The European Commission (EC) is seeking public comments on its proposed definition of nanomaterial. The proposal defines a nanomaterial as that material which meets at least one of the following criteria: (i) it consists of particles with one or more external dimensions in the size range of 1 nanometer to 100 nanometers for more than 1 percent of their size distribution; (ii) it has internal or surface structures in one or more dimensions in the size range of 1 nanometer to 100 nanometers; or (iii) it has a specific surface area by volume greater than 60 square meters by per cubic centimeter, excluding materials consisting of particles with a size lower than 1 nanometer. Comments may be electronically submitted to the EC by November 19, 2010.