Mining Contract: Filter Media and Holder Compatible with Personal Dust Monitor and End-of-Shift Crystalline Silica Quantification by Raman and FTIR Spectroscopy

Contract #	75D20121C11871
Start Date	9/1/2021
Research Concept	Coal mine dust inhalation is known to be associated with coal workers pneumoconiosis (CWP) and silicosis. There is a well-established relationship between exposure to RCS, a component often found in respirable coal mine dust (RCMD), and lung damage. RCS is typically found in rocks adjacent to the mined coal seams. As coal seams become thinner, more rock strata from the immediate roof and floor are mined, generating more RCS-containing dust. More powerful machinery may also create smaller silica particles. These changes could have contributed to the recent CWP increase in central Appalachian regions.

Contract Status & Impact

This contract is ongoing. For more information on this contract, send a request to mining@cdc.gov.

This contract research aims to find alternative filter media and redesign the filter holder for the continuous personal dust monitor (CPDM) to make the filter compatible with end-of-shift respirable crystalline silica (RCS) quantification by (FTIR) and Raman spectroscopy. The current filter media interferes with FTIR, making it useless to determine RCS. Furthermore, the particle deposit on the CPDM filter is not uniform, so the deposit portion measured by either method cannot be extrapolated to the entire filter.

For the above reasons, the filter holder needs to be redesigned to enable easy assembly and disassembly and to create a spatially uniform particle deposit. These goals are theoretically achievable via three-dimensional (3D) printing or plastic machining. Different models of portable Raman spectrometers are commercially available, but few studies have reported their use in RCMD analysis.

To overcome these barriers, this contract research will undertake four tasks, as described below.

A comprehensive literature review will be conducted to evaluate past studies on particulate sampling filter media as well as RCS quantification by FTIR and Raman. The review will first focus on filter media that have been used for CPDM, FTIR, or Raman analysis to define their specific requirements, and then will be expanded to a broader range of filter media used for ambient and workplace sampling.
Researchers will conduct an experimental evaluation of filter media to test their suitability for gravimetric mass as well as RCS analysis by FTIR and Raman. Specifically, tests will be done to evaluate background FTIR and Raman spectra and filtration efficiency and pressure drop.
The CPDM filter holder will be redesigned for easy filter retrieval. The current CPDM filter assembly is constructed from three components that are permanently assembled by sonic welding and therefore cannot be disassembled. New "snap-together" and "screw-together" designs used in many commercial filter holders will be explored. Prototype components will be made by 3D printing. After the design is finalized, the components will be made by plastic injection molding and machining.
Researchers will develop a direct-on-filter (DoF) RCS quantification by Raman spectroscopy with attention to selecting the most suitable laser wavelength, assessing interferences from other components found in respirable coal mine dust, refining sample collection and Raman measurements, and developing robust data analysis algorithms.