NanoEHS – defining fundamental science needs: no easy feat when the simple itself is complexVicki Grassian – workshop co-organizer, workshop moderator and perspective writer and primary editor. Amanda Haes – workshop co-organizer, workshop speaker on Nanomaterials are not just small– fate from biological, chemical, and physical stability perspectivesand workshop moderator and perspectives article writer and primary editor. Imali Mudunkotuwa – workshop scribe and perspectives article major writer. Philip Demokritou workshop speaker on Dosimetry for in vitro nanotoxicology– too complicated to consider, too important to ignore. Agnes Kane workshop speaker on Nano-bio interactions: Mechanistic data gaps using carbon nanotubes as a case study. Catherine Murphy workshop speaker on Nanomaterials are not just small– fundamentals of size dependent behavior/properties. All other co-authors (James Hutchison, Jacqueline Isaacs, Young-Shin Jun, Barbara Karn, Saiful Khondaker, Sarah Larsen, Boris La

Nanotechnology is no longer in its infancy and has made significant advances since the implementation of the National Nanotechnology Initiative (NNI) in 2000. Incorporation of nanotechnology in many fields including information technology, medicine, materials, energy, catalysis and cosmetics has led to an increase in engineered nanomaterial (ENM) production, and consequently, increased nanomaterial use. In comparison, the generation of concrete and consistent evidence related to the environmental health and safety of nanomaterials (NanoEHS) is lacking. The main factors contributing to the slower progress in NanoEHS versusconventional EHS are related to the complexity, property transformations, life cycles and behavior of nanomaterials even in carefully controlled environments. Therefore, new systematic, integrated research approaches in NanoEHS are needed for overcoming this complexity and bridging current knowledge gaps. A workshop on “NanoEHS: Fundamental Science Needs” brought together scientists and engineers to identify current fundamental science challenges and opportunities within NanoEHS. Detailed discussions were conducted on identifying the fundamental properties that are critical in NanoEHS, differentiating between conventional and NanoEHS studies as well as understanding, the effect of dynamic transformations on nanometrology, role of dosimetry and mechanistic data gaps in nanotoxicology. An important realization that even simple nanoscale materials can be complex when considering NanoEHS implications was noted several times during the workshop. Despite this fact, a number of fundamental research areas to further the scientific foundation to address NanoEHS needs are suggested.