personal, active air samplers, showed a median air Hg of 1.8 micrograms/m3 for the dentists, and 2.1 micrograms/m3 for the dental nurses. Spot measurements with a direct reading instrument displayed temporarily elevated air Hg, especially during the preparation and application of amalgam. The average concentration of mercury in whole blood (B-Hg) was 18 nmol/L, in plasma (P-Hg) 5.1 nmol/L, and in urine (U-Hg) 3.0 nmol/mmol creatinine. Possible effects on the central nervous system (CNS) were registered with three questionnaires: Q16, Eysenck Personality Inventory (EPI), and the Profile of Mood Scales (POMS). In the Q16, the number of symptoms was statistically significantly higher in the dentistry group compared with an age- and gender-matched control group (n = 44). The urinary excretion of albumin and urinary activity of the tubular enzyme N-acetyl-beta-glucose-aminidase (NAG) did not differ between the two groups. The results confirm that exposure to mercury in the dental profession in Sweden is low. The air Hg levels were mainly influenced by the method of amalgam preparation and inserting, and by the method of air evacuation during drilling and polishing.

Cloning of mercury-resistance gene from R-plasmid in Escherichia coli isolated from dental hospital sewage

1. Mercury-resistance gene was cloned from a drug-resistance plasmid in Escherichia coli isolated from dental hospital sewage. 2. A 7.7 kb mercury-resistance gene was successfully cloned and expressed in pJC74 cosmid and pBR 322 plasmid vectors. 3. High activities of mercury reductase and 203Hg vaporization were demonstrated in cell extracts of mercury-resistant clone. 4. Mercury reductase activity was localized in the cytoplasm. 5. By colony DNA-DNA hybridization, 32P-labelled 7.7-kb DNA hybridized with mercury-resistant E. coli isolates from dental hospital sewage.

A study of mercury in the hair of dentists and dental-related professionals in 1985 and subcohort comparison of 1972 and 1985 mercury hair levels

Dentists may be exposed to mercury used in dental restorations. An epidemiologic study was conducted in central New York in 1985 comparing the concentration of mercury in the hair of 85 dentists to that of 23 dental-related health professionals (mainly orthodontists and oral surgeons) who do not use mercury. Mercury in the hair of dentists was nominally higher (2.98 +/- 0.57 ppm, mean +/- SE) than that of the control group (1.84 +/- 0.20 ppm) but not significantly so. There was a significant positive linear trend in the concentration of mercury in the dentists' hair with the number of years they had been in practice. Those dentists who wore masks when removing old mercury containing fillings showed significantly (p = 0.03) lower mercury concentrations in hair (1.7 +/- 0.26 ppm, mean +/- SE) than those who did not (3.65 +/- 0.85 ppm). Mercury concentration in the hair of 23 of the above dentists analyzed in 1972 was 16.77 +/- 4.00 ppm (mean +/- SE), significantly higher (p = 0.008) than that of the same dentists in 1985 (5.27 +/- 1.85 ppm). The reduction is believed due to the currently used pre-prepared disposable or reusable capsules containing the amalgam versus formerly mixing the ingredients manually. This may also account for the lack of a significant difference in mercury in the hair of the dentists versus that of the control group in 1985. The statistical relationships between mercury concentrations in hair of the two groups and reported health effects, as well as other factors including fish consumption, number of restorations per day, office floor covering, and urban or rural domicile, are discussed.

Chronic low-level mercury exposure and neuropsychological functioning

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.

Reduction of mercury vapour in a dental surgery

A restricted survey in one dental practice has shown that a considerable reduction in contamination by mercury vapour can be achieved by the use of a fume cupboard. Failure to employ this added protection may have legal implications.

Mercury toxicity in the pregnant woman, fetus, and newborn infant. A review

This paper reviews the reported cases of mercury poisoning in pregnancy and the data based on sources of contamination, maternal uptake, and distribution. It analyzes current knowledge of placental transfer of various mercury compounds, fetal uptake, and distribution. It identifies the embryopathic and fetal toxic effects of mercury in general while emphasizing the greater toxicity of methylmercury compounds. Since maternal exposure to methylmercury is primarily through fish consumption, it recommends that women of childbearing age should not consume more than 350 Gm. of fish per week. In addition, they should not be occupationally exposed to air concentrations of mercury vapor greater than 0.01 mg. per cubic meter, of inorganic and phenylmercuric compounds greater than 0.02 mg. per cubic meter, or any detectable concentration of methylmercury.