Mining Project: Measurement and Analysis Tools for Elongate Mineral Particle Exposure in Mining
| Principal Investigator |
|
|---|---|
| Start Date | 10/1/2023 |
| Objective |
The current standard method for assessing exposure to airborne fibers uses a cowl sampling head and fibers are counted by a trained technician using a phase contrast microscope (PCM). The detection limit of fiber counting is defined by the magnification of the microscope, which can vary according to the optics and set-up, while the analytical sensitivity is a function of air volume collected onto the filter and the area of the filter analyzed. The variability of counting asbestos fibers has improved but it is still higher compared to other analytes. Because the cowl sampling head is not a size-selective sampler, it collects particles not correlated with mesothelioma or other respiratory disease. As a result, the decision about whether the elongate mineral particle (EMP) is a regulated fiber is left to the professional judgment of the analytical technician. A recent finding from a related NIOSH Mining Program project, “Understanding Elongate Mineral Particle Exposure in Mining,” showed that classification of asbestos types with Fourier transform infrared (FTIR) and multivariate data analysis is possible and that classification of asbestos types and their non-asbestiform analogues is also possible. By using these techniques, an end-of-shift measurement method for EMP exposure may provide for relatively rapid EMP monitoring and improve the protection of miners from EMP exposure. |
| Topic Areas |
Research Summary
Approach
The NIOSH publication, “Asbestos Fibers and Other Elongate Mineral Particles: State of the Science and Roadmap for Research,” recommended the development of improved sampling and analytical methods for asbestos fibers and other EMPs. The research undertaken as part of the current project would create a size-selective sampler capable of collecting EMPs that have been shown to be relevant to occupational diseases. The current EMP method uses a cowl sampling head during EMP collection; however, the cowl sampling head is not a size-segregated sampler and it will collect particles not correlated with mesothelioma or other respiratory diseases.
In this first task as part of this pilot project research, both asbestiform and non-asbestiform particles will be collected using size-selective sampling heads capable of collecting particles with an aerodynamic diameter in the respirable range, and these data will be compared with samples collected using the cowl sampling head. A fluidized bed aerosol generator will be used to generate a mixed dust atmosphere of elongate mineral particles, and Arizona road dust and samples will be collected in an aerosol chamber. The analysis of samples will be completed using a scanning electron microscope to collect information on size and geochemistry.
Planned Impacts and Outcomes
This pilot project will use the PLS_Toolbox (v8.9.1) and multivariate data analysis, involving principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA), to elucidate patterns of similarity within FTIR spectra derived from distinct mineral types. The comprehensive spectral range of each sample will be employed in all subsequent data analyses. Each model utilizes cross-validation using Venetian blinds with 10 splits and a blind thickness of 1. Both analyses will be preprocessed via the Savitzky-Golay 1st derivative (second-order polynomial with a 15-wavenumber smoothing window), with 1-normalization followed by mean centering.
The NIOSH project, “Understanding Elongate Mineral Particle Exposure in Mining,” showed that analysis of FTIR spectra, using multivariate data analysis for EMP measurement, may be applied for qualitative and/or quantitative bulk and/or airborne asbestos sample analysis. However, further research is needed to first validate the procedures by comparing to the current standard asbestos analytical methods and then finalizing development of the methods. Toward this end, the above investigations will be conducted in this research project.