In the course of the German project nanoGRAVUR to develop a framework for the grouping of nanomaterials concerning their risks, the IFA performed the determination of exposure during grinding of selected nanocomposites. The goal was to investigate whether grouping of physical-chemical characteristics of nanomaterials influences the exposure and thus the risk.
Composites on basis of epoxy resin, hardened cement mixtures, and aluminium with the additives of nano objects from the groups of fibres (CNT, WS2), platelets (graphene) and compact particles (TiO2, SiO2, carbon black) were chosen. Grinding exposure tests were carried out and number and mass concentrations were determined at the worker and near to him. Particle number concentrations ranged between 5600 and 23000 1/cm³ and only the epoxy resin composites showed a decrease with adding nano-objects, lowest with WS2. The added nanomaterial is less influencing the exposure than the matrix material, which is in accordance to pure release measurements.
Besides the exposure determination, the assessment scheme for describing the risk at workplaces had been worked out. The influence of material properties on their hazard like bio-resistance, toxicity (or rigidity for fibres) and modulating properties (agglomeration, critical dimensions, dustiness) has been grouped and class boundaries defined. Similarly, the exposure was classified by using information on material processing and concentrations at the workplace. Combining the information on hazard and exposure leads to the risk specified in three levels.