Complex nanominerals and ultrafine particles assemblages in phosphogypsum of the fertilizer industry and implications on human exposure

Phosphogypsum (CaSO₄·2H₂O), a by-product of phosphate-rock processing, contains high amounts of impurities such P₂O₅, F, radioactive elements, organic substances, secondary nanominerals, and ultrafine particles (UFP) enriched in metals and metalloids. In this study, we examine phosphogypsum (PG) collected from abandoned fertilizer industry facility in south Brazil (Santa Catarina state). The fragile nature of nanominerals and UFP assemblages from fertilizer industry systems required novel techniques and experimental approaches. The investigation of the geochemistry of complex nanominerals and UFP assemblages was a prerequisite to accurately assess the environmental and human health risks of contaminants and cost-effective chemical and biogeological remediation strategies. Particular emphasis was placed on the study and characterization of the complex mixed nanominerals and UFP containing potentially toxic elements. Nanometer-sized phases in PG were characterized using energy-dispersive X-ray spectrometer (EDS), field-emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM) images. The chemical composition and possible correlations with morphology of nanominerals and UFP, as well as aspects of nanominerals and UFP, are discussed in the context of human health exposure, as well as in relation to management of the nanominerals and UFP in PG environments.     

Numerical investigation of coal and gas outbursts in underground collieries

Coal and gas outbursts are a complex catastrophic unstable phenomenon that involve the ejection of large volumes of coal, and are often accompanied by gas, such as methane, carbon dioxide or a mixture of the two. Coal and gas outbursts are prevalent in deep and gassy mines where face advance rates are rapid, and where gas drainage is either poor or absent. The occurrence of progressively larger coal and gas outbursts, and the potential for the catastrophic collapse of coal pillars, is of increasing importance as mining is extended deeper in seams rich in methane and other hydrocarbons. A unique coupled gas flow and solid deformation numerical model, viz., RFPA^2D-GasFlow, has been developed and is applied to simulate the evolutionary process of such catastrophic coal failures in underground collieries. The finite element model, which incorporates the physics of gas flow in the coal seam, the physics of coal deformation and instantaneous failure, and the cross-couplings between them, is proposed. The model also incorporates small-scale variability in deformation modulus and strength of the coal and surrounding rock. The variability in modulus and strength is distributed via a fine-scale resolution model according to the Weibull distribution, where the distribution parameter determines the level of heterogeneity. This numerical model is applied to simulate the whole process of coal and gas outbursts, including stress concentration, coal fracturing, gas pressure-driven expansion, and outburst. The instantaneous outburst process and associated stress fields, gas pressure gradients and displacement vectors are presented step by step. The numerical simulations indicate that the instantaneous outburst is a complex phenomenon involving interactions between gas pressure, stress and the physico-mechanical properties of the coal, and it can occur under a variety of conditions. Successful numerical simulation of the whole coal and gas outburst process provides the basis for identifying the outburst mechanisms, parameterizing the causative processes, and to defining potential precursors of failure.     

王庄矿矸石混凝土间隔充填连续采煤工艺研究

为了解决煤矿资源紧缺问题,提高矿井产量、延长矿井服务年限,针对王庄煤矿的煤层赋存条件,提出了一种利用矸石混凝土间隔充填,连续采煤机短臂机械化采煤工艺,并对采煤工作面设备进行了选型,实践证明该采煤方法可用于开采＂三下＂压煤及不适合布置长壁工作面的边角煤。     

Mercury contamination in fish from gold mining areas in Indonesia and human health risk assessment

This study investigates the effects on fish and assesses human health hazards from mercury released in two gold mining areas in Indonesia: Tatelu (North Sulawesi Province) and Galangan (Katingan District, Central Kalimatan Province). In Tatelu, 154 fish specimens of 10 freshwater species were collected, as well as five marine species from the fish market. The mean concentration of total mercury in muscles of freshwater fish from this area was 0.58+/-0.44 microg/g, with more than 45% of fish having Hg levels above the WHO guideline for human consumption of 0.5 microg/g. In Galangan, where 263 fish specimens of 25 species were collected, the total mercury in muscles averaged 0.25+/-0.69 microg/g. Excluding data from flooded open pits in sub-area P4, mean Hg levels in fish from Galangan were 2 to 4 times lower than 0.5 microg/g, while fewer than 10% of fish from Galangan exceeded WHO guidelines. The Hazard Quotient (HQ) was applied to both areas to determine the threat of MeHg exposure for communities in both areas. The HQ is a risk assessment indicator which defines the ratio of exposure level to a single substance in relation to a reference dose. Samples from Tatelu (excluding marine species) had an HQ above one, while those from Galangan resulted in values of 2.4 for the whole area and 9.9 for sub-area P4, pointing to potentially harmful fish consumption for the local population. By using the single-compartment model to estimate mercury levels in blood and hair from daily intake dose, sub-area P4 showed the highest levels, higher than the upper limit guideline for pregnant women, but still lower than threshold levels associated with observed clinical effects.     

欧洲矿业遗产价值识别、保护与再生经验及启示

煤炭、金属与非金属等各类采矿地是现代工业遗产的重要组成,同时又是目前生态修复工程的主要对象.不恰当的修复治理方式极易破坏有价值的采矿工业遗迹,这使得中国矿业遗产保护与再生面临诸多挑战.通过文献和案例整理,系统分析了欧洲在矿业遗产价值识别、保护与再生领域的经验,比较不同欧洲国家的法律依据,总结出区域一体化统筹、多元主体参...     

Assessment of DNA damage in coal open-cast mining workers using the cytokinesis-blocked micronucleus test and the comet assay

Coal mining is one of the most important causes of environmental pollution, as large quantities of coal dust particles are emitted. Colombia-South America has large natural coal reserves and “El Cerrejón” is the world's largest open-cast mine located in the northern department of Guajira. The aim of the present study was to evaluate genotoxic effects in a population exposed to coal residues from the open-cast mine “El Cerrejón”. 100 exposed workers and 100 non-exposed control individuals were included in this study. The exposed group was divided according to different mining area activities: (i). Transport of extracted coal, (ii). Equipment field maintenance, (iii). Coal stripping and, (iv). Coal embarking. Blood samples were taken to investigate biomarkers of genotoxicity, specifically, primary DNA damage as damage index (DI), tail length and% of tail DNA using the Comet assay (alkaline version) and chromosome damage as micronucleus (MN) frequency in lymphocytes. Both biomarkers showed statistically significantly higher values in the exposed group compared to the non-exposed control group. No difference was observed between the exposed groups executing different mining activities. These results indicate that exposure to coal mining residues may result in an increased genotoxic exposure in coal mining workers. We did not find a correlation between age, alcohol consumption and service time with the biomarkers of genotoxicity. Our results are the first data of genotoxic effects induced by coal mining exposure in Colombia, and thus, contribute to the exploration of test batteries use for monitoring of exposed populations and may stimulate designing control, hygiene and prevention strategies for occupational health risk assessment in developing countries.     

Emissions of mercury and other trace elements from coal-fired power plants in Japan

To evaluate trace element emissions from modern coal-fired power plants into the atmospheric environment in Japan, trace elements in the coal used in electric utility boilers, stack concentrations, emission rates and emission ratios of coal-fired power plants, and proportions of trace elements in coal-fired power plants were studied. The elements were As, B, Be, Cd, Co, Cr, F, Hg, Mn, Ni, Pb, Sb, Se and V, which are designated in the Law of Pollutant Release and Transfer Register. The particulate trace elements were collected in an electrostatic precipitator and a wet desulfurization scrubber. Emissions into the atmosphere were lower than 1% of the quantity in coal, but the volatile trace elements showed somewhat higher emission ratios. For mercury, the mean concentration in coal was 0.045 ppm, the mean emission rate was 4.4 microg/kW h, and the mean emission ratio was 27%, the highest ratio among all elements in this study. The total annual emission of mercury from coal-fired power plants of the electric power industry in Japan was estimated to be 0.63 t/y. On the basis of these data, the atmospheric environment loads from a coal-fired power station were investigated. The calculation of stack gas dispersion showed that maximum annual mean ground level concentrations were in the order of 10(-2) to 10(-5) of the background concentrations, and that the adverse effect of the emissions from the coal-fired power station was small.     

Numerical simulation of spatial distributions of mining-induced stress and fracture fields for three coal mining layouts

In this study, the spatial distributions of stress and fracture fields for three typical underground coal mining layouts, i.e. non-pillar mining (NM), top-coal caving mining (TCM) and protective coal-seam mining (PCM), are modeled using discrete element software UDEC. The numerical results show that different mining layouts can lead to different mining-induced stress fields, resulting in diverse fracture fields. For the PCM, the mining influenced area in front of the mining faces is the largest, and the stress concentration factor in front of the mining faces is the lowest. The spatial shapes of the mining-induced fracture fields under NM, TCM and PCM differ, and they are characterized by trapezoidal, triangular and tower shapes, respectively. The fractal dimensions of mining-induced fractures of the three mining layouts decrease in the order of PCM, TCM and NM. It is also shown that the PCM can result in a better gas control effect in coal mines with high outburst potential. The numerical results are expected to provide a basis for understanding of mining-induced gas seepage fields and provide a reference for high-efficiency coal mining.     

Phylogenetic consistencies among chondrichthyan and teleost fishes in their bioaccumulation of multiple trace elements from seawater

Multi-tracer experiments determined the accumulation from seawater of selected radioactive trace elements (Mn-54, Co-60, Zn-65, Cs-134, Am-241, Cd-109, Ag-110m, Se-75 and Cr-51) by three teleost and three chondrichthyan fish species to test the hypothesis that these phylogenetic groups have different bioaccumulation characteristics, based on previously established contrasts between the carcharhiniform chondrichthyan Scyliorhinus canicula (dogfish) and the pleuronectiform teleost Psetta maxima (turbot). Discriminant function analysis on whole body: water concentration factors (CFs) separated dogfish and turbot in two independent experiments. Classification functions grouped the perciform teleosts, seabream (Sparus aurata) and seabass (Dicentrarchus labrax), with turbot and grouped the chondrichthyans, undulate ray (Raja undulata; Rajiformes) and spotted torpedo (Torpedo marmorata; Torpediniformes), with dogfish, thus supporting our hypothesis. Hierarchical classificatory, multi-dimensional scaling and similarity analyses based on the CFs for the nine radiotracers, also separated all three teleosts (that aggregated lower in the hierarchy) from the three chondrichthyan species. The three chondrichthyans were also more diverse amongst themselves compared to the three teleosts. Particular trace elements that were more important in separating teleosts and chondrichthyans were Cs-134 that was elevated in teleosts and Zn-65 that was elevated in chondrichthyans, these differences being due to their differential rates of uptake rather than loss. Chondrichthyans were also higher in Cr-51, Co-60, Ag-110m and Am-241, whereas teleosts were higher only in Mn-54. These contrasts in bioaccumulation patterns between teleosts and chondrichthyans are interpreted in the context of both proximate causes of underlying differences in physiology and anatomy, as well as the ultimate cause of their evolutionary divergence over more than 500 million years before present (MyBP). Our results and interpretation point to the possibility that radiation exposure regimes may be influenced by phylogeny, with implications for the adequacy of the marine reference organism approach in marine environmental protection.     

Indoor concentrations of nitrogen dioxide and sulfur dioxide from burning solid fuels for cooking and heating in Yunnan Province,China

The Chinese national pollution census has indicated that the domestic burning of solid fuels is an important contributor to nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) emissions in China. To characterize indoor NO₂ and SO₂ air concentrations in relation to solid fuel use and stove ventilation in the rural counties of Xuanwei and Fuyuan, in Yunnan Province, China, which have among the highest lung cancer rates in the nation, a total of 163 participants in 30 selected villages were enrolled. Indoor 24‐h NO₂ and SO₂ samples were collected in each household over two consecutive days. Compared to smoky coal, smokeless coal use was associated with higher NO₂ concentrations [geometric mean (GM) = 132 μg/m³ for smokeless coal and 111 μg/m³ for smoky coal, P = 0.065] and SO₂ [limit of detection = 24 μg/m³; percentage detected (%Detect) = 86% for smokeless coal and 40% for smoky coal, P < 0.001]. Among smoky coal users, significant variation of NO₂ and SO₂ air concentrations was observed across different stove designs and smoky coal sources in both counties. Model construction indicated that the measurements of both pollutants were influenced by stove design. This exposure assessment study has identified high levels of NO₂ and SO₂ as a result of burning solid fuels for cooking and heating.     

Distribution of trace elements in organs of six species of cetaceans from the Ligurian Sea (Mediterranean), and the relationship with stable carbon and nitrogen ratios

Mercury (total and organic), cadmium, lead, copper, iron, manganese, selenium and zinc concentrations were measured in different organs of 6 different cetacean species stranded in an area of extraordinary ecological interest (Cetaceans' Sanctuary of the Mediterranean Sea) along the coast of the Ligurian Sea (North-West Mediterranean). Stable-isotopes ratios of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) were also measured in the muscle. A significant relationship exists between (15)N/(14)N, mercury concentration and the trophic level. The distribution of essential and non-essential trace elements was studied on several organs, and a significant relationship between selenium and mercury, with a molar ratio close to 1, was found in the cetaceans' kidney, liver and spleen, regardless of their species. High selenium concentrations are generally associated with a low organic to total mercury ratio. While narrow ranges of concentrations were observed for essential elements in most organs, mercury and selenium concentrations are characterised by a wide range of variation. Bio-accumulation and bio-amplification processes in cetaceans can be better understood by comparing trace element concentrations with the stable-isotopes data.     

The Ribble/Wyre observatory: major, minor and trace elements in rivers draining from rural headwaters to the heartlands of the NW England historic industrial base

Information on a new observatory study of the water quality of two major river basins in northwestern England (the Ribble and Wyre) is presented. It covers upland, intermediate and lowland environments of contrasting pollution history with sufficient detail to examine transitional gradients. The upland rivers drain acidic soils subjected to long-term acidic deposition. Nonetheless, the acidic runoff from the soils is largely neutralised by high alkalinity groundwaters, although the rivers retain, perhaps as colloids, elements such as Al and Fe that are mobilised under acid conditions. The lowland rivers are contaminated and have variable water quality due to variable urban/industrial point and diffuse inputs reflecting local and regional differences in historic and contemporary sources. For most determinands, pollutant concentrations are not a major cause for concern although phosphate levels remain high. Set against earlier studies for other regions, there may be a general decline in pollutant levels and this is most clearly observed for boron where effluent inputs have declined significantly due to reductions in household products that are flushed down the drain. High concentrations of sodium and chloride occurred briefly after a severe cold spell due to flushing of road salts.A major inventory for water quality within rural, urban, industrial and agricultural typologies is provided within data summary attachments for over 50 water quality determinands. Within the next year, the full dataset will be made available from the CEH website. This, with ongoing monitoring, represents a platform for water quality studies across a wide range of catchment typologies pertinent to environmental management of clean and impacted systems within the UK. The study provides a base of research “from source to sea” including extensions to the estuary and open sea for a semi-confined basin, the Irish Sea, where there are many issues of pollution inputs and contamination.     

Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina)

In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Salí River alluvial basin in NW Argentina (Tucumán Province; 7000 km²), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km²) which is one of the world’s largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Salí River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 μg L⁻¹ leaving 100% of the investigated waters above the provisional WHO guideline value of 10 μg L⁻¹. A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO₃) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined groundwaters with high pH and high concentrations of potential competitors for adsorption sites (HCO₃, V, P, etc.). Under these geochemical conditions, desorption of the above mentioned anions and oxyanions occurs as a key process for As mobilization, resulting in an increase of minor and trace element concentrations. These geochemical processes that control the concentrations of dissolved As and other trace elements and which determine the groundwater quality especially in the shallow aquifers, are comparable to other areas with high As concentrations in groundwater of oxidizing aquifers and semi-arid or arid climate, which are found in many parts of the world, such as the western sectors of the USA, Mexico, northern Chile, Turkey, Mongolia, central and northern China, and central and northwestern Argentina.     

Long-term changes in quality of discharge water from abandoned underground coal mines in Uniontown Syncline, Fayette County, PA, USA

Changes in water quality over 25 years have been documented for discharges from an extensive network of abandoned underground coal mines in the Uniontown Syncline, Fayette County, PA, USA. A baseline study of 136 mine discharges in the syncline was conducted in 1974-1975. In 1998-2000, follow-up water flow and quality monitoring was conducted at 21 selected discharges for 2 years to assess the degree of mine water-quality improvement since 1974-1975. The data from the two periods of time were compared, with consideration of differences in measurement methods. The degree and rate of water-quality improvement was found to be highly dependent on the amount and duration of flooding in the mine voids. Water quality of discharges from the substantially flooded mine voids improved significantly, going from acidic water with high sulfate and iron concentrations in 1974-1975 to alkaline water with substantially lower sulfate and iron concentrations in 1998-2000. In contrast, the water quality in the unflooded mines showed less improvement over the 25 years between studies. The water discharging from the unflooded mines in 1974-1975 was acidic with high sulfate concentrations and in 1998-2000 was still acidic but showed somewhat lower sulfate and iron concentrations, reflecting depletion of readily available pyrite. The data obtained provide insight into the potential and rate of natural amelioration of mine water quality in different abandoned underground coal mine systems.     

Implications for wildlife and humans of dietary exposure to lead from fragments of lead rifle bullets in deer shot in the UK

Lead poisoning caused by ingested spent lead shotgun pellets has long been known to be a cause of unnecessary mortality in waterfowl and has led to legislation limiting its use in many countries. Recent evidence has shown that the problem extends to terrestrial ecosystems and to fragmented rifle bullets eaten by scavengers as well as shotgun pellets. Dietary exposure of human consumers to lead from spent ammunition in game meat also poses potential risks to human health. To assess the degree of fragmentation of lead bullets used to kill wild deer, twelve deer were shot in the thorax using copper-jacketed lead-cored bullets, as part of planned deer management operations. The thoracic region of the eviscerated carcasses and the abdominal viscera of each deer were X-rayed. An average of 356 metal fragments was visible on radiographs of the carcass and 180 fragments in the viscera. The weight of fragments was estimated by reference to an X-rayed scale of fragments of known weight. The average total weight of metal fragments, likely to be mostly lead, was estimated to be 1.2 g for the carcass and 0.2 g for the viscera. The total estimated weight of fragments in the entire carcass was estimated to be 17% of the weight of the bullet. Most fragments were small in size, with those in the viscera being smaller than those in the carcass. Metal fragments in the viscera were sufficiently small that at least 80% of the metallic bullet-derived lead in the viscera would be expected to be ingested by scavenging birds, such as buzzards and eagles, which feed on them.     

Levels, chemical composition and sources of fine aerosol particles (PM1) in an area of the Mediterranean basin

Daily samples of fine aerosol particles (i.e., PM1, aerosol particles with an aerodynamic diameter less than 1.0 μm) were collected in Tito Scalo — Southern Italy — from April 2006 to March 2007. Measurements were performed by means of a low-volume gravimetric sampler, and each PM1 sample was analyzed by means of Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Atomic Absorption Spectrometry (GFAAS and FAAS) techniques in order to determine its content in fourteen trace elements (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Ti and Zn). During the period examined, PM1 daily concentrations ranged between 0.3 µg m^− 3 and 55 µg m^− 3 with a mean value of 8 µg m^-3, a standard deviation of 7 µg m^− 3 and a median value of 6 µg m^− 3. As far as PM1 chemical composition is concerned, the mean values of the trace element concentrations decreased in the following order: Ca > Fe > Al > Na > K > Cr > Mg > Pb > Ni ≈ Ti ≈ Zn > Cd ≈ Cu > Mn. Principal Component Analysis (PCA) allowed the identification of three probable PM1 sources: industrial emissions, traffic and re-suspension of soil dust. Moreover, the results of a procedure applied to study the potential long-range transport contribution to PM1 chemical composition, showed that trace element concentrations do not seem to be affected by air mass origin and path. This was probably due to the strong impact of the local emission sources and the lack of the concentration measurements of some important elements and compounds that could better reveal the long-range transport influence on PM1 measurements at ground level.     

Theories and techniques of coal bed methane control in China

Coal bed methane control with low permeability is a hot issue at present.The current status of coal bed methane control in China is introduced.The government-support policies on coal bed methane control are presented.This paper proposes the theories of methane control in depressurized mining,including methane extraction in depressurized mining,simultaneous mining technique of coal and methane without coal pillar,and circular overlying zone for high-efficiency methane extraction in coal seams with low permea...     

Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository—BMT1 of the DECOVALEX III project. Part 2: Effects of THM coupling in continuous and homogeneous rocks

An evaluation of the importance of the thermo-hydro-mechanical couplings (THM) on the performance assessment of a deep underground radioactive waste repository has been made as a part of the international DECOVALEX III project. It is a numerical study that simulates a generic repository configuration in the near field in a continuous and homogeneous hard rock. A periodic repository configuration comprises a single vertical borehole, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery. The thermo-hydro-mechanical evolution of the whole configuration is simulated over a period of 100 years. The importance of the rock mass's intrinsic permeability has been investigated through scoping calculations with three values: 10⁻¹⁷, 10⁻¹⁸ and 10⁻¹⁹ m². Comparison of the results predicted by fully coupled THM analysis as well as partially coupled TH, TM and HM analyses, in terms of several predefined indicators of importance for performance assessment, enables us to identify the effects of the different combinations of couplings, which play a crucial role with respect to safety issues. The results demonstrate that temperature is hardly affected by the couplings. In contrast, the influence of the couplings on the mechanical stresses is considerable.     

Accounting for pH heterogeneity and variability in modelling human health risks from cadmium in contaminated land

The authors have previously published a methodology which combines quantitative probabilistic human health risk assessment and spatial statistical methods (geostatistics) to produce an assessment, incorporating uncertainty, of risks to human health from exposure to contaminated land. The model assumes a constant soil to plant concentration factor (CF_veg) when calculating intake of contaminants. This model is modified here to enhance its use in a situation where CF_veg varies according to soil pH, as is the case for cadmium.The original methodology uses sequential indicator simulation (SIS) to map soil concentration estimates for one contaminant across a site. A real, age-stratified population is mapped across the contaminated area, and intake of soil contaminants by individuals is calculated probabilistically using an adaptation of the Contaminated Land Exposure Assessment (CLEA) model.The proposed improvement involves not only the geostatistical estimation of the contaminant concentration, but also that of soil pH, which in turn leads to a variable CF_veg estimate which influences the human intake results. The results presented demonstrate that taking pH into account can influence the outcome of the risk assessment greatly.It is proposed that a similar adaptation could be used for other combinations of soil variables which influence CF_veg.     

Mercury exposure in female artisanal small-scale gold miners (ASGM) in Mongolia: An analysis of human biomonitoring (HBM) data from 2008

Background

Many poor in developing countries have turned to artisanal small-scale gold mining (ASGM) in an attempt to improve their situation. However, the mercury used to extract gold from ore is discharged in vaporized form into the environment, where it poses a hazard for human health.

Methods

As part of an environmental epidemiological study in Mongolia—to evaluate the burden of environmental mercury contamination—urine, blood and hair samples were collected from residents of areas with or without mercury contamination. A total of 200 blood, urine and hair samples were analyzed for mercury and divided into three subgroups according to mercury content: (1) occupational exposure (high/medium); (2) environmental exposure (low); and (3) no exposure. Internal mercury distributions of the subgroups were compared using the Kruskal-Wallis and Mann-Whitney U-test. The Chi-square test and likelihood ratio proportion were used to compare the findings with threshold limits.

Results

The highest values and greatest differences were seen in the urine samples (p < 0.001, Kruskal-Wallis). The occupational group showing the highest exposure with a median mercury level of 4.36 μg/l (control group: 0.10 μg/l, p < 0.001), 7.18 μg/g creatinine and 12 results above the threshold limit HBM I (Human Biomonitoring I). Even participants from the low-exposure subgroup showed elevated mercury levels (median 2.88 μg/l urine and 2.98 μg/g creatinine, p < 0.001), with 10 individuals above the HBM I threshold limits.

Discussion

The body burden resulting from the use of mercury in artisanal gold mining is high not only in the miners themselves, an increased mercury hazard was also found for inhabitants of mining areas who were not actively involved in mining. Public health support measures are urgently needed to alleviate the situation.