M1: Research Roundup Aerosols and Airborne Particulates/Standards and Regulations

Numerous studies have established a strong link between occupational exposure to aerosols and adverse health effects. It is important to characterize aerosols to understand their dispersion capabilities and their epuration kinetics in proximal and distal areas within work environments. For this reason, our research focuses on developing a network of optical particle counters (OPCs) that enables real-time measurement of aerosol dispersion and epuration kinetics across multiple points. OPCs are direct-reading instruments that measure particle distribution based on optical diameter. Before using these sensors as part of a network for workplace applications, several steps are necessary: 1) investigating the relationship between aerodynamic and optical diameters for different types of aerosols, as well as for various particle sizes; 2) checking the concordance of several OPCs when exposed to the same aerosol to identify and correct any systematic biases among the sensors; and 3) evaluating the precision of particle counting across a range of concentrations and different particle sizes. 

Direct-on-filter X-ray diffraction analysis (DOF-XRD) of respirable crystalline silica RCS) is a method for quantifying the different polymorphs of respirable crystalline silica in aerosol samples. XRD has the advantage of enhanced selectivity over other methods like Fourier-transformed infrared spectrometry or Raman spectrometry. The direct-on-filter XRD measurement: 1) is less cumbersome; 2) has lower overall uncertainty; 3) does not involve the destruction of the sample substrate; and 4) does not need redeposition on another substrate for measurement. This session will present: a) a guideline for optimizing the XRD measurement; b) the effect of measurement parameters and several optical elements in XRD systems demonstrated with actual RCS measurements; and c) preparation of an adequate calibration series for DOF-XRD. In addition, the outcomes of different validation schemes (limits of detection and quantification, expanded uncertainty) obtained from the same set of calibration measurements will be discussed. The last part of this contribution will deal with the potential of external standards, single reflection, multi-reflection, and full pattern methods for the quantification of respirable crystalline silica.