The validation of the method must be done with a good choice of positive and negative controls (TiO2, carbon black ...). The choice is difficult, data from exposed human or animal are poor.

The vehicle used for the negative controls will include all the components used for dispersion except the MNs. For the positive controls, several genotoxic chemicals (depending on the test performed, for instance mitomycin C is used in the in vitro micronucleus assay) will be included which would anyway be done for the validation of the method. There are only few data available on possible nanoparticle positive controls in the different tests. Partners have chosen nanoparticle controls to be included in all experimental series, based on preliminary positive data available in some of the participating laboratories. ZnO will be used in the in vitro studies, and carbon black in the in vivo studies. The tests responding positively shall be identified with these candidate nanomaterials.