Health and environmental assessment of mercury exposure in a gold mining community in Western Mindanao, Philippines

The small-scale gold mining activities using mercury began in the late 1980s in Sibutad, Western Mindanao. It is located very near the Murcielagos Bay with tailing ponds directly discharging into bodies of water. This cross-sectional study aimed to determine the health and environmental effects of gold mining activities on the community. Residents were randomly selected and classified into two groups, namely, the directly exposed and indirectly exposed populations using a set inclusion criteria. Complete medical and laboratory examinations were performed. Environmental and biologic samples were collected for total mercury and methylmercury determinations. The results showed that the directly exposed group had significantly higher mean blood total mercury and methylmercury levels in comparison with the indirectly exposed population. Although there were no significant differences between hair total mercury and methylmercury levels, there was a trend for higher levels of these biomarkers among the directly exposed residents as compared with the unexposed group. The absence of statistically significant differences may be attributable to the small sample size. Ambient air quality monitoring for mercury exceeded the allowable levels. However, levels of mercury in drinking water and sediments were within allowable limits. Frequency of gastrointestinal complaints was significantly associated with elevated hair methylmercury levels (p=0.02). Also, there appears to be a trend towards higher blood total mercury levels and frequency of gastrointestinal complaints (p=0.09). An interesting finding in this study was the increasing incidence of elevated diastolic blood pressure with elevated hair total mercury levels (p=0.07). Mercury storage at home is a risk factor.     

Environmental assessment of mercury dispersion, transformation and bioavailability in the Lake Victoria Goldfields, Tanzania

Environmental dispersion and transformation of mercury discharged from gold mining operations has been investigated in field and laboratory studies in order to provide better understanding of the degree of mercury (Hg) pollution and bioavailability in the Lake Victoria goldfields (LVGF) ecosystems. This paper reviews results already published elsewhere and presents additional data on Hg dynamics in the LVGF. Studies conducted at the Mugusu and Rwamagaza artisanal mines indicated different degrees of Hg contamination and dispersion in environmental matrices. Mercury concentration in contaminated river sediments near the Mugusu mine varied from 6.0 to 0.5 mg/kg on a dry weight basis. The highest Hg contamination levels (165-232 mg/kg) were associated with mine tailings at the Rwamagaza mine. Mercury concentrations in fish representing different dietary habits on the southwestern shore of Lake Victoria at the Nungwe Bay were very low (2-35 microg/kg) and thought to represent background levels. These and other results suggested that the use of Hg in gold extraction in the LVGF has not caused high Hg levels in lake fish. The study of Hg in lichens showed Parmelia lichen to be an effective bioindicator for atmospheric Hg contamination due to Hg emissions from gold-amalgam firing and purification operations. The Hg levels in the lichens around the Mugusu mine ranged from 3.1 to 0.1 microg/g; the highest levels were recorded in the lichens sampled close to gold-amalgam processing sites. The regional background level in the Parmelia lichen was 0.05-0.10 microg/g, with a mean level of 0.07 microg/g. Studies of Hg transformation in the mine tailings revealed unexpectedly high methylmercury (MeHg) levels in the tailings (629-710 ng/g), which indicated that oxidation and methylation of metallic Hg in the tailings occurred at significant levels under tropical conditions. Re-equilibration of the tailings with freshwater (FW) indicated the MeHg was firmly bound in the tailings and therefore very little MeHg was released to the water column (0.2-1.5 ng/L). The methylation of Hg in tropical loamy clay soil contaminated with HgCl(2) (5 mg Hg/kg) yielded MeHg concentrations of 11 and 14 ng/g when inundated with seawater and FW, respectively, for 4 weeks. Little MeHg was transferred from the soil to the equilibrated water (< or = 0.4 ng/L). Atmospheric exposure of the soil pre-inundated with FW resulted in net degradation of MeHg during the 1st week of exposure, followed by net production and accumulation of MeHg in the soil (up to 15.5 ng/g) during atmospheric desiccation. Mercury uptake by fish from the Hg(0)-contaminated aquatic sediment-tailings system in the aquarium experiment was found to be low, suggesting the low availability of MeHg for bioaccumulation in the system. These and other results provide useful insights into Hg transformation, mobility and bioavailability in tropical aquatic systems affected by Hg pollution from gold mining operations.     

The public good dilemma of a non-renewable common resource: A look at the facts of artisanal gold mining

Millions of people worldwide are involved in artisanal and small-scale gold mining. Many of them live in conditions of poverty and insalubrities due to the mercury amalgamation of gold and the application of other rudimentary techniques. In spite of this, the sector has been nearly overlooked by resource economists. In this paper we analyze the sector based on a survey of the existing literature. We find some commonalities of artisanal and small-scale gold mining in different countries of the developing world as follows: low levels of mechanization and technology, labor intensiveness, low awareness of environmental degradation, poor training, high transience among some miners, and lack of financial savings. Moreover, with these commonalities in mind, we present some topics and challenges for a research agenda in the field of environmental, ecological, and development economics.     

The source and fate of sediment and mercury in the Tapajós River, Pará, Brazilian Amazon: Ground- and space-based evidence

We present results of mercury (Hg) in surface waters and soils and an analysis of satellite imagery from the Tapajós River basin, Brazilian Amazon, and the Reserva Garimpeira do Tapajós, the legal gold mining district of the basin. Hg bound to suspended sediment was roughly 600 and 200 times the concentration of dissolved Hg per litre of water, in impacted and pristine areas, respectively. Suspended sediments thus represent the major pathway of river-borne Hg. Median concentrations of Hg in suspended load from both impacted and pristine waters were 134 ppb, and 80% of samples were below 300ppb-in the range of naturally occurring surficial materials in the tropics. Regionally, riverine Hg fluxes were proportional to the concentration of total suspended solids. This shows that the dominant source of Hg is the sediment itself rather than anthropogenic mercury discharge from the small-scale mines. To independently test this conclusion, a mass balance was performed. A conservative calculation of the annual export of mercury (Hg) from the Creporí River (a minimum) was 1.6 tonnes for the year 1998-it could be significantly larger. This amount of Hg is difficult to account for by anthropogenic discharge alone, confirming that enhanced physical erosion caused by sluicing and dredging operations is the dominant source of Hg. We therefore conclude that gold mining operations are primarily responsible for elevated Hg concentrations. The dominant source of contamination is not, however, the loss of Hg in the gold amalgamation process. Rather, the disturbance and mobilization of large quantities of Hg-rich sediment and floodplain soil into the water column during mining operations is the source of contamination. These findings shift the focus of remediation and prevention efforts away from Hg control toward soil and sediment erosion control. The minimization or elimination of Hg losses in the mining process remains important for the health of local peoples and environments, but keeping basin soils and sediments in place would be a much more effective means of minimizing Hg fluxes to the region's rivers. To gain a spatial and historical perspective on the source and extent of emissions, satellite imagery was used. We were able to reconstruct historical mining activity, locate impacted areas, and estimate historical Hg fluxes with the imagery. To do so, the spectral characteristics of satellite images were calibrated to the concentration of suspended sediment in the rivers, which, in turn, is proportional to the Hg concentration. This analysis shows that mining-induced sediment plumes have been a dominant source of sediment to the Tapajós River system for decades. As well, the intensity and location of these emissions has varied through time. For example, sediment discharge from the Creporí River was greater in 1985 than in 1998; and the tributaries on the west bank of the Tapajós were actively being mined in 1985 but had been abandoned in 1998. This type of information should greatly assist in understanding original and ongoing sources of emissions, and in managing prevention and remediation efforts.     

GOLD-MINING EFFECTS ON HEAVY METALS IN STREAMS,CIRCLE QUADRANGLE,ALASKA1

Placer gold mining, which extracts gold from buried or exposed alluvia, is often conducted on or near streams. Such mining has the potential to adversely affect water quality. Other heavy metals associated with the gold (such as arsenic, cadmium, lead, zinc, and copper) may be freed to enter streams. Mercury may also enter streams if miners are using it to recover fine particles of gold. These heavy metals are toxic and thus may be harmful to the aquatic life of the streams receiving effluent or runoff from placer mines. In 1982 we sampled two streams intensively - one heavily mined and one unmined - for total recoverable arsenic, mercury, lead, zinc, and copper. Only mercury was not significantly higher in concentration in the mined streams. In 1983 we sampled two stream pairs three times, and 10 other sites at least once, for total and dissolved arsenic, cadmium, mercury, lead, zinc, and copper. Mercury and cadmium were not significantly elevated in mined streams, but the concentrations of total arsenic, lead, zinc, and copper, and dissolved arsenic and zinc were significantly higher in streams below active placer mining sites than in these that were not being mined or those that had never been mined. Additionally, total arsenic, lead, zinc, and copper and dissolved arsenic and copper became elevated after mining began in 1983 on a previously unmined stream.     

Environmental impact of mining in Ghana: issues and answers

As part of the process of drafting environmental guidelines for mining, a study of the impact of mining on the environment was undertaken by the Ghanaian Minerals Commission. The study evaluated the impact of underground mines and surface mines on the physical environment as well as their socio-economic impact. Among its conclusions: for both types of mines, drainage emptying out into rivers is a major cause of pollution; mine roads open up uninhabited regions to farming and other uses. Underground mines employ more workers than surface mines; the socioeconomic benefits of the surface mines to local people are less than those of underground mines.     

MINE DRAINAGE AND ROCK TYPE INFLUENCES ON EASTERN OHIO STREAM WATER QUALITY1

ABSTRACT: Stream water during fair weather (base flow) is largely ground water discharge, which has been in contact with minerals of the underlying aquifer. Base flow water quality should therefore reflect aquifer mineralogy as well as upstream land use. Three upstream mining categories (unmined lands, abandoned coal mines, and reclaimed coal mines) differed in pH, specific conductance, sulfate, iron, aluminum, and alkalinity for 122 streams in eastern Ohio. Aquifer rock type influenced pH, specific conductance, sulfate, iron, and alkalinity. Reclamation returned many components of acid mine drainage to near unmined levels, although sulfate and specific conductance were not improved. Acid mine drainage problems were less severe in watersheds underlain by the calcareous Monogahela Formation. These results should ayply to other Appalachian coal regions having similar rock units. The water quality data distributions were neither consistently normal nor lognormal. Statistical tests utilizing ranks of the water quality data, instead of the data themselves, proved useful in analyzing the influences of mining category and rock type.     

Comparative observations on levels of mercury in scalp hair of humans from different Islands

Following the Minamata events, an extraordinary number of studies concerning mercury toxicity and human health have been undertaken. Particular attention has been given to the evaluation of the dose-response relationship, i.e., the body burden at which (evaluated through the mercury analyses in blood or hair) the risk of poisoning begins. The results of a comparative study concerning levels of mercury in the hair of fishermen living in small islands who eat seafood more than four times per week show that in two areas only, and only in a few cases in these areas, the mercury in the hair exceeds the limit at which a possible risk could exist. In fact, the limit of 50 mg/g of total mercury in the hair (indicated as the lower limit above which a possible risk could occur) is surpassed by nine fishermen out of a total of 39 at station 1 and by four fishermen out of a total of 26 at station 3. The average value at station 1 is 36.38 mg/g and that at station 3 is 30.31 mg. Many countries have set legal limits of mercury for seafood, but evidently the system does not offer a true protection for man. Only the provisional tolerable weekly intake (PTWI), as repeatedly suggested by WHO, should be considered the best guideline to prevent possibly harmful consequences.     

Distribution and mobility of mercury in soils of a gold mining region, Cuyuni river basin, Venezuela

An extensive and remote gold mining region located in the East of Venezuela has been studied with the aim of assessing the distribution and mobility of mercury in soil and the level of Hg pollution at artisanal gold mining sites. To do so, soils and pond sediments were sampled at sites not subject to anthropological influence, as well as in areas affected by gold mining activities. Total Hg in regionally distributed soils ranged between 0.02 mg kg(-1) and 0.40 mg kg(-1), with a median value of 0.11 mg kg(-1), which is slightly higher than soil Hg worldwide, possibly indicating long-term atmospheric input or more recent local atmospheric input, in addition to minor lithogenic sources. A reference Hg concentration of 0.33 mg kg(-1) is proposed for the detection of mining affected soils in this region. Critical total Hg concentrations were found in the surrounding soils of pollutant sources, such as milling-amalgamation sites, where soil Hg contents ranged from 0.16 mg kg(-1) to 542 mg kg(-1) with an average of 26.89 mg kg(-1), which also showed high levels of elemental Hg, but quite low soluble+exchangeable Hg fraction (0.02-4.90 mg kg(-1)), suggesting low Hg soil mobility and bioavailability, as confirmed by soil column leaching tests. The vertical distribution of Hg through the soil profiles, as well as variations in soil Hg contents with distance from the pollution source, and Hg in pond mining sediments were also analysed.     

概率积分法在矿山环境开采沉陷预测评估中的应用

随着采矿业的不断发展,给矿区环境带来了多方面的、不同程度的破坏,产生了一系列的生态环境问题。本文利用概率积分法,以河南省登封市某煤矿矿区为例,对矿山环境保护与综合治理中的矿山环境地表移动预测评估进行了研究,为确定采煤塌陷对地表各建筑物的影响程度提供了依据。     

Restoring Forests and Associated Ecosystem Services on Appalachian Coal Surface Mines

Surface coal mining in Appalachia has caused extensive replacement of forest with non-forested land cover, much of which is unmanaged and unproductive. Although forested ecosystems are valued by society for both marketable products and ecosystem services, forests have not been restored on most Appalachian mined lands because traditional reclamation practices, encouraged by regulatory policies, created conditions poorly suited for reforestation. Reclamation scientists have studied productive forests growing on older mine sites, established forest vegetation experimentally on recent mines, and identified mine reclamation practices that encourage forest vegetation re-establishment. Based on these findings, they developed a Forestry Reclamation Approach (FRA) that can be employed by coal mining firms to restore forest vegetation. Scientists and mine regulators, working collaboratively, have communicated the FRA to the coal industry and to regulatory enforcement personnel. Today, the FRA is used routinely by many coal mining firms, and thousands of mined hectares have been reclaimed to restore productive mine soils and planted with native forest trees. Reclamation of coal mines using the FRA is expected to restore these lands’ capabilities to provide forest-based ecosystem services, such as wood production, atmospheric carbon sequestration, wildlife habitat, watershed protection, and water quality protection to a greater extent than conventional reclamation practices.     

Mine size and the structure of costs

The number of operating mines has fallen sharply for most mineral products, and the average size of mine risen, with the changes gathering momentum during the 1990s. The paper looks at trends in copper, zinc and gold, and then explores the relationship between size and unit costs in copper mining, separately for underground and open-pit mines, in order to ascertain the existence and importance of economies of scale. Changes in mine size have been accompanied by major technological and geographical shifts. There is only a weak relationship between the scale of mines and overall unit costs per tonne of copper produced. The paper discusses the data and explores some of the reasons.     

Non-point source mercury emission from the Idrija Hg-mine region: GIS mercury emission model

A mercury emission model was developed to estimate non-point source mercury (Hg) emissions occurring over the year from the Idrijca River catchment, draining the area of the world's second largest Hg mine in Idrija, Slovenia. Site-specific empirical correlations between the measured Hg emission fluxes and the parameters controlling the emission (comprising substrate Hg content, soil temperature, solar radiation and soil moisture) were incorporated into the mercury emission model developed using Geographic Information System technology. In this way, the spatial distribution and significance of the most polluted sites that need to be properly managed was assessed. The modelling results revealed that annually approximately 51 kg of mercury are emitted from contaminated surfaces in the catchment (640 km(2)), highlighting that emission from contaminated surfaces contributes significantly to the elevated Hg concentrations in the ambient air of the region. Very variable meteorological conditions in the modelling domain throughout the year resulted in the high seasonal and spatial variations of mercury emission fluxes observed. Moreover, it was found that mercury emission fluxes from surfaces in the Idrija region are 3-4 fold higher than the values commonly used in models representing emissions from global mercuriferous belts. Sensitivity and model uncertainty analysis indicated the importance of knowing not only the amount but also the type of mercury species and their binding in soils in future model development.     

Toxic mercury versus appropriate technology: Artisanal gold miners’ retort aversion

Mercury-usage in artisanal and small-scale gold mining (ASGM) has accelerated in developing countries during the last thirty years resulting in negative environmental and health impacts. As awareness of mercury contamination from ASGM has grown, a number of strategic initiatives have been introduced to reduce the impact of the toxic substance. The adoption of the retort, a device capable of recycling up to 95 per cent of mercury in gold extraction, constitutes a broadly recognized approach. Based on case-study research in Tanzania, this paper examines an ASGM area, which has been targeted by several mercury-reducing efforts. Based on survey data, key informants interviews, and visitor observations, the paper examines the impact of these efforts on mining techniques and residents’ attitudes towards the use of mercury. Despite the seemingly obvious advantages from adopting retorts or other mercury-reducing techniques – economic, environmental, and health-wise – miners continue to use mercury haphazardly, while demonstrating an only limited awareness of the toxicity of the substance. The paper discusses the possible explanations behind this as well as possible ways forward in facilitating the reduction of mercury in ASGM operations.     

Labour challenges and mercury management at gold mills in Zimbabwe: Examining production processes and proposals for change

The use of mercury in small-scale gold mining has been a growing concern in many parts of Africa. However, although the negative effects of mercury pollution are increasingly reported, little has been written about how labour relationships and gold production challenges in mining communities affect mercury management practices. This article provides an integrative analysis of small-scale gold extraction processes, labour challenges, and mercury use at gold mills in Zimbabwe, focusing on a gold rush area in Mashonaland West Province. It examines practices employed by miners who have limited economic capacities to upgrade technologies, and how the complex relationships between miners, mill owners and government regulators affect environmental performance. The study draws attention to how poor environmental management practices relate to labour inequities, low gold recovery as well as the informal gold trade dynamics amid the country's economic crisis. Results of a United Nations-supported stakeholder consultation process are discussed, with proposals for improving labour conditions and reducing environmental risk. The article highlights why the government should develop and support local programs to assist miners, as well as the decisive roles mill owners could take in ensuring improved standards on their sites.     

The regional impacts of small-scale gold mining in Amazonia

Gold mining is the major economic activity in the Upper Tapajós River Basin of the Brazilian Amazon. This article studies the structure, economy and impacts of gold mining operations in this region. Mining has significant environmental impacts in this region resulting in the removal of approximately 67 million m³ of sub-soil per year and accompanied by an annual release of some 12 tons of mercury to air, ground and rivers. In the early 1990s there were 245 mines in operation, employing some 30000 people and producing around 35t gold per year, valued at approximately $400 million yr^-1, the profits being about $110 million yr^-1. Miners spent most of their earnings on local goods and services, while mine owners and merchants in the gold towns invested in land (mainly for ranching), business ventures and money markets. Wealth gained from mining has served as an engine for development in other regions of the world and could, theoretically, achieve the same for Amazonia. However, before this could happen, the Government of Brazil would need to mark a strong presence in the area by providing technical assistance and developing and enforcing mining/environmental regulations. The likelihood of such a development materializing in the foreseeable future is small. In the meantime, gold mining acts, not as an 'engine for development', but as a destabilizing force — provoking environmental damage, social discord and public health hazards in the region.     

SMALL SCALE MINING AND ECONOMIC AID IN BOLIVIA

Although the small-scale mining sector in Bolivia has absorbed economic aid, little or no improvement has resulted. It appears that much closer technical and financial co-operation with those operating small mines is called for, including rigid credit supervision. Problems in small-scale mines arise from difficult mining conditions, the tax structure and capital market situation as well as the employment patterns of the mine operators. It is suggested that mechanized projects may not always be the best way to overcome poor conditions, but where they are, lack of collateral is frequently an obstacle. In such cases, a three stage approach to project implementation is proposed.     

A Review on the Present Scenario of Air Quality Associated with Indian Mining Operations

Compositional changes to air quality from coal mining are not only the most visible impact from these activities on the environment, they can also immediately affect the health of mine professionals and adjoining populations. The presence of gases and suspended solids emitted by mining activities affects the human respiratory system and decreases production in mines. This article summarizes a case study of several Northern Coalfields Limited (NCL) coal mines with an emphasis on particulate matter (PM) to report the status of air quality connected to coal production and overburden removal. The concentrations of sulfur dioxide (SO₂), nitrogen oxides (NO_x), and suspended particulate matter (SPM) reported in the literature are also summarized in table form to allow comparisons to the permissible standards set by the Indian Central Pollution Control Board (CPCB) and other standards used around the world. An up‐to‐date status of air quality at coal mines is compared for mines located in different parts of India. Subsequently, all coal mines were divided into different classes in regard to the severity of their emissions. These classes are, in increasing order of severity, green, yellow, red, and black. SPM measurements were tabulated in regard to concentration and composition. Our article concludes with the recommendation that an environmental impact assessment (EIA) to be conducted to better characterize changes in the environment from mining emissions to develop integrated mitigation measures and to identify additional parameters to define air quality at mines.     

MERCURY CONTAMINATION AND FLOODPLAIN SEDIMENTATION FROM FORMER GOLD MINES IN NORTH GEORGIA1

ABSTRACT: Gold was discovered in Georgia in 1829 and mined until about 1940 in the Dahionega Gold Belt of the north Goorgia Piedmont. Streams there are characterized by gravel beds and fine sandy to silty banks. Historical mining-related alluvium is clearly distinguished from prehistoric alluvium because it is contaminated with mercury (Hg), which was used by miners to amalgamate gold. Mercury concentrations in historical floodplain sediments range from 0.04 to 4.0 mg kg^?1, exceeding background (0.04 mg kg¹) by as much as two orders of magnitude near the core of the mining district and decreasing in the downstream direction. Low levels (≤ 0.1 mg kg¹) of Hg are established within about 10–15 km from the source mines. The mercury-contaminated sediment exceeds sediment quality guidelines set by many agencies, and is a significant nonpoint source for mercury pollution. Hydraulic mining of saprolite, which began in 1868, and cutting of forests associated with mining and settlement caused unusually rapid sedimentation (1–3 cm yr^?l) and floodplain aggradation in the region. After mining ceased, streams adjusted by downcutting and forming an historical-age terrace. A new floodplain is currently being formed as streams migrate lateraily and erode the mining-related sediment of the historical terrace. High magnitude floods are contained within the confines of the historical terrace, thus limiting quantities of over-bank sedimentation, causing channel bank erosion, and transmitting high sediment yields to reservoirs in the region.