Towards a surface metric to measure the dustiness of nanomaterial powders
Résumé
The relevance of dustiness methods is increasingly recognized in the preliminary exposure evaluation of workers handling nanomaterials in powder form, and should also be transposed to the assessment of environmental risk in the future. So far, the methods recommended in the current European standards mainly indicate to determine a mass-based dustiness index [mg.kg-1 ], whereas the surface area is regularly put forward as a more appropriate determinant to assess the pulmonary toxicity of nanoparticles. In this study, we describe an operational methodology leading us to propose a surface metric to determine the dustiness index [m 2 .kg-1 ] of nanoparticulate matter. To this end, we demonstrate the equivalence between the external specific surface area of a nanopowder and that of its aerosol with five nanomaterials produced and used on an industrial scale, and covering a range of external specific surface areas from 35 to 230 m².g-1. Compared to the conventional mass-based dustiness index, the surface-based dustiness index is 1) more discriminating, allowing to cover an additional order of magnitude, and 2) has an impact on the powder ranking with potential consequences on the preventive measures to be implemented. Finally, our proposal has the potential to be included in future revisions of European standards for workplace exposure and dustiness measurement, provided that further experimental results on surface-based dustiness indices comfort these preliminary data.
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