AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Measurement of Silica on Filter Samples of Coal Dust Using a Field-Portable FTIR Method
NATE MURPHY, Zachary Briggs, Andrew Kilpatrick, Courtney Quinn, Mackenzie Wadas, Emanuele Cauda, Art Miller, NIOSH
Abstract Number: 432 Working Group: Aerosol Exposure
Abstract The inhalation of toxic substances is a serious danger faced by miners. Inhalation of silica is of particular concern due to the recent rise in cases of coal workers pneumoconiosis and silicosis. There is currently no field-portable instrument to measure airborne silica to give miners timely feedback on their exposure. NIOSH is therefore investigating and developing technologies for end-of-shift or real time measurement of silica in coal mine dusts. In a recent study, Fourier Transform Infra-Red spectrometry (FTIR), conducted in transmission mode, was used to estimate the mass of silica in coal dust samples deposited onto a PVC filter. However, transmission-based FTIR is not applicable for analyzing filters used in the Personal Dust Monitor (PDM) that will be increasingly employed in US coal mines. This study therefore focused on the use of FTIR conducted in Diffuse Reflectance (DR) mode as a method for measuring silica on PDM filters. The DR method was used to analyze lab-generated filter samples of pure silica (Minusil) and coal dust, prepared at five different mass loadings in the ranges 100-800 µg and 500-4000 µg respectively. Results suggest that DR can accurately quantify silica in coal dust deposited on PVC filters, and to a lesser degree on the newly developed “ashable PDM filters”. The DR measurements correlated well with the mass of silica on PVC and ashable filter samples (linear regressions yielded R^2 values of approximately 0.95 and 0.90 respectively). However, when applied to PDM filters in their current form, DR-quantification of silica is not possible. It was determined that the problem stems from the current use of quartz fiber filters in the PDM. It was concluded that the PDM filters could be analyzed for silica more accurately if redesigned with silica quantification in mind, and if the new ashable filters are used, the accuracy will be limited to approximately +/- 15% RSD.