Using funds from the Federal Environment Ministry, the Federal Environment Agency (UBA) commissioned a study of the long-term effects of two selected nanomaterials on environmental organisms (2009 to 2012). Various tests were carried out with nanoscale titanium dioxide and nanoscale silver. The aims of the study were to increase the knowledge on how to investigate nanomaterials with regard to their ecotoxicological effects and to show whether the standardised testing methods of the time were suitable for the investigation of nanomaterials. The results of the project were included in the work of the OECD Working Party on Manufactured Nanomaterials (WPMN) regarding safety research on nanomaterials. They also supported the WPMN in reviewing the applicability of the OECD Test Guidelines to nanomaterials.