Coming soon to a workplace near you: Field-based respirable crystalline silica monitoring
The NIOSH Mining Program aims to eliminate mining fatalities, injuries, and illnesses through relevant research and impactful solutions. More than 65 engineers work in the NIOSH Mining Program representing many disciplines including chemical, electrical, mechanical, industrial, mining, software, and general engineering. It is through the various lenses of these disciplines that NIOSH tackles a host of challenges in the mining industry. One such example is exposure to silica.
Worker exposure to respirable crystalline silica (RCS)—which can cause severe lung diseases—remains a major health concern in mining as well as in construction, oil & gas, and general industry. Having a quick, effective way to monitor RCS concentrations is crucial to combatting the potential negative effects of RCS exposure. Current RCS monitoring requires samples to be sent to an external laboratory for analysis, and it can take days or weeks for results to be available.
This time lag can mean workers who unknowingly worked in conditions with high RCS concentrations could continue to work subsequent shifts in similar conditions before getting sample results back and realizing they’ve been overexposed to RCS.
Researchers and engineers in the NIOSH Mining Program are addressing this problem by developing a novel, field-based monitoring approach that enables dust samples to be analyzed for RCS right at the mine site in only a few minutes. With this sort of on-the-spot analysis available, mines can assess the efficacy of engineering controls and work practices, and make necessary changes to optimize these controls.
This field-based monitoring approach for RCS is designed around the use of commercially available portable Fourier-transform infrared (FTIR) instruments. A transmission direct-on-filter (DOF) analysis was selected because it is readily compatible with the respirable samplers already used by health and safety professionals. DOF analysis also does not require any pre-treatment of samples, and it can be done without removing the dust sample from the cassette in which it was collected. A complete analysis takes only one to two minutes per sample, then that same sample can be sent to an outside laboratory if confirmation is desired.
Shown above: A dust sample is first collected using traditional samplers. The sampling cassette is removed and placed in a portable Fourier-transform infrared (FTIR) instrument in the field. The FTIR instrument examines the dust sample and offers a complete analysis in one to two minutes.
Engineers and physical scientists in the NIOSH Mining Program are currently working to refine and optimize the monitoring approach. The goal is to create an approach that will provide useful information to the health and safety professional, while keeping implementation as simple and user-friendly as possible.
The accuracy of the RCS analysis takes first priority. Research has identified confounding minerals present in the dust of mining environments that could affect accuracy. NIOSH is focused on designing specific quantification models to account for the presence of these minerals. An optimized 37-mm sampling cassette is currently under development through a cooperative research and development agreement between NIOSH and a sampling equipment manufacturer. The cassette is similar to the standard three-piece design used by most health and safety professionals, with a few key modifications that enable the DOF analysis while limiting the possibility that the sample could be damaged during analysis. Additionally, NIOSH is exploring combining the DOF technique with commercially available real-time respirable dust monitors to enhance the monitoring capability.
Finally, NIOSH is developing tutorials and a dedicated software application to support users in the implementation of this new approach. When finalized, the tutorials will guide users about how to select and set up equipment, analyze respirable dust samples, and interpret the resultant data using the NIOSH software.
This ongoing research has been supported and advanced by beta testers in the mining industry, who have used this method and provided feedback to NIOSH to improve both accuracy and usability. While this approach was developed specifically with the mining industry in mind, the tools and technologies are easily transferrable to other non-mining environments where exposure to RCS is a concern.
This is one example of how NIOSH engineers are working to protect U.S. workers. Please click here to go to the NIOSH Science Blog web page and share in the comments examples of workplace safety and health problems that engineers in your organization have helped solve.