RESUMEN
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 µg/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.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Carbón Mineral/análisis , Polvo/análisis , Monitoreo del Ambiente/instrumentación , Dióxido de Silicio/análisis , Contaminantes Ocupacionales del Aire/química , Minas de Carbón , Monitoreo del Ambiente/métodos , Humanos , Exposición por Inhalación/análisis , Exposición por Inhalación/prevención & control , Exposición por Inhalación/estadística & datos numéricos , Exposición Profesional/análisis , Exposición Profesional/prevención & control , Exposición Profesional/estadística & datos numéricos , Medición de Riesgo , Dióxido de Silicio/química , Espectrofotometría Infrarroja/instrumentación , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Accurate measurement of workplace respirable dust concentration is an essential step in eliminating lung disease in any occupational setting. In the United States (U.S.) coal mining industry, this measurement process has relied upon a personal sampler that includes a 10 mm Dorr-Oliver (DO) nylon cyclone operated at a flow rate of 2.0 L min(-1) to collect a respirable dust sample. Dust concentrations measured with this sampler are multiplied by 1.38, which was empirically derived, to convert them to measurements approximating the United Kingdom British Medical Research Council (BMRC) definition of respirable dust upon which the health effects of coal mine dust are based. The International Organization for Standardization (ISO) subsequently refined the respirable dust definition and the U.S. National Institute for Occupational Safety and Health (NIOSH) 1995 Criteria for a Recommended Standard presented a conversion multiplier of 0.857 to apply to the 2.0 L min(-1) DO (in addition to the1.38 multiplier) to obtain equivalent ISO concentrations, as approximated by the 1.7 L min(-1) DO. However, the conversion multiplier 0.857 was derived indirectly from a limited size distribution data set rather than a direct comparison of the DO samplers. The present analysis focuses on providing a more accurate conversion multiplier derived from direct comparisons of the 2.0 L min(-1) (with 1.38 BMRC equivalency multiplier) and 1.7 L min(-1) DO cyclones. A weighted linear regression analysis of this database suggests that a more accurate estimate of the conversion multiplier is 0.815.
Asunto(s)
Contaminantes Atmosféricos/química , Monitoreo del Ambiente/instrumentación , Monitoreo del Ambiente/métodos , Carbón Mineral , Exposición a Riesgos Ambientales/prevención & control , Minería , Exposición Profesional , Tamaño de la PartículaRESUMEN
Research by the National Institute for Occupational Safety and Health (NIOSH) has pursued quartz analysis for the specialized filter assemblies of a new worker-wearable personal dust monitor (PDM). The PDM is a real-time instrument utilizing a tapered element oscillating microbalance (TEOM). Standard fiberglass TEOM filters cannot accommodate the desired P-7 infrared analytical method used by the Mine Safety and Health Administration (MSHA). Novel filter materials were tested with the objective of demonstrating this type of analysis. Low temperature ashing and spectrometric examination were employed, revealing that nylon fiber candidate filters left minimal residual ash and produced no significant spectral interference. Avoiding titanium dioxide in all filter materials proved to be a key requirement. Fine quartz particulates were collected on prototype filters in a Marple chamber, either open-faced or through PDMs during test runs. The filters were then subjected to MSHA P-7 analysis and the spectrometrically based analytical results for quartz mass were compared to reference measurements. Also, PDM instrumental mass readings were compared to filter gravimetric measurements. Results suggest that the P-7 method is adaptable to variations in filter materials and that quartz dust analysis by the P-7 method when utilizing the new ashable PDM filters can have accuracy and precision within 10% and 4%, respectively. This is within the declared 13% accuracy and 7-10% precision of the P-7 method itself. Instrument mass readings had modest positive bias but met NIOSH accuracy criteria. Continued work with specialized PDM filters is merited, as they are a new type of TEOM sample amenable to ashing analysis of particulates.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Polvo/análisis , Monitoreo del Ambiente/instrumentación , Cuarzo/análisis , Minas de Carbón , Filtración/instrumentación , Tamaño de la Partícula , Espectrofotometría InfrarrojaRESUMEN
A primary means to reduce environmental levels of diesel particulate matter (DPM) exposure to miners is to reduce the amount of DPM emission from the engine. A quick and economic method to estimate engine particulate emission levels has been developed. The method relies on the measurement of pressure increase across a filter element that is briefly used to collect a DPM sample directly from the engine exhaust. The method has been refined with the inclusion of an annular aqueous denuder to the tube which permits dry filter samples to be obtained without addition of dilution air. Tailpipe filter samples may then be directly collected in hot and water-supersaturated exhaust gas flows from water bath-cooled coal mine engines without the need for dilution air. Measurement of a differential pressure (DP) increase with time has been related to the mass of elemental carbon (EC) on the filter. Results for laboratory and field measurements of the method showed agreement between DP increase and EC collected on the filter with R(2) values >0.86. The relative standard deviation from replicate samples of DP and EC was 0.16 and 0.11, respectively. The method may also have applications beyond mining, where qualitative evaluation of engine emissions is desirable to determine if engine or control technology maintenance may be required.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Gasolina/efectos adversos , Material Particulado/análisis , Emisiones de Vehículos/análisis , Contaminantes Ocupacionales del Aire/efectos adversos , Carbono/efectos adversos , Carbono/análisis , Monitoreo del Ambiente/métodos , Monitoreo del Ambiente/estadística & datos numéricos , Diseño de Equipo/normas , Femenino , Humanos , Masculino , Minería , Material Particulado/efectos adversosRESUMEN
The United States National Institute for Occupational Safety and Health, through an informal partnership with industry, labor, and the United States Mine Safety and Health Administration, has developed and tested a new instrument known as the Personal Dust Monitor (PDM). The new dust monitor is an integral part of the cap lamp that coal miners normally carry to work and provides continuous information about the concentration of respirable coal mine dust within the breathing zone of that individual. Previous laboratory testing demonstrated that there is a 95% confidence that greater than 95% of individual PDM measurements fall within +/-25% of reference measurements. The work presented in this paper focuses on the relationship between the PDM and respirable dust concentrations currently measured by a coal mine dust personal sampler unit utilizing a 10 mm Dorr-Oliver nylon cyclone. The United Kingdom Mining Research Establishment instrument, used as the basis for coal mine respirable dust standards, had been designed specifically to match the United Kingdom British Medical Research Council (BMRC) criterion. The personal sampler is used with a 1.38 multiplier to convert readings to the BMRC criterion. A stratified random sampling design incorporating a proportionate allocation strategy was used to select a sample of mechanized mining units representative of all US underground coal mines. A sample of 180 mechanized mining units was chosen, representing approximately 20% of the mechanized mining units in production at the time the sample was selected. A total of 129 valid PDM/personal sampler dust sample sets were obtained. A weighted linear regression analysis of this data base shows that, in comparison with the personal sampler, the PDM requires a mass equivalency conversion multiplier of 1.05 [95% C.I.=(1.03, 1.08)] when the small intercept term is removed from the analysis. Removal of the intercept term results in a personal sampler-equivalent concentration increase of 2.9% at a PDM measurement of 2.0 mg m(-3).
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Minas de Carbón , Polvo/análisis , Monitoreo del Ambiente/instrumentación , Exposición por Inhalación/análisis , Exposición Profesional/análisis , Estados UnidosRESUMEN
A diesel particulate matter analyzer capable of direct, real-time measurement of engine exhaust particulate is necessary to effectively institute source control technology currently being used on diesel equipment and to ensure that the control measures are working. To investigate the potential of a differential pressure monitor to measure diesel particulate matter in undiluted exhaust, samples were collected from three different diesel engines--Kubota, Isuzu, and Deutz--running under 12 different RPM and load scenarios. These measurements were compared to elemental carbon concentrations in the sampled exhaust as determined by using the NIOSH 5040 analytical method. Elemental carbon is used as a surrogate measurement for diesel particulate matter. The results of the two data sets were then compared using a linear regression analysis. The coefficient of determination (or R2) was calculated to be 0.98, 0.94, and 0.74 for the Kubota, Deutz, and Isuzu engines, respectively. R2 values of this magnitude indicate that this method can be successful in estimating elemental carbon emissions in the engines tested. In addition, for replicate samples, the coefficient of variation ranged from 7.1% to 10.2% with an average of 8.5%. These data indicate that this method could prove useful to mechanics as they work to maintain engines and DPM control technologies.
Asunto(s)
Química Física/métodos , Monitoreo del Ambiente/métodos , Emisiones de Vehículos/análisis , Carbono/análisis , Tamaño de la Partícula , Presión , Análisis de RegresiónRESUMEN
This study investigated the bias introduced by an inlet sampling line on a respirable mass monitor. The 1.5-m electrically conductive, flexible sampling line conducts aerosol at a flow rate of 2.2 Lpm from a helmet-mounted inlet to a waist-mounted sensor for mass concentration measurement. Particulate transport was modeled for each section of the sampling line and considered the effects of diffusion, gravitational settling, and inertial impaction. An estimate of respirable mass concentration measured with the sampling line was determined by integrating assumed workplace aerosols with the transport curves. The bias introduced by the sampling line was then calculated by dividing the difference between the respirable mass concentration with and without the sampling line by that without the sampling line. For the current sampling line, in which the inner diameter is 4.83 mm, bias was calculated as -0.3 percent, -2.4 percent, -4.6 percent, and -6.7 percent for four test aerosols with mass median aerodynamic diameters of 0.6 microm, 4 microm, 12 microm, and 30 microm, respectively. Optimization studies suggest that increasing the sampling line with a larger inner diameter by a factor of 1.25 to 1.75 will minimize bias to below -3.0 percent. An experimental study confirmed that bias due to the presence of the sampling line is small.