Last data update: Jun 24, 2024. (Total: 47078 publications since 2009)
Records 1-18 (of 18 Records) |
Query Trace: Miller AL [original query] |
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Evaluation of a non-dispersive infrared spectrometer for quantifying organic and elemental carbon in diesel particulate matter
Parks DA , Zhao Y , Griffiths PR , Miller AL . Aerosol Sci Technol 2024 Diesel particulate matter (DPM) is a common and well-known health hazard in the mining environment. The regulatory method for monitoring both the organic and elemental carbon (OC, EC) portions of DPM is a laboratory-based thermal-optical method with a typical turnaround time of one week. In order to evaluate exposure levels and take corrective action prior to overexposure, a portable real-time device capable of quantifying both OC and EC is needed. To that end, researchers from the National Institute for Occupational Safety and Health (NIOSH) designed and tested the feasibility of a device based on bandpass optical filters that target key infrared wavelengths associated with DPM and its spectroscopic baseline. The resulting device, referred to here as a non-dispersive infrared (NDIR) spectrometer could serve as the basis of a cost-effective, field-portable alternative to the laboratory thermal-optical method. The limits of quantification (LOD) indicate that the NDIR spectrometer can quantify EC, OC, and TC provided they are present at 20, 37, and 46 μg/m3 or more, respectively. In the event that the NDIR spectrometer is integrated with a sampler and filter tape the LOD is estimated to be reduced to 13, 7, and 10 μg/m3 for EC, OC, and TC, respectively. These LOD estimates assume a face velocity of 59 cm/s and a sampling time of 30 min. ©, This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 USC. 105, no copyright protection is available for such works under US Law. |
Quantifying elemental and organic carbon in diesel particulate matter by mid-infrared spectrometry
Parks DA , Griffiths PR , Weakley AT , Miller AL . Aerosol Sci Technol 2021 55 (9) [Epub ahead of print] A method for the quantification of airborne organic carbon (OC) and elemental carbon (EC) within aerosolized diesel particulate matter (DPM) is described in this article. DPM is a known carcinogen encountered in many industrial workplaces (notably mining) and in the ambient atmosphere. The method described here collects DPM particles onto a quartz fiber filter, after which reflection-mode infrared spectra are measured on a mid-infrared Fourier transform (FT-IR) spectrometer. Several infrared absorption bands are investigated for their efficacy in quantifying OC and EC. The thermo-optical (T-O) method is used to calibrate a linear regression model to predict OC and EC from the infrared spectra. The calibrated model, generated from laboratory DPM samples, is then utilized to quantify OC and EC in mine samples obtained from two metal mine locations under a variety of operating conditions. The feasibility of further improving these results by partial least squares (PLS) regression was investigated. A single calibration that is broadly applicable would be considered an improvement over currently available portable instruments, which require aerosol-specific calibration. |
A predictive model for elemental carbon, organic carbon and total carbon based on laser induced breakdown spectroscopy measurements of filter-collected diesel particulate matter
McLaughlin RP , Parks DA , Grubb AI , Mason GS , Miller AL . Spectrochim Acta Part B At Spectrosc 2020 168 105871 Diesel particulate matter (DPM) produced from vehicle and equipment diesel exhaust (DE) is a common industrial inhalation hazard, particularly in underground mines. The sub-micron particles of DPM (< 800 nm) are composed of a carbonaceous core operationally defined as elemental carbon (EC), which are irregularly arranged graphitic- like "spherule" structures, and a wide-variety of adsorbed, semivolatile organic carbon compounds (OC). In addition to associating chronic exposure to DPM with immunological, respiratory and cardiovascular health issues, the International Agency for Research on Cancer (IARC) categorizes this material as carcinogenic to humans, with workers regularly exposed to it demonstrating an elevated risk for lung cancer. Given the long-term health risks associated with repeated and prolonged exposure to DPM, efforts are being directed at reducing the exposure of miners and other workers who may encounter high levels of DPM over the course of a typical working day. |
"Submergence" of Western equine encephalitis virus: Evidence of positive selection argues against genetic drift and fitness reductions.
Bergren NA , Haller S , Rossi SL , Seymour RL , Huang J , Miller AL , Bowen RA , Hartman DA , Brault AC , Weaver SC . PLoS Pathog 2020 16 (2) e1008102 ![]() ![]() Understanding the circumstances under which arboviruses emerge is critical for the development of targeted control and prevention strategies. This is highlighted by the emergence of chikungunya and Zika viruses in the New World. However, to comprehensively understand the ways in which viruses emerge and persist, factors influencing reductions in virus activity must also be understood. Western equine encephalitis virus (WEEV), which declined during the late 20th century in apparent enzootic circulation as well as equine and human disease incidence, provides a unique case study on how reductions in virus activity can be understood by studying evolutionary trends and mechanisms. Previously, we showed using phylogenetics that during this period of decline, six amino acid residues appeared to be positively selected. To assess more directly the effect of these mutations, we utilized reverse genetics and competition fitness assays in the enzootic host and vector (house sparrows and Culex tarsalis mosquitoes). We observed that the mutations contemporary with reductions in WEEV circulation and disease that were non-conserved with respect to amino acid properties had a positive effect on enzootic fitness. We also assessed the effects of these mutations on virulence in the Syrian-Golden hamster model in relation to a general trend of increased virulence in older isolates. However, no change effect on virulence was observed based on these mutations. Thus, while WEEV apparently underwent positive selection for infection of enzootic hosts, residues associated with mammalian virulence were likely eliminated from the population by genetic drift or negative selection. These findings suggest that ecologic factors rather than fitness for natural transmission likely caused decreased levels of enzootic WEEV circulation during the late 20th century. |
Towards a field-portable real-time organic and elemental carbon monitor
Parks DA , Raj KV , Berry CA , Weakley AT , Griffiths PR , Miller AL . Min Metall Explor 2019 36 (4) 765-772 Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. As a result of its potential carcinogenic nature, DPM exposure is regulated by the Mine Safety and Health Administration. Currently, diesel emissions in the workplace are monitored by collecting the aerosol onto filters, which are then sent to a laboratory for thermal-optical analysis using the NIOSH method 5040. This process can take days or even weeks, and workers can potentially be exposed to excessive levels of DPM before the problem is identified. Moreover, the delay involved in getting the loaded filter to the lab inevitably means the loss of some of the more volatile organic carbon. To remedy this delay, researchers from the National Institute for Occupational Safety and Health are seeking to develop a field-portable, real-time method for measuring elemental and organic carbons in DPM aerosols. In the current study, the use of mid-infrared spectrometry was investigated. It is believed that mid-infrared spectroscopy is more suitable for use in a real-time field-portable device than thermo-optical analysis methods. This article presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. The method has been successfully applied to laboratory-generated and mine samples. |
Evaluation of an improved prototype mini-baghouse to control the release of respirable crystalline silica from sand movers
Alexander BM , Esswein EJ , Gressel MG , Kratzer JL , Feng HA , Miller AL , Cauda E , Heil G . J Occup Environ Hyg 2017 15 (1) 0 The OSHA final rule on respirable crystalline silica (RCS) will require hydraulic fracturing companies to implement engineering controls to limit workers' exposure to RCS. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. Chronic inhalation of RCS can lead to serious disease, including silicosis and lung cancer. NIOSH research identified at least seven sources where RCS aerosols were generated at hydraulic fracturing sites. NIOSH researchers developed an engineering control to address one of the largest sources of RCS aerosol generation, RCS escaping from thief hatches on the top of sand movers. The control, the NIOSH Mini-Baghouse Retrofit Assembly (NMBRA), mounts on the thief hatches. Unlike most commercially-available engineering controls, the NMBRA has no moving parts and requires no power source. This article details the results of an evaluation of generation 3 of the NMBRA at a sand mine in Arkansas from May 19 - 21, 2015. During the evaluation, 168 area air samples were collected at 12 locations on and around a sand mover with and without the NMBRA installed. Analytical results for respirable dust and RCS indicated the use of the NMBRA effectively reduced concentrations of both respirable dust and RCS downwind of the thief hatches. Reductions of airborne respirable dust were estimated at 99+%; reductions in airborne RCS ranged from 98-99%. Analysis of bulk samples of the dust showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Use of an improved filter fabric and a larger area of filter cloth led to substantial improvements in filtration and pressures during these trials, as compared to the generation 2 NMBRA. Planned future design enhancements, including a weather cover, will increase the performance and durability of the NMBRA. Future trials are planned to evaluate the long-term operability of the technology. |
Direct-on-filter alpha-quartz estimation in respirable coal mine dust using transmission fourier transform infrared spectrometry and partial least squares regression
Miller AL , Weakley AT , Griffiths PR , Cauda EG , Bayman S . Appl Spectrosc 2016 71 (5) 1014-1024 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 alpha-quartz, in mine dusts. In this study we demonstrate the feasibility of end-of-shift measurement of alpha-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. |
Note: a portable laser induced breakdown spectroscopy instrument for rapid sampling and analysis of silicon-containing aerosols
McLaughlin RP , Mason GS , Miller AL , Stipe CB , Kearns JD , Prier MW , Rarick JD . Rev Sci Instrum 2016 87 (5) 056103 A portable instrument has been developed for measuring silicon-containing aerosols in near real-time using laser-induced breakdown spectroscopy (LIBS). The instrument uses a vacuum system to collect and deposit airborne particulate matter onto a translatable reel of filter tape. LIBS is used to analyze the deposited material, determining the amount of silicon-containing compounds present. In laboratory testing with pure silica (SiO2), the correlation between LIBS intensity for a characteristic silicon emission and the concentration of silica in a model aerosol was determined for a range of concentrations, demonstrating the instrument's plausibility for identifying hazardous levels of silicon-containing compounds. |
The development and testing of a prototype mini-baghouse to control the release of respirable crystalline silica from sand movers
Alexander BM , Esswein EJ , Gressel MG , Kratzer JL , Amy Feng H , King B , Miller AL , Cauda E . J Occup Environ Hyg 2016 13 (8) 0 Inhalation of respirable crystalline silica (RCS) is a significant risk to worker health during well completions operations (which include hydraulic fracturing) at conventional and unconventional oil and gas extraction sites. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. National Institute for Occupational Safety and Health (NIOSH) researchers identified concentrations of RCS at hydraulic fracturing sites that exceed 10 times the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and up to 50 times the NIOSH Recommended Exposure Limit (REL). NIOSH research identified at least seven point sources of dust release at contemporary oil and gas extraction sites where RCS aerosols were generated. NIOSH researchers recommend the use of engineering controls wherever they can be implemented to limit the RCS released. A control developed to address one of the largest sources of RCS aerosol generation is the NIOSH mini-baghouse assembly, mounted on the thief hatches on top of the sand mover. This manuscript details the results of a trial of the NIOSH mini-baghouse at a sand mine in Arkansas, November 18 - 21, 2013. During the trial, area air samples were collected at 12 locations on and around a sand mover with and without the mini-baghouse control installed. Analytical results for respirable dust and RCS indicate the use of the mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. Reduction of airborne respirable dust ranged from 85% to 98%; reductions in airborne RCS ranged from 79% to 99%. A bulk sample of dust collected by the baghouse assembly showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Planned future design enhancements will increase the performance and durability of the mini-baghouse, including an improved bag clamp mechanism and upgraded filter fabric with a modified air-to-cloth ratio. Future trials are planned to determine additional respirable dust and RCS concentration reductions achieved through these design changes. |
Evaluation of diffuse reflection infrared sectrometry for end-of-shift measurement of alpha-quartz in coal dust samples
Miller AL , Murphy NC , Bayman SJ , Briggs ZP , Kilpatrick AD , Quinn CA , Wadas MR , Cauda EG , Griffiths PR . J Occup Environ Hyg 2015 12 (7) 421-30 The inhalation of toxic substances is a major threat to the health of miners, and dust containing respirable crystalline silica (alpha-quartz) is of particular concern, due to the recent rise in cases of coal workers' pneumoconiosis and silicosis in some U.S. mining regions. Currently, there is no field-portable instrument that can measure airborne alpha-quartz and give miners timely feedback on their exposure. The U.S. National Institute for Occupational Safety and Health (NIOSH) is therefore conducting studies to investigate technologies capable of end-of-shift or real-time measurement of airborne quartz. The present study focuses on the potential application of Fourier transform infrared (FT-IR) spectrometry conducted in the diffuse reflection (DR) mode as a technique for measuring alpha-quartz in respirable mine dust. A DR accessory was used to analyze lab-generated respirable samples of Min-U-Sil 5 (which contains more than 90% alpha-quartz) and coal dust, at mass loadings in the ranges of 100-600 microg and 600-5300 microg respectively. The dust samples were deposited onto three different types of filters, borosilicate fiberglass, nylon and polyvinyl chloride (PVC). The reflectance, R, was calculated by the ratio of a blank filter and a filter with deposited mine dust. Results suggest that for coal and pure quartz dusts deposited on 37-mm PVC filters, measurements of log R correlate linearly with known amounts of quartz on filters, with R2 values of approximately 0.99 and 0.94, respectively, for samples loaded up to ~4000 microg. Additional tests were conducted to measure quartz in coal dusts deposited onto the borosilicate fiberglass and nylon filter media used in the NIOSH-developed Personal Dust Monitor (PDM). The nylon filter was shown to be amenable to DR analysis, but quantification of quartz is more accurate when the filter is "free", as opposed to being mounted in the PDM filter holder. The borosilicate fiberglass filters were shown to produce excessive interference, making quartz quantification impossible. It was concluded that, while the DR/FT-IR method is potentially useful for on-filter measurement of quartz in dust samples, the use of PVC filters produced the most accurate results. |
Quantifying silica in filter-deposited mine dusts using infrared spectra and partial least squares regression
Weakley AT , Miller AL , Griffiths PR , Bayman SJ . Anal Bioanal Chem 2014 406 (19) 4715-24 ![]() The feasibility of measuring airborne crystalline silica (alpha-quartz) in noncoal mine dusts using a direct-on-filter method of analysis is demonstrated. Respirable alpha-quartz was quantified by applying a partial least squares (PLS) regression to the infrared transmission spectra of mine-dust samples deposited on porous polymeric filters. This direct-on-filter method deviates from the current regulatory determination of respirable alpha-quartz by refraining from ashing the sampling filter and redepositing the analyte prior to quantification using either infrared spectrometry for coal mines or x-ray diffraction (XRD) from noncoal mines. Since XRD is not field portable, this study evaluated the efficacy of Fourier transform infrared spectrometry for silica determination in noncoal mine dusts. PLS regressions were performed using select regions of the spectra from nonashed samples with important wavenumbers selected using a novel modification to the Monte Carlo unimportant variable elimination procedure. Wavenumber selection helped to improve PLS prediction, reduce the number of required PLS factors, and identify additional silica bands distinct from those currently used in regulatory enforcement. PLS regression appeared robust against the influence of residual filter and extraneous mineral absorptions while outperforming ordinary least squares calibration. These results support the quantification of respirable silica in noncoal mines using field-portable infrared spectrometers. |
Deposition uniformity of coal dust on filters and its effect on the accuracy of FTIR analyses for silica
Miller AL , Drake PL , Murphy NC , Cauda EG , LeBouf RF , Markevicius G . Aerosol Sci Technol 2013 47 (7) 724-733 Miners are exposed to silica-bearing dust which can lead to silicosis, a potentially fatal lung disease. Currently, airborne silica is measured by collecting filter samples and sending them to a laboratory for analysis. Since this may take weeks, a field method is needed to inform decisions aimed at reducing exposures. This study investigates a field-portable Fourier transform infrared (FTIR) method for end-of-shift (EOS) measurement of silica on filter samples. Since themethod entails localized analyses, spatial uniformity of dust deposition can affect accuracy and repeatability. The study, therefore, assesses the influence of radial deposition uniformity on the accuracy of the method. Using laboratory-generated Minusil and coal dusts and three different types of sampling systems, multiple sets of filter samples were prepared. All samples were collected in pairs to create parallel sets for training and validation. Silica was measured by FTIR at nine locations across the face of each filter and the data analyzed using a multiple regression analysis technique that compared various models for predicting silica mass on the filters using different numbers of "analysis shots." It was shown that deposition uniformity is independent of particle type (kaolin vs. silica), which suggests the role of aerodynamic separation is negligible. Results also reflected the correlation between the location and number of shots versus the predictive accuracy of the models. The coefficient of variation (CV) for the models when predicting mass of validation samples was 4%-51% depending on the number of points analyzed and the type of sampler used, which affected the uniformity of radial deposition on the filters. It was shown that using a single shot at the center of the filter yielded predictivity adequate for a field method, (93% return, CV approximately 15%) for samples collected with 3-piece cassettes. |
Comparison of field portable measurements of ultrafine TiO: X-ray fluorescence, laser-induced breakdown spectroscopy, and Fourier-transform infrared spectroscopy
Lebouf RF , Miller AL , Stipe C , Brown J , Murphy N , Stefaniak AB . Environ Sci Process Impacts 2013 15 (6) 1191-8 Laboratory measurements of ultrafine titanium dioxide (TiO2) particulate matter loaded on filters were made using three field portable methods (X-ray fluorescence (XRF), laser-induced breakdown spectroscopy (LIBS), and Fourier-transform infrared (FTIR) spectroscopy) to assess their potential for determining end-of-shift exposure. Ultrafine TiO2 particles were aerosolized and collected onto 37 mm polycarbonate track-etched (PCTE) filters in the range of 3 to 578 mcg titanium (Ti). Limit of detection (LOD), limit of quantification (LOQ), and calibration fit were determined for each measurement method. The LOD's were 11.8, 0.032, and 108 mug Ti per filter, for XRF, LIBS, and FTIR, respectively and the LOQ's were 39.2, 0.11, and 361 mcg Ti per filter, respectively. The XRF calibration curve was linear over the widest dynamic range, up to the maximum loading tested (578 mcg Ti per filter). LIBS was more sensitive but, due to the sample preparation method, the highest loaded filter measurable was 252 mcg Ti per filter. XRF and LIBS had good predictability measured by regressing the predicted mass to the gravimetric mass on the filter. XRF and LIBS produced overestimations of 4% and 2%, respectively, with coefficients of determination (R2) of 0.995 and 0.998. FTIR measurements were less dependable due to interference from the PCTE filter media and overestimated mass by 2% with an R2 of 0.831. |
Evaluation of laser-induced breakdown spectroscopy (LIBS) for measurement of silica on filter samples of coal dust
Stipe CB , Miller AL , Brown J , Guevara E , Cauda E . Appl Spectrosc 2012 66 (11) 1286-93 Airborne silica dust (quartz) is common in coal mines and represents a respiratory hazard that can lead to silicosis, a potentially fatal lung disease. With an eye toward developing a portable monitoring device for rapid analysis of silica dust, laser-induced breakdown spectroscopy (LIBS) was used to quantify quartz in coal dust samples collected on filter media. Pure silica (Min-U-Sil(TM) 5), Georgia kaolin, and Pittsburgh-4 and Illinois-6 coal dusts were deposited separately and at multiple mass loadings onto 37-mm polyvinylchloride (PVC) filters. LIBS-generated silicon emission was monitored at 288.16 nm, and non-silica contributions to that signal from kaolinite were removed by simultaneously detecting aluminum. Measurements of the four samples were used to calculate limits of detection (LOD) for silicon and aluminum of approximately 0.08 mug/cm(2) and 0.05 mug/cm(2), respectively (corresponding to 0.16 mug/cm(2) and 0.20 mug/cm(2) for silica and kaolinite, respectively). Relative errors of prediction are around 10%. Results demonstrate that LIBS can dependably quantify silica on filter samples of coal dust and confirm that accurate quantification can be achieved for very lightly loaded samples, which supports the potential application of LIBS for rapid, in-field monitoring. |
Toward developing a new occupational exposure metric approach for characterization of diesel aerosols
Cauda EG , Ku BK , Miller AL , Barone TL . Aerosol Sci Technol 2012 46 (12) 1370-1381 The extensive use of diesel-powered equipment in mines makes the exposure to diesel aerosols a serious occupational issue. The exposure metric currently used in U.S. underground noncoal mines is based on the measurement of total carbon (TC) and elemental carbon (EC) mass concentration in the air. Recent toxicological evidence suggests that the measurement of mass concentration is not sufficient to correlate ultrafine aerosol exposure with health effects. This urges the evaluation of alternative measurements. In this study, the current exposure metric and two additional metrics, the surface area and the total number concentration, were evaluated by conducting simultaneous measurements of diesel ultrafine aerosols in a laboratory setting. The results showed that the surface area and total number concentration of the particles per unit of mass varied substantially with the engine operating condition. The specific surface area (SSA) and specific number concentration (SNC) normalized with TC varied two and five times, respectively. This implies that miners, whose exposure is measured only as TC, might be exposed to an unknown variable number concentration of diesel particles and commensurate particle surface area. Taken separately, mass, surface area, and number concentration did not completely characterize the aerosols. A comprehensive assessment of diesel aerosol exposure should include all of these elements, but the use of laboratory instruments in underground mines is generally impracticable. The article proposes a new approach to solve this problem. Using SSA and SNC calculated from field-type measurements, the evaluation of additional physical properties can be obtained by using the proposed approach. (Copyright 2012 American Association for Aerosol Research.) |
Evaluating portable infrared spectrometers for measuring the silica content of coal dust
Miller AL , Drake PL , Murphy NC , Noll JD , Volkwein JC . J Environ Monit 2011 14 (1) 48-55 Miners face a variety of respiratory hazards while on the job, including exposure to silica dust which can lead to silicosis, a potentially fatal lung disease. Currently, field-collected filter samples of silica are sent for laboratory analysis and the results take weeks to be reported. Since the mining workplace is constantly moving into new and often different geological strata with changing silica levels, more timely data on silica levels in mining workplaces could help reduce exposures. Improvements in infrared (IR) spectroscopy open the prospect for end-of-shift silica measurements at mine sites. Two field-portable IR spectrometers were evaluated for their ability to quantify the mass of silica on filter samples loaded with known amounts of either silica or silica-bearing coal dust (silica content ranging from 10-200 mug/filter). Analyses included a scheme to correct for the presence of kaolin, which is a confounder for IR analysis of silica. IR measurements of the samples were compared to parallel measurements derived using the laboratory-based U.S. Mine Safety and Health Administration P7 analytical method. Linear correlations between Fourier transform infrared (FTIR) and P7 data yielded slopes in the range of 0.90-0.97 with minimal bias. Data from a variable filter array spectrometer did not correlate as well, mainly due to poor wavelength resolution compared to the FTIR instrument. This work has shown that FTIR spectrometry has the potential to reasonably estimate the silica exposure of miners if employed in an end-of-shift method. |
Morphological and elemental classification of freshly emitted soot particles and atmospheric ultrafine particles using the TEM/EDS
Tumolva L , Park JY , Kim JS , Miller AL , Chow JC , Watson JG , Park K . Aerosol Sci Technol 2010 44 (3) 202-215 The Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS) were used to determine morphology and elemental composition of a variety of freshly emitted soot particles ( acetylene flame, candle flame, kerosene flame, diesel exhaust, electric arc, plastic burning, styrofoam burning, wood burning [white oak and pine bark], and rice straw burning), which can be possible candidate soot in the ambient atmosphere, and ultrafine particles sampled in urban, industrial, and coastal sites during ultrafine particle formation events ( combustion and photochemical events). By using mobility-classified non-refractory ((NH4)(2)SO4) and refractory ( Polystyrene latex (PSL) and salt ( NaCl)) particles, limitation of the TEM was tested. Data showed that the TEM method can be used to examine shapes of both volatile particles such as (NH4)(2)SO4 (100 nm) at low, but not high magnification ( refer to low and high beam intensity, respectively), and nonvolatile particles like NaCl ( 100 nm) and PSL ( 84 nm) at either low or high magnification. Distinct differences in morphological properties such as primary particle diameter, fractal dimension, and microstructure were observed among the different types of fresh soot particles. The atmospheric ultrafine particles were classified as agglomerates, sulfate mixtures ( spherical), metallic oxides ( spherical and polygonal), C-rich refractory ( not agglomerated), C-rich non-refractory ( not agglomerated), Si-rich ( spherical), Na-rich ( porous), or P-containing (non-spherical) particles. At the urbanGwangju site, a higher fraction of fresh and aged agglomerates was observed than at other sites. The C-rich non-refractory and sulfate mixtures were often observed in the photochemical event. The C-rich refractory particles were abundant at the Gwangju and Yeosu sites. The coastal Taean site had few agglomerates due to limited anthropogenic combustion source. |
Chemical-related injuries and illnesses in U.S. mining
Scott DF , Merritt EM , Miller AL , Drake PL . Min Eng 2009 61 (7) 41-46 The purpose of this study was to determine if miners were at risk from exposures to chemicals used in the mining industry and determine the nature and sources of the illnesses and injuries. The U.S. Mine Safety and Health Administration’s (MSHA) employment and accident, injury and illness database was reviewed. There were 2,705 cases of chemical-related injuries and illnesses reported from 1999 through 2006, involving 66 different chemicals. The main source (cause) of chemical-related cases was acids/alkalis (about 39%). The primary nature (effect) of chemical-related cases was chemical burns (about 57%). The job classifi cation where workers incurred the most chemical-related injuries and illnesses was cleaning plant operator/media operator/boney preparation plant operator/crusher worker (cleaning plant operators are responsible for maintenance of plants, media operators are responsible for handling reagents, boney preparation plant operators oversee removal of "bone" from coal, and crusher workers use large crushers to break mined material). From 1999 through 2006, the rate of "nonfatal days lost" and "no days lost" (resulting from injuries) did not change signifi cantly; however, the rate of illnesses decreased signifi cantly. Chemical burns accounted for a large number of injuries; mining companies should carefully examine their personal protective equipment (PPE) requirements, training methods and safety culture to ensure that their workers are protected. |
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