Activities with fibrous nanomaterials and other materials may put workers at health risk if alveolar fibre dusts are inhaled that are biopersistent and exceed a critical fibre length.
In addition, toxicological studies on fibrous nanomaterials have shown indications of a correlation between the bending stiffness (rigidity) and the toxic potency of fibre dusts. However, there is still a lack of standardised methods for determining the bending stiffness of fibres that enable using this correlation for risk assessment and hazardous substances and chemicals legislation.
In this project, the Federal Institutes for Occupational Safety and Health (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, BAuA) and for Materials Research and Testing (Bundesanstalt für Materialforschung und -prüfung, BAM) developed a method for determining the rigidity of fibres with diameters ranging from a few nanometres to a few micrometres. The method uses so-called dynamic scanning electron microscopy to measure a fibre's shape, diameter and length and to determine its resonance frequencies. The method was successfully tested on carbon nanotubes and silicon carbide nanowires.
The high experimental effort for preparation and analysis of fibres to be characterised currently prevents the procedure from being established as a routine method for regulatory purposes. Nevertheless, the method is being used to characterise reference fibre dusts for ongoing research work at BAuA. The research investigates in culture experiments how scavenger cells of the immune system (macrophages) react to fibre dusts and whether rigid fibres can cause cell-damage already in such relatively short-lived cultures.
Unit 4.5 "Particulate Hazardous Substances, Advanced Materials"