The European Commission recently published its recommendation on a common definition of the term "nanomaterial" for regulatory purposes. Proper implementation of this definition requires appropriate tools and methodologies for which measurement aspects are crucial. This report describes the requirements for particle size measurements of nanomaterials based on the definition. It discusses the related generic measurement issues and reviews the capabilities of the measurement methods currently available. Moreover, it illustrates with practical examples the measurement issues that remain to be solved. This report does not cover other related issues, such as the implementation of the definition by means other than through measurements, or methods to detect specific nanomaterials (such as fullerenes and single-wall carbon nanotubes), measurements to assess exposure to or effects of nanomaterials, or the detection and measurement of nanomaterials in consumer products. These will be addressed in a follow-up report.
