British Columbia Mine Reclamation Symposium

Urban artisanal gold shops and mercury emissions Cordy, Paul; Veiga, Marcello M. (Marcello Mariz); Gonzalez Carrasco, Victor Hugo 2008

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URBAN ARTISANAL GOLD SHOPS AND MERCURY EMISSIONS  Paul Cordy, MSc. Marcello Veiga, PhD Victor Hugo Gonzalez Carrasco, MSc candidate  University of British Columbia Mining Engineering 5th Floor, 6350 Stores Road Vancouver, BC V6T 1Z4   ABSTRACT  In developing nations across the globe, artisanal miners use mercury amalgamation to extract gold.  The resulting amalgam is refined to varying degrees before being sold to urban gold shops.  However, this doré may still contain 2-40% mercury; and sometimes unburned amalgam is sold directly to the gold shops.  There is a potentially serious health risk for shop employees and surrounding populations when the gold is melted and further purified.  Field studies in Suriname, Ecuador, Peru, and Chile reveal that mercury concentrations in the ambient air of gold shops frequently exceed the WHO limit of occupational exposure by an order of magnitude or more.  This paper provides an overview of the diverse practices and technologies used in gold shops in Latin America and Indonesia, with a focus on the resulting atmospheric mercury emissions.  Furthermore, we compare and contrast the various different methods of reducing mercury emissions in urban air that have been developed by governments, NGOs, and local people.  For example, the US EPA has devised a filtration system that captures at least 80% of mercury emissions, and the Kalimantaan water filtration method is estimated to capture between 75% and 90% of emitted mercury, depending on the configuration.  Finally, we review existing and potential barriers to implementation of these means of remediation.   1 INTRODUCTION 1.1 Artisanal Mining and Gold Shops Millions of people in more than 55 countries are involved with artisanal gold mining, producing 20-30% of the world supply at 500-800 tonnes/year (Telmer et al. 2006).  Gold is recovered by mercury amalgamation, which is sometimes burned to isolate the gold before being sold to gold shops (Veiga and Baker, 2004).  Artisanal miners sell their gold in the nearest town in order to get their pay as fast as possible, minimize costs, and avoid robbery.  Emissions from gold shop hoods during a burn can exceed 60 μg/m3 (Garcia-Sanchez et al. 2006).  Mercury is a potent neurotoxin, and airborne emissions pose significant health and environmental concerns.  The health of gold trade workers is obviously at risk, but nearby residents can also suffer symptoms of chronic mercurialism when vapour and mercury laden dust enter and deposit in their homes.  Several mercury condenser designs have been developed to mitigate mercury emissions from gold shops, and there are advantages and drawbacks to each.  It is also important to consider the important social, political, and educational dimensions of this work, as these can generate complex barriers that impede or negate efforts at remediation.  These must be carefully navigated if the world’s limited mercury abatement funds are to be put to maximal use.  This paper will examine current gold shop mercury filtration technology, and elucidate some of the human issues that can accelerate or exasperate efforts to implement and nurture urban mercury abatement solutions.  2 MERCURY EXPOSURE AND HEALTH  For reference, the WHO (World Health Organization 2003) places the limit of public exposure at 1000 ng/m3 (annual average) and the recommended health-based exposure limit for metallic Hg is 20000 ng/m3 (this value is an average exposure over a normal 8 hour day and 40 hour workweek, the limit would be lower for workers who observe longer hours).  Gold shop workers often report that they have symptoms of Hg intoxication such as dizziness, headaches, tremors, erethism, paresthesia, insomnia, lack of self-control, weakness, and renal alteration (Akagi et al. 1995, Veiga, M. and Baker, R. 2004).  The onset of these symptoms progresses over time.  Victims may not realize that they are suffering from mercurialism, as many of these symptoms could be attributed to aging or diseases that are common in developing nations (such as dysentery and malaria). 2.1 Mercury Dispersion Gold shops are not a major source of mercury contamination in rural areas far (>2km) from the shops (Hacon et al. 1995, Marins et al. 2000), though mercury that adsorbs onto finer dust (<1μm in diameter, such as biomass burning particles) can remain aloft and be transported regionally.  Coarse particulates laden with mercury are the most significant contributor to proximate contamination (Lacerda 2003), as mercury emitted in the gold shops associates with airborne dust particles that are deposited at much higher rates than mercury vapour.  Malm et al. (1995) compared street dust and soil mercury concentrations, and found that street dust contained on average 2-3 times more mercury than soil.  As mercury vapour cools it forms airborne liquid droplets, or aerosols.  This component rapidly deposits on nearby walls and in soil, adding to the high proximate contamination around and inside gold shops. This mercury presents a chronic exposure to employees and patrons of the gold shop even when no amalgam is being burned.  Therefore the emissions from gold shops can have consequences for nations at distant locations on the planet, and also for people living near sources.  The fine mercury contaminated dust can contribute to long range transport of mercury, the coarser dust and aerosol mercury may be of greater concern in terms of local health.  3 MERCURY CAPTURE  Artisanal mercury condensers have been developed previous to the current international remediation efforts.  Commonly these use water to condense the mercury and are thus called “wet” condensers, but it is also possible to build a “dry” condenser that does not use water.  Though there are distinct advantages and disadvantages to any given design, a mercury condenser should have as many of the following qualities as possible: a. Efficient mercury capture b. A spigot that enables collection and reuse of captured mercury c. Low cost d. Components that are locally available e. Simplicity f. Adaptability (at the local level) g. Scalability h. A fume hood to collect the vapour and a chimney communicating it with the outside air i. Sufficient air flow at the hood opening j. A “cap” that prevents mercury evaporation k. Components that are easily decontaminated l. No new mercury contaminated waste is produced m. No major changes in work habits are required  No single filtration system achieves the complete ideal described above; however mercury capture can be greater than 90% if the system is designed well.  The remaining mercury can be captured using a secondary filter made of activated carbon infused with iodine (Veiga and Fernandes 1990).  Carbon filters, however, must be changed on a regular basis (six months to one year depending on the mercury throughput), and therefore regularly create ancillary contamination that is difficult to dispose of. Furthermore, old filters can become clogged and therefore drastically decrease the efficiency of the system.  Costlier filtration systems are available, but this paper only describes those methods that are financially accessible to gold shops in developing nations. 3.1 Wet Condensers The simplest and most obvious method of capturing mercury is to pump the vapour through water.  This method has the advantage of cooling the vapour and preventing evaporation of the captured mercury pool. A fan on the exhalant side of the water tank must be powerful enough to create negative pressure in the reservoir and draw the vapour through the water.  The efficiency of this system depends on the power of the fan and the size of the air droplets that pass through the water.  When the condenser is no longer needed, the mercury can be eliminated from the water by precipitation, with iodine infused activated carbon, or by pouring it into laterite soil where it will bind to ferrous compounds (Veiga and Fernandes, 1990).  On the Island of Kalimantaan, the UNIDO GMP developed a wet gold shop condenser for small gold shops (approximate cost:  $60).  It consists of PVC piping, a sealable plastic container (filled with water), and a blower.  A demonstration system was developed at a local university, and this further evolved in cooperation with gold shop owners.  It also has a screen around the incoming vapour that decreases the size of the droplets as they enter the water, thus cooling the vapour faster and increasing the capture efficiency.  When fitted correctly, the water barrier alone captures over 75% of the mercury.  In some gold shops, the amount of Hg recovered from amalgam burned, is estimated to enter the 80% - 90% range (Yayasan Tambuhak Sinta post-GMP report ).   The YTS study estimates that a total of 645kg of Hg was recycled in 2007 as a result of condensers installed in 19 gold shops, and presently there are a total of 30 such systems installed.  US EPA also constructed and tested an Indonesian style condenser and found it to be 75% efficient in terms of overall capture and 98% efficient in capturing aerosol mercury.  The advantage of the Indonesian system is that gold shop owners themselves can build, repair, and adapt it.  This greatly increases the likelihood that the technology will spread without the intervention of foreign development organizations.  This system was primarily designed for use in small gold shops, but it can be scaled up for use in larger gold shops that trade a higher volume of gold.  The cost will vary depending on the country, but in Indonesia the total cost of the wet condenser was around 60 US dollars. 3.2 The US EPA’s Dry Condenser Design The US EPA condenser design (ANL 2007) forces the airborne mercury droplets through tight curves that increase their size and cause them to impact with the condenser surfaces.  This mercury then runs down the sides of the collector and pools at the bottom, where it can be collected through a small siphon and re- used.  This design uses a 200 L oil drum, through which air is moved by a large fan at the top of the oil drum.  Unfortunately, this condenser design holds a large reservoir of mercury at the bottom of the vat which is free to evaporate.  The cost of construction and installation of the baffle plate prototype was approximately US$400.  This condenser must be fabricated by metal workers, therefore the technology cannot be passed on from one gold shop owner, and the installation, adaptation, and maintenance must be contracted out to a metal shop.  The US EPA collected mercury at the top of the fume hood and above the condensing system fan in each, allowing them to estimate that the efficiency of a properly built system could be approximately 80% (ANL 2007).  It can be considerably less if there is an insufficiently long air path before the vapour enters the condenser.  Thus the actual efficiencies of the three US EPA baffle plate systems built in Brazil were 37%, 76%, and 91% in terms of overall mercury capture.  4 GOLD SHOPS TODAY 4.1 Brazil Though locally made water based condensers exist in some parts of Brazil, they are not ubiquitous.  The EPA installed the first prototypes of its system in Creporizao and Itaituba, Brazil, because there was previously no condenser system used there.  This program was highly successful, partly because it was advertised as part of the mayor of Itaituba’s own municipal beautification and cleanup program (called Cuide de Seu Tesouro, or Take Care of your Treasure). 4.2 Suriname Artisanal gold mining in Suriname has changed dramatically with the influx of Brazilian miners.  They brought with them industrial scale extraction methods, but they also brought a wet mercury condenser design (similar to the Indonesian type) that gold shop owners in Suriname are legally obligated to use when operating in the capital city of Paramaribo.  Elevated mercury contamination at all of the gold shops (almost always greater than 10 000 ng/m3) shows that these systems are not 100% efficient, probably largely because the fume hoods where the gold is melted and purified provide insufficient suction to pull all of the mercury vapour through the pipes and water tanks.  Well ventilated buildings had lower mercury concentrations in rooms where gold was not being reburned compared with the gold work rooms, whereas poorly ventilated shops had similar mercury concentrations throughout.  Mercury concentrations outside the front door of the shop varied with wind speed and direction, but could jump to 10 000 ng/m3 or more, so there is definitely an intermittent exposure concern for those passing by the shops. 4.3 Ecuador A brief visit was made to the gold shops in Ponce Enriquez, near Machala, Ecuador, in which gold is refined without any mercury filtration systems.  Mercury concentrations in these shops were high (between 10 000 and 40 000 ng/m3), even though no amalgam was being burned at the time of the measurements.  This is likely due to the long history of mercury contamination in these shops and to improper storage and unsafe handling of mercury.  The shop owners were open to having mercury measurements taken inside their shops, but they expected that we would find no mercury contamination because the miners were supposed to be using retorts in the field and they did not know that the field retorts were burning at temperatures that would not fully liberate the mercury.  There is clearly a need for targeted education of miners and gold shop workers, as well as a program to establish a tradition of using gold shop condensers. 4.4 Peru Peru is a stunning case of a well meant mercury emissions remediation effort gone horribly wrong. Previously, a non-governmental organization had come to implement wet gold shop condensers, but complexity of the design was too great and there was too little capacitation of local gold shop workers and government.  As a result, some disastrous adaptations were made.  The water bucket was retained, but they omitted the fan that would draw the air through the water.  There was also no conduit to the outside air, though this hardly mattered:  the air probably would rise into the pipes and get blocked by the water.  Remarkably, the extreme mercury concentrations in the air of these shops (usually greater than 25 000 ng/m3) dissipate quite rapidly once burning stops.  The roll-up metal security barriers are the only shop doors, so during business hours the shop is wide open and the mercury is quickly mixed with the outside air.  Unfortunately, the gold shops are across the street from the main market and are themselves a social gathering spot.  Thus, due to the combination of mercury dispersion into the outside air with a high concentration of street dust, there is likely to be a large number of people who are not involved in the gold trade but are exposed to dangerous levels of mercury. 4.5 Chile The mercury amalgamation tradition in Andacollo dates back to Incan times.  Centuries of mercury contaminated mine tailings intermingle with residential neighbourhoods.  As recently as 15 years ago there were an estimated 5000 artisanal gold and copper miners in Andacollo, though since the prime mineral properties were awarded to foreign mining companies, the number of artisanal gold miners has dropped to near 200.  Unfortunately, despite the steep decline there remains an acute exposure risk to the local population because many gold shops are located in residential areas and miners burn small amounts of amalgam in their homes.  Two gold shops are located within a two block radius of the elementary school.  Furthermore, three open pit mines within 2 km of the centre of town are a constant source of airborne particulates that could be actively recruiting mercury from the air.  This dust is settling in residential houses, thus providing a constant source of low level exposure that could lead to mercurialism in residents who are not directly involved in the gold trade.  The gold shop operators themselves are well aware of the dangers of mercury inhalation, but seem not to believe that there are harmful quantities of mercury in the gold that they purchase from miners.  Large quantities of amalgam, for which recovery of mercury is economically significant, are sometimes burned using retorts.  Normally, they burn the amalgam directly under fume hoods that have no fans.  The mercury vapour either escapes the chimney into the urban air or stays in the enclosed burning rooms, where mercury concentrations exceed the detection limit of our Lumex Vapour Analyzer (>50 000 ng/m3 at 3 metres from the amalgam burning).  5 DISCUSSION  Across Latin America there is a need to install gold shop mercury condensers to protect the health of communities and the atmosphere.  The advantage of the US EPA dry condenser system is that the components are easier to decontaminate when the condenser is no longer needed, and the system does not create any mercury contaminated water.  The disadvantage of the US EPA system is that individual gold shop owners are not able to construct, repair, maintain, or adapt the system without hiring a metal worker, and this increases the cost of the system.  The collection efficiency of the US EPA system depends on the length of pipe that separates the condenser and the fume hood, as the vapour needs time to condense and form large enough mercury aerosol droplets to be captured by the baffle plates (the condenser that was installed immediately above the fume hood was only 37% efficient).   This is not as much of a concern for wet condensers as the water cools the vapour as it passes.  The Indonesian wet condenser system has the advantage of being tested and evolved through experimentation by local universities.  Thanks to its simple design and construction, it has already been installed in 30 gold shops and has potential to spread without the intervention of governments or development organizations.  Any effort to implement mercury condensers in gold shops must be accompanied by a comprehensive education program and accessible design plans that explain the function of all components of the system in plain language.  Not only could this foster local innovation and improvement of the system, but it will also help to avoid installation of ineffective systems that give a false sense of security.  If gold shop workers are convinced that the condenser totally eliminates the mercury problem, they may suppose that burning raw amalgam is not a problem.  Even if the capture rate is 90% or greater, shops should not accept unburned amalgam, as 10% of the fugitive emissions from a doré of 40% mercury could pose an unacceptable threat to urban populations.  The cheapest and most immediate way to reduce exposure to gold shop workers is to improve ventilation in the shops (Drake 2001, Malm et al. 1998, Bastos et al. 2004, Garcia-Sanchez 2006).  The health of innocent populations can only be safeguarded by banning raw amalgam burning in urban areas and implementing gold shop condensers.  Finally, reducing the particulate content in air and promoting regular dust removal from inside of homes is necessary in order to reduce the chronic exposure of families and neighbourhoods.  Efficient condensers, with sufficient suction at the fume hood opening, are essential for reducing mercury emitted by gold shops. 5.1 Implementation Barriers and Possible Solutions There are many things that could potentially impede remediation and development initiatives, such as improper community education, illegality, and lack of political support.  Where artisanal mining activities are illegal, governmental bodies such as the US EPA cannot intervene for fear of breaking diplomatic due process.  Furthermore, illegal ASM may be forced to arm themselves to protect their income, and illicit traffic of mercury and cyanide may come under the control of drug traffickers and organized crime. These associations would inevitably make artisanal miners and gold shop owners uneasy about accepting official assistance and could endanger the lives of locals and development staff.  Education of gold shop owners and the surrounding community is essential to guarantee the long term sustainability of any mercury abatement project.  Gold shop owners themselves are sometimes unaware of the degree of risk to their own health, and are therefore reticent about spending money to resolve a seemingly irrelevant problem.  Provincial and local ministries are sometimes unable to legislate any filtration system for lack of a proven and cost effective alternative to unventilated burning.  Unfortunately, at present, some developing nations still need western scientists to bring solutions to these problems, but in a sustainable future it will have to be local scientists and practitioners who spread change throughout their own countries.  A good model for this is the Indonesian condenser design, which was a partnership between Indonesian universities and the Global Mercury Project (YTS 2007).  There is also a desperate need to educate miners and shop owners about the dangers of burning amalgam. It is imperative that the practice of burning amalgam within the city limits be banned in order to vastly decrease urban contamination.  This may be especially important if, as in other countries, people gain a false sense of security from the perception that the gold shop condensers eliminated the problems produced by urban amalgam burning.  6 CONCLUSIONS  Artisanal gold shops emit high concentrations of mercury in the air, and this mercury accumulates in street and household dust.  Therefore innocent urban populations, as well as gold shop workers, are at risk from lower level chronic exposure, and/or intermittent, instantaneously extreme exposures.  Therefore it is important to reduce mercury emissions in urban areas through education and installation of gold shop condensers.  The ideal goal of any such effort should be the banning of amalgam burning in urban centres, and the eventual relegation of gold shops to the urban periphery or to purely industrial zones.  Proper shop ventilation and efficient fume hoods are the best means of safeguarding the health of gold shop workers in the short term.  Properly designed wet or dry mercury condensers can reduce mercury emissions by more than 80%, but the details of the design and installation can drastically affect mercury capture (especially in the case of the EPA dry condenser).  Immediate improvement of gold shop condensers can be achieved by using iodine impregnated charcoal condensers, but it may be difficult to ensure that they are regularly changed and disposed of properly.  Installation efforts must be accompanied by thorough education efforts, support from local governments, clear design documents, and dedicated follow-up.  Governments are sometimes powerless to act on mercury contamination by gold shops because it is a central aspect of the local economy that cannot be suddenly banned or taxed without adverse effects on the community.  Efficient mercury capture systems can enable governments to take regulatory action to reduce mercury emissions.  Implementation must be done with a focus on capacitation of local universities as well as gold shop owners and metal workers (depending on the design).  Mercury capture must become part of the local artisanal mining tradition. Regardless of the efficiency of gold shop condensers, it is imperative that miners burn the amalgam in the field using retorts before selling the gold in urban shops.  7 REFERENCES  Akagi, H., Malm, O., Branches, F.J.P., Kinjo, Y., Kashima, Y., Guimaraes, J.R.D., Oliveira, R.B., Haraguchi, K., Pfeiffer, W.C., Takizawa, Y. & Kato, H. 1995. Human exposure to mercury due to goldmining in the Tapajos River basin, Amazon, Brazil: Speciation of mercury in human hair, blood and urine. Water, Air, & Soil Pollution vol.80 no.1 pp.85-94.  Bastos, W.R., de Freitas Fonseca, M., Pinto, F.N., de Freitas Rebelo, M., Silva dos Santos, S., Glória da Silveira, E., Torres, J.P.M., Malm, O. & Pfeiffer, W.C. 2004. Mercury persistence in indoor environments in the Amazon Region, Brazil. Environmental Research vol.96 no.2 pp.235-238.  de Lacerda. 2003. Updating global Hg emissions from small-scale gold mining and assessing its environmental impacts. Environmental Geology [Online] vol.43 no.3 pp.308.  Drake, P.L. 2001. Occupational exposure to airborne mercury during gold mining operations near El Callao, Venezuela. International archives of Occupational and Environmental Health [Online] vol.74 no.3 pp. 206.  GarcÃ-a-Sánchez, A., Contreras, F., Adams, M. & Santos, F. 2006. Atmospheric mercury emissions from polluted gold mining areas (Venezuela). Environmental Geochemistry and Health vol.28 no.6 pp. 529-540.  Hacon, S., Artaxo, P., Gerab, F., Yamasoe, M.A., Campos, R.C., Conti, L.F. & De Lacerda, L. D. 1995. Atmospheric mercury and trace elements in the region of Alta Floresta in the Amazon Basin. Water, Air, & Soil Pollution vol.80 no.1 pp.273-283.  Malm, O., Castro, M.B., Bastos, W.R., Branches, F.J.P., Guimarães, J.R.D., Zuffo, C.E. & Pfeiffer, W.C. 1995. An assessment of Hg pollution in different goldmining areas, Amazon Brazil. Science of The Total Environment vol.175 no.2 pp.127-140.  Malm, O., de Freitas Fonseca, M., Hissnauer Miguel, P., Rodrigues Bastos, W. & Neves Pinto, F. 1998. Use of epiphyte plants as biomonitors to map atmospheric mercury in a gold trade center city, Amazon, Brazil. The Science of The Total Environment vol.213 no.1-3 pp.57-64.  Marins, R.V., de Andrade, J.B., Pereira, P.A., Paiva, E.C. & Paraquetti, H.M. 2000. Sampling techniques for the assessment of anthropogenic vapour and particulate mercury in the Brazilian Amazon atmosphere. Journal of Environmental Monitoring vol.2 pp.325-328.  Telmer, K., Costa, M., Simões Angélica, R., Araujo, E.S. & Maurice, Y. 2006. The source and fate of sediment and mercury in the Tapajós River, Pará, Brazilian Amazon: Ground- and space-based evidence. Journal of Environmental Management vol.81 no.2 pp.101-113.  Argonne National Laboratory, Environmental Science Division 2007. Technology for Mercury Emission Reductions in Small-Scale Gold Refining Facilities: Construction, Installation, and Testing., pp. 30.  Veiga, M. and Baker, R. 2004. Protocols for Environmental and Health  Assessment of Mercury Released by Artisanal and Small-Scale Gold Miners. GEF/UNDP/UNIDO, Vienna, Austria.  Veiga, M.M. and Fernandes, F.R.C. 1990. Poconé: an Opportunity  for Studying the Environmental Impact of the Goldfields. pp. 185.  World Health Organization. 2003. Elemental mercury and Inorganic Mercury  Compounds:  Human Health Aspects.  Accessed July 5, 2008.  Yayasan Tambuhak Sinta. 2007.  Yayasan Tambuhak Sinta post-GMP report to UNIDO.  Kereng Pangi, Indonesia


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