AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
How Deposition Uniformity Affects FTIR Analysis of Filter Samples
ART MILLER, Pamela Drake, Ryan LeBouf, Nate Murphy, Emanuele Cauda, NIOSH
Abstract Number: 489 Working Group: Health Related Aerosols
Abstract Miners face a variety of respiratory hazards, including exposure to silica-bearing coal dust which can lead to silicosis, a potentially fatal lung disease. The current method for measuring airborne silica is to collect a filter sample of coal dust, send it to a laboratory for analysis and wait for a report, which may take weeks. The mining workplace is dynamic, transitioning among different geological strata with potentially varied silica levels, and more timely data on silica levels could help reduce exposures. To address this, NIOSH is investigating field portable end-of-shift (EOS) methods for measuring silica on filter samples of coal dust. Since many field portable methods entail partial, localized analyses on the filters, spatial uniformity of dust deposition can affect the accuracy and repeatability of the EOS methods. This study was designed to assess the influence of deposition uniformity on the accuracy of a portable Fourier transform-infrared method used for measuring silica on coal dust samples. Using laboratory-generated silica and coal dusts and three different types of sampling trains, multiple sets of filter samples were generated at five different dust loadings. Silica was measured by FTIR at nine locations across the face of each filter and the data analyzed by a multiple regression analysis technique using SAS software. This entailed comparing various models for predicting total silica mass on the filters using different numbers of “analysis shots”. Results show that the predictive accuracy of the various models increases with the number of shots used for the analysis, and ranges from about 4% to 10% depending on the number of points analyzed and the type of sampling train used (which was shown to affect the uniformity of deposition on the filter). Data indicate that single shot analyses of coal dust samples collected onto PVC filters in 3-piece cassettes, yield predictivity of silica mass with error of less than +/- 10% for a wide range of filter loadings. The RSD of that simplified approach is approximately 8% which makes it a simple, accurate method for EOS measurement of airborne silica in mines.