Nanomaterials are increasingly used due to their diversity of applications. Fibrous nanomaterials in particular pose new challenges for the determination of exposure at workplaces.
Up to now, the measurement of fibrous inorganic particles has been carried out according to VDI Guideline 3492 or, at workplaces, according to DGUV Information 213-546. However, both methods are not suitable for determining the concentration of airborne, nanoscale fibers, which are to be assessed as critical according to the WHO (length > 5 µm, diameter < 3 µm, L : D > 3 : 1). Both methods only count fibers down to a diameter of 0.2 μm. Therefore, in the nanoGRAVUR project funded by the Federal Ministry of Education and Research, the Federal Institute for Occupational Safety and Health (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, BAuA), together with the Institute for Occupational Safety and Health (Institut für Arbeitsschutz, IFA) of the German Social Accident Insurance (Deutsche Gesetzliche Unfallversicherung, DGUV) and the Swiss Social Accident Insurance Institution (Schweizerische Unfallversicherung, SUVA), laid the foundations for a new measurement and evaluation method for nanoscale fibrous materials. In particular, the need was emphasized to extend the counting range of VDI 3492 and DGUV-Information 213-546 at least down to a fiber diameter of 0.02 µm.
Within the DGUV-funded project, a validation of the new measurement method was now carried out at workplaces. The aim of the work was to check the measurement method for its suitability for practical use, both in terms of sampling, scanning electron microscopic evaluation and fiber morphology assignment, and also for a statistically reliable determination of concentration. After evaluation of the workplace measurements and adaptation of the measurement and analysis procedure, a revision of the first convention on the measurement strategy can now be carried out together with the partner institutes and the results of the work can be incorporated into relevant regulations (DGUV Information 213-546, VDI 3492, European Committee for Standardization CEN TC 137, OECD).
At the same time, the project compiled information on possible exposures to fiber dust during activities involving nanoscale fiber materials. An assessment of exposures to multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT) and other nanoscale fibers was made possible for the first time in relation to a benchmark concentration of 10,000 F/m³. It could be demonstrated that exposure determination by means of the new measurement method is in principle feasible at a detection limit of 10,000F/m³. Depending on the material properties, different fiber releases are expected with respect to the fiber shapes as well as the exposures. With the use of effective protective measures, fiber dust exposures are avoidable.
Unit 4.5 "Particulate Hazardous Substances, Advanced Materials"