Evaluating particle complexity in respirable coal mine dust using automated SEM-EDX with an integrated mineral...

Respirable coal mine dust (RCMD) is typically characterized assuming particles are compositionally homogeneous and independent; however, many particles may contain multiple constituents. In this study, pixel-level automated SEM-EDX with mineral liberation analysis was applied to 26 RCMD samples to quantify the prevalence and variability of complex particles composed of multiple constituents. Results show that complex particles are ubiquitous in RCMD and occur across mines, regions, and sampling locations, with variability dominated by mine-specific and mineralogical factors rather than spatial trends. Comparisons between direct-on-filter and recovered dust analyses indicate that complex particle populations include both mechanically fragile agglomerates and more persistent associations, including strongly bound aggregates. These findings demonstrate that particle complexity represents an important structural dimension of respirable dust exposure that is not captured by traditional metrics and highlight the value of advanced automated tools for improving characterization and interpretation of occupational aerosol exposures.