Abstract
Continuous personal dust monitors (CPDMs) are mandated in US coal mines for sampling to demonstrate compliance with respirable coal dust exposure standards. They collect a physical sample to enable real-time mass monitoring, but no methods currently exist to directly analyze the sample. Capabilities for respirable crystalline silica (RCS) analysis could be quite valuable to determine an estimated RCS exposure. To this end, a three-step method has been previously proposed to (1) recover dust from the CPDM's filter stub, (2) transfer it onto a 25-mm polyvinyl chloride (PVC) filter, and (3) analyze for quartz (i.e., as a proxy for RCS) using Fourier Transform Infrared Spectrometry (FTIR). This study evaluated the method using 170 samples generated in a Marple chamber using five different dust materials. Results showed that predicted quartz mass values were well correlated with expected values (i.e., based on measured recovered sample mass and estimated quartz percentage for each material), with R2 = 0.97 across all samples. However, dust recovery efficiency was variable, ranging from 8 to 99% across all samples. For a field-based method, this could be problematic since the total recovered sample mass must be known to relate measured quartz mass to the RCS concentration in the sampling environment; thus, if recovery efficiency is variable, a means of estimating total recovered sample mass is needed.
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