An unambiguous definition of the term “nanomaterial” is needed for regulatory purposes, a July 2 report from the European Commission’s Joint Research Center concludes. The report suggests that the definition apply only to particulate nanomaterials, be broadly applicable to legislation in the European Union and worldwide, and use size as the only defining property. Concerns about the potential health and environmental risks of nanomaterials have prompted calls for strong government oversight of products that contain nanoscale substances. But the word nanomaterial currently has numerous definitions. Regulatory agencies must define what needs to be regulated before they can issue regulations, the report emphasizes. “No internationally harmonized definition yet exists that would fulfill the requirements for entering into legislation, even though a wide range of definitions have indeed been discussed and proposed,” the report notes.