Both reports arose from the Danish project “NanoDEN”, commissioned by the Danish EPA.Environmental fate and behaviour of nanomaterials by Hartmann N, Skjolding L, Foss Hansen S, Gottschalk F, Baun A (2014)The report 1 provides an overview of the to date knowledge regarding processes relevant for environmental fate and behaviour of ENMs. Key environmental processes are identified, discussed and prioritized according to their relevance as inputs for fate modelling for ENMs. Furthermore, knowledge gaps are identified and prioritised with regard to