Dustiness and aerosol characteristics of nanocellulose powders: Implications for workplace exposure and safety management.

Nanocellulose materials, including cellulose nanofibers and cellulose nanocrystals, are promising renewable materials with diverse industrial applications. However, potential worker exposure during the handling of dry powders remains a concern. In this study, the dustiness and aerosol characteristics of nine nanocellulose powders were evaluated using the small rotating drum method specified in EN 17199. Aerosolized nanocellulose was characterized using real-time instruments, gravimetric analysis, and microscopic observation of filter-collected particles. All samples generated respirable particles, with mass-based dustiness indices ranging from 10 to 300 mg/kg, comparable to those of other nanomaterials. Aerosolized nanocellulose did not appear as isolated fibers but rather as aggregated or agglomerated particles approximately 0.1-10 μm in size. These findings suggest that, under conditions represented by the rotating drum method, aerosolized nanocellulose predominantly appears as particulate matter rather than isolated fibers. Nonetheless, emission and exposure control measures can be necessary when handling dry nanocellulose powders, given the magnitude of their mass-based dustiness indices. The performance and limitations of portable aerosol instruments were also assessed. Optical particle sizer measurements were occasionally influenced by artifacts that may arise from high concentrations of particles larger than the respirable size range, while dust monitors tended to underestimate concentrations for samples containing a large fraction of coarse particles. Despite these limitations, these instruments can provide useful information for workplace safety management when their constraints are taken into account. Overall, this study provides a scientific basis for developing effective exposure assessment and control strategies to support safe handling of nanocellulose powders in occupational environments.