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Deposition uniformity of coal dust on filters and its effect on the accuracy of FTIR analyses for silica.

Authors
Miller-AL; Drake-PL; Murphy-NC; Cauda-EG; LeBouf-RF; Markevicius-G
Source
Aerosol Sci Tech 2013 Jul; 47(7):724-733
NIOSHTIC No.
20042844
Abstract
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 the method 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.
Keywords
Mining-industry; Miners; Coal-mining; Coal-miners; Coal-dust; Silica-dusts; Coal-processing; Analytical-instruments; Analytical-processes; Airborne-dusts; Air-filters; Equipment-reliability; Air-sampling; Air-sampling-equipment; Air-sampling-techniques; Filters; Samplers; Sampling-methods; Sampling-equipment; Dust-exposure; Dust-particles; Dust-samplers; Dust-sampling; Laboratory-equipment; Laboratory-techniques; Laboratory-testing; Mathematical-models; Particle-aerodynamics; Infrared-spectroscopy; Measurement-equipment
Contact
Arthur L. Miller, National Institute for Occupational Safety and Health, Spokane Research Lab, 315 E. Montgomery Ave., Spokane, WA 99207, USA
CODEN
ASTYDQ
CAS No.
7631-86-9; 14808-60-7
Publication Date
20130701
Document Type
Journal Article
Email Address
ALMiller@cdc.gov
Fiscal Year
2013
NTIS Accession No.
NTIS Price
Identifying No.
B20130801
Issue of Publication
7
ISSN
0278-6826
NIOSH Division
OMSHR; DRDS
Priority Area
Mining
Source Name
Aerosol Science and Technology
State
WA; PA; WV
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