The problem of plastic debris in the aquatic environment receives exponentially growing public and governmental awareness. At this moment, we urgently need a risk assessment (RA) framework for plastics. To develop a RA, major knowledge gaps with respect to nano- and microplastic fate and effects in fresh waters should be filled. In collaboration with two other PhD candidates and more than 20 other partners, this project will study the most important questions related to these knowledge gaps. Major tasks relate to (a) emission based mass balance modelling of plastic pollution, (b) mechanistic spatially explicit transport modelling of plastics, (c) quantification of fate and bioavailability processes for nano- and microplastics and finally (d) risk assessment for plastic pollution in the Dutch freshwater environment with implications for the marine system.