Characterization Of Forms Of Silica With Varying Degrees Of Crystallinity In Respirable Mine Dust
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| Author | : Saboor Ahmad Torabi |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2023 |
| Genre | : |
| ISBN | : |
Coal was, is, and will be one of the major energy sources for our society. Coal mining activities, from extraction to utilization, intrinsically produce coal dust and its associated aerosols, which are known to be safety and health hazards. Within the mine dust aerosols, the exposure of the respirable crystalline silica (RCS) dust is the most toxic component for the coal workers. Excessive RCS exposure can potentially cause the development of disabling and irreversible lung disease which is known as silicosis. The silicosis cases and its related mortality trend are still high in the United States, and the recent resurgence of coal miners' lung disease sends an alarming sign for the industry. Characterization of the physiochemical properties of RCS is the prerequisite for the improved understanding of its toxicity and adverse effects on miners' respiratory system. In this study, the mineral composition of respirable coal mine dust (RCMD), and type (s) of crystalline silica with its varying degrees of crystallinity in the mine dust were investigated. For this purpose, samples were collected from the top of coal (ToC) and bottom of coal (BoC) rock strata, which are believed to have the highest amount of crystalline silica. In addition, we also collected rock samples from both the roof and pillar of a limestone mine in Pennsylvania to define its crystalline components for potential silica characterization. After preparing the lab-generated respirable dust using a cryomill, the X-ray diffraction (XRD) technique in combination with JADE software was employed to identify the mineral phases and determine the quantitative mineral composition. The results from the quantitative analysis revealed that quartz (crystalline silica), muscovite, kaolinite, and clinochlore are the most abundant minerals in the ToC and BoC strata. The average amount of crystalline silica (quartz) was assessed to be 25% in the ToC and 17.3% in the BoC samples from the Lower Freeport coal seam. The quartz content in the samples from the ToC strata of Lower Kittanning was found to be 16.5%. Furthermore, phase identification analyses determined that, among the quartz types, alpha quartz ([alpha]-quartz) is the only type that exists in the samples. The quantitative analysis also reported a considerable amount of amorphous content for all samples. The amorphous content associated with the samples from near the coal seam comparatively showed a higher quantity, suggesting that the coal-ToC and coal-BoC interfaces contain a significant amount of amorphous. The quantitative analyses of limestone samples reported high calcite and dolomite with negligible quartz content. The amount of quartz in the sample from the pillar of the limestone mine was 0.22%, whereas no quartz was reported for the sample from the roof of the same mine. According to the results, it is advisable to conduct additional elemental analysis to verify the mineral composition of the samples. Additionally, it is recommended to undertake comprehensive investigations into the mineralogy and toxicity of the amorphous content found in coal mine dust, especially those originating from the interfaces of coal and rock strata.
| Author | : Robert W. Freedman |
| Publisher | : |
| Total Pages | : 16 |
| Release | : 1971 |
| Genre | : Mine dusts |
| ISBN | : |
| Author | : Sarkis G. Ampian |
| Publisher | : |
| Total Pages | : 36 |
| Release | : 1992 |
| Genre | : Silica |
| ISBN | : |
In 1987, the International Agency for Research Against Cancer conducted a review of the health literature and concluded that crystalline silica was a probable human carcinogen. As a result of this finding, OSHA was required to regulate crystalline silica under its Hazard Communication Standard (HCS). The standard requires that all materials handled by OSHA-regulated facilities be labeled according to the requirements of HCS and that workers receive proper training on the handling of the material if the crystalline silica content equals or exceeds 0.1 weight percent (0.1%). MSHA currently is considering enacting its own HCS. This will be similar to OSHA's HCS. If the standard is enacted, most mineral producers will have to determine the respirable monitor filter and bulk crystalline silica contents of their ores and products so that workers and/or customers will know whether they are in compliance with the 0.1% HCS and/ or the OSHA permissible exposure level (PEL) of 50 micro-g for an 8-hour workday for respirable crystalline silica as determined from monitor samples. Two major concerns with the HCS are the widespread occurrence of crystalline silica in nature and the suitability of current technology for routinely determining crystalline silica concentrations at the 0.1% HCS level. Most ores are extracted from silica-bearing deposits, and silica is a common constituent of rocks and soils. OSHA's HCS will have the greatest impact on the producers of crushed stone, diatomite, dimension stone, gravel, industrial sand, perlite, pumice, pyrophyllite, sand, and talc because these materials frequently are shipped directly from the mill to the customer. MSHA's HCS would affect nearly all mineral producers. Those producers that have crystalline silica present in concentrations near the 0.1% cutoff point will have the most difficulty with the analysis. Crystalline silica can be quantified at the 0.1% level by X-ray difractometry in simple systems containing one, two, and possibly three minerals if (l) none of the accessory minerals has X-ray diffraction reflections that coincide or overlap with those of crystalline silica and (2) the standard has a particle size distribution and crystallinity similar to those of the sample. In some instances, it may not be possible to determine the crystalline silica content of a sample with any degree of certainty using the recommended regulatory protocol. In all cases, it is recommended that a qualified mineralogist identify the minerals in a sample prior to any regulatory analysis. Additionally, the uncertainty as to whether some silica polymorphs should be classified as crystalline or noncrystalline and the suitability of metastable high-temperature standards, such as cristobalite and tridymite, for regulatory analysis at ambient temperatures should be addressed further. This overview is written both to highlight these problems and to serve as a guide for analysts, regulators, and industry personnel who are involved in the crystalline silica issue. It also covers some of the difficulties and/or shortcomings in quantifying crystalline silica, such as the ubiquitous mineral quartz, in the workplace.
| Author | : SJ. Page |
| Publisher | : |
| Total Pages | : 14 |
| Release | : 2006 |
| Genre | : Analysis |
| ISBN | : |
Since 1982 standard calibration materials recommended for respirable crystalline silica analysis by the Mine Safety and Health Administration (MSHA) P7 Infrared Method and the National Institute for Occupational Safety and Health (NIOSH) X-ray Diffraction (XRD) Analytical Method 7500 have undergone minor changes in size distribution. However, a critical assumption has been made that the crystalline silica in ambient mine atmosphere respirable dust samples has also remained essentially unchanged in particle size distribution. The objective of this work, therefore, is to compare recent particle size distributions of underground coal mine dust and the silica component of these dusts with estimated aerodynamic particle size distributions of calibration standard materials MIN-U-SIL 5, Berkeley 5, and SRM 1878 used by two crystalline silica analysis techniques. This work provides resolution to a previously reported discrepancy involving the proper sample dilution for the particle sizing method used.
| Author | : Emily Allyn Sarver |
| Publisher | : |
| Total Pages | : 44 |
| Release | : 2022 |
| Genre | : Coal miners |
| ISBN | : |
The project aims to characterize the relative toxicity and contribution of respirable crystalline silica from specific dust sources using coal dust samples from working mines and samples representative of major dust sources within mine in order to better understand each element's potentially unique contribution to the development of silicosis, as well as other lung diseases, such as coal workers' pneumoconiosis (CWP) and its most severe form, progressive massive fibrosis (PMF).
| Author | : Society for Mining, Metallurgy, and Exploration (U.S.) |
| Publisher | : SME |
| Total Pages | : 57 |
| Release | : 1998 |
| Genre | : Medical |
| ISBN | : 0873351665 |
In practical language, Crystalline Silica addresses what crystalline silica is, where it is found and used, and how it is identified. In addition, the book discusses the regulatory decisions yielding new interest in this ubiquitous substance and presents an overview of the techniques used to determine its presence and abundance. A list of selected readings and supplemental resources and a glossary of terms beyond the scope of this publication round out the text.
| Author | : Steven Mischler |
| Publisher | : |
| Total Pages | : 16 |
| Release | : 2014 |
| Genre | : Dust |
| ISBN | : |
Exposure to crystalline silica in mining can lead to silicosis, a potentially fatal lung disease, and it may be contributing to the increase of coal workers' pneumoconiosis (CWP) seen in Appalachian miners. Exposure to silica in mines is controlled indirectly by reducing the respirable dust exposure limit through a formula that employs the % of silica in the dust. To reduce this exposure, control technologies and specific monitoring techniques need to be developed and implemented and the knowledge of the % of silica in mine dusts can help this process. This manuscript analyzes the % of silica in dust samples for the U.S. mining industry collected from 1997 to 2011. In the metal/nonmetal (M/NM) industry, metal and sand and gravel mines showed the highest silica % (8.2 %, 9.8 %) along with the highest variability. The silica % was found to be lower for samples collected in underground by comparison to surface and mill. In the coal industry, the samples collected in surface locations showed high silica % in the dust. For both the coal and M/NM industries, the % of silica and the respirable dust concentration were inversely related--i.e., the lower the dust concentration, the higher and more variable silica percentages were observed. The respirable dust limit formula suggests the first explanation: a mine with a high silica % in the dust is required to keep the dust concentration low under the reduced standard. Additional explanations are also proposed: the variability of the % of silica in the dust, the selective efficiency of control technologies, and different transport properties for dust with variable silica content. The findings improve the understanding of exposure to silica in mining environments and the data presented will be helpful in developing monitoring strategies for the measurement of silica and for the design of control technologies.
| Author | : E.F. Vansant |
| Publisher | : Elsevier |
| Total Pages | : 573 |
| Release | : 1995-04-25 |
| Genre | : Science |
| ISBN | : 0080528953 |
Oxide surface materials are widely used in many applications, in particular where chemically modified oxide surfaces are involved. Indeed, in disciplines such as separation, catalysis, bioengineering, electronics, ceramics, etc., modified oxide surfaces are very important. In all cases, the knowledge of their chemical and surface characteristics is of great importance for the understanding and eventual improvement of their performances. This book reviews the latest techniques and procedures in the characterization and chemical modification of the silica surface, presenting a unified and state-of-the-art approach to the relevant analysis techniques and modification procedures, covering 1000 references integrated into one clear concept.
| Author | : |
| Publisher | : |
| Total Pages | : 456 |
| Release | : 1996 |
| Genre | : Mine dusts |
| ISBN | : |
| Author | : Steven Verpaele |
| Publisher | : |
| Total Pages | : 30 |
| Release | : 2014 |
| Genre | : Arizona Road Dust |
| ISBN | : |
Members of an international standards working group for silica measurement (ISO/TC146/SC2/WG7 Silica) collaborated to assess the differences between sample preparation approaches for the analysis of respirable crystalline silica (RCS) by X-ray diffraction (XRD). They also assessed the relative collection efficiencies of 13 respirable samplers. The evaluation involved nine laboratories from eight countries. Samplers were exposed to airborne concentrations of ultrafine and medium Arizona road dust (ARD) in a calm air chamber. Each participating laboratory analysed samples following their own method and the Health and Safety Laboratory (HSL) retained a third of the samples for verification. All methods and analytical approaches applied in this study obtained comparable results (most were within 12 %). An exception was a method used with the CIP10 R sampler, which reported lower values. Correcting for the crystallinity of the calibration quartz dust using a verified value tested against a certified reference material has one of the largest impacts on the comparability of results. When following good analytical practice, the main factors affecting the comparability of results for RCS are significant differences in sampler efficiencies. In particular, the conductive sampler from SKC obtained a higher concentration of respirable dust (1.3-1.4x) when compared with the average air concentration. The Dorr Oliver, SKC aluminium, CIP10 R, and IOM head (with polyurethane foam separator) samplers all reported lower respirable dust air concentrations than average with the ultrafine ARD. Their lower collection efficiency compared with other samplers is explainable from published sampler information. The Dorr Oliver sampler also had a tendency to collect a lower proportion of RCS in the respirable dust than others. The working group propose that more stringent particle size selection and mass collection criteria are used to improve consistency and cross-utilisation of exposure data between countries.
