One of the challenging aspects of attempts to regulate emerging nanotechnology is the definition. Proposing a "definition" for nanotechnology is not as straightforward a process as it may seem; applying a strict, universal definition of nanotechnology to all applicable fields and products may not be an appropriate science-based approach. Inclusion of nanometer-sized active ingredients or excipients in a product does not by itself determine a product's safety and efficacy (i.e. size alone is not always itself an indicator of toxicity). Then there is the issue of distinguishing between engineered nanomaterials and those naturally occurring at the nanoscale.

Last week, the European Commission took another step in this debate, unveiling a new, common nanomaterial definition as a basis for regulation. Nanomaterials are defined as those whose main constituents measure between 1 and 100 billionth of a meter; that is, a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the target size range.