150 The Innomat.Life Extended Fibre Human Risk Banding Scheme

Abstract High aspect ratio materials (HARMs) like multi-walled carbon nanotubes (MWCNTs) show material properties that enable innovative applications but also raise concerns about harmful effects to humans due to their asbestos-like pathogenicity. The fibre-pathological paradigm was established for asbestos and other HARM, linking fibre-specific adverse effects to certain material properties such as fibre length, respirability and bio-persistence. A new risk banding scheme for such hazard- and exposure-related properties is introduced. For each relevant property, we defined descriptors and developed/validated methods for their measurement. Based on results from studies conducted in the project or obtained from literature, we defined quantitative band limits. While the fibre-pathological paradigm acted as a starting point, observations of in vitro effect of nanofibers motivated us to incorporate additional properties. Studying macrophage-fibre interactions led us to highlight the importance of the flexural rigidity of fibres for their uptake by macrophages. Also, the bundling of thin constituent fibres was recognized as a mechanism possibly generating less flexible and, therefore, more harmful inhalable particles with high aspect ratio from harmless precursors. Transformation dynamics of fibres in fluids like the phagolysosomal medium were investigated as well to gain a better understanding about fibre bio-durability. Overall, the risk for humans exposed to HARMs is described by the risk banding scheme in which property bands relevant for the hazard potential were juxtaposed to the respective exposure potential. We present results for a selection of HARMs including multiple MWCNTs with varying properties, TiO2 fibres, SiC whiskers, as well as silver and copper nanowires.