The Netherlands National Institute for Public Health and the Environment (RIVM) announced on September 6, 2017, that an RIVM researcher, Joris Meesters, modified SimpleBox, a distribution model for chemicals, to create SimpleBox4nano, a model to calculate concentrations of nanoparticles in water, soil, and air.  SimpleBox4nano includes new processes that specifically apply to nanoparticles, such as the clustering of particles.  Meesters tested the model using three metal oxide nanoparticles:  titanium dioxide, zinc oxide, and cerium dioxide.  According to RIVM, the SimpleBox model results confirm the clumping of nanoparticles with the many natural particles in the environment (clay, sediment, organic matter).  The research shows that SimpleBox4nano can be used to estimate the distribution of nanoparticles in the environment.  RIVM describes SimpleBox4nano as a “major step forward in the environmental risk assessment of nanoparticles.”