Coal Mine Dust Samples Research Articles

Direct-on-Filter FTIR Spectroscopy to Estimate Calcite as A Proxy for Limestone ‘Rock Dust’ in Respirable Coal Mine Dust Samples

Application of fine, inert ‘rock dust’ (RD) to the surfaces in underground coal mines is a common method for mitigating coal dust explosion hazards. However, due to its size, RD has the potential to contribute to the respirable coal mine dust (RCMD) concentration. Though the RD component of RCMD does not appear to pose the sort of health hazards associated with other components such as crystalline silica, understanding its relative abundance may be quite helpful for evaluating and controlling primary dust sources. Given that RD products are frequently comprised of high-purity limestone (i.e., primarily calcite mineral), calcite may serve as a suitable proxy for measuring RD. To estimate the mass percentage of calcite in RCMD samples, this study demonstrates the successful application of direct-on-filter (DOF) Fourier-transform infrared (FTIR) spectroscopy. Incidentally, DOF FTIR has been the focus of recent efforts to enable rapid measurement of crystalline silica in RCMD. Concurrent measurement of other constituents such as calcite is thus a logical next step, which can allow a broader interpretation of dust composition and source contributions.

Respirable coal mine dust at surface mines, United States, 1982-2017.

Exposure to respirable coal mine dust can cause pneumoconiosis, an irreversible lung disease that can be debilitating. The mass concentration and quartz mass percent of respirable coal mine dust samples (annually, by occupation, by geographic region) from surface coal mines and surface facilities at U.S. underground mines during 1982-2017 were summarized. Mine Safety and Health Administration (MSHA) collected and analyzed data for respirable dust and a subset of the samples were analyzed for quartz content. We calculated the respirable dust and quartz concentration geometric mean, arithmetic mean, and percent of samples exceeding the respirable dust permissible exposure limit (PEL) of 2.0 mg/m3, and the average percent of quartz content in samples. The geometric mean for 288 705 respirable dust samples was 0.17 mg/m3 with 1.6% of the samples exceeding the 2.0 mg/m3 PEL. Occupation-specific geometric means for respirable dust in active mining areas were highest among drillers. The geometric mean for respirable dust was higher in central Appalachia compared to the rest of the U.S. The geometric mean for respirable quartz including 54 040 samples was 0.02 mg/m3 with 15.3% of these samples exceeding the applicable standard (PEL or reduced PEL). Occupation-specific geometric means for respirable quartz were highest among drillers. Higher concentrations of respirable dust or quartz in specific coal mining occupations, notably drilling occupations, and in certain U.S. regions, underscores the need for continued surveillance to identify workers at higher risk for pneumoconiosis.

Respirable coal mine dust in underground mines, United States, 1982-2017.

This study summarized the mass concentration and quartz mass percent of respirable coal mine dust samples (annually, by district, and by occupation) from underground coal mines during 1982-2017. Respirable dust and quartz data collected and analyzed by Mine Safety and Health Administration (MSHA) were summarized by year, coal mining occupation, and geographical area. The older (before August 2016) 2.0 mg/m 3 respirable dust MSHA permissible exposure limit (PEL) was used across all years for comparative purposes. For respirable dust and quartz, geometric mean and percent of samples exceeding the respirable dust PEL (2.0 mg/m 3 or a reduced standard for samples with >5% quartz content) were calculated. For quartz samples, the average percent quartz content was also calculated. The overall geometric mean concentration for 681 497 respirable dust samples was 0.55 mg/m 3 and 5.5% of the samples exceeded the 2.0 mg/m 3 PEL. The overall respirable quartz geometric mean concentration for 210 944 samples was 0.038 mg/m 3 and 18.7% of these samples exceeded the applicable standard. There was a decline over time in the percent of respirable dust samples exceeding 2.0 mg/m 3 . The respirable dust geometric mean concentration was lower in central Appalachia compared to the rest of the United States. However, the respirable quartz geometric mean concentration and the mean percent quartz content were higher in central Appalachia. This study summarizes respirable dust and quartz concentrations from coal mine inspector samples and may provide an insight into differences in the prevalence of pneumoconiosis by region and occupation.

Direct-on-Filter α-Quartz Estimation in Respirable Coal Mine Dust Using Transmission Fourier Transform Infrared Spectrometry and Partial Least Squares Regression.

In order to help reduce silicosis in miners, the National Institute for Occupational Health and Safety (NIOSH) is developing field-portable methods for measuring airborne respirable crystalline silica (RCS), specifically the polymorph α-quartz, in mine dusts. In this study we demonstrate the feasibility of end-of-shift measurement of α-quartz using a direct-on-filter (DoF) method to analyze coal mine dust samples deposited onto polyvinyl chloride filters. The DoF method is potentially amenable for on-site analyses, but deviates from the current regulatory determination of RCS for coal mines by eliminating two sample preparation steps: ashing the sampling filter and redepositing the ash prior to quantification by Fourier transform infrared (FT-IR) spectrometry. In this study, the FT-IR spectra of 66 coal dust samples from active mines were used, and the RCS was quantified by using: (1) an ordinary least squares (OLS) calibration approach that utilizes standard silica material as done in the Mine Safety and Health Administration's P7 method; and (2) a partial least squares (PLS) regression approach. Both were capable of accounting for kaolinite, which can confound the IR analysis of silica. The OLS method utilized analytical standards for silica calibration and kaolin correction, resulting in a good linear correlation with P7 results and minimal bias but with the accuracy limited by the presence of kaolinite. The PLS approach also produced predictions well-correlated to the P7 method, as well as better accuracy in RCS prediction, and no bias due to variable kaolinite mass. Besides decreased sensitivity to mineral or substrate confounders, PLS has the advantage that the analyst is not required to correct for the presence of kaolinite or background interferences related to the substrate, making the method potentially viable for automated RCS prediction in the field. This study demonstrated the efficacy of FT-IR transmission spectrometry for silica determination in coal mine dusts, using both OLS and PLS analyses, when kaolinite was present.

Determining the Spatial Variability of Personal Sampler Inlet Locations

This article examines the spatial variability of dust concentrations within a coal miner's breathing zone and the impact of sampling location at the cap lamp, nose, and lapel. Tests were conducted in the National Institute for Safety and Health Pittsburgh Research Laboratory full-scale, continuous miner gallery using three prototype personal dust monitors (PDM). The dust masses detected by the PDMs were used to calculate the percentage difference of dust mass between the cap lamp and the nose and between the lapel and the nose. The calculated percentage differences of the masses ranged from plus 12% to minus 25%. Breathing zone tests were also conducted in four underground coal mines using the torso of a mannequin to simulate a miner. Coal mine dust was sampled with multi-cyclone sampling cans mounted directly in front of the mannequin near the cap lamp, nose, and lapel. These four coal mine tests found that the spatial variability of dust levels and imprecision of the current personal sampler is a greater influence than the sampler location within the breathing zone. However, a one-sample t-test of this data did find that the overall mean value of the cap lamp/nose ratio was not significantly different than 1 (p-value = 0.21). However, when applied to the overall mean value of the lapel/nose ratio there was a significant difference from 1 (p-value < .0001). This finding is important because the lapel has always been the sampling location for coal mine dust samples. But these results suggest that the cap location is slightly more indicative of what is breathed through the nose area.

Infrared Analysis of Respirable Coal Mine Dust for Quartz: Thirty-Five Years

Abstract The Mine Safety and Health Administration (MSHA) analyzes respirable coal mine dust samples for quartz content using infrared spectrometry. Samples are low-temperature ashed in an oxygen plasma, suspended in isopropanol, and redeposited onto a vinyl/acrylic copolymer filter for analysis using a Fourier transform infrared spectrometer. The on-filter infrared method was developed by the United States Bureau of Mines and collaboratively tested by Stanford Research Institute (SRI) under contract to the National Institute for Occupational Safety and Health and the Bureau of Mines. The results of the collaborative study were published in 1983. Although much work has been performed since then to improve the precision of the method, details of those improvements have not always been published. Standard methods often do not discuss analytical theory and the preliminary steps necessary to achieve precise results. This paper gives a brief background of the changes that have been made in the procedures used for the analysis of respirable coal mine dust samples for quartz and discusses the current procedures used by MSHA to analyze such samples. Factors affecting the analysis such as optimization of the deposit size of the ashed sample, the importance of centering the sample in the infrared beam, baseline selection points, and peak measurement techniques, as well as the quality assurance procedure and the precision of the analysis, are discussed.

The Effects of Low Quartz Mass Loading and Spatial Variability on the Quartz Analysis of Surface Coal Mine Dust Samples

Monitoring the miner respirable quartz dust exposure for compliance with U.S. federal regulations is mandatory to protect the health of coal miners. However, there is no technique available for the direct measurement of the respirable quartz dust concentration in the mining environment. The only means to estimate the respirable quartz dust concentration is to perform an analysis of the respirable dust sample collected, which contains both coal and quartz dust as well as other mineral constituents. For samples collected at coal mines, the U.S. Mine Safety and Health Administration (MSHA) utilizes the P7 method for respirable quartz analysis. The objectives of this work are to 1) evaluate the performance of the P7 method on field samples of low quartz mass loadings, 2) evaluate the magnitude of dust mass spatial variability within an enclosed cab environment, and 3) estimate the subsequent propagation of error in calculating the percentage of quartz over a broad range of mass and quartz filter loadings at a...

The Effects of Low Quartz Mass Loading and Spatial Variability on the Quartz Analysis of Surface Coal Mine Dust Samples

Monitoring the miner respirable quartz dust exposure for compliance with U.S. federal regulations is mandatory to protect the health of coal miners. However, there is no technique available for the direct measurement of the respirable quartz dust concentration in the mining environment. The only means to estimate the respirable quartz dust concentration is to perform an analysis of the respirable dust sample collected, which contains both coal and quartz dust as well as other mineral constituents. For samples collected at coal mines, the U.S. Mine Safety and Health Administration (MSHA) utilizes the P7 method for respirable quartz analysis. The objectives of this work are to 1) evaluate the performance of the P7 method on field samples of low quartz mass loadings, 2) evaluate the magnitude of dust mass spatial variability within an enclosed cab environment, and 3) estimate the subsequent propagation of error in calculating the percentage of quartz over a broad range of mass and quartz filter loadings at a surface coal mine. These objectives were achieved by obtaining surface coal mine dust samples over a 9-month time period in enclosed cabs of three drills and three bulldozers. By measuring weighing precision and using reasonable estimates for sampler variability, the dust mass spatial variability component was calculated by difference. The results show that 1) the P7 method can be precise and linear with quartz mass loadings as low as approximately 5 µ mg of quartz, 2) the dust mass spatial variability, even within an enclosed cab environment, is the dominant factor of variability in propagation of error in estimating the quartz content of the obtained dust samples on a percentage basis, and 3) weighing precision is not a significant factor in error propagation. In addition to the enclosed cab samples, samples from eight surface coal mine drills were collected at various locations exterior to the drill cab. Significant data scatter at these outside locations strongly suggests that the ambient dust mass spatial variability has a significant effect on the propagation of error in estimating quartz content of the dust samples on a percentage basis.

Surface composition of respirable silica particles in a set of U.S. anthracite and bituminous coal mine dusts

Respirable particles of high-percentage silica content from anthracite and bituminous coal mine dust samples were analyzed for aluminosilicate clay surface coating, by measuring silicon and aluminum X-ray spectra using scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS). Silicon and aluminum elemental ratios were determined with incident electron energies of 20 and 5 keV to reveal whether surface occlusion was present. Some 20 respirable-sized, non-agglomerated particles with silicon fraction of signal of 75% or more (for elements above sodium) were analyzed for each of 12 coal mine dust samples. Mine dust samples were from U.S. anthracite and bituminous coal mining regions involved in epidemiological studies of the U.S. National Study of Coal Workers' Pneumoconiosis. Some particles of high-percentage silica content exhibited a decrease in the ratio of silicon-to-aluminum K-alpha line intensities with decreasing electron beam accelerating voltage, consistent with aluminosilicate clay surface contamination or occlusion of a silica particle. Significantly lower frequencies of particles manifesting occluded behavior were found for anthracite dusts versus all bituminous dusts. It is suggested that such occlusion alters the biological availability of the surface of those particles. This may be a factor in the results of attempts to correlate disease prevalence with conventionally measured dust composition, as in the classical failure of coal workers' pneumoconiosis disease prevalence to correlate with silica exposure while being correlated with cumulative total respirable dust exposure and with coal rank.

The Need for Determining the Bioavailability of Quartz in Coal Mine Dust Samples

Abstract A 3-year project focusing on the depth profiling of particles and giving their elemental characterizations at various depths has suggested that the reaction of lung tissues to coal mine dust exposures may be dependent upon coal rank-related surface coating of the particles, and ultimately upon specific quartz bioavailability. Previous research clearly indicates a coal rank relationship for the incidence of coal workers' pneumoconiosis and a hypothesized inhibitory role of clays on quartz fibrogenicity. Specifically, epidemiological studies conducted in 1961 and 1963 showed a greater disease incidence for a given cumulative dust exposure among Pennsylvania coal miners who worked in higher rank coal seams. Workers in anthracite mines had a higher incidence of coal workers' pneumoconiosis and progressive massive fibrosis than miners who worked in lower rank coal at equal cumulative exposures. This rank effect in Pennsylvania extended to all ranks of coal seams, that is, the lower the rank, the lower...

Analysis of Quartz Exposure Data Obtained from Underground and Surface Coal Mining Operations

Abstract The Mine Safety and Health Administration (MSHA) yearly performs quartz analysis on approximately 9000 respirable coal mine dust samples collected for various occupations in U.S. coal mines. All occupational quartz exposure data gathered by MSHA since 1985 have been compiled and analyzed to characterize current occupational exposures to quartz; to determine if the quartz percentages of samples collected for different occupations have changed during the period 1985 through 1992; and to study the intramine variability associated with quartz sample percentages of selected occupations. Analysis of the occupational data shows that regardless of the type of coal extraction process used, there are a substantial number of occupational samples that contain greater than 5 percent quartz and show quartz exposures that exceed 100 μg/m3. In underground mining operations, approximately 30 percent of the samples collected at the continuous-miner operator and continuous-miner helper occupations on continuous-min...

Mine Inspection Data Analysis System

Abstract In 1980, the U.S. Bureau of Mines developed the Mine Inspection Data Analysis System. It is a computerized industrial hygiene database capable of statistically analyzing Mine Safety and Health Administration compliance data collected in coal and noncoal mines and mills. Data are collected by inspectors and mine operators, and are provided to the Bureau annually on magnetic tape. The Bureau extracts, merges, and edits these data to reduce storage requirements and to facilitate analysis. Selected data are stored in ASCII format and are analyzed using a 486/DX4–100 personal computer. The database contains approximately 1.5 million records of respirable coal mine dust samples collected since 1981, and about 45,000 records of respirable coal mine dust samples analyzed for quartz. Another 6 million records of respirable coal mine dust samples dating from 1970 are archived on magnetic tape. The database also contains records of approximately 750,000 personal and area samples collected at metal and nonmetal mines and mills from 1974 through 1992. These samples were collected to determine the concentration of about 130 different substances and noise in noncoal mines and mills. In addition, there are approximately 4000 records of samples collected from 1976 through 1978 for a variety of contaminants at 22 underground non-coal mines using diesel-powered equipment. Analyses of data have shown which commodities, locations, and job categories have the highest exposures. These analyses have assisted the Bureau in planning, prioritizing, and conducting industrial hygiene research activities at surface and underground mines and mills. They have also been used by the Mine Safety and Health Administration to assess the potential impact of proposed changes in occupational health standards and to evaluate compliance sampling strategies. The objectives of this report are to describe the database and software, and to provide examples of how the database has been used to evaluate exposure to respirable dust containing at least 1 percent quartz in metal and non-metal mines and mills. Watts, Jr., W.F.; Parker, D.R.: Mine Inspection Data Analysis System. Appl. Occup. Environ. Hyg. 10(4):323–330; 1995.

Hydroxyl radical generation by coal mine dust: Possible implication to coal workers' pneumoconiosis (CWP)

Occupational exposure to coal mine dust causes coal workers' pneumoconiosis (CWP) and other pulmonary diseases by mechanisms that remain unclear. Because the hydroxyl radicals ( ·OH) may play an important role in the pathogenesis of CWP, we studied the potential role of bituminous coal mine dust samples for catalyzing the generation of ·OH from hydrogen peroxide (H 2O 2). These coal mine dusts evaluated represented two geographic areas with diversity in CWP prevalence. Electron spin resonance (ESR), with the aid of spin trapping techniques, was used to measure the ·OH radical generation. Bituminous coal mine dusts representing the Pittsburgh seam in the eastern United States and Blind Canyon seam in the mid-westem United States were used together with a standard coal dust obtained from the National Institute of Standards and Technology, Galthersburg, MD. All the coal mine dust samples generated varying levels of ·OH radicals from H 2O 2 in the presence of a ·OH spin trap 5,5,-dimethyl-l-pyrroline-N-oxide (DMPO). ·OH radical generation by the coal from H 2O 2 was effectively inhibited by deferoxamine and catalase, but only partially inhibited by superoxide dismutase. Metal chelators DETAPAC and EDTA enhanced the radical generation. These results indicated that the Fenton reaction is predominantly involved in the generation of ·OH radicals from H 2O 2. The ·OH-generating potential of all the coal dusts showed a positive correlation with the surface iron content of coal mine dusts. In addition, the potential to induce lipid peroxidation by the coal samples exhibited a good correlation with the available surface iron. Based on the results presented here, we propose that higher concentrations of surface iron in coal mine dust may be involved in the generation of increased levels of ·OH radicals and may play an important role in the development of CWP in different coal mining areas.

A Methodology for Determining the Mineral Content and Particle Size Distribution of Airborne Coal Mine Dust

Abstract Exposure to airborne dust in coal mines has caused respiratory disease in coal miners. The causal agent in these diseases remains unknown, although the minerals found in and around the coal seam have been implicated. Toxicological studies designed to establish the effect of different mineral combinations and concentrations are lacking because the mineral content of coal mine dust has not been defined. This paper reports the initial results of a study done to characterize the mineral content of the coal mine dust found in a mine in the Upper Freeport seam in Northern West Virginia. Coal mine dust samples were collected using 4-stage cassette impactors at nine locations in the mine. The samples were analyzed by an x-ray microdiffraction film technique supplemented by energy dispersive scanning electron microscopy. Primary size modes of about 17 to 20 micrometers from the samples collected at the haulageway and the returnside of the continuous miner were found. From the returnside of the roof bolter...

Comparison of the Particle Size Distribution of Alpha Quartz in Respirable Coal Mine Dust Samples With Four Reference Standards

For the past 3 years the Bureau of Mines, Avondale Research Center, has been doing extensive particle size measurements on respirable coal dust collected at surface and underground mines in the eastern United States. Respirable dust is the portion of airborne dust that penetrates the deepest portion of the lungs and is generally considered to be particles less than 10 μm in size. To monitor dust exposure, approximately 40,000 respirable dust samples are collected by inspectors annually. The quartz in these samples is determined by either infrared spectrophotometry or x-ray diffraction. Both methods require quartz standards. The response of both methods, however, as shown by Tuddenham, Huggins, and Klug is particle size dependent. Joint studies by the Bureau of Mines and Mine Safety and Health Administration show that inaccuracy in quantitative quartz values may be as much as 30% when the particle size of the quartz standard does not match that of the quartz in coal dust.

A re-evaluation of radiological evidence from a study of U.S. strip coal miners.

In 1972, the U.S. Public Health Service examined 1438 workers employed at seven bituminous and one anthracite U.S. strip coal mines. One conclusion from the study was that workers without previous dust exposures were not at risk of category 2 or higher pneumoconiosis from their strip coal mining environment. Because of recent concerns for silicosis among strip coal miners, the radiographs were reinterpreted and the data re-evaluated. In addition, data from respirable coal mine dust samples collected from 1972 to 1979 in all surface coal mines were analyzed. The results showed that category 2 or higher pneumoconiosis was prevalent among strip coal miners with experience in an underground coal mine. Among those without underground coal mine experience, category 2 or higher was prevalent among anthracite strip miners, but not among bituminous strip miners. Average respirable coal mine dust exposures in the anthracite mine were less than 1 mg/m3 prior to 1975 and, coupled with the radiographic findings, suggest further study of the efficacy of the 2 mg/m3 U.S. Federal surface coal mine dust standard in anthracite coal mines.

Measurement Assurance Program for Weighings of Respirable Coal Mine Dust Samples

A program is presented to control the weighing of respirable coal mine dust samples and to provide information on a continuing basis on the quality of the weighing operation. In addition to the description of such monitoring procedures, measurements are..

Shape factors of narrow size range samples of respirable coal mine dust

Respirable coal mine dust samples from three different U.S. mines were aerodynamically classified in a Bahco centrifugal classifier to yield four particle size fractions. Fractions were analyzed for density, particle size by optical microscopy, random and oriented projected area, and specific surface area (BET). These measures enabled us to define additional characterizing parameters which yielded insight into the physical nature of the size fractions. Differences in parameters for size fractions obtained form the same sample and from samples collected in different mines are discussed. It is suggested that to understand the differences in reported incidences of coal workers' pneumoconiosis in different mines, analyses of this type, together with the dust chemical composition as a function of particle size within the respirable size range, will be necessary.