Identification of nanomaterials through measurements : points to consider in the assessment of particulate materials according to the European Commission’s Recommendation on a definition of nanomaterial

This report addresses identification of nanomaterials according to the European Commission's Recommendation on the definition of nanomaterial (2011/696/EU) by measurements and discusses options and points to consider when assessing whether a particulate material is a nanomaterial or not. The primary criterion to identify nanomaterials is the median of the number-based distribution of the constituent particles' external dimensions, regardless of whether these particles appear separate from one another or are parts of aggregates or agglomerates. The main steps in the nanomaterial identification process are collecting information on the material, acquiring knowledge of the measurement method(s), matching method(s) and material, sample preparation, measurement/analysis and decision (nanomaterial / no nanomaterial). Assessment of particle size measurements requires specification of the measurand, the physical principle of the measurement technique, the applied sample preparation protocol, the covered size range and the data analysis procedure to allow a reliable classification of a material according to the EC nanomaterial definition. A variety of screening and confirmatory techniques is available to analyse particle size distributions. Screening techniques do not measure directly the number-based distribution of the external particle dimensions, but they are fast and inexpensive and still allow to positively identify a material as a nanomaterial. Confirmatory techniques are usually more costly and time-intensive, but may provide a more reliable classification and allow resolving doubts or disputes. The volume specific surface area can serve as proxy to identify nanomaterials, provided that certain requirements are fulfilled. For a correct classification whether a material is a nanomaterial or not, a thorough knowledge of the applied measurement method is needed to correctly interpret the outcome of a measurement and to understand whether a specific technique is fit for the purpose. Reliable measurement results can be obtained if a reference measurement system is implemented, which is typically based on documented and validated methods and reference materials. Best practices should be applied when reference measurement systems are not available. This report provides examples and practical options for consideration, including a flowchart that can assist users with relevant technical knowledge in the identification of nanomaterials.