How to Define a Nanomaterial

It is commonly assumed that the science community has established a definitive definition of a nanomaterial. ie “Nanomaterial’ means 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 size range 1 nm-100 nm.  
Should this be the accepted definition?
With regulatory bodies continuing to assess to legislate on safety/toxicology of nanomaterials a realistic, real-world definition is needed, with emphasis perhaps based more on application? For example, if a material at 80nm behaves exactly the same way as it does at 200nm, then why should it be regulated differently?
The problem we all have is that different materials change their properties at differing sizes – so to define a nanomaterial purely based on its size is being questioned.
Posted in Reference, Research, Safety.