Mining Contract: Novel Application of Fourier-Transform Infrared Spectroscopy and Optical Particle Counting for the Real-time Quantification of Respirable Crystalline Silica and Dust in the Mining Environment

Keywords: Particle sizing instruments Silica dust

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Contract #	75D30120C09916
Start Date	9/15/2020
End Date	5/26/2023
Research Concept	Current commercially available methods do not allow for timely or continuous assessment of respirable crystalline silica (RCS) concentrations, either on site or on-person and in the breathing zone (i.e., monitor wearability for direct exposure assessment). These factors represent a substantial barrier to widespread, actionable RCS exposure assessment in mine workers.

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

Under this contract, existing technologies will be combined to produce and validate a portable real-time monitor capable of assessing mining dust and, specifically, RCS. A wearable version of this instrument will be produced and validated. This research will begin by adapting existing commercially available technologies used to assess particulate matter (PM) mass concentrations, size distributions, and composition for the real-time assessment of miners' exposures to dust and corresponding RCS, and then will aim to reduce the size into a wearable form factor for personal applications. This research proposes to integrate a Fourier-transform infrared (FTIR) spectrometer and suitable light source with the hardware of an AethLabs MA200 Black Carbon instrument—a palm sized, battery-powered, wearable, multi-wavelength instrument with a mechanized filter tape advance mechanism—in order to realize a wearable RCS monitor. Candidate FTIR interferometers, detectors, and light sources will be evaluated.

The research will confirm wavelength specificity at the detector accomplished by means of diffraction grating, Michelson interferometer, linear filter array, tunable filters, diode, pyroelectric detectors and others to achieve optimized designs for RCS sampling and analysis techniques amenable to using a "direct-on-filter" method, and to apply those techniques to the development of the integrated analyzer. Performance comparison to laboratory grade FTIR for quantification of RCS lab-generated and field-collected samples will be completed.

Further development will be completed of prototype monitors, targeting a miniaturized wearable monitor for RCS, producing at least two units. The size of the system components will be reduced, with a target of operation through an 8- to 10-hour work shift with a quick and easily replaceable lightweight battery. Ideal dimensional specifications will be identified for the product relying on examples of existing wearable mining technology such as the Thermo PDR3700 wearable dust monitor to help guide the design. As size, weight, and power are important feasibility constraints for a wearable RCS monitor, the applicability of the off-the-shelf commercially available interferometers and spectrometers that were evaluated in previous miniaturization efforts will be determined. The end focus will be to ready a fully contained, reproducible device that can be used to make RCS measurements with the smallest possible form factor.