TOP > PROCEEDINGS OF NIMD FORUM



 
National Institute for Minamata Disease (NIMD), Ministry of the Environment, Japan, annually invites international and national experts, and organizes the NIMD Forum as an academic and open conference on a theme relevant to mercury. NIMD would like to show our appreciation to the guest speakers and all the participants.


Date: 11/1/2018 to 11/2/2018 Venue: Minamata Disease Archives (55-10 Myojin, Minamata City, Kumamoto) Main Theme: International mercury problems and NIMD contribution Reception: Fukuda Farm






Abstract


国立水俣病総合研究センター創立40周年記念事業

NIMD Forum 2018


世界の水銀問題とNIMDの国際貢献

International mercury problems and NIMD contribution



Program & Abstracts



November 1-2, 2018

Venue: Minamata Disease Archives, Conference Hall

55-10 Myojin, Minamata City, Kumamoto 867-0055, Japan



Program

NIMD Forum 2018
November 1, 2018


Facilitator Akito Matsuyama


13:15~13:20    Opening remarks Kazuhiro Shigeto (Director General, NIMD)

13:20~14:35    Session 1
                            “Simplifying mercury analysis technology”
                            Chair Masatake Fujimura (NIMD)
                            Vice-Chair Steven J. Balogh (Metropolitan Council Environmental Services, USA)

13:20~13:45    1-1  Koichi Haraguchi (NIMD)
                            Simplified method for determination of mercury and new reference
                             materials for human biomonitoring.


13:45~14:10    1-2 Ray Bright Voegborlo
                            (Department of Chemistry Kwame Nkrumah Univ of Sci & Tech, Ghana)
                             Evaluation of digestion procedures for the determination of total mercury
                             in fish tissue and optimization of a simple one suitable for low technology
                             environment.


14:10~14:35    1-3 Megumi Yamamoto (NIMD)
                            Simple analysis of methylmercury in seafood and its application to
                             assessing methylmercury exposure


14:35~14:50    Coffee break

14:50~16:55     Session 2
                            “The current state of mercury pollution in Japan and elsewhere:
                             Case studies”

                             Chair Koichi Haraguchi (NIMD) Vice-Chair Mitsugu Saito
                            (Ministry of the Environment, Japan)

14:50~15:15     2-1 Masatake Fujimura (NIMD)
                             Examination of hair mercury in areas concerned with methylmercury
                             pollution around the world
.

15:15~15:40     2-2 Akito Matsuyama (NIMD)
                            Current state of mercury pollution in Minamata Bay.

15:40~16:05     2-3 Steven J. Balogh (Metropolitan Council Environmental Services, USA)
                             A history of successful mercury control efforts at a large
                            urban wastewater treatment plant, 1994-2018.


16:05~16:30    2-4 Natalia Barboza (Ministry of Housing, Territorial Planning and the
                            Environment, Uruguay)
                            Environmental diagnosis of a site potentially contaminated with mercury.
                             Case study in Uruguay.


16:30~16:55     2-5 Francisco Picado Pavon
                            (Research Center for Aquatic Resources of Nicaragua, Nicaragua)
                             Environmental mercury pollution in Nicaragua; Xolotlán
                             Lake a case of pollution.


18:30~              Reception


November 2, 2018

Facilitator Akito Matsuyama
9:30~11:10     Session 3
                             “Reduction of exposure to mercury and its associated
                             health risks in human”

                            Chair      Megumi Yamamoto (NIMD)
                            Vice-Chair Ray Bright Voegborlo (Department of Chemistry Kwame Nkrumah
                             Univ of Sci & Tech, Ghana)

9:30~9:55         3-1 Mineshi Sakamoto (NIMD)
                            Health impacts and exposure assessment of different chemical
                             forms of mercury.


9:55~10:20         3-2 Hung The Dang (Laboratory Center, Hanoi University of Public Health, Vietnam)
                            Recent epidemiological studies on the relationship between
                            environmental chemicals and breast cancer risk: a pilot case-control
                             study in Vietnam.


10:20~10:45       3-3 Hiroshi Ogawa (WHO Collaborating Centre for Translation of Oral Health
                             Science, Niigata University, Japan)
                            Phasing down of dental amalgam use – future challenge-

10:45~11:10       3-4 Mitsugu Saito (Ministry of the Environment, Japan)
                            Multi-media mercury monitoring and effectiveness evaluation of the
                            Minamata convention.


11:10~11:30       Summary report
                                  Steven J. Balogh (Metropolitan Council Environmental Services, USA)

Several minutes    Closing remarks
                                   Mineshi Sakamoto (NIMD)

Several minutes     The next NIMD forum
                                   Megumi Yamamoto (NIMD)


1-1

Simplified method for determination of mercury and new reference materials for human biomonitoring



Koichi Haraguchi
Department of International Affairs and Research, National Institute for Minamata Disease


   Our research project consists of two major parts: 1) development of a simple method for the determination of Hg compounds; 2) development of reference materials for evaluating the accuracy of Hg analysis for human biomonitoring. These are part of the MINUS program aimed at promoting to support the parties to the Minamata Convention with their efforts in Hg monitoring.
   One of the main problems in methylmercury (MeHg) monitoring in the least developed countries (LDCs) is the difficulty of obtaining pure reagent and carrier gas. Commonly used methods for MeHg determination require several reagents for short-term storage. Additionally, the use of toxic reagents can be a drawback in laboratories in LDCs. Therefore, new methods with lower reagent consumption are an important improvement in human health protection efforts in LDCs. An analytical method based on thin-layer chromatography (TLC) and thermal decomposition amalgamation atomic absorption spectrometry (TDA AAS) has been developed, which is capable of separating and quantifying MeHg. This method involves several steps, including acid leaching, dithizone extraction, and preparative TLC analysis. The MeHg collected by TLC can then be measured as elemental Hg by TDA AAS. The performance of the method suggested that sub-ng amount of Hg present in a few mg hair samples can be measured. This new method, therefore, represents a simplified tool for monitoring human exposure to MeHg in a low technology environment.
   The purpose of the development of a new human hair and urine reference materials are to support human biomonitoring for general populations with exposure to MeHg and elemental mercury (Hg0), respectively. MeHg exposure can result from seafood consumption. Hg0 and inorganic Hg exposure can result from dental amalgams, inhalation of indoor air, to broken thermometers, and fluorescence lights. The requirements for certified reference materials is growing with an increasing body of research from surveys to evaluate the health risks to the exposure to Hg. We are characterizing property values to developed reference materials. Hair reference material will be distributed next year. The present reference materials will be of value for the parties to the Minamata Convention to assure the analytical quality of their monitoring.



1-2

Evaluation of Digestion Procedures for the determination of total mercury in fish tissue and optimization of a simple one suitable for low technology environment.


Ray Bright Voegborlo
Department of Chemistry, Kwame Nkrumah University of Science & Technology
Kumasi, Ghana


   Nine digestion procedures for the determination of total mercury were compared for accuracy and method performance. The procedures used different combinations of reagents namely hydrochloric acid, nitric acid, perchloric acid, sulphuric acid, potassium permanganate and hydroxylamine hydrochloride. The digestions were carried out at different temperatures and digestion periods. The acid digests were analysed by Cold Vapour Atomic Absorption Spectrometry. The accuracies were determined using Certified Reference Material (CRM), Fish Homogenate IAEA-407, obtained from International Atomic Energy Agency, Vienna, Austria; and method performances were compared using Linsinger Test. One-way ANOVA of the total mercury concentrations in the CRM from the different procedures showed F (4, 20) = 1.193, p = 0.344 which implied that there were no significant differences between the values obtained by the procedures for determination of total mercury in fish muscle. The procedure which employed 1 ml of HCl 4 ml of HNO3-HClO4 mixture (1:1) and 5 ml of H2SO4; and digestion at 200 ℃ for 30 minutes was found to be the best in terms of accuracy and performance. The procedure was studied for optimisation. The optimal conditions were found to be 220 ℃ and 50 minutes. Analytical determination of total mercury in the CRM using optimal conditions gave mean percentage recovery of 98.56 ± 4.54 % (2.19 ± 0.010 µg/g dry weight). The mean percentage recoveries from the spiking studies was 103.31 ± 3.08 %. This optimized procedure was employed to determine total mercury levels in two hundred and five (205) fish samples covering twenty-nine species. The total mercury levels ranged between 0.036 ± 0.016 µg/g wet weight and 0.469 ± 0.003 µg/g wet weight. All the species had total mercury levels below the threshold limit of 0.500 µg/g wet weight of fish set by Joint FAO/WHO Expert Committee on Food Additives. The optimized and validated method in this study has the advantage of requiring low technology and less period for analysis, and therefore suitable for most laboratories with limited budget in low technology environments



1-3

Simple analysis of methylmercury in seafood and its application to assessing methylmercury exposure



Megumi Yamamoto
Department of Environment and Public Health, National Institute for Minamata Disease


   Methylmercury (MeHg) is a well-known environmental neurotoxicant that is absorbed from the gastrointestinal tract and crosses the blood–brain and blood–placental barriers. People are exposed to MeHg mainly through the consumption of seafood; therefore, determining the concentration of MeHg in seafood is important for assessing the risks of MeHg exposure. For routine analysis of MeHg concentration in seafood, easy and low-cost method has been required. Therefore, we tried to develop a simple analysis of MeHg in biological samples such as seafood. We have developed a simpler method for determining the total mercury (T-Hg) and MeHg concentrations in common biological samples by using methyl isobutyl ketone in the degreasing step. The advantages of this method are that: (1) a single apparatus (heating vaporization atomic absorption spectrometry) is used for both T-Hg and MeHg determination; (2) both T-Hg and MeHg can be measured using the same biological sample in two consecutive steps; (3) only one standard solution needs to be prepared for T-Hg and MeHg in each experiment. This method will be useful for the routine analysis of T-Hg and MeHg in a large number of biological samples such as the tissues of seafood.
   Next, this method was applied to determine T-Hg and MeHg in imported and domestic-produced commercial shrimp in Kumamoto and Kagoshima prefecture to obtain information for assessing the risk of MeHg exposure. The T-Hg and MeHg levels in imported and domestically-produced commercial shrimp in Japan were lower than the Japanese regulation level of 300 ng/g for MeHg in fish. In addition, the average selenium/mercury (Se/Hg) molar ratios in the muscles of commercial shrimp were comparatively high in the range of 16–106. Consequently, the shrimp commercially available in Japan will not cause a risk of MeHg exposure to Japanese consumers.
   Recently, fish consumption is increasing in Vietnam. However, little information is available on estimating the health risk of MeHg exposure through fish consumption in Vietnam. The association between Hg levels in hair and Se in toenails of 196 Vietnamese people and their fish consumption, using a dietary questionnaire to obtain information pertinent for assessing health risk owing to MeHg exposure was examined. The geometric mean of Hg levels in the hair of males and females was 617 ng/g and 575 ng/g, respectively. In addition, Hg levels in hair and Se levels in toenails increased with the increased frequency of marine fish consumption, and showed a significant positive correlation among subjects who consumed marine fish ≥ once/week. This is the first cross-sectional study to investigate the association between hair Hg levels and fish consumption in Vietnam. These findings provide valuable information for future assessments of the health risk of MeHg exposure through fish consumption in Vietnam.



2-1
Examination of hair mercury in areas concerned with methylmercury pollution around the world


Masatake Fujimura
Basic Medical Science, National Institute for Minamata Disease


   The most effective method to understand the human health risk of harmful substances such as methylmercury at the early stage is assessment of the exposure level.
      "How much of the harmful substance is taken into the body?”
   It is clear that methylmercury uptake from food etc. into the body is eliminated by urine etc., and accumulates in hair and fingernail at a constant rate. The concentration of methylmercury in hair is an effective indicator to understand the level of human exposure to methylmercury. The purpose of this investigation is to assess the methylmercury exposure level around the world by measuring the hair mercury level of the inhabitants in regions where methylmercury pollution is possible by gold mining, factory pollution related and fish dining habits etc., and to contribute to prevention of related health hazard.
   First we advertised hair mercury analysis in National Institute for Minamata disease using homepage in our web and flyer distribution at international conference. After keeping in contact with on-site collaborator over the E-mail, collaborators in 11 countries (Kazakhstan, China, South Korea, Colombia, Philippine, Malaysia, Bolivia, Benin, Indonesia, Venezuela and French Guiana) sent us approximately 4,000 hair samples from 2003 to 2018. The concentrations of total mercury in the hair were determined according to the oxygen combustion-gold amalgamation method using a mercury analyzer MA 2000 (Nippon Instruments). Methylmercury analysis was involved immersion of the samples in 2N HCL, heating at 100C for 5 minutes to leach out methylmercury from the sample, methylmercury extraction into toluene, and determination by gas-liquid chromatography with electron capture determination method using a gas chromatograph G 3800 (Yanaco).
   Among sampling areas, hair samples from Upper Maroni in French Guiana between 2004 and 2009 included high concentration of mercury. The average concentration of total mercury was remarkably high at 9.4 ppm for male (153 samples) and 9.9 ppm for female (234 samples), respectively. In 52 individuals that showed highly contaminated hair samples (> 10 ppm), we found that 94.5% of the mercury was in methylmercury form. Next we examined fish consumption by 37 residents in this area. There was a significant correlation between hair mercury concentration and fish consumption. We also measured mercury concentration in polluted fishes from mercury polluted river (upper reaches of the Maroni River). The mercury concentrations were high in muscle as an eatable part. These results indicate that the high concentration of methylmercury was ascribed to consumption of mercury-polluted fishes in Upper Maroni of French Guiana.



2-2
 
Current state of mercury pollution in Minamata Bay



Akito Matsuyama
Department of International affairs and Research, National Institute for Minamata Disease


   A factory of the Chisso Corporation in Minamata, Japan, produced acetaldehyde from acetylene, using mercury sulfate as a catalyst. Methylmercury (MeHg) was a by-product formed during the synthesis of acetaldehyde. From 1932 until 1968, the Chisso factory wastewater containing inorganic mercury and MeHg was discharged directly into Minamata Bay, completely damaging the rich marine environment there. Discharge of mercury (Hg) from the factory stopped in 1968, and total Hg (total-Hg) concentrations of fish in Minamata Bay decreased simultaneously (Kumamto prefecture 1998). To restore the bay’s marine environment and to prevent further dispersion of polluted sediments, a large-scale dredging project for remediation was carried out from 1977 to 1990. This involved the dredging of all bottom sediments with total-Hg concentrations greater than 25 mg∕kg (ppm, DW). Also, according to the project guidelines, bottom sediments with Hg concentrations below 25 ppm were allowed to remain in Minamata Bay. On the other hand, before dredging, Hg concentrations in Minamata Bay sediments ranged from 0.04 to 553 mg∕kg (ppm,DW), as indicated by a survey performed in 1985 by Kumamoto prefecture.
   In 1987, Kumamoto prefecture reported that Hg concentrations in surface sediments had decreased to 0.06 – 16 mg∕kg (ppm,DW) following the dredging project. Approximately 25 years have passed since the remediation project ended. Therefore, to evaluate the current state of Hg pollution in the bottom sediments of Minamata Bay, we performed a detailed survey with the same sampling resolution as the survey performed almost 25 years ago by Kumamoto Prefecture. As a result, an average value of total-Hg concentration in Minamata Bay sediment, and total mass of mercury in Minamata Bay were 2.3 mg∕kg (ppm,DW), 3.4ton respectively. Also, an average value of Me-Hg concentration of Minamata Bay surface bottom sediment was 3.1μg/kg (ppb,DW). Almost 95%-98% of total mass of mercury that was discharged from Chisso Corporation has been removed by the dredging project that was performed by Kumamoto Prefecture.



2-3
A history of successful mercury control efforts at a large urban wastewater treatment plant, 1994-2018



Steven J. Balogh,
Metropolitan Council Environmental Services, Saint Paul, Minnesota, USA


   The Minamata Convention has established a global mechanism for the elimination, reduction, and/or control of mercury (Hg) currently used in a wide range of industrial and manufacturing processes, commercial uses, and consumer products. Prior efforts to reduce the deliberate use of Hg in modern industrialized societies have had some success, but further controls and minimization efforts are needed to protect human health and environmental systems. Municipal wastewater treatment plants collect and treat domestic, commercial, and industrial wastewaters, and the removal and control of Hg in wastewater treatment processes is essential for protecting receiving waters, aquatic wildlife, and human health. Here, we review 25 years of efforts to characterize and control Hg at the Metropolitan (Metro) Wastewater Treatment Plant in Saint Paul, Minnesota, USA. A mass balance at the Metro Plant in 1994 showed the mean daily mass load of Hg entering the plant was 248 g d-1, and the mean daily load in the plant effluent was 10 g d-1. The Hg removed from the wastewater was collected in primary and secondary sludges which were combined, dewatered, and burned in multiple-hearth incinerators. Air pollution controls on the incinerator exhaust gas focused on particulate removal by cyclones and venturi wet scrubbers, with no explicit attempt to remove or control Hg. As a result, >95% (approximately 240 g d-1) of the Hg entering the treatment plant was emitted to the atmosphere in the incinerator exhaust gas. Between 2003 and 2008, a community-wide effort sought to reduce Hg discharged in wastewater from dental clinics, and by 2008, the mass load of Hg entering the Metro Plant had been reduced to 139 g d-1. A new incineration facility built in 2004 included explicit Hg capture within the air pollution control train, resulting in a drastic reduction of Hg emissions to the atmosphere. Reductions in the Metro Plant influent Hg daily mass loading continue today due, in part, to the Minamata Convention and the general societal trend to reduce or eliminate the use of Hg. The daily mass load of Hg entering the Metro Plant in 2017 was approximately 98 g d-1, and that discharged from the plant to the Mississippi River was 1 g d-1. The current mass load of Hg emitted to the atmosphere from sludge incineration is less than 0.2 g d-1. Thus, since 1994, Hg discharges in plant effluent and incinerator exhaust have decreased by 90% and 99.9%, respectively, culminating a quarter century of effort to reduce Hg discharges from the Metro Plant.



2-4
Environmental diagnosis of eventual site contaminated with mercury. Case study in Uruguay



Natalia Barboza.
National Director of the Environment Ministry of Housing, Territorial Planning and the Environment Republica Oriental del Uruguay


   Ministry of Housing, Territorial Planning and Environment is in charge of the policies applied to environmental management. Its mission is to design and implement participatory and integrated public policies on housing, environment, territory and water, to promote equity and sustainable development, contributing to the improvement of the quality of life of the inhabitants of the country.
   DINAMA is part of this and is the one that exercises environmental control and monitoring. The Environmental Laboratory reports an annual average of 20,000 analytical data from samples of natural waters, sediments, soils, industrial solid waste and liquid effluents.
   Uruguay have the Basel Coordinating Center, Stockholm Regional Center for Latin America and the Caribbean, through which projects related to the Minamata Convention are also coordinated. (http://www.ccbasilea-crestocolmo.org.uy/es/mercurio/), where a series of projects related to mercury are managed actually.

   Mercury, element naturally present in the environment in place 67 in terms of abundances (0.08ppm) is widely human used since ancient times. In addition to what has been naturally released, mercury was extracted from mines for anthropogenic uses, which means that the environment presents ever higher mercury values now. Once the mercury is released into the environment, it undergoes chemical transformation and another one for the action of microorganisms present in the area, which complicates the forms and proportion of tipe of mercury that can be found in the environment. From an analytical perspective, it is important to be clear about the mercury species that could be in the different components, in order to combine efforts in efficient and pertinent determinations for the type of study that is intended to be carried out. It is generally accepted that the formation and bioaccumulation of MeHg is the most critical point of environmental quality in mercury pollution.

   In Uruguay, there is a chlor-alkali which process using mercury cells, since 1900. The industry has been inspected since 1990 about effluents, sediments and solid waste. Chronologically, the most important activities related to the industry are: from 2003 to 2011, the administration carried out studies to know the situation on water quality (water and sediment) in the Santa Lucía River. Based on previous experience, between 2005 and 2009 and subsequently between 2012 and 2013, DINAMA carried out campaigns to monitor the quality of water and sediment, finding at certain points, high concentrations of mercury in sediments (> 50 mg HgT /kg-dry). This situation, motive to request support the Japanese government to make a diagnosis of the potential contaminated area and evaluate remediation possibilities. This cooperation happened between 2015 and 2017 and allowed to have a complete diagnose the area of influence of the industry. Mercury contamination is located at certain points, without drift. Biota and groundwater does not yield quantifiable values in the monitoring carried out. Workers exposed to junks in the area were monitored and did not present results that exceed the regulations.
   The link with the NIMD is generated in the training in the technique of organic mercury in Minamata, Japan, and in a regional seminar in Montevideo, Uruguay, where the institute participated as a guest to offer its experience in the subject.



2-5
Environmental mercury pollution in Nicaragua; Xolotlán Lake a case of pollution.



Fransisco Picado Pavon
Center for Research in Aquatic Resources of Nicaragua, National Autonomous University of Nicaragua


   The volcanic emissions and geothermal manifestations are important sources of mercury (Hg) in Nicaragua. Nevertheless, two emblematic cases of anthropogenic pollution, which still call for more attention, are the Hg pollution due to Artisanal and Small-scale Gold Mining (ASGM) and the pollution of Xolotlán Lake. The reported highest Hg concentrations from areas affected by the ASGM are: 7.0 µg/g sediment, 7.0 µg/l water, and 0.4 µg/g wet wt. fish. These anomalous concentrations are similar to those observed thirty years ago in Xolotlán Lake, which was polluted with forty tons of inorganic Hg released by a Chlor-Alkali production facility. Nowadays, it is believed that Hg in Xolotlán Lake could be a threat for populations whose have been eating fish from it for long.
   In Nicaragua, the few studies on environmental Hg pollution have been carried out by academic institutions and most of their results have end up as unpublished reports. Moreover, due to lack of analytical capacities for Hg speciation, the reported total Hg concentrations have limited the scientific interpretation of the problem and consequently the decision making. Therefore, the effort of Nicaragua government was aimed for: i) strengthening capacities for Hg analysis at the Research Center for Aquatic Resources of the National Autonomous University of Nicaragua (CIRA/UNAN-Managua) and ii) assessing the current Hg concentrations in Xolotlán Lake for continue benefiting from its hydrobiological resources. This was possible by the economic support of the Japanese government through the Japan International Cooperation Agency (JICA) and the Nicaraguan counterpart.
   Two campaigns to collect samples from the Xolotlán Lake were carried out. Hg in the collected sediments (n=20), water (n=105), and fish (n=629) were analyzed by atomic absorption spectrometry (HG-201, IL=0.001 ng; DM80, IL=0.005 ng). Water temperature, pH, electric conductivity, etc., were measured in situ. The bioavailable (total dissolved) aqueous Hg concentrations varied between less than detection limit (0.24 ng/l) and 8.93 ng/l and the total Hg concentrations in the sediment were between 0.003 and 12.970 μg/g. The average total Hg concentrations in fish was: Parachromis managuensis, Parachromis dovii (0.46 μg/g; n=146) > Amphilophus citrinellus (0.25 μg/g; n=215) > Gobiomorus dormitor (0.23 μg/g; n=194) > Oreochromis niloticus, Oreochromis mossambicu, Oreochromis aureus (0.02 μg/g; n=74). No statistic difference (p=0.52, =0.05) of the total dissolved Hg concentrations was observed between sampling campaigns, but significant difference (p = 0.03,  = 0.05) was observed in the values of concentration of particulate Hg. The few data of Hg concentrations exceeding the Canadian values for aquatic life protection (water=26.0 ng/l, sediment=0.17 μg/g) were observed close to anthropogenic or natural Hg sources and 19.1% of all four studied species of edible fish is above of 0.40 μg/g the recommended concentration for fish consumption in Japan. 
   The low Hg bioavailable aqueous concentrations suggest that fish Hg intake occurs mainly through food chain and sediments are an important source of Hg for it. Current Hg content in edible fish indicates a bioaccumulation that in the future could increase and consequently turn a threat whether people increase the consumption of these fish. Therefore, a multimedia Hg monitoring, including Hg speciation, of Xolotlán Lake is needed.



3-1
Health impacts and exposure assessment of different chemical forms of mercury



Mineshi Sakamoto
Department of Environment and Public Health, National Institute for Minamata Disease


   Mercury has been used by humans for centuries due to its unique physical and chemical properties. However, the different chemical forms of mercury, which include elemental mercury (Hg0), inorganic divalent mercury (Hg2+), and organic mercury (mainly methylmercury, CH3Hg+), cause a variety of toxic effects. Differences in exposure sources, the affected organs, toxic effects, and metabolism are seen among the various chemical forms of mercury. For example, the general population is exposed to small amounts of elemental mercury due to its use in dental amalgams. On the other hand, workers at artisanal small-scale gold mining sites and gold shops in Amazon River regions can be exposed to high levels of elemental mercury, as they often have to heat gold-mercury amalgams to evaporate the mercury and obtain the gold. A large proportion of inhaled gaseous elemental mercury (approximately 80%) is absorbed into the blood via the lungs, and, as an uncharged and therefore lipid-soluble substance, it can easily pass through the blood-brain barrier. With time, the gaseous elemental mercury in the patient’s brain is oxidized to inorganic divalent mercury and causes damage to the brain, and the inorganic mercury also accumulates in the kidneys, where it causes renal damage. In the environment, a part of the divalent mercury can be changed to methylmercury by some micro-organisms and sunlight. It then bioaccumulates in fish and marine mammals which exhibit elevated, food-web dependent methylmercury levels. Most human methylmercury exposure occurs from the consumption of fish and seafood. Methylmercury is readily absorbed by the digestive tract (>90% is absorbed). In addition, it exhibits high affinity for sulfhydryl groups, and some methylmercury combines with L-type cysteine to form l-cysteine-methylmercury conjugates, which have similar chemical structures to methionine, an essential amino acid. The conjugates are then distributed to all tissues, including the brain (via the blood brain barrier), as they are treated like L-type neutral amino acids. In the epidemics of marked methylmercury intoxications in Minamata, Japan and Iraq, the brain was the organ that was most severely affected, particularly in that the developing brains of fetuses were damaged. In this presentation, I introduce 1) kinetics, toxicity of and biomarkers of different chemical forms of mercury; 2) elemental mercury exposure assessment and health survey of mercury mine workers in China; 3) methylmercury transfer from mothers to fetuses during gestation; 4) risks and benefits of fish consumption; 5) NIMD contributions as a WHOCC to the health survey requested by WHO.



3-2
Recent epidemiological studies on the relationship between environmental chemicals and breast cancer risk: a pilot case-control study in Vietnam



Hung The Dang
Laboratory Center, Hanoi University of Public Health, Vietnam


   Breast cancer is the most frequent neoplasm occurring in women globally. Approximately 1.7 million women worldwide were diagnosed with breast cancer and over 522,000 women died from this disease in 2012. Although it is thought to be a disorder primarily of the developed world due to the high incidence rate, 50% of new breast cancer cases occurred in less developed countries in 2007, and this number reached 53% in 2012. Breast cancer is predicted to continue to increase in less developed countries over the next decade and become the leading cause of cancer-related deaths among women throughout the world. The disease has also been becoming an important public health problem in Vietnam. The incidence rate increased from 13.8 per 100,000 women in 2000 to 28.1 per 100,000 women in 2010. In 2010, it was reported that there were 12,533 women with breast cancer in the country. Along with other etiological factors like genetics, family history, age, etc. there is growing scientific evidence that exposure to environmental carcinogens, especially endocrine disrupting chemicals-EDCs (e.g., heavy metals, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and bisphenol A-BPA), is potentially associated with increased incidence of some non-communicable diseases including breast cancer in previous studies.
   In recent years increasing the use of agrochemicals in agriculture without proper management may result in negative effects on the environment and human health in Vietnam. Food safety is another issue that Vietnamese has to face and the risk of consuming unhealthy foods is of critical concern in Vietnam nowadays. In addition, Vietnam is facing an increasing number of environmental pollution challenges including air, water, and solid waste. Thus, the increasing rate of cancer in general and breast cancer in particular in recent years in Vietnam may be influenced by environment factors, including exposure to environmental carcinogens through foods, water, plastic products, etc. In this hospital-based case-control study, we will present our preliminary data to provide epidemiologic evidence that chemical exposure is a risk factor for breast cancer in Vietnam.



3-3
Phasing down of dental amalgam use – future challenge-



Hiroshi Ogawa
WHO Collaborating Centre for Translation of Oral Health Science, Niigata University, Japan


   The restorative model for managing dental caries was developed in the 1900s, alongside dental amalgam as one of the restorative materials commonly used to treat dental caries. Together they still provide the backbone of oral health services in many countries today. The Minamata convention addresses mercury-added products, including dental amalgam, which is made of approximately 50% of elemental mercury by weight, and proposes nine measures to phase down the use of dental amalgam. These measures show the interconnected and interdependent nature of phasing down dental amalgam and reinforce the need for a multipronged approach as called for by WHO.

   Quality mercury-free materials are now selected and used as alternatives to dental amalgam, as a part of informed people-centered oral health care. However, it is important to distinguish between offering quality mercury-free materials as alternatives to dental amalgam and suggesting that one of these alternative materials could be a global replacement for dental amalgam. Large-scale systematic studies on the economic and social costs and benefits of quality mercury-free materials would be needed more.

   Efforts to phase down the use of amalgam should be directed towards a multipronged approach that combines waste management, knowledge management and health systems strengthening. It is suggested that a national coordination committee would facilitate efforts to phase down the use of dental amalgam. Such a committee could raise public awareness and support country level communication strategies, which must be an early priority in the process.
   Coordinating stakeholders can help, guide and inform the process of change, contribute to understanding how to influence policy and facilitate taking action to strengthen oral health-care systems, particularly with respect to oral health-care financing.

   Oral health societies are in a period of transition from a conventional model of restorative dentistry, one largely based on the use of dental amalgam, to an oral health model oriented towards health promotion and integrated disease prevention. The phase down of the use of dental amalgam can become a catalyst to renew and revitalize dentistry and tackle the health, social and economic burden of oral disease by prioritizing oral health as part of the global health agenda.



3-4
Multi-media Mercury Monitoring and Effectiveness Evaluation of the Minamata Convention



Mick SAITO
Deputy Director, Office of Mercury Management, Ministry of the Environment, Japan


   The toxicity of mercury has been known since ancient times but for the first time in 1950’s, the environmental pollution of mercury was officially acknowledged as Minamata disease. Since 1970’s, the characteristics of mercury as a global environmental issue beyond traditional pollution problem has been discovered. Minamata Convention on Mercury was adopted as a legally-binding instrument to reduce mercury risks in October 2013, which entered into force in August 2017. Recognizing the substantial lessons of Minamata disease, the Convention aims to protect the human health and the environment from anthropogenic emissions and releases of mercury and its compounds. The Convention tackles mercury reduction throughout its life-cycle; from supply, to use, emission and disposal in order to prevent global pollution with the cooperative actions by both developed and developing countries.

   Mercury monitoring and analysis are required at various stage for implementating the Convention. The effectiveness evaluation in particular is a framework of evaluation that the Conference of the Parties will periodically undertake based on defined effectiveness indicators. Mercury in the environment generally behaves as follows: emission to air, oxidization and sedimentation, methylation at seabed or sediment, bioaccumulation and uptake by fish, shellfish and human. Since the nature of the Minamata Convention is to manage mercury in its entire lifecycle, the questions how the individual control measures bring effects to the Convention and how far such interventions as a whole contributed the improvement of mercury pollution must be evaluated. Various indicators requiring multi-media monitoring, which captures transport in a medium or between media are thus needed.


   Global environmental issues have, as is the case on climate change, complex situations beyond a typical pollution-to-damage scenario so that scientific survey to disclose its mechanism as well as comprehensive programmes to address the issues are essential. It is therefore anticipated that mutli-media mercury monitoring together with appropriate mathematical modelling will contribute more realistic evaluation of the Convention effectiveness.



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Proceedings of NIMD Forum



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