Mercury

“The main objectives of our study were to estimate the impact of a mercury cell chlor-alkali (MCCA) complex in Rosignano Solvay (Tuscany, Italy) on the local environment and to assess mercury exposure of inhabitants living near the plant. Measurement campaigns of atmospheric Hg near the MCCA plant showed that the impact of the emitted Hg from the industry on the terrestrial environment is restricted to a close surrounding area. Total gaseous mercury concentrations in ambient air of inhabited area around the MCCA plant were in the range of 8.0-8.7 ng/m3 in summer and 2.8-4.2 ng/m3 in winter. Peaks of up to 100 ng/m3 were observed at particular meteorological conditions. Background levels of 2 ng/m3 were reached within a radius of 3 km from the plant. Reactive gaseous mercury emissions from the plant constituted around 4.2% of total gaseous mercury and total particulate mercury emission constituted around 1.0% of total gaseous mercury emitted. Analysis of local vegetables and soil samples showed relatively low concentrations of total mercury (30.1-2919 microgHg/kg DW in the soil; <0.05-111 microgHg/kg DW in vegetables) and methylmercury (0.02-3.88 microgHg/kg DW in the soil; 0.03-1.18 microgHg/kg DW in vegetables). Locally caught marine fish and fresh marine fish from the local market had concentrations of total Hg from 0.049 to 2.48 microgHg/g FW, of which 37-100% were in the form of methylmercury. 19% of analysed fish exceeded 1.0 microgHg/g FW level, which is a limit set by the European Union law on Hg concentrations in edible marine species for tuna, swordfish and shark, while 39% of analysed fish exceeded the limit of 0.5 microgHg/g FW set for all other edible marine species. Risk assessment performed by calculating ratio of probable daily intake (PDI) and provisional tolerable daily intake (PTDI) for mercury species for various exposure pathways showed no risks to human health for elemental and inorganic mercury, except for some individuals with higher number of amalgam fillings, while PDI/PTDI ratio for methylmercury and total mercury exceeded the toxicologically tolerable value due to the potential consumption of contaminated marine fish.”

“INTRODUCTION:

The property of mercury to amalgamate with other metals is used to create a material for filling teeth. This material remains the cheapest and most efficient in tooth restoration. Mercurial toxicity has been documented since Antiquity but the metal remains widely used in some countries. This study compared mercury impregnation in dentists and dental assistants in Monastir (Tunisia) to another population not exposed professionally.

SUBJECTS AND METHODS:

A cross-sectional study was made on 52 dentists and dental assistants working in private offices and in the stomatology unit of the Monastir teaching hospital, with a control group of 52 physicians and nurses working in the Monastir Fattouma Bourguiba hospital. The groups were paired according to age and gender. The study lasted three months. A questionnaire investigated the socioprofessional features of the study population, non professional mercury exposure, work environment, the various amalgam handling and preparation techniques, and preventive hygiene measures. Urinary and salivary sampling was performed so as to prevent any accidental mercurial contamination. Mercury level was assessed by atomic absorption spectroscopy in an automatic sampler, urine creatinine with Jaffé’s colorimetric reaction. The results of mercury level assessment were expressed in microg/g of creatinine, salivary mercury in mug/l. The statistical analysis was made with the Epi.info 6 software. Khi(2) and Fisher tests were used to compare qualitative variables. The ANOVA test was used to compare averages with a statistic significance threshold at 0.05.

RESULTS:

Sixty-one percent of individuals with risk exposure worked in a dental clinic. Bruxism and onychophagia were more important in the control group with a significant statistical difference (respectively, p=0.01 and p<0.0001). The urinary and salivary mercury levels were significantly increased in the exposed group, with respective values of 20.4+/-42.4microg/g of creatinine and 10.6+/-13.02microg/l versus 0.04+/-0.3microg/g of creatinine and 0microg/l in the control group. Disposing of amalgam waste was inadequate in 94% of the cases. The variation of mercury in urine was significantly influenced by the presence of fabric curtains (p=0.04). Eating lunch at meals at the work place was also linked to a significant increase of mercury levels in urine (p=0.04). The storage mode of mercury in open containers was a significant factor for variation of mercury level (p=0.03).

DISCUSSION:

Most dentists’ private offices in Monastir do not comply or comply weakly with prevention measures linked to risk of mercury poisoning. Awareness campaigns were launched as well as actions for the improvement of work conditions: efficient aspiration of offices containing fixed sources of mercury, adequate storage of mercury and waste, and compliance to occupational hygiene rules.”

“The Food and Drug Administration (FDA) has developed this guidance as the special control to support the classification of dental amalgam into Class II (special controls), the reclassification of dental mercury1 from Class I to Class II, and the current classification of amalgam alloy in Class II. The three devices are now classified in a single regulation, Dental Amalgam, Mercury, and Amalgam Alloy, 21 CFR 872.3070. Mercury is elemental mercury, supplied as a liquid in bulk, sachet, or predosed capsule form, intended to be combined with amalgam alloy for the direct filling of carious lesions or structural defects in teeth. Amalgam alloy is composed primarily of silver, tin, and copper, supplied as a powder in bulk, tablet, or predosed capsule form, and is intended to be combined with mercury for the direct filling of carious lesions or structural defects in teeth. Dental amalgam consists of a combination of mercury and amalgam alloy, and is intended for the direct filling of carious lesions or structural defects in teeth. FDA is issuing this guidance in conjunction with a Federal Register (FR) notice announcing the final rule classifying dental amalgam, mercury, and amalgam alloy into Class II (special controls). The classification regulation designates this guidance document as the special control for these three devices.”

“SUMMARY: The Food and Drug Administration (FDA) is issuing a final rule classifying dental amalgam into class II, reclassifying dental mercury from class I to class II, and designating a special control to support the class II classifications of these two devices, as well as the current class II classification of amalgam alloy. The three devices are now classified in a single regulation. The special control for the devices is a guidance document entitled, ‘Class II Special Controls Guidance Document: Dental Amalgam, Mercury, and Amalgam Alloy.’ This action is being taken to establish sufficient regulatory controls to provide reasonable assurance of the safety and effectiveness of these devices. Elsewhere in this issue of the FEDERAL REGISTER, FDA is announcing the availability of the guidance document that will serve as the special control for the devices.”

“The U.S. Food and Drug Administration today issued a final regulation classifying dental amalgam and its component parts – elemental mercury and a powder alloy—used in dental fillings. While elemental mercury has been associated with adverse health effects at high exposures, the levels released by dental amalgam fillings are not high enough to cause harm in patients.”

“Abstract: Dental amalgams containing 50% mercury (Hg) have been used in dentistry for the last 150 years, and Hg exposure during key developmental periods was associated with autism spectrum disorders (ASDs). This study examined increased Hg exposure from maternal dental amalgams during pregnancy among 100 qualifying participants born between 1990-1999 and diagnosed with DSM-IV autism (severe) or ASD (mild). Logistic regression analysis (age, gender, race, and region of residency adjusted) by quintile of maternal dental amalgams during pregnancy revealed the ratio of autism:ASD (severe:mild) were about 1 (no effect) for < or =5 amalgams and increased for > or =6 amalgams. Subjects with > or =6 amalgams were 3.2-fold significantly more likely to be diagnosed with autism (severe) in comparison to ASD (mild) than subjects with < or =5 amalgams. Dental amalgam policies should consider Hg exposure in women before and during the child-bearing age and the possibility of subsequent fetal exposure and adverse outcomes.”

“The U.S. Food and Drug Administration today issued a final regulation classifying dental amalgam and its component parts – elemental mercury and a powder alloy—used in dental fillings. While elemental mercury has been associated with adverse health effects at high exposures, the levels released by dental amalgam fillings are not high enough to cause harm in patients.”

“The Food and Drug Administration (FDA) is issuing a final rule classifying dental amalgam into class II, reclassifying dental mercury from class I to class II, and designating a special control to support the class II classifications of these two devices, as well as the current class II classification of amalgam alloy. The three devices are now classified in a single regulation. The special control for the devices is a guidance document entitled, “Class II Special Controls Guidance Document: Dental Amalgam, Mercury, and Amalgam Alloy.” This action is being taken to establish sufficient regulatory controls to provide reasonable assurance of the safety and effectiveness of these devices. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of the guidance document that will serve as the special control for the devices.”

“PURPOSE: Nearly all eye drops contain preservatives to decrease contamination. Nonpreservatives such as disodium-ethylene diamine tetra-acetate (EDTA) and phosphate-buffered saline are also regularly added as buffering agents. These components can add to the toxicity of eye drops and cause ocular surface disease. To evaluate the potential toxicity of these common components and their comparative effects on the ocular surface, a tissue culture model utilizing immortalized corneal and conjunctival epithelial cells was utilized.

METHODS:
Immortalized human conjunctival and corneal epithelial cells were grown. At confluency, medium was replaced with 100 microL of varying concentrations of preservatives: benzalkonium chloride (BAK), methyl paraben (MP), sodium perborate (SP), chlorobutanol (Cbl), and stabilized thimerosal (Thi); varying concentrations of buffer: EDTA; media (viable control); and formalin (dead control). After 1 h, solutions were replaced with 150 microL of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazonium bromide). After 4 h, solutions decanted, 100 microL of acid isopropanol added, and the optical density determined at 572 nm to evaluate cell viability.

RESULTS:
Conjunctival and corneal cell toxicity was seen with all preservatives. Depending upon concentration, BAK exhibited from 56% to 89% toxicity. In comparison, Cbl exhibited from 50% to 86%, MP from 30% to 76%, SP from 23% to 59%, and Thi from 70% to 95%. EDTA with minimal toxicity (from 6% to 59%) was indistinguishable from SP.

CONCLUSIONS:
Generally, the order of decreasing toxicity at the most commonly used concentrations: Thi (0.0025%) > BAK (0.025%) > Cbl (0.25%) > MP (0.01%) > SP (0.0025%) approximately EDTA (0.01%). Even at low concentration, these agents will cause some degree of ocular tissue damage.”

“This Addendum was prepared in response to the recommendations of the Dental Products Panel and the Peripheral and Central Nervous System Drugs Advisory Committee (the Panel) concerning a 2006 White Paper presented in draft form to the Panel on September 6 and 7, 2006. FDA prepared this Addendum to address the Panel’s comments on the White Paper.”