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PubMed2005

Role of organic acids in promoting colloidal transport of mercury from mine tailings.

A number of factors affect the transport of dissolved and particulate mercury (Hg) from inoperative Hg mines, including the presence of organic acids in the rooting zone of vegetated mine waste. We examined the role of the two most common organic acids in soils (oxalic and citric acid) on Hg transport from such waste by pumping a mixed organic acid solution (pH 5.7) at 1 mL/min through Hg mine tailings columns. For the two total organic acid concentrations investigated (20 microM and 1 mM), particle-associated Hg was mobilized, with the onset of particulate Hg transport occurring later for the lower organic acid concentration. Chemical analyses of column effluent indicate that 98 wt % of Hg mobilized from the column was particulate. Hg speciation was determined using extended X-ray absorption fine structure spectroscopy and transmission electron microscopy, showing that HgS minerals are dominant in the mobilized particles. Hg adsorbed to colloids is another likely mode of transport due to the abundance of Fe-(oxyhydr)oxides, Fe-sulfides, alunite, and jarosite in the tailings to which Hg(II) adsorbs. Organic acids produced by plants are likely to enhance the transport of colloid-associated Hg from vegetated Hg mine tailings by dissolving cements to enable colloid release.

Chemical Fractionation↗
PubMed2003

Advances in biotreatment of acid mine drainage and biorecovery of metals: 2. Membrane bioreactor system for sulfate reduction.

Several biotreatmemt techniques for sulfate conversion by the sulfate reducing bacteria (SRB) have been proposed in the past, however few of them have been practically applied to treat sulfate containing acid mine drainage (AMD). This research deals with development of an innovative polypropylene hollow fiber membrane bioreactor system for the treatment of acid mine water from the Berkeley Pit, Butte, MT, using hydrogen consuming SRB biofilms. The advantages of using the membrane bioreactor over the conventional tall liquid phase sparged gas bioreactor systems are: large microporous membrane surface to the liquid phase; formation of hydrogen sulfide outside the membrane, preventing the mixing with the pressurized hydrogen gas inside the membrane; no requirement of gas recycle compressor; membrane surface is suitable for immobilization of active SRB, resulting in the formation of biofilms, thus preventing washout problems associated with suspended culture reactors; and lower operating costs in membrane bioreactors, eliminating gas recompression and gas recycle costs. Information is provided on sulfate reduction rate studies and on biokinetic tests with suspended SRB in anaerobic digester sludge and sediment master culture reactors and with SRB biofilms in bench-scale SRB membrane bioreactors. Biokinetic parameters have been determined using biokinetic models for the master culture and membrane bioreactor systems. Data are presented on the effect of acid mine water sulfate loading at 25, 50, 75 and 100 ml/min in scale-up SRB membrane units, under varied temperatures (25, 35 and 40 degrees C) to determine and optimize sulfate conversions for an effective AMD biotreatment. Pilot-scale studies have generated data on the effect of flow rates of acid mine water (MGD) and varied inlet sulfate concentrations in the influents on the resultant outlet sulfate concentration in the effluents and on the number of SRB membrane modules needed for the desired sulfate conversion in those systems. The pilot-scale data indicate that the SRB membrane bioreactors systems can be applied toward field-scale biotreatment of AMD and for recovery of high purity metals and an agriculturally usable water.

Acids↗
PubMed2002

Radiological study of exposure levels in El Maghara underground coal mine.

Coal is largely composed of organic matter, but it is the inorganic matter in coal minerals and trace elements that have been cited as possible causes of health, environmental and technological problems associated with the use of coal. Some trace elements in coal are naturally radioactive. These radioactive elements include uranium (U), thorium (Th) and their numerous decay products, including radium (Ra) and radon (Rn). Although these elements are less chemically toxic than other coal constituents, such as arsenic, selenium or mercury, questions have been raised concerning the possible risk from radiation. In order to accurately address these questions and to predict the mobility of radioactive elements during the coal fuel cycle, it is important to determine the specific activity, distribution and form of radioactive elements in coal. The assessment of the radiation exposure from coal burning is critically dependent on the specific activity of radioactive elements in coal and in the fly ash that remains after combustion. The El-Maghara coal mine is the only producing coal mine in Egypt. It is located in the middle of the Sinai desert about 250 km north-east of Cairo, where a coal-fired power plant is intended to be built. In this study, a pre-operational radiological baseline of the site and the occupational radiation exposures due to radon progeny in the mine were determined. The specific activities of 226Ra, 232Th and 40K in soil and coal dust samples collected along the main gallery ranges were found to be 6-22.9, 9.6-47.3 and 77-489 Bq kg-1, respectively. Soil samples collected around the mine showed concentrations of 226Ra, 232Th and 40K in the ranges 2.7-20.2, 3.2-12.6 and 14.6-201 Bq kg-1, respectively. All of the mean values of radon progeny were lower than the action levels for working places recommended in the International Commission on Radiological Protection (ICRP) 65.

Coal↗
PubMed2004

Evaluation of the SKC DPM cassette for monitoring diesel particulate matter in coal mines.

In a previous study, the efficacy of commercial and prototype impactors for sampling diesel particulate matter (DPM) in coal mines was investigated. Laboratory and field samples were collected on quartz-fiber filters and analyzed for organic and elemental carbon. Coal dust contributed a minimal amount of elemental carbon when commercial cascade impactors and prototype impactors, designed by the University of Minnesota (UMN) and the US Bureau of Mines (BOM), were used to collect submicrometer dust fractions. Other impactors were not as effective at excluding coal dust. The impactors evaluated in that study were either not commercially available or were multi-stage, expensive, and difficult to use for personal measurements. A commercial version of the BOM impactor, called the DPM Cassette, was recently introduced by SKC. Tests were conducted to evaluate the performance of the DPM Cassette for measuring diesel-source elemental carbon in the presence of coal dust. Bituminous coals from three mines in two different coal provinces were examined. The dust particle diameters were small and the coal dust contained a high percentage of carbon, thereby giving a worst-case condition for non-anthracite coal mines. Results for the DPM Cassette were essentially identical to those obtained by the BOM impactors in a previous study. At a respirable coal dust concentration of 5.46 mg m(-3), which is 3.8 times the regulatory limit, the DPM Cassette collected only 34 microg m(-3) of coal-source elemental carbon.

Air Pollutants, Occupational↗
PubMed1975

Effect of the 2.0 mg/m3 coal mine dust standard on underground environmental dust levels.

The 1969 Federal Coal Mine Health and Safety Act established environmental dust standards for underground coal mines. The Act requires that the average concentration of respirable dust in the active workings of a mine be maintained at or below 3.0 mg/m3; and, that effective December 30, 1972, the 3.0 mg/m3 standard be reduced to 2.0 mg/m3. This paper discusses the current status of dust levels in our underground coal mines, the effect of the 2.0 mg/m3 standard on underground dust levels, and associates the current levels with specific operations and occupations. The comparison is made between current levels and those existing prior to December 30, 1972.

Coal Mining↗
PubMedDate not supplied

Relationship between lead mining and blood lead levels in children.

The authors studied blood lead levels of 226 randomly selected children, aged 6-92 mo, who lived in either a lead-mining area or a nonmining area, and 69 controls. The authors sought to determine to what extent mining activities contributed to blood lead levels in the children. The mean blood lead levels in the study and control groups were 6.52 microg/dl and 3.43 microg/dl, respectively. The corresponding proportions of children with elevated blood lead levels were 17% and 3%. Soil and dust lead levels were up to 10 times higher in the study than the control group. Elevated blood lead levels appeared to result from exposure to both lead-mining waste and lead-based paint. Mining waste was the cause of the higher prevalence of elevated blood lead levels in these children.

Case-Control Studies↗
PubMed2001

Origin and distribution of sulphate in surface waters of the Mansfeld mining district (Central Germany)--a sulphur isotope study.

In the Mansfeld region (Central Germany) copper mining contributed to an enormous pollution of the environment. Metal- and sulphate-bearing sediments and leachates emerge from the former copper smelters and mining waste heaps, spread along local rivers and finally reach the Saale river. A sulphur isotope study on water and stream sediments was performed along the River "Böse Sieben" and from its tributaries to determine the different sulphur sources. Four major sulphur sources exist in the area: metal sulphide mineralisations (Kupferschiefer), met alliferous sulphidic flue dust, slag, and anhydrite and gypsum of Permian and Triassic age. We obtained delta34S(SO4)-values in water samples varying from +4 per thousand to -18 per thousand CDT, clearly reflecting the input of sulphate from different sources. Sulphate from the oxidation of sulphidic mining residues is restricted to the mining area and cannot be traced for more than 5 km downstream. The major source for sulphate is the dissolution of gypsum and anhydrite. The sulphur isotope composition in dissolved and sedimentary adsorbed sulphate differs only slightly from each other. Microbial dissimilatory sulphate reduction can not be excluded in the shallow sediment layers.

Adsorption↗
PubMed1979

Assessment of the respirable dust levels in the nation's underground and surface coal mining operations.

This report presents a chronological overview of the status of respirable dust exposures in underground and surface bituminous coal mines since inception of the 1969 Federal Coal Mine Health and Safety Act. Data for various intervals from 1970 through 1977, are presented for selected mining operations. Comparisons are made using data available from the mine operators' sampling program and from MSHA surveys. The data demonstrate the marked decrease that has occurred in respirable dust exposures since inception of the 1969 Act.

Coal↗
PubMed1985

A critique of MSHA procedures for determination of permissible respirable coal mine dust containing free silica.

The literature in selected technical subject areas related to the Mine Safety and Health Administration's (MSHA) respirable mine dust control policy was critically reviewed. Specific topics included: (1) the technical aspects of respirable dust sampling, (2) the development of a sampling strategy and (3) currently used analytical techniques for free silica content of respirable coal mine dust. The 2.0 Lpm MSHA respirable dust sampling flow rate does not conform with published results which indicate that to simulate existing pulmonary particle deposition models, the sampling flow rate should range from 1.4 to 1.7 Lpm. MSHA's sampling strategy focuses on controlling respirable coal mine dust with both area and personal samples of workers in selected occupations or activities. Many uncertainties are encountered as area samples are used to estimate personal exposures. Although all of the analytical methods for crystalline free silica are sufficiently sensitive to be able to detect and quantitate free silica at environmentally significant concentrations, they are all plagued with similar difficulties. Analytical standards representing the various forms of silica are not available. Available analytical methods do not differentiate among polymorphs of silica. Recommendations are presented to resolve identified problem areas.

Air Pollutants, Occupational↗
PubMed1987

Comparison of respirable dust samplers for use in hard rock mines.

Five respirable dust size selectors and eleven filter holders were compared, some at two flow rates. These included horizontal elutriators, impactors, metal cyclones and nylon cyclones. The comparisons were carried out both in the laboratory and in mines. The respirable dust on the filters was assessed by weighing, and where relevant, by X-ray diffraction for quartz with the use of a direct-on-filter method. The results obtained showed that the relation between most pairs of samplers could be represented by a straight line through the origin and that the personal samplers collecting more dust--the CAMPEDS impactor and the B.C.I.R.A. cyclone--gave higher reproducibility in the low dust concentrations found in many hard rock mines. The samplers based on the nylon cyclone were less suitable for hard rock mines containing a substantial proportion of quartz, though satisfactory in coal mines with their higher dust control standards.

Air Pollutants↗
PubMed1989

Assessment of respiratory exposures during gilsonite mining and milling operations.

An industrial hygiene study of the entire United States gilsonite industry was done by the National Institute for Occupational Safety and Health (NIOSH) to evaluate the potential for occupational health problems resulting from exposures to gilsonite and its constituents. Gilsonite is a solidified hydrocarbon substance mined only in northeastern Utah to Colorado. Industrial hygiene samples were collected at four gilsonite mining companies including nine mines and three mills. Gilsonite workers had no measurable exposures to polynuclear aromatic hydrocarbon (PNA) compounds, asbestos fibers, or hydrogen sulfide gas. Several organic gases/vapors and metals were detected in the airborne samples; but, none exceeded the current exposure standards/health criteria of the Mine Safety and Health Administration (MSHA), the American Conference of Governmental Industrial Hygienists (ACGIH), or NIOSH. Gilsonite workers in some job categories were exposed to high levels of dust, exceeding ACGIH nuisance dust recommendations. These dusts, comprised largely of aliphatic hydrocarbons, had a large aerodynamic size distribution with average mass median aerodynamic diameters (MMAD) above 30 microns.

Air Pollutants, Occupational↗
PubMed1991

Regulatory implications of airborne respirable free silica variability in underground coal mines.

The respirable dust standard for respirable free crystalline silica in underground coal mines is expressed as milligrams per cubic meter (mg/m3) of respirable dust and is determined by the silica content of the dust. The Mine Safety and Health Administration (MSHA) regulates silica exposure by determining and enforcing compliance with the respirable dust standard for each active mine section. The MSHA strategy for regulation is examined in the context of respirable free crystalline silica and dust data. Deficiencies of the strategy include the same enforcement efforts regardless of compliance history, inappropriate treatment of data, and emphasis on short-term variability of silica content. These deficiencies result in inadequate enforcement in chronically dusty mines, "game playing" with optional samples, and an overall approach that does not focus on the long-term impact of silica exposure on lung health. Alternative approaches include enforcement efforts proportional to compliance history, use of a moving average silica content, and more statistically sound approaches to data interpretation.

Air Pollutants, Occupational↗
PubMed2003

Cancer mortality in a Texas county with prior uranium mining and milling activities, 1950-2001.

Uranium was discovered in Karnes County, Texas, in 1954 and the first uranium mill began operating in 1961 near Falls City. Uranium milling and surface and in situ mining continued in Karnes County until the early 1990s. Remediation of uranium tailings ponds was completed in the 1990s. There were three mills and over 40 mines operating in Karnes County over these years and potential exposure to the population was from possible environmental releases into the air and ground water. From time to time concerns have been raised in Karnes County about potential increased cancer risk from these uranium mining and milling activities. To evaluate the possibility of increased cancer deaths associated with these uranium operations, a mortality survey was conducted. The numbers and rates of cancer deaths were determined for Karnes County and for comparison for four 'control' counties in the same region with similar age, race, urbanisation and socioeconomic distributions reported in the 1990 US Census. Comparisons were also made with US and Texas general population rates. Following similar methods to those used by the National Cancer Institute, standardised mortality ratios (SMRs) were computed as the ratio of observed numbers of cancers in the study and control counties compared to the expected number derived from general population rates for the United States. Relative risks (RRs) were computed as the ratios of the SMRs for the study and the control counties. Overall, 1223 cancer deaths occurred in the population residing in Karnes County from 1950 to 2001 compared with 1392 expected based on general population rates for the US. There were 3857 cancer deaths in the four control counties during the same 52 year period compared with 4389 expected. There was no difference between the total cancer mortality rates in Karnes County and those in the control counties (RR = 1.0; 95% confidence interval 0.9-1.1). There were no significant increases in Karnes County for any cancer when comparisons were made with either the US population, the State of Texas or the control counties. In particular, deaths due to cancers of the lung, bone, liver and kidney were not more frequent in Karnes County than in the control counties. These are the cancers of a priori interest given that uranium might be expected to concentrate more in these tissues than in others. Further, any radium intake would deposit primarily in the bone and radon progeny primarily in the lung. Deaths from all cancers combined also were not increased in Karnes County and the RRs of cancer mortality in Karnes County before and in the early years of operations (1950-64), shortly after the uranium activities began (1965-79) and in two later time periods (1980-89, 1990-2001) were similar, 1.0, 0.9, 1.1 and 1.0, respectively. No unusual patterns of cancer mortality could be seen in Karnes County over a period of 50 years, suggesting that the uranium mining and milling operations had not increased cancer rates among residents.

Death Certificates↗
PubMed2006

Sustained acclimatization in Chilean mine workers subjected to chronic intermittent hypoxia.

Farias, Jorge G., Jorge Osorio, Gustavo Soto, Julio Brito, Patricia Siques, and Juan G. Reyes. Sustained acclimatization in Chilean mine workers subjected to chronic intermittent hypoxia. High Alt. Med. Biol. 7:302-306, 2006--We wanted to know if sea-level mine workers exposed previously to chronic intermittent hypoxia reached a steady acclimatization at 36 months under hypobaric hypoxia. An intermittently exposed group of mine workers (IE, n = 25) were subjected to submaximal exercise (100 W) at 4500 m. Their systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and hemoglobin oxygen saturation (HbSatO(2)) were monitored. Two comparison groups of unacclimatized sea-level workers (n = 17) were studied. A nonexposed group (NE) performed 5 min of submaximal exercise at sea level. Some kind of exercise was performed both by an acutely exposed group (AE) and IE group at 4500 m. No statistical differences were found for HR, SBP, and DBP (p > 0.05) during exercise between IE and AE groups. Resting HbSatO(2) of IE (87 +/- 6%) was lower than NE (97 +/- 3%) (p < 0.05), but was higher than AE (82 +/- 4%) (p < 0.05). In the exercise condition, HbSatO(2) of IE (85 +/- 5%) was lower than NE (95 +/- 3%) (p < 0.05), but was higher than AE (76 +/- 2%) (p < 0.05). These responses were maintained through the 6 months of the study period. Thus, mine workers subjected to intermittent hypobaric condition for 3 years showed a good degree of acclimatization that was maintained through time.

Acclimatization↗
PubMed2002

Coal dust exposures in the longwall mines of New South Wales, Australia: a respiratory risk assessment.

This paper presents an analysis of personal respirable coal dust measurements recorded by the Joint Coal Board in the underground longwall mines of New South Wales from 1985 to 1999. A description of the longwall mining process is given. In the study, 11 829 measurements from 33 mines were analysed and the results given for each occupation, for seven occupational groups, for individual de-identified mines and for each year of study. The mean respirable coal dust concentration for all jobs was 1.51 mg/m(3) (SD 1.08 mg/m(3)). Only 6.9% of the measurements exceeded the Australian exposure standard of 3 mg/m(3). Published exposure-response relationships were used to predict the prevalence of progressive massive fibrosis and the mean loss of FEV(1), after a working lifetime (40 years) of exposure to the mean observed concentration of 1.5 mg/m(3). Prevalences of 1.3 and 2.9% were predicted, based on data from the UK and the USA, respectively. The mean loss of FEV(1) was estimated to be 73.7 ml.

Coal↗
PubMed2004

Occupational safety risk management in Australian mining.

In the past 15 years, there has been a major safety improvement in the Australian mining industry. Part of this change can be attributed to the development and application of risk assessment methods. These systematic, team-based techniques identify, assess and control unacceptable risks to people, assets, the environment and production. The outcomes have improved mine management systems. This paper discusses the risk assessment approach applied to equipment design and mining operations, as well as the specific risk assessment methodology. The paper also discusses the reactive side of risk management, incident and accident investigation. Systematic analytical methods have also been adopted by regulatory authorities and mining companies to investigate major losses.

Accidents, Occupational↗
PubMed2006

Occupational fatalities among coal mine workers in Zonguldak, Turkey, 1994-2003.

BACKGROUND: Fatal underground coal mine injuries are a worldwide problem. Zonguldak holds 95% of all Turkey's coal reserves. AIM: To investigate fatalities in the underground coal-mining industry in the Zonguldak province. METHODS: Retrospective study of fatal underground coal-mining accidents from 1994 to 2003 through evaluation of industry records. RESULTS: There were 164 deaths available for analysis. The median age was 36 years (range: 14-56 years). Eighty-one fatalities (49%) were due to subsidence, 33 (20%) were due to underground railway accidents and 18 (11%) were due to gas poisoning. Asphyxia was the most common cause of death (99, 60%). The majority of fatalities (144, 87%) occurred instantaneously at the scene of the incident. The remainder (20, 13%) occurred on the way to the hospital or in the emergency room or the intensive care unit. CONCLUSION: The underground coal-mining industry in Turkey requires strategies to improve safety and reduce the number of fatalities occurring. These strategies should focus on improved underground safety through engineering measures.

Accidents, Occupational↗
PubMed1986

Excess mortality from stomach cancer, lung cancer, and asbestosis and/or mesothelioma in crocidolite mining districts in South Africa.

To determine whether exposure to crocidolite is associated with excess mortality, the authors calculated standardized mortality ratios based on deaths in South African crocidolite mining districts from 1968 to 1980 for selected causes of death. Contiguous districts were used as controls. To take account of background geographic variability, they divided the control districts into groups of population size similar to those of the crocidolite mining districts. Standardized mortality ratios in crocidolite mining districts were elevated for asbestosis and/or mesothelioma, and cancer of the lung and stomach. These findings could not be explained by background geographic variability in mortality and are likely to be due to exposure to South African crocidolite during mining and milling or to environmental contamination. The increased standardized mortality ratios for stomach cancer are of particular interest, since excess deaths have not previously been shown in individuals exposed to crocidolite alone.

Adolescent↗