Elemental Mercury Vapor Research Articles

Developments of the Plasma-Enhanced Electrostatic Precipitator for Mercury Removal in Offgas

This paper presents the latest results of testing using a scaled up 28-standard liter per minute (slpm) [1-standard cubic foot per minute (scfm)] version of the recently designed and constructed plasma-enhanced electrostatic precipitator (PEESP). Previous results were published at bench scale. The PEESP technology injects a selected reagent gas mixture through a corona discharge generated by central electrodes. By adapting the electrode for reagent gas injection directly into the active zone, the area surrounding the sharp discharge points, chemical radicals are immediately formed from the absorption of ozone at the corona discharge points. Experimental evidence suggests that reactive species and radicals are formed that selectively oxidize the elemental mercury vapor, which forms water-soluble compounds and fine particulate that are absorbed by the condensing water droplets. In the electric field, the water droplets acquire a negative charge and are attracted to the grounded positive electrode (reactor wall) where they are removed from the system. The aqueous mercuric ions, thus formed, are collected on the electrode walls and removed as a liquid slurry. The PEESP has no moving parts, minimizing maintenance. The PEESP process is expected to be economical. The PEESP electrode assembly is intended to replace the existing electrostatic precipitator central electrode and use the existing power supply. While oxidized forms are largely removed by scrubbing systems, highly volatile elemental mercury is not. The only known effective control technology for mercury is carbon or other types of sorbent injection followed by a baghouse. Since the PEESP uses gases as a reagent to oxidize the elemental mercury, it can greatly minimize the issues of storage, handling, and associated hazardous waste disposal typical of solid injection systems for mercury removal.

Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil

We evaluated vision loss in workers from fluorescent lamp industries ( n = 39) who had retired due to intoxication with mercury vapour and had been away from the work situation for several years (mean = 6.32 years). An age-matched control group was submitted to the same tests for comparison. The luminance contrast sensitivity (CSF) was measured psychophysically and with the sweep visual evoked potential (sVEP) method. Chromatic red–green and blue–yellow CSFs were measured psychophysically. Colour discrimination was assessed with the Farnsworth–Munsell 100-hue test, Lanthony D-15d test and Cambridge Colour Vision Test. Patient data showed significantly lower scores in all colour tests compared to controls ( p < .001). The behavioural luminance CSF of the patients was lower than that of controls ( p < .001 at all frequencies tested). This result was confirmed by the electrophysiologically measured sweep VEP luminance CSF except at the highest frequencies—a difference that might be related to stimulus differences in the two situations. Chromatic CSFs were also statistically significantly lower for the patients than for the controls, for both chromatic equiluminant stimuli: red–green ( p < .005) and blue–yellow ( p < .04 for all frequencies, except 2 cycles per degree (cpd), the highest spatial frequency tested) spatial gratings. We conclude that exposure to elemental mercury vapour is associated with profound and lasting losses in achromatic and chromatic visual functions, affecting the magno-, parvo- and koniocellular visual pathways.

Adsorption Enhancement Mechanisms of Silica−Titania Nanocomposites for Elemental Mercury Vapor Removal

A novel nanocomposite that combines high-surface area silica with the photocatalytic properties of titania has been developed that allows for effective capture of elemental mercury vapor. The adsorption capability of the developed material has been found to improve after periods of photocatalytic oxidation. In this study, the mechanisms for adsorption enhancement were identified. BET nitrogen adsorption and mercury porosimetry were used to evaluate pore structure, and the results suggest that a decrease in contact angle was likely to be responsible for improved mercury capture over time. Contact angle measurements showed a significant change of more than 10 degrees, indicating greater attraction to mercury for the used pellets due to deposited mercuric oxide. ICP and TGA analyses showed that mercury was captured as both elemental mercury (Hg0) and mercuric oxide (HgO). In addition, it was shown that pellets used for nearly 500 h still showed greater than 90% removal efficiency and had an average capacity of 10 mg of Hg/g based on mass balance calculations, while some pellets had a capacity over 30 mg of Hg/g according to ICP and TGA analyses. Mercuric oxide doped pellets removed 100% of elemental mercury without pretreatment. The superior mercury removal efficiency combined with various advantages of the novel composite demonstrates its use as an effective alternative to conventional activated carbon injection technology.

Analysis of the relationship between pineal hormone melatonin level and occupational mercury exposure in ex-miners with machine learning methods

The aim of this study was an analysis of the relationship between pineal hormone melatonin level and long-term occupational exposure to elemental mercury vapour (Hg°) of ex-mercury miners. Melatonin (MEL) is a hormonal product of the pineal gland. Hg accumulation in the pineal gland in ex-miners could modify the synthesis of melatonin and there are no data available in the scientific literature on the possible effects of Hg on melatonin excretion. Regression/model trees were used to perform the analyses and investigate the interactions between melatonin secretion and excretion on one hand, and various indicators of occupational Hg exposure and some other medical variables on the other. The results point us towards some previously unknown factors that influence the excretion of melatonin and support some assumptions that melatonin also has antioxidative effect. In the process of antioxidation activity melatonin decomposes and we assume this is the reason for decreased excretion of melatonin in mercury miners.

Neurobehavioral changes in metallothionein-null mice prenatally exposed to mercury vapor

We studied the neurobehavioral effects of prenatal exposure of MT-null and wild-type mice to elemental mercury vapor (Hg 0). Pregnant mice of both strains were repeatedly exposed to Hg 0 vapor at 0.50 and 0.56 mg/m 3 for 6 h/day until the 18th day of gestation. The behavioral effects were evaluated with locomotor activity in the open field, learning ability in the passive avoidance response and spatial learning ability in the Morris water maze at 12 weeks of age. Hg 0-exposed MT-null mice showed a significant decrease in total locomotor activity in males, and a learning disability in the passive avoidance response and a retarded acquisition in the Morris water maze in females as compared with the control. In contrast, Hg 0-exposed wild-type mice did not differ from controls in the three behavioral measurements. The results indicate that MT-null mice would be more susceptible than wild-type mice to the behavioral neurotoxicity of prenatal Hg 0 exposure. Mercury concentrations in the brain of both strains were slightly higher in the exposed group than in the control group, indicating the retention of residual mercury even 12 weeks after the cessation of the exposure. Brain concentrations of mercury were also significantly higher in the exposed-females than exposed-males in either strain. From these results, we suggest that the increased susceptibility of MT-null females to behavioral changes caused by prenatal Hg 0 exposure is due to a greater retention of mercury and lack of MT-I,-II in the brain.

An inexpensive method to test for mercury vapor in herbarium cabinets

AbstractMercuric chloride has been used for control of insect and fungal infestations in herbarium collections for over two centuries. One of the lasting effects of this use is the long­term evolution of elemental mercury vapor from treated specimens. The vapor can contaminate untreated specimens sharing the same closed environment and can pose a human health hazard. By modifying the technique for use of a commercially available mercury indicating powder (Mallinckrodt Baker, Inc., J. T. Baker Mercury Indicator) it is possible to create an inexpensive and fairly rapid test for mercury vapor in herbarium cabinets. The indicator is mixed with deionized water and applied to glass microscope slides. One or more slides are placed inside a cabinet and any color change in the indicator is compared to unexposed controls. In the authors’ experiments, the indicator results were compared against readings taken using a Jerome 431­X Mercury Vapor Analyzer and a Lumex RA­915+ Multifunctional Mercury Analyzer and were found to be broadly related to the concentration of mercury vapor present in each cabinet. The method can be used to check for mercury contamination in incoming shipments of specimens and to identify cabinets that currently contain or formerly contained contaminated specimens. Practical safety guidelines have been developed for accessing cabinets that give a positive test for the vapor and for handling contaminated specimens.

METHYLMERCURY TOXICOLOGY PROBED

HUMANS ARE EXPOSED TO MORE mercury from eating fish, marine mammals, and crustaceans than from any other source, according to the Food & Drug Administration and the Environmental Protection Agency. Last month, they issued a joint draft advisory about fish consumption to women who are or might become pregnant, and they plan to issue a new general consumer advisory in the coming months. According to the December advisory, nearly all fish contain at least traces of methylmercury, although the amount of mercury can vary considerably. Methylmercury, a biologically active form of mercury, is derived from inorganic mercury. Elemental mercury vapor that occurs naturally in the environment and is released by industrial plants is oxidized to Hg 2+ in the atmosphere and returned to Earth's surface in rainwater. Inorganic mercury from both natural and human sources is laid down in sediments in the ocean and in bodies of freshwater. Inorganic mercury is ...

Bench-Scale Experimental Study on the Effect of Flue Gas Composition on Mercury Removal by Activated Carbon Adsorption

This paper outlines the results of a systematic study on the capture of trace mercury vapor from simulated flue gases, using activated carbons. The experiments were conducted on a bench-scale fixed-bed test rig with intensive focus on the variable flue gas components and compositions. To understand the interaction and competitive adsorption of different gas components well, these gases (O2, CO2, SO2, and moisture) were introduced, one by one, into the simulated flue gas system, which basically contained only nitrogen and elemental mercury vapor. The performances of five commercially available activated carbons and one prepared H2S-exhausted activated carbon were evaluated under different flue gas compositions. The experimental data suggested that the adsorption of mercury is greatly dependent upon the flue gas compositions. For sulfur-impregnated carbon, adsorption capacity is more constant than virgin carbon over a wide range of humidities and CO2 and SO2 concentrations. The H2S-exhausted activated carbo...

Color Discrimination Impairment in Workers Exposed to Mercury Vapor

Objective: To study color discrimination impairment in workers exposed to elemental mercury (Hg) vapor. Subjects: Twenty-four male workers from a chloralkali plant exposed to Hg vapor, aged 42±9.8 years, duration of exposure 14.7±9.7 years, were examined. The 8 h TWA air-borne Hg concentration in workplace was 59 μg/m 3; mean Hg urinary excretion (HgU) was 20.5±19.3 μg/g creatinine; mean Hg urinary excretion after the administration of a chelating agent, sodium 2,3-dimercapto-1-propane-sulfonate (DMPS), was 751.9±648 μg/48 h. Twenty-four age- and gender-matched control subjects were compared. Visual acuity, alcohol intake, smoking habits, and history of diseases or drugs potentially influencing color vision were registered. Methods: The Lanthony 15-Hue desaturated test (L-D15-d) was used to assess color vision. The results were expressed quantitatively as Bowman’s Color Confusion Index (CCI), and qualitatively according to Verriest’s classification of acquired dyschromatopsias. Results: The CCI was significantly higher in the exposed group than in the control (mean CCI 1.15 versus 1.04; P=0.04). The proportion of subjects with errorless performance on the Lanthony test was significantly lower in the Hg exposed group compared to referents (52% versus 73%; P=0.035). The exposed group showed higher frequency of type III dyschromatopsias (blue–yellow confusion axis) in comparison with the control group (12.5% versus 8.3%), however, the difference did not reach statistical significance. Multiple regression did not show any significant relationship between the CCI, and age, alcohol consumption, or measures of exposure. Conclusion: In agreement with previous studies by Cavalleri et al. [Toxicol. Lett. 77 (1995) 351; Environ. Res. Sec. A 77 (1998) 173], the results of this study support the hypothesis that exposure to mercury vapor can induce sub-clinical color vision impairment. This effect was observed at an exposure level below the current biological limit for occupational exposure to mercury. This raises doubts on the actual protection afforded by this limit concerning the effect of mercury on color vision.

Genomic analysis of the rat lung following elemental mercury vapor exposure.

Elemental mercury (Hg0) is a highly toxic chemical with increasing public health concern. Although the lung receives the highest exposure to Hg0 vapor, it is resistant to Hg0 toxicity relative to the kidney and brain. In an earlier study, exposure of rats to 4 mg Hg0 vapor/m3, 2 h per day for 10 days, did not produce pathological alterations in the lung but increased metallothionein and glutathione S-transferase in the kidney. This study was undertaken to examine pulmonary gene expression associated with Hg0 vapor inhalation. Total RNA was extracted from lung tissues of rats, previously exposed to air or Hg0 vapor, and subjected to microarray analysis. Hg0 vapor exposure increased the expression of genes encoding inflammatory responses, such as chemokines, tumor necrosis factor-alpha (TNFalpha), TNF-receptor-1, interleukin-2 (IL-2), IL-7, prostaglandin E2 receptor, and heat-shock proteins. As adaptive responses, glutathione S-transferases (GST-pi, mGST1), metallothionein, and thioredoxin peroxidase were all increased in response to Hg exposure. Some transporters, such as multidrug resistance-associated protein (MRP), P-glycoprotein, and zinc transporter ZnT1, were also increased in an attempt to reduce pulmonary Hg load. The expression of transcription factor c-jun/AP-1 and PI3-kinases was suppressed, while the expression of protein kinase-C was increased. Expression of epidermal fatty acid-binding protein was also enhanced. Real-time RT-PCR and Western blot analyses confirmed the microarray results. In summary, genomic analysis revealed an array of gene alterations in response to Hg0 vapor exposure, which could be important for the development of pulmonary adaptation to Hg during Hg0 vapor inhalation.

Release of Mercury from Broken Fluorescent Bulbs

Mercury is a persistent, bioaccumulative toxin. Although the primary human exposure is from ingestion of fish contaminated with methyl mercury (HgCH3 ), exposures to elemental mercury vapor and mercury compounds via inhalation and dermal contact may also occur. Fluorescent bulbs contain mercury. Estimates of the amount of this mercury released when the bulbs are discarded and broken have varied widely. A new method was developed for measuring mercury released from broken bulbs. With the assumption that all mercury released is elemental vapor, it was found that between 17 and 40% of the mercury in broken low-mercury fluorescent bulbs is released to the air during a two-week period immediately following breakage, with higher temperatures contributing to higher release rates. One-third of the mercury release occurs during the first 8 hr after breakage. Many bulbs contain more mercury than the low-mercury bulbs tested. A typical discarded bulb releases between 3 and 8 mg of elemental mercury vapor over two weeks. Approximately 620 million fluorescent bulbs are discarded annually in the United States, and many are broken during disposal. Based on the estimated release rate of 3-8 mg per broken bulb developed in this study, discarded bulbs release approximately 2-4 tons of mercury per year in the United States. Waste management systems that minimize breakage before final disposal could reduce this total, as would the reduction of mercury content of bulbs. Elevated airborne levels of mercury could exist in the vicinity of recently broken bulbs, and under certain conditions, mercury concentrations could exceed occupational exposure

Nanostructured Silica-Gel Doped with TiO 2 for Mercury Vapor Control

A novel high surface area SiO2–TiO2 composite has been developed for elemental mercury vapor removal from combustion sources. The composite exhibits synergistic adsorption and photocatalytic oxidation. Mercury vapor in the gas stream is adsorbed, oxidized and stays on the composite. The composite has demonstrated a high mercury capacity (1512ug/g) although in its current 3-mm pellet form only the outer layer is effectively utilized. The loading of 13% TiO2 shows the best removal, both with and without UV irradiation. Increasing TiO2 loading beyond this level does not enhance the removal further. It has also been observed that the composite after being 'activated' by photocatalytic oxidation has better performance, probably due to the change of surface functional groups. The examination of the effects of flow velocity reveals that mass transfer is the rate limiting step. Relative humidity has been found to impede adsorption therefore decreasing the overall removal efficiency. By rinsing with acid, both the deposited mercury and composite can be regenerated.

Elemental mercury poisoning in occupational and residential settings

In its elemental form, mercury is the only metal that is in a liquid state at room temperature. It readily volatilizes at standard temperature and pressure, and its presence in open containers can result in biologically significant air concentrations in unventilated or poorly ventilated spaces. In recent years, elemental mercury has proven to be a potential source of toxicosis through either unintentional exposure or exposure resulting from inappropriate handling of liquid mercury acquired from school science laboratories or abandoned industrial facilities or warehouses. The shiny, silvery appearance of mercury in its liquid form makes it particularly enticing to children, and its insolubility in water and tendency to form beads when disturbed add to its mystique. This paper presents two case studies in which excessive exposure to elemental mercury vapor has resulted in adverse health effects in the exposed individuals: one in the workplace and one in a residential setting. These case studies serve to emphasize that primary care physicians, public health officials, and science educators need to recognize the potential risk posed by inhalation exposure to mercury vapors, and health practitioners need to be able to recognize the health signs and symptoms of such exposure. Public health professionals and those in charge of public and private education facilities should also be keenly aware of the necessity of prompt mitigation of human exposure should a spill or other mercury exposure scenario occur.

Heterogeneous oxidation of mercury in simulated post combustion conditions

Heterogeneous mercury oxidation was studied by exposing whole fly ash samples and magnetic, nonmagnetic, and size-classified fly ash fractions to elemental mercury vapor in simulated flue gas streams. Fly ash from sub-bituminous Wyodak–Anderson PRB coal and bituminous Blacksville coal were used. Scanning electron microscopy, X-ray diffraction, thermogravimetric analyses, and BET N 2 isothermal sorption analyses were performed to characterize the fly ash samples. Mercury speciation downstream from the ash was determined using the Ontario Hydro method. Results showed that the presence of fly ash was critical for mercury oxidation, and the surface area of the ash appears to be an important parameter. However, for a given fly ash, there were generally no major differences in catalytic oxidation potential between different fly ash fractions. This includes fractions enriched in unburned carbon and iron oxides. The presence of NO 2, HCl, and SO 2 resulted in greater levels of mercury oxidation, while NO inhibited mercury oxidation. The gas matrix affected mercury oxidation more than the fly ash composition.

Maternal-to-fetus transfer of mercury in metallothionein-null pregnant mice after exposure to mercury vapor

This study examined the role of placenta metallothionein (MT) in maternal-to-fetal mercury transfer in MT-null and wild-type mice after exposure to elemental mercury (Hg 0) vapor. Both strains were exposed to Hg 0 vapor at 5.5–6.7 mg/m 3 for 3 h during late gestation. Twenty-four hours after exposure to Hg 0 vapor, accumulation of mercury in the major organs, except the brain, of MT-null maternal mice was significantly lower than that in organs of wild-type mice. In contrast to mercury levels in maternal organs, fetal mercury levels were significantly higher in MT-null mice than in wild-type mice. In placenta, mercury concentrations were not significantly different between the two strains.. Although MT levels in major organs, except the brain, of wild type mice were markedly elevated after the exposure to Hg 0 vapor, the placental MT levels were not elevated. However, endogenous MT level in the placenta is significantly higher than that in other organs, except the liver. Gel filtration profile of the placental cytosol in the wild-type mice revealed that a large amount of placental mercury was associated with MT. In MT-null mice, mercury in placental cytosol appeared mainly in the high-molecular-weight protein fractions. Mercury in the placenta was localized mainly in the yolk sac and decidual cells in the deep layer of the decidua in both mouse strains. The similar localization of MT was found in the placenta of wild type mice. These results suggest that MT in the placenta has a defensive role in preventing maternal-to-fetal mercury transfer.

Disposition of inhaled mercury vapor in pregnant rats: maternal toxicity and effects on developmental outcome.

The disposition and toxicity of inhaled elemental mercury (Hg0) vapor for pregnant Long-Evans rats, and potential adverse effects on reproductive outcome were investigated. Rats were exposed to 0, 1, 2, 4, or 8 mg Hg0/m(3) for 2 h/day from gestation day (GD) 6 through GD 15. Maternal toxicity occurred primarily in rats exposed to 4 and 8 mg/m(3) and was manifested as a concentration-related decrease in body weight gain and mild nephrotoxicity. Control rats gained about 13% of their initial body weight during the 10-day exposure. Rats exposed to 4 mg/m(3) Hg0 gained about 7% less than controls, and rats exposed to 8 mg/m(3) Hg0 lost about 17% of their initial body weight during the 10-day exposure period. Maternal kidney weights were significantly increased in the 4 and 8 mg/m(3) concentration groups, and urinalysis revealed increased levels of protein and alkaline phosphatase activity in urine of all Hg0-exposed rats. Dams exposed to 8 mg/m(3) were euthanized in moribund condition on postnatal day (PND) 1. There was no histopathological evidence of toxicity in maternal lung, liver, or kidney of exposed rats at GD 6, GD 15, or PND 1. The incidence of resorptions was significantly increased, litter size and PND 1 neonatal body weights were significantly decreased only in the 8-mg/m(3) group. Total Hg concentrations in maternal tissues increased with increasing number of exposure days and concentration. In general, approximately 70% of Hg was eliminated from maternal tissues during the week following the last exposure (GD 15 to PND 1). Elimination of Hg from maternal brain and kidney was slower than in other tissues, possibly due to higher levels of metallothionein. Total Hg concentrations in fetal tissues increased with increasing number of exposure days and concentration, demonstrating that a significant amount of Hg crossed the placenta. One week after the last exposure, significant amounts of Hg were still present in brain, liver, and kidney of PND 1 neonates. Metallothionein levels in neonatal tissues were not significantly increased by exposure to 4 mg/m(3) Hg0. The total amount of Hg in neonatal brain (ng/brain) continued to increase after termination of inhalation exposure, suggesting a redistribution of Hg from the dam to neonatal brain. These data demonstrate that inhaled Hg0 vapor is distributed to all maternal and fetal tissues in a dose-dependent manner. Adverse effects of Hg on developmental outcome occurred only at a concentration that caused maternal toxicity.

Antarctic springtime depletion of atmospheric mercury.

Unlike other heavy metals that are inherently associated with atmospheric aerosols, mercury in ambient air exists predominantly in the gaseous elemental form. Because of its prolonged atmospheric residence time, elemental mercury vapor is distributed on a global scale. Recently, Canadian researchers have discovered that total gaseous mercury levels in the lower tropospheric boundary layer in the Canadian Arctic are often significantly depleted during the months after polar sunrise. A possible explanation may involve oxidation of elemental mercury, followed by adsorption and deposition of the oxidized form, leading to an increased input of atmospheric mercury into the Arctic ecosystem. Here we present the first continuous high-time-resolution measurements of total gaseous mercury in the Antarctic covering a 12-month period between January 2000 and January 2001 at the German Antarctic research station Neumayer (70 degrees 39' S, 8 degrees 15' W). We report that mercury depletion events also occur in the Antarctic after polar sunrise and compare our measurements with a data setfrom Alert, Nunavut, Canada. We also present indications that BrO radicals and ozone play a key role in the boundary-layer chemistry during springtime mercury depletion events in the Antarctic troposphere.

Assessing Elemental Mercury Vapor Exposure from Cultural and Religious Practices

Use of elemental mercury in certain cultural and religious practices can cause high exposures to mercury vapor. Uses include sprinkling mercury on the floor of a home or car, burning it in a candle, and mixing it with perfume. Some uses can produce indoor air mercury concentrations one or two orders of magnitude above occupational exposure limits. Exposures resulting from other uses, such as infrequent use of a small bead of mercury, could be well below currently recognized risk levels. Metallic mercury is available at almost all of the 15 botanicas visited in New York, New Jersey, and Pennsylvania, but botanica personnel often deny having mercury for sale when approached by outsiders to these religious and cultural traditions. Actions by public health authorities have driven the mercury trade underground in some locations. Interviews indicate that mercury users are aware that mercury is hazardous, but are not aware of the inhalation exposure risk. We argue against a crackdown by health authorities because it could drive the practices further underground, because high-risk practices may be rare, and because uninformed government intervention could have unfortunate political and civic side effects for some Caribbean and Latin American immigrant groups. We recommend an outreach and education program involving religious and community leaders, botanica personnel, and other mercury users.

Use of inductively coupled plasma-emission spectroscopy and mercury vapor analyses to evaluate elemental release from a high-copper dental amalgam: A pilot study

Statement of problem. The use of dental amalgam as a direct restorative material has been a subject of controversy for many years. The potential safety of amalgam has been questioned because of leakage of elements such as mercury, copper, tin, and silver. Purpose. This study evaluated the elemental leaching from Tytin dental amalgam placed in deionized water for 2 months. Both mercury vapor and elemental (silver, copper, tin, and mercury) analyses were performed. Material and methods. Two capsules of Tytin amalgam were triturated (one for the precipitate and liquid analysis, and the other for the mercury vapor analysis) and stored in a polypropylene tube with 10 mL deionized water for 60 days at room temperature. The amalgam pellet then was removed and rinsed with deionized water. The resulting liquid was separated from a precipitate, and 2 separate analyses were run: one on the liquid without any precipitate and another on the precipitate. Elemental analyses for copper (Cu), tin (Sn), mercury (Hg), and silver (Ag) were determined by inductively coupled plasma-emission spectroscopy with a Perkin-Elmer P2000 spectrometer. Mercury vapor analyses were performed daily for 60 days with a Jerome 431-X vapor analyzer. Results. The maximum amount of copper (80 μg), silver (2.6 μg), mercury (15 μg), and tin (550 μg) was found in the precipitate. The maximum amount of mercury vapor released was 67 μg/m3/d. Conclusion. Under the conditions of this in vitro study, there was a significant amount of elemental leaching and mercury vapor release from the Tytin amalgam over a 60-day period. (J Prosthet Dent 2001;85:409-12.)

Review article: acute inorganic mercury vapor inhalation poisoning.

Mercury contamination is a serious environmental problem worldwide. Two primary sources of contamination are dumping of large quantities of inorganic mercury and exposure in the mining industry. Although the actual fatal level of mercury vapor is not known, exposure to more than 1-2 mg/m3 of elemental mercury vapor (Hg0) for a few hours causes acute chemical bronchiolitis and pneumonitis. Two hours after exposure, lung injury appears as hyaline membrane formation, and finally, extensive pulmonary fibrosis occurs. Clinical findings correlate with the duration of exposure, the concentration of mercury, and the survival time after exposure. There is no correlation between pathological findings and the concentration of mercury in the tissues. Necrosis of proximal convoluted tubules may be attributed to the disruption of the enzyme systems of Hg2+-sulfhydryl compounds. Metallothionein protein (MT), induced by the accumulation of Hg2+ in the kidneys, may play an important role in detoxication after it forms a non-toxic Hg2+-MT compound. Despite the deposition of mercury in the brain, compared with organic mercury, inorganic mercury did not seem to damage the neurons. Drugs such as chelating agents and corticosteroids appear to effectively decrease the inflammation and delay pulmonary fibrosis.