The aim of this project is to establish an in vitro test platform for inhalation toxicity of nanoparticles. In order to work close to real conditions, it is planned to use materials and conditions for exposure according to the subacute and chronic in vivo studies carried out within the EU-project NANoREG. Cerium dioxide, barium sulphate and zinc oxide in nanoform will be tested first. For the establishment of the test platform, the alveolar epithelial cell line A549 will we used, which is already employed in numerous other studies on inhalation toxicity. In the following, the MucilAir system, a fully differentiated three dimensional model of human lung epithelium will be included in the investigations. The MucilAir system possesses all functional features of the airway epithelium, e.g. mucus secretion, beating cilia responsible for clearance of airways and tight junctions, membrane proteins functioning as intercellular links. As a further system, Precision Cut Lung Slices (PCLS) should be used in comparison. PCLS represent slices of rat lung that can be kept alive and exposed against particles under laboratory conditions. This system is of particular importance to mimic the interaction between different cell types as occurring in vivo. In order to perform exposition as realistic as possible, all investigated cell models will be cultivated on microporous membranes at the Air-Liquid Interface (ALI) within a exposure chamber. The cell cultures will be supplemented with medium from the basal side, nanoparticles will be applied within a dried aerosol. It is foreseen to analyse applied as well as internal dose by mass spectrometric methods and to compare the results with data out of subacute and chronic studies within NANoREG. Cytotoxicity, genotoxicity and oxidative stress will be investigated as toxicological endpoints.