S17 (II) Mercury in artisanal and small-scale gold mining

In Zimbabwe, gold placers are known to derive from the Archean greenstone belts that cover the country. Thus, nearly every river draining a greenstone belt has some degree of placer mineralization. In the Angwa River area, about 5000 t0 5500 people are currently working the river placer in an area of about 20 km long along the river. Across the country the numbers are in tens of thousands, spurred by the collapse of the Zimbabwean formal employment sector in the years 2005-2009. Thus both sides of the river bank have been extensively damaged by silting and excavation of pits in the zones believed to contain the coarse fraction of the river sediments. Several Artisanal Gold Small scale Miners (ASGM) derive their livelihood from selling gold to individuals and primarily to the Zimbabwean Central bank. The methods of extraction are panning for the coarse gold and the use of mercury for fine gold. The use of mercury is uncontrolled, as the whole mining process is deemed “illegal”, yet it is tolerated as it is a significant source of income for the government. It is important to note that, in this area, this gold has historically been worked by the “Mashona” people since at least 1540, when trade with the Portuguese on the east coast of Africa was recorded (Summers, 1969; Hall, 1992). Therefore this type of work was a traditional source of income, until the 1800’s when the European settlers took them over (Summers, 1969). This type of work has as well attracted “immigrant workers”, who have settled on the river banks; that has now impacted on other issues such as sanitation, health, land use conflicts, and social conflicts. The artisanal miners live in overcrowded, small, poorly built and unhygienic squatter camps, which would under normal circumstances be unsuitable for human habitation. The situation has been made worse by the fact that the government, despite buying gold from these miners, still classifies them as “illegal”. Yet this source of income was a main stay for many people in Zimbabwe, especially during the time when the economy had been in doldrums (2005-2009). Currently, both women, men and family units work these deposits across the country. It is therefore imperative, to come up with a legislative framework that will give these miners a right to work on these alluvial deposits, such is the case in Ghana, and in the process, regulate the mining methods and save the environment, regulate mercury use and improve sanitation and mining techniques. The current situation is not tenable for social development, and especially in the fight to minimize mercury use among the workers and reduce poverty in rural communities. The government needs to find solutions to make them legal, and therefore institute legal means of gold recovery openly.

Background:
Mercury is employed in artisanal small-scale gold mining (ASGM) to extract the gold from ore; consequently miners and residents are under risk to develop mercury-related symptoms. To assess the impact of ASGM use of mercury on population health, the burden of chronic mercury intoxication in Zimbabwe was estimated for 2004 using the Environmental Burden of Disease (EBD) approach.

Methods:
The EBD method was used to calculate the disability-adjusted life years (DALYs). Epidemiological and demographic information about the entire and the exposed Zimbabwean population, as well as about chronic mercury intoxication were collected from different data sources: two field studies in Zimbabwe, international literature review, and United Nations and World Health Organization (WHO) databases. The WHO software tool DisMod II was used to model missing data. Occupationally as well as environmentally exposed Zimbabweans were considered. In case of uncertainty, those data yielding the lowest DALYs were used to avoid overestimation. To estimate the impact of chronic mercury intoxication on population health, the resulting DALYs were compared with disease burdens as published in the latest Global Burden of Disease study.

Findings:
The preliminary results present a burden of 4.24 DALYs per 1,000 inhabitants due to chronic mercury intoxication from ASGM in Zimbabwe in 2004 (total: 52,932 DALYs). The subgroup affected the most is occupationally exposed men aged 15-29 years with 9.72 DALYs per 1,000 inhabitants. The total DALYs are comparable to asthma in Zimbabwe, road traffic accidents in Europe, and cancer (except lung) attributable to indoor and outdoor air pollution, water, sanitation and hygiene in Hungary (the highest country rate in the world).

Interpretation:
The data clearly indicate that the use of mercury in ASGM poses a serious public health issue. The overall DALYs due to chronic mercury intoxication are comparable with well-recognized international public health problems, although the lower bound was estimated. The results highlight the urgent need for action to reduce the burden. The analysis is limited by the scarcity of data, by reason of the informal character of ASGM. Refined analyses are currently in progress to characterize the level of uncertainty and to improve the quality of the first estimates.

It is well established that residents of small-scale gold mining communities are exposed to potentially harmful levels of mercury, but few have integrated mercury measurements across multiple media and little is known about exposures to other potentially toxic metals that may be released during mining. During the summers of 2009 and 2010, we conducted field research in a small-scale gold mining community in Ghana’s Upper East Region. Our studies focused on women of childbearing age (n=91), children under five (n=11), and miners (n=120), as these are three groups who are exceptionally vulnerable to mercury exposure and toxicity. From each participant we obtained hair, urine, and survey information concerning demographics, diet and fish consumption, health status, and occupation. For many we also collected information on household location (particularly in relation to mining sites), drinking water, yard soil and data from a personal air monitor. From the at-large community, we obtained samples of fish, water, and soil. We also took geographic coordinates of households, mining activities, and ecological samples, and mapped these data with Esri’s ArcGIS software. Mercury levels are being measured in all samples, and in a subset of miners we measured exposures to 11 other metals. Several results are of note. More than one-fifth of miners had moderately high levels of urinary mercury (>10 µg/L), and in a subset of 57 male miners we found that 10-40% of the participants had urinary chromium, arsenic, aluminum, copper, manganese, nickel, selenium, and zinc that fell outside reference range values. Women of CBA in the mining community had elevated levels of urinary (7.74 ± 37 µg/L, n=86) and hair (1.7 ± 10.3 mg/L, n=80) mercury. Preliminary stream sediment samples (n=6) and household yard soil samples (n=7) had total mercury levels of 28.0 ± 12.3 µg/kg and 3323.8 ± 4414.9 µg/kg, respectively. We are currently assembling data from all other media and will present a multimedia assessment of mercury exposure and make use of GIS-derived maps to document spatial trends. In general, our data show elevated mercury levels in human biomarkers and ecological samples throughout the community, regardless of individual use of or involvement with mercury.

India is one of the largest users of the hazardous metal mercury in the world. The average use of mercury over the last decade has been of the order of 170 to 190 mtons/a., that is, 7 to 10% of the total global mercury use. The different sectors that consume mercury are: chlor-alkali (16%), batteries (16%), thermometer and other measuring equipments (14%), thermostats (12%) and lighting (4%), accounting for 62% of the total mercury use. According to available statistics, 38% of mercury imported remains unaccounted for. Based on our surveys on artisanal and small scale gold mining (ASGM) in different parts of India it is proposed here that the major part of this unaccounted mercury is actually utilized in recovery of gold through amalgamation and subsequent burning, causing significant environmental pollution. Most of these miners are poor indigenous tribal people and a substantial part of the work force comprises women.

Gold occurrences in India are mainly confined to the Precambrian rocks of Dharwar craton in south India. The other primary gold occurrences are scattered in central and eastern India: in Mahakoshal belt in eastern Uttar Pradesh, in the Sakoli basin of Maharashtra, in the Dongargarh Group in Chattisgarh and in the Singhbhum region of Jharkhand state. In the west, gold occurrences are known in the Banswara district of Rajasthan. All these areas are known for ASGM.

Primary auriferous quartz reefs are worked by local communities in the Wynad gold field, in the contiguous parts of Tamil Nadu and Kerala, particularly in the abandoned mines and adits in Pannur, Pandalur-Devala areas. Similarly, in the Hosur area of northern Karnataka, illegal ASGM is carried out in the abandoned shafts and inclines of the Bharat Gold Mines Ltd. in the Gadag gold field.

ASGM is carried out extensively in the Nilambur region, south of the Wynad gold field, in the alluvial tracts of the Cheliyar and Punna Puzha Rivers and also in the nearby Attapady valley of Pallakkad district in Kerala by the local Paniyar tribe. Alluvial gold mining is practiced by local villagers in Maru River (a tributary of Waynganga) bed in Bhiwapur in Nagpur district of Maharashtra, in the wide alluvial tract of the Subarnarekha River in Jharkhand and in the Himalayan foothills near Rampur in Himachal Pradesh, in the bed of the meandering Sutlej River.

Artisanal Small-scale Gold Mining (ASGM) and mercury use is widespread throughout the Indonesian archipelago, including the province of Central Kalimantan. Miners process ore in several different ways but the use of mercury is ubiquitous. In Central Kalimantan alone, more than 50 tons of mercury is used annually by 55,000 miners. The practice of whole ore amalgamation on milled hard rock ores consumes and emits a disproportionately large amount of this mercury. Whole ore amalgamation is typically followed by processing with cyanide, a practice known to create soluble mercury species and mobilize these complexes into ecosystems around and downstream of processing operations.

The majority of Indonesian miners use sluices to process sediments. Concentrates are panned with mercury to extract gold by amalgamation. Instead of amalgamation, sluice concentrates can be concentrated further using a tuneable micro-scale concentrator, which reduces the mass of a concentrate without losing gold. Up to 100 grams of resulting concentrate with gold content 5% or greater can be directly smelted. Direct smelting can recover un-liberated gold, providing an incentive for this approach in some contexts.

Where mercury has been used for amalgamation, retorts and fume-hoods can be used to recover the mercury released when amalgam is heated, and to reduce occupational exposure. Retorts can be effective tools for mercury recovery but their design needs to be tailored to regional behaviours. A cheap and easy to operate fume-hood add on has been designed in Indonesia to recover mercury from heated amalgam. The device consists of a blower fan, a plastic vessel and some plumbing fixtures.

Replacing whole ore amalgamation with cyanide is a viable concept but requires both business (economic) and behavioural shifts in ASM communities. Demonstrating the economical, health and environmental benefits of cyanide use by developing a processing operation with local partners may be the best approach to overcome this challenge. A model facility should operate for profit, and act as a center for best practices and miner outreach.

In locations where whole ore amalgamation has operated for years, thousands of tonnes of pre-processed tailings contain both gold and mercury. If processed efficiently, significant amounts of both metals can be recovered economically. This represents business opportunities for ASM community members, but also presents technical challenges for which they will require expertise and assistance.

A passive sampler, which does not require an electric power supply and is suitable for multi-point sampling, was developed to measure the atmospheric mercury. A fairly good performance of the passive sampler was confirmed by comparing the analysis data with that obtained from the active sampler. The passive samplers were applied to measure the atmospheric mercury concentration in West Sumatra, Indonesia, where artisanal and small-scale gold mining plants are under operation. The passive sampler worked quite well to determine the space distribution of gaseous mercury around a gold purification plant in the Datar Luas Village in the Aceh Jaya District of Aceh, West Sumatra. In this research, we confirmed the existence of two major plants with about 100 tumblers and two smaller plants with 20 and 4 tumblers for amalgamation. However, as all plants are illegal in this area, other plants function illegally in the backyards of homes. Therefore, there could be some gold mining plants that the government has not been able to identify. Based on an interview with miners in July 2010, approximately 0.25 kg of mercury is put in a single tumbler. The amalgamation process is repeated three times per day. The total mercury used in this activity is estimated to be 168 kg/day. Although the mercury is re-used, some amounts of mercury are still believed to be released into the environment during the gold separation process, which involves the discharge of waste water and burning of the amalgam form. The mercury concentration was measured at nine stations around the plants and inside of the shed of one of the major gold mining plants. The highest gaseous mercury concentration, 1740 ng/m³, was observed inside the plant shed. In a residential area, a gaseous mercury concentration of more than 200 ng/m³ was observed. This indicates that not only the workers in the plants but also the residents near the plants could suffer adverse effects from exposure to high concentrations of mercury.

Background:
Inorganic mercury (Hg) is used in gold mining. Earlier studies, conducted in gold mining areas in Indonesia (Böse-O’Reilly et al. Sci Total Environ 2010), Philippines (Drasch et al. Sci Total Environ 2001), Tanzania (Böse-O’Reilly et al. Sci Total Environ 2010), and Zimbabwe (Lettmeier et al. Sci Total Environ 2010), have shown that individuals working or living in gold mining areas demonstrate high levels of Hg in urine, hair, and blood. However, there were large differences in levels of Hg among individuals with similar exposure. This may be due to genetic differences in Hg toxicokinetics, involving its uptake, biotransformation, distribution and elimination.

Objective:
The aim of this study is to identify genetic variants that affect Hg toxicokinetics.

Materials and Methods:
This study included 1113 participants from the above-mentioned studies in Indonesia, Philippines, Tanzania, and Zimbabwe, sampled as a part of the Global Mercury Project. Individuals were classified as controls (with no specific Hg exposure), or with low (living in a contaminated mining area) or high (working with Hg) exposure. Urine, hair, and blood were collected for analysis of Hg by cold-vapor atomic absorption spectrometry. Genotyping was done for 45 polymorphisms potentially involved in the toxicokinetics of Hg (i.e glutathione-related genes and Hg transporters).

Preliminary Results:
Some polymorphisms modified the relation between exposure group and Hg levels. For some, the effect was in the same direction in all countries studied, whereas for other polymorphisms, the effect modification could only be seen in one or two.

Conclusion: This is the largest study performed, addressing how genetic factors influence the toxicokinetics of inorganic Hg. The results can be used for development of appropriate occupational exposure limit values taking genetic variability into account.

Although its definition may lead the public to think that its scale is limited, Artisanal and Small-Scale Gold Mining (ASGM) produces up to 30% of the annual gold output employing more than 10 million miners in over 65 countries. For the sector, mercury amalgamation remains the method of choice to extract gold from the ore and because of generally low technical awareness, unnecessary high quantities of mercury are used with almost all ending up in the environment. However, successfully and sustainably transferring new techniques is not trivial. As they generally have low level of technical expertise, miners learn by example and the acceptance of a new technique is a long learning process. UNIDO, as the UN organisation dealing with industrial activity, has been actively involved in ASGM projects for more than 15 years. Although ASGM interventions have to be holistic as it arises from and is the source of a number of issues, technical assistance is always at the center of UNIDO’s interventions. UNIDO’s strategy is to first transfer technologies to ensure that the sector drastically reduces its mercury emissions and then to assist miners to move to non-mercury techniques. In the ore processing, two steps are responsible for the majority the emissions: metallic mercury is released to the water body during the amalgamation process and mercury vapours are released during amalgam burning. For the first step, UNIDO’s projects concentrate in eliminating the worst practices such as whole ore amalgamation and instead promote pre-amalgamation ore concentration reducing the amount of mercury needed followed by controlled amalgamation in dedicated vessels or cemented pools, depending on the amount to process. For amalgam burning, UNIDO promotes the replacement of the traditional open burning with the utilisation of locally made retorts allowing mercury recycling. In any case, for a technology transfer to be successful, the new equipments have to be built locally. For more advanced sites, replacement with non-mercury techniques is also possible. UNIDO is now working with its partners in the UNEP Global Mercury Partnership to develop more projects and encourage replication. A separate presentation is planned in session 18.