Mercury Vapor Levels Research Articles

Comprehensive Occupational and Environmental Risk Assessment of Elemental Mercury at the Edison National Historic Site in West Orange, NJ

The Thomas A. Edison National Laboratory in West Orange, NJ was used to research and develop many inventions including experiments with a mercury oxide battery. Historical letter from Ms. Kellogg to Thomas Edison in 1884 reported the outcome of using mercury while conducting research. Preliminary test results showed spread of some contamination to artifact throughout the laboratory but the majority of the mercury was confined to a specific area of the lab. Spillage of elemental mercury in the Small Dry Cell Lab on the third floor of Building 5 leaked through the floor and ceiling on the second floor below. A comprehensive preliminary site risk assessment was conducted to evaluate the location and extent of the mercury contamination. Remediation work was conducted to remove the wood floor and ceiling but the work plan and health and safety plan for the project was inadequate. Workers were exposed to elevated levels of mercury vapor. Changes were made to reduce the risk and occupational exposure. The work was accomplished successfully without mercury poisioning after implementing more elaborate engineering and administrative controls.

Mercury poisoning within the dental clinic Myth or reality in Côte d’Ivoire

The amalgam, a material that has been used for more than 150 years for posterior teeth restoration, has been controversial because of the poisoning risk related to its mercury-content. Its manipulation exposes the practitioner and his staff members to chronic mercury poisoning, which causes some pathologies. It is, therefore, less often used or even abandoned in developed countries. However, in Côte d'Ivoire, it remains the material of choice for posterior restorations for its mechanical properties and relatively low cost. This study aimed to analyze mercury vapor levels measurement within dental clinics. The study involved forty-six dental clinics in the district of Abidjan using exclusively or not the amalgam. A spectrophotometer, Lumex, was used to measure mercury vapor at two levels (garbage cans and ambient air) at the opening of dental offices’ doors. Ten measurements equally spaced by ten seconds were done for each level. The data were analyzed using the SPSS and the Student test as a statistical test. Very high levels of mercury vapors have been recorded in 3/4 of dental clinics using exclusively or not the amalgam compared to the WHO threshold value (999ng/m3), whatever the measured level.: Mercury poisoning remains a reality within dental clinics in Abidjan.

Measuring and mitigating mercury vapour in the collection cabinets at Museums Victoria

Mercury is present in the Museums Victoria collections in a variety of forms. These include mercuric chloride applied as a pesticide, pigments and paints containing mercury sulfide, scientific equipment containing liquid mercury and geoscience specimens including native mercury and cinnabar. All these materials can release mercury vapour into storage cabinets and have the potential to contaminate both storage surfaces and other nearby specimens. Extensive testing identified higher than acceptable levels of mercury vapour inside storage cabinets. Air from cabinets was sampled across all collecting disciplines including First Peoples, Society and Technology and Natural Sciences. Results showed levels of mercury vapour above 25 μg/m3 (TWA) in cabinets of bird skins and First Peoples’ artefacts treated with mercuric chloride pesticides and above 150 μg/m3 (TEEL) in the mineralogy collection. Mercury contamination was also detected on cabinet surfaces and storage boxes. Mitigation strategies implemented to reduce or handle this hazard include enclosing mercury minerals in gas barrier film, replacing contaminated cabinets with vented cabinets and engineering controls during the handling of specimens. Improved staff practices include procedures to dissipate vapour before accessing cabinets. Follow up testing confirmed a significant reduction of mercury vapour levels after the implementation of these mitigation strategies.

Mercury vapor volatilization from particulate generated from dental amalgam removal with a high-speed dental drill \u2013 a significant source of exposure

BackgroundThe ubiquitous use of dental amalgam for over 180 years has resulted in the exposure of millions of dental workers to mercury. Dental amalgam contains approximately 50% mercury. Dental workers, including dentists, dental assistants, and dental hygienists, have been shown to have increased levels of mercury and suffer more from health issues related to mercury exposure than the general public. Mercury is known to be absorbed via inhalation or through the skin. There are many routine dental procedures that require the removal of dental amalgam by using the dental high-speed drill, which we suspected generates an occupational mercury exposure that is not sufficiently recognized.ResultsWe showed that drilling dental amalgam generates particulate that volatilizes significant amounts of mercury vapor generally for more than an hour after removal. The levels of mercury vapor created by this procedure frequently exceed the safety thresholds of several jurisdictions and agencies.ConclusionsA significant, underrecognized source of localized exposure to mercury vapor was identified in this study. The vapor was created by microgram levels of particulate generated from dental amalgam removal with a high-speed dental drill, even when all feasible engineering controls were used to reduce mercury exposure. This exposure may explain why dental workers incur health effects when safety thresholds are not breached. The dispersion patterns for the particulate are not known, so the use of effective skin barriers and inhalation protection are required during amalgam removal to protect the dental worker from this form of occupational mercury exposure. Standard methodologies for occupational mercury exposure assessment appear to be inadequate when assessing mercury exposure during amalgam removal.

Occupational exposure to mercury vapor in a compact fluorescent lamp factory: Evaluation of personal, ambient air, and biological monitoring.

Compact fluorescent lamps (CFLs) have become a popular lighting choice in recent years despite the good performance of light-emitting diode (LED) lamps. The CFLs that have been produced recently contain 1.5-3.5 mg Hg/lamp. There is evidence that even low doses of mercury are toxic. This study aimed to assess occupational exposure to mercury vapor in workers of a CFLs factory by determining mercury levels in personal and ambient air samples and urine of workers. This cross-sectional study was conducted on 59 workers in a CFLs factory in Iran. Personal and ambient air sampling of mercury vapor levels (MVLs) was performed during a workday. In total, 10 personal samples and 10 ambient air samples of mercury vapor were collected simultaneously from different units of the factory. Urine samples were collected before the work shift. Samples were analyzed using a cold-vapor atomic absorption spectrophotometer (CVAAS). The mean of the MVLs in the personal and ambient air samples was 14.78 ± 5.76 and 67.10 ± 59.37 µg.m-3, respectively. The highest MVL was measured for the production line supervisor (25 µg.m-3). There was a significant correlation between the MVLs in the ambient air and personal samples ( r = 0.84, p = 0.005). The mean urinary mercury level (UML) was 13.85 ± 13.14 µg/g creatinine. The UML of 86.4% workers was below the 20 µg/g creatinine recommended by the Centre of Environmental and Occupational Health in Iran. There were significant differences between the UMLs in different areas of the factory ( p = 0.041). Lamp breakage was an important determinant of exposure to mercury vapor; hence, effective programs to control mercury vapor are essential in the CFLs industry.

Reversible chemiresistive sensing of ultra-low levels of elemental mercury vapor using thermally reduced graphene oxide.

A chemiresistor sensor for ultra-low levels of elemental mercury (Hg0) vapor is described. The sensor was prepared through thermal reduction of graphene oxide (GO) deposited on an interdigitated electrode using only low temperature annealing typically at 230°C. The sensor responds to the presence of Hg0 vapor within <1min and spontaneously recovers its baseline through flushing with a Hg0-free carrier gas. The sensor has a linear response in the range of 0.5 to 12.2 ppbv ofHg0 vapor and a detection limit of 0.10 ppbv. The amount of GO and annealing temperature affect the sensor response and were optimized. The sensor can find use in monitoring exposure of persons to Hg0 vapors, for which a threshold value of 6.1 ppbv has been set by the World Health Organization. Graphical abstract Schematic of an interdigitated electrode modified with a layer ofthermally reduced graphene oxide. It can be used as a chemiresistive sensor for Hg0 vapor. The sensor displays a rapid and reversible response and has an ultralow detection limit of 0.10 ppbv.

The risk of occupational exposure to mercury vapor in some public dental clinics of Baghdad city, Iraq

Background: Dental workers are exposed to elevated levels of elemental mercury vapor substantially above the occupational exposure standards when placing or removing mercury/silver tooth restorations and disposing of mercury waste. This results in a significant increase in occupational exposure and risk of mercury intoxication.Methods: To evaluate the occupational exposure of dental workers to amalgam in four dental clinics in Baghdad city, the concentrations of mercury vapor were measured seasonally from February to November 2016. Samples of blood and urine were collected from 30 dental workers (exposed individuals) and five non-occupationally exposed individuals. Biochemical parameters such as cholesterol, liver enzymes (alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase), renal enzymes (urea and creatinine), total protein and reduced glutathione (GSH) were observed.Results: The results indicated that mercury vapor levels varied from 84.7 ± 18.67 to 609.3 ± 238.90 µg/m3 and most concentrations were above the occupational exposure standards. The results of the biochemical parameters showed a significant increase in levels of cholesterol, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and no significant increase in blood urea and creatinine in dental workers in comparison with unexposed persons (control). Although the results showed a significant reduction in the levels of glutathione and total protein, there was no significant decrease in the levels of alkaline phosphatase (ALP) in exposed dental workers when compared with non-occupationally exposed individuals.Conclusions: It is concluded that mercury vapor concentrations in the indoor air of some dental clinics in Baghdad city are high and exceed the OSHA STEL(Occupational Safety and Health Administration Short Term Exposure Limit). The present data showed that altered biochemical parameters can be used as efficient bioindicators for mercury toxicity.

Mercury Spill Responses - Five States, 2012-2015.

Despite measures to educate the public about the dangers of elemental mercury, spills continue to occur in homes, schools, health care facilities, and other settings, endangering the public's health and requiring costly cleanup. Mercury is most efficiently absorbed by the lungs, and exposure to high levels of mercury vapor after a release can cause cough, sore throat, shortness of breath, nausea, vomiting, diarrhea, headaches, and visual disturbances (1). Children and fetuses are most susceptible to the adverse effects of mercury vapor exposure. Because their organ systems are still developing, children have increased respiratory rates, and they are closer to the ground where mercury vapors are most highly concentrated (2). To summarize key features of recent mercury spills and lessons learned, five state health departments involved in the cleanup (Iowa, Michigan, Missouri, North Carolina, and Wisconsin) compiled data from various sources on nonthermometer mercury spills from 2012 to 2015. The most common sites of contamination were residences, schools and school buses, health care facilities, and commercial and industrial facilities. Children aged <18 years were present in about one third of the spills, with approximately one in seven incidents resulting in symptoms consistent with acute mercury exposure. To protect the public's health after a mercury spill, it is important that local, state, and federal agencies communicate and coordinate effectively to ensure a quick response, and to minimize the spread of contamination. To reduce the number of mercury spills that occur in the United States, public health officials should increase awareness about exchange programs for mercury-containing items and educate school and health care workers about sources of mercury and how to dispose of them properly.

Managing Amalgam Phase Down: An Evaluation of Mercury Vapor Levels in a Dental Center in Lagos, Nigeria

Background: Occupational exposure to elemental mercury vapor in a dental setting is mainly through inhalation exposure during preparation, insertion, polishing, and removal of amalgam fillings including storage of amalgam waste before disposal. This study aims to determine the indoor air levels of elemental mercury vapor in the dental operatories and ancillary sites at the Lagos State University Teaching Hospital (LASUTH). Materials and Methods: Samples of the ambient air were taken at seven locations the Dental Center of LASUTH by a trained technician between 9:00 and 11:00 a.m. This was done at a predetermined height (41/2feet) above the floor for mercury vapor concentration using Lumex 915 light data logger mercury vapor analyzer manufactured by Ohio Lumex Company Incorporation, USA®. Results: The highest level of 1434 ng/m3 of mercury vapor in the air was found in the restorative clinic while the lowest of 23 ng Hg/m3 was found in the ambient air at the entrance of the dental Center. The Oral Surgery clinic had mercury vapor level of 318 ng/m3 which was slightly higher than Environmental Protection Agency recommended value of 0.3 μg/m3. Conclusion: An unacceptably high level of mercury vapor was detected, especially in the restorative clinic. Every dental clinic should have its ambient air evaluated for mercury vapor level for the purpose of forming a baseline data for monitoring purposes during the period of phase down of amalgam use. Best practices should also be instituted to reduce the level of exposure of patients and dental care workers to mercury vapor.

Characterization and risk of exposure to elements from artisanal gold mining operations in the Bolivian Andes

Artisanal and small-scale gold mining (ASGM) offers low-skilled workers an opportunity to elevate themselves out of poverty. However, this industry operates with little to no pollution controls and the cost to the environment and human health can be large. The objectives of this study were to measure levels of arsenic (As), manganese (Mn), cobalt (Co), lead (Pb), and mercury (Hg) in the environment and characterize health risks to miners and residents in an area with active ASGM operations. An exposure assessment was conducted at two different mining sites and a nearby village in the Bolivian Anders. The resulting measurements were then used to quantify cancerous and noncancerous health risks to children and adults working at and living near ASGM areas. Soil concentrations of As were well above background levels and showed great variations between the village and mining area. Mercury vapor levels at the two mining sites were approximately 30 times larger than the EPA reference concentration. The risk of developing non-cancerous health effects were primarily due to exposure to As and Hg. The probability of individuals developing cancer was considerably increased with adult miners having a probability of 1.3 out of 100. Cancer potential was driven by exposure to As, with de minimus cancer risk from all other elements. Based on the environmental characterization of elements in soils and Hg vapors, the risk of developing cancerous and non-cancerous health outcomes were above a level of concern based on EPA risk assessment guidance. Personal protective equipment was not worn by workers and Hg amalgam is commonly heated in workers’ homes. Better education of the risks of ASGM is needed as well as simple controls to reduce exposure.

Neurobehavioral changes in response to alterations in gene expression profiles in the brains of mice exposed to low and high levels of mercury vapor during postnatal development

This study examined the relationship between neurobehavioral changes and alterations in gene expression profiles in the brains of mice exposed to different levels of Hg(0) during postnatal development. Neonatal mice were repeatedly exposed to mercury vapor (Hg(0)) at a concentration of 0.057 mg/m(3) (low level), which was close to the current threshold value (TLV), and 0.197 mg/m(3) (high level) for 24 hr until the 20(th) day postpartum. Behavioral responses were evaluated based on changes in locomotor activity in the open field test (OPF), learning ability in the passive avoidance response test (PA), and spatial learning ability in the Morris water maze (MM) at 12 weeks of age. No significant differences were observed in the three behavioral measurements between mice exposed to the low level of Hg(0) and control mice. On the other hand, total locomotive activity in mice exposed to the high level of Hg(0) was significantly decreased and central locomotion was reduced in the OPF task. Mercury concentrations were approximately 0.4 μg/g and 1.9 μg/g in the brains of mice exposed to the low and high levels of Hg(0), respectively. Genomic analysis revealed that the expression of 2 genes was up-regulated and 18 genes was down-regulated in the low-level exposure group, while the expression of 3 genes was up-regulated and 70 genes was down-regulated in the high-level exposure group. Similar alterations in the expression of seven genes, six down-regulated genes and one up-regulated gene, were observed in both groups. The results indicate that an increase in the number of altered genes in the brain may be involved in the emergence of neurobehavioral effects, which may be associated with the concentration of mercury in the brain. Moreover, some of the commonly altered genes following exposure to both concentrations of Hg(0) with and without neurobehavioral effects may be candidates as sensitive biomarker genes for assessing behavioral effects in the early stages of development.

Mercury poisoning dentistry: high-level indoor air mercury contamination at selected dental sites

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.

Mercury vapour exposure during dental student training in amalgam removal

BackgroundAmalgam that is used for dental fillings contains approximately 50% elemental mercury. During dental student training, amalgam is often removed by drilling without the use of water spray and suction, which are protective measures in preventing mercury aerosol. In this study we measured mercury vapor levels in ambient air during amalgam removal as is typically performed in dental training.MethodsMercury vapor levels in ambient air were measured in a dental school laboratory during removal of amalgam fillings from artificial teeth set into a dental jaw simulator. Mercury vapor was measured under three conditions (25 measurements each): with the simultaneous use of water spray and suction, with the use of suction only, and with the use of neither suction nor water spray. These three conditions are all used during dental student training. Results were compared to Alberta occupational exposure limits for mercury vapor in order to assess potential occupational risk to students. Analysis of variance testing was used to compare data obtained under the three conditions.ResultsWhen water spray and suction were used, mercury vapor levels ranged from 4.0 to 19.0 μg/m3 (arithmetic mean = 8.0 μg/m3); when suction only was used, mercury vapor levels ranged from 14.0 to 999.0 (999.0 μg/m3 represents the high limit detection of the Jerome analyzer) (arithmetic mean = 141.0 μg/m3); when neither suction nor water was used, the vapor levels ranged from 34.0 to 796.0 μg/m3 (arithmetic mean = 214.0 μg/m3).ConclusionsThe Alberta Occupational Health and Safety threshold limit value for mercury vapor over an eight-hour time-weighted period is 25.0 μg/m3. The absolute ceiling for mercury vapor, not to be exceeded at any time, is 125.0 μg/m3. When both water spray and suction were used, mercury vapor levels were consistently below this threshold. When suction without water spray was used, mercury vapor levels exceeded the safety threshold 8% of the time. When neither water spray nor suction was used, 36% of the mercury vapor readings exceeded the absolute ceiling value. To maximize safety, dental schools should train students to remove amalgam only while using water spray and high volume suction. Alternatively, students should use appropriate occupational hygiene personal protective equipment during amalgam removals.

Emergence of delayed behavioral effects in offspring mice exposed to low levels of mercury vapor during the lactation period

This study examined the emergence of delayed behavioral effects in offspring mice exposed to low levels of mercury vapor (Hg(0)) during the lactation period. Female offspring of mice were repeatedly exposed to Hg(0) at 0.057 mg/m(3), similar to the current threshold value (TLV), for 24 hr until the 20(th) day postpartum. The behavioral effects were evaluated with locomotor activity in the open field (OPF), learning activity in the passive avoidance response (PA) and spatial learning ability in the Morris water maze (MM) at the ages of 3 and 15 months. Hg(0)-exposed mice did not differ from controls in the three behavioral measurements at 3 months of age, and no neurobehavioral effects were observed. On the other hand, the mice exhibited significantly more central locomotion in the OPF task when tested at 15 months of age, but no abnormality in other behavioral performance. Immediately after postnatal exposure, the brain mercury concentration of offspring was about 150 times that of the control, in which the concentrations were approximately 0.4 µg/g. The results indicate that mice exposed to Hg(0) at concentrations around TLV during the developing period resulted in the emergence of delayed behavioral effects at a later stage in life.

Neurobehavioral changes and alteration of gene expression in the brains of metallothionein-I/II null mice exposed to low levels of mercury vapor during postnatal development

This study examined the neurobehavioral changes and alteration in gene expression in the brains of metallothionein (MT)-I/II null mice exposed to low-levels of mercury vapor (Hg(0)) during postnatal development. MT-I/II null and wild-type mice were repeatedly exposed to Hg(0) at 0.030 mg/m(3) (range: 0.023-0.043 mg/m(3)), which was similar to the current threshold value (TLV), for 6 hr per day until the 20th day postpartum. The behavioral effects were evaluated with locomotor activity in the open field (OPF), learning ability in the passive avoidance response (PA) and spatial learning ability in the Morris water maze (MM) at 12 weeks of age. Hg(0)-exposed MT-I/II null mice showed a significant decrease in total locomotor activity in females, though learning ability and spatial learning ability were not affected. Immediately after Hg(0) exposure, mercury concentrations in the brain did not exceed 0.5 µg/g in any animals. Hg(0) exposure resulted in significant alterations in gene expression in the brains of both strains using DNA microarray analysis. The number of altered genes in MT-I/II null mice was higher than that in wild-type mice and calcium-calmodulin kinase II (Camk2a) involved in learning and memory in down-regulated genes was detected. These results provide useful information to elucidate the development of behavioral toxicity following low-level exposure to Hg(0).

Estimating historical atmospheric mercury concentrations from silver mining and their legacies in present-day surface soil in Potosí, Bolivia

Detailed Spanish records of mercury use and silver production during the colonial period in Potosí, Bolivia were evaluated to estimate atmospheric emissions of mercury from silver smelting. Mercury was used in the silver production process in Potosí and nearly 32,000 metric tons of mercury were released to the environment. AERMOD was used in combination with the estimated emissions to approximate historical air concentrations of mercury from colonial mining operations during 1715, a year of relatively low silver production. Source characteristics were selected from archival documents, colonial maps and images of silver smelters in Potosí and a base case of input parameters was selected. Input parameters were varied to understand the sensitivity of the model to each parameter. Modeled maximum 1-h concentrations were most sensitive to stack height and diameter, whereas an index of community exposure was relatively insensitive to uncertainty in input parameters. Modeled 1-h and long-term concentrations were compared to inhalation reference values for elemental mercury vapor. Estimated 1-h maximum concentrations within 500 m of the silver smelters consistently exceeded present-day occupational inhalation reference values. Additionally, the entire community was estimated to have been exposed to levels of mercury vapor that exceed present-day acute inhalation reference values for the general public. Estimated long-term maximum concentrations of mercury were predicted to substantially exceed the EPA Reference Concentration for areas within 600 m of the silver smelters. A concentration gradient predicted by AERMOD was used to select soil sampling locations along transects in Potosí. Total mercury in soils ranged from 0.105 to 155 mg kg−1, among the highest levels reported for surface soils in the scientific literature. The correlation between estimated air concentrations and measured soil concentrations will guide future research to determine the extent to which the current community of Potosí and vicinity is at risk of adverse health effects from historical mercury contamination.

Influence of condensation method and alloy type on mercury vapor release and residual porosity of dental amalgams

Objective: To verify the influence of condensation method and alloy type on mercury vapor emission and residual po­rosity of dental amalgams. Material and Methods: Three pre-dispensed amalgams were tested: one lathe-cut (F-4000), one spherical (Logic Plus) and one admixed (Permite-C). They were condensed in cylindrical cavities following three techniques: manual (Ward # 2), mechanical (Densco-Teledyne) and piezoelectric ultrasonic (Gnatus). Procedures were performed inside an acrylic box (50 x 50 x 35 cm, or 0.0875 m3) with an exhaustion pump (6 l/min). The level of mercury vapor was monitored during 15 min after trituration. Specimen’s porosity was assessed using metallographic polished surfaces, digitalized under 100x magnification. Results were submitted to ANOVA and Tukey’s test (p&gt;0.05). Results: Significant differences were found in mercury vapor emission among alloys (p&lt;0.01) and condensation tech­niques (p&lt;0.01). The lathe-cut alloy produced significantly higher mercury vapor levels than the spherical alloy. The ultrasonic condensation led to significantly higher levels of mercury vapor than the other techniques. Residual porosity was not influenced by the type of alloy. The use of the ultrasonic device led to higher porosity in the amalgam than the other condensation techniques (p&lt;0.05). Conclusion: Condensation method and alloy type influenced the mercury vapor release and residual porosity of dental amalgams.

Potential Flue Gas Impurities in Carbon Dioxide Streams Separated from Coal-Fired Power Plants

For geological sequestration of carbon dioxide (CO2) separated from pulverized coal combustion flue gas, it is necessary to adequately evaluate the potential impacts of flue gas impurities on groundwater aquifers in the case of the CO2 leakage from its storage sites. This study estimated the flue gas impurities to be included in the CO2 stream separated from a CO2 control unit for a different combination of air pollution control devices and different flue gas compositions. Specifically, the levels of acid gases and mercury vapor were estimated for the monoethanolamine (MEA)-based absorption process on the basis of published performance parameters of existing systems. Among the flue gas constituents considered, sulfur dioxide (SO2) is known to have the most adverse impact on MEA absorption. When a flue gas contains 3000 parts per million by volume (ppmv) SO2 and a wet flue gas desulfurization system achieves its 95% removal, approximately 2400 parts per million by weight (ppmw) SO2 could be included in the separated CO2 stream. In addition, the estimated concentration level was reduced to as low as 135 ppmw for the SO2 of less than 10 ppmv in the flue gas entering the MEA unit. Furthermore, heat-stable salt formation could further reduce the SO2 concentration below 40 ppmw in the separated CO2 stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available in the literature and are critical to estimating the levels and compositions of flue gas impurities in sequestered CO2 streams. In addition to SO2, mercury, and other impurities in separated CO2 streams could vary depending on pollutant removal at the power plants and impose potential impacts on groundwater. Such a variation and related process control in the upstream management of carbon separation have implications for groundwater protection at carbon sequestration sites and warrant necessary considerations in overall sequestration planning, engineering, and management.

Dental amalgam and mercury myths

Stansbury, Bowman, and Newman reply: The amalgam health risks were described as “perceived” while the environmental risks were termed “real” to convey that the former lacks credible scientific evidence to support health concerns for dental patients receiving amalgam restorations. We are in full agreement with Berol Robinson in that regard. There is a legitimate health concern for dentists and their clinical and clerical staffs who potentially are exposed to chronic low levels of mercury vapor. However, we teach our dental students the precautions necessary to mitigate that exposure and that as dentists they can reassure their patients that an amalgam filling poses no significant health risk. © 2009 American Institute of Physics.

Mercury vapor in residential building common areas in communities where mercury is used for cultural purposes versus a reference community

Background Exposure to elemental mercury (Hg 0) in residential buildings can occur from accidental spills, broken objects (thermometers, fluorescent fixtures, thermostats), and deliberate introduction, one mode of which involves cultural practices by individuals who believe dispersal of mercury in a residence will bring luck, enhance health or ward off harm. Objectives To determine whether mercury vapor levels in common areas of residential buildings is higher in a community where cultural uses are likely (study areas S1, S2) than in a reference community (C1) where cultural use is unlikely, and whether levels can serve as a signal of significant cultural mercury use. Methods We monitored Hg 0 vapor with a portable spectrophotometer in the three communities. We randomly selected sites in S1 and C1 community, and also include sites in S2 specified by local health officials who suspected cultural mercury use. We evaluated 122 multifamily buildings and 116 outdoor locations. Findings We found > 25 ng/m 3 Hg 0 in 14% of buildings in study areas compared to only one reference building. In the latter we identified an accidental mercury spill from a bottle that had been brought into the building. Both the mean and maximum indoor mercury vapor levels were greater in the study communities than in the reference community. In all communities, we observed mean indoor Hg 0 vapor concentration greater than outdoors, although in two-thirds of buildings, indoor levels did not exceed the area-specific outdoor upper-limit concentration. Conclusion After controlling for factors that might influence Hg 0 vapor levels, the most plausible explanation for greater Hg 0 levels in the study area is a relationship to cultural use of mercury. None of the measured levels exceeded the ATSDR minimum risk level for residences of 200 ng/m 3 Hg 0 although levels in living quarters might be greater than those in the common areas.