Respirable crystalline silica (RCS) dust with an aerodynamic diameter below 10 µm is a significant occupational health hazard associated with silicosis and other respiratory diseases. Reliable mineralogical characterisation of low-mass airborne dust is therefore important for workplace exposure assessment and risk management. This study investigates the application of thin-film X-ray diffraction (XRD) for the simultaneous identification and quantification of crystalline silica and clay minerals collected on air-filtration membranes.
Thin-film calibration standards were prepared using known masses of quartz ranging from 12.6 to 461.6 µg and kaolinite ranging from 12.4 to 231.2 µg. Characteristic diffraction peaks were fitted and integrated to distinguish the target minerals from contributions associated with the filter membrane. Calibration curves demonstrated linear relationships between integrated peak area and deposited mineral mass across the investigated concentration ranges.
The method was applied to respirable dust generated from an industrial mining-related material. Bulk quantitative XRD analysis showed that the source material was dominated by amorphous material at approximately 82 wt%, with kaolinite at 7 wt% and quartz at 1 wt% as the principal crystalline phases. Analysis of two respirable dust samples quantified kaolinite at 6.4–6.7 wt% and quartz at 0.8–1.2 wt%.
These results demonstrate that thin-film XRD can reliably quantify low levels of quartz and clay minerals in complex, low-mass respirable dust samples. The approach provides greater mineral specificity than infrared-based methods, differentiates silica polymorphs and supports quantitative multi-mineral analysis for improved occupational exposure assessment.