Several authors have highlighted the potential risks of nanoparticles (NPs). Still, little is known about the magnitude of emissions of NPs from society. Here, the method of explorative particle flow analysis (PFA), a modification of the more well-known substance flow analysis (SFA), is suggested. In explorative PFA, particle number instead of mass is used as flow and stock metric and explorative scenarios are used to account for potential technology diffusion and, consequently, potentially higher emissions. The method has been applied in a case study of the use phase of titanium dioxide (TiO2) NPs in paint, sunscreen and self-cleaning cement. The results indicate that the current largest emissions of TiO2 NPs originate from the use of sunscreen. One scenario implies that, in the future, the largest flows and stocks of TiO2 NPs could be related to self-cleaning cement. Gaps in current knowledge are identified and suggestions for future research are given.