Hygienists increasingly perform on-site quantification of Respirable Crystalline Silica (RCS) from dust samples collected over each shift. This cost-saving methodology determines the percentage of RCS over a full shift as soon as it ends, providing a rare window of opportunity to take corrective actions and implement controls.
Both UK’s Health and Safety Executive as well as the National Institute for Occupational Safety and Health (NIOSH) have developed a direct-on-filter analysis method using a portable Fourier Transform Infrared Spectrometry (FTIR). Health and Safety Executive developed the FTIR method for 25 mm filters whereas NIOSH’s Field Analysis of Silica Tool (FAST) was developed for 37 mm filters. This analysis method takes advantage of the specific silicon-oxygen doublet peak in the infrared spectroscopy to identify and quantify silica collected on a PVC filter. The application of the FAST method to copper mines has proven to be challenging because of the vastly different mineral content that interferes with the silicon-oxygen doublet peak.
At Nanozen, using our internal DustCount 25 mm filter, we have successfully combined the FAST method with the analytical Standard Addition technique for Coal, and metal mines such as copper and iron. Mineral contents are not only different from mine to mine, they are often very different between processes and regions within one mine. Thus, combining NIOSH FAST method with Standard Addition we were able to account for the variability of interferences in different mines and different areas within mines. Our ability to apply and validate the standard addition technique calibrated with Inductively Coupled Plasma Mass Spectrometer (ICPMS) as well as by NIOSH 7500 XRD analysis, to quantify RCS in copper and iron mine matrixes is very encouraging for us. The detection limit on the pure quartz on PVC filter is 0.001 mg.
Effective and timely quantitation of respirable crystalline silica is crucial to reduce and eliminate exposure to RCS-related lung diseases and cancer. Imagine being able to determine the percentage RCS post-shift, and perhaps correct and mitigate exposure situations the very next day or on the same day of sampling! The standard Addition technique combined with NIOSH’s FAST method has proven to be a very powerful tool for us and our industry partners to identify problem areas and focus control investment and management, particularly during this challenged post-Covid budget situation worldwide.
Please feel free to contact us if you would like to learn more or to find out how to send us dust samples to enable us to develop FTIR methods for your specific situation.