Adventures in number metrics: Regulatory nanodefinitions applied to large portfolios containing small particles

W. Wohlleben, P. Mueller

Keywords: nanodefinition, counting, dispersion, specific surface, decision-tree


Regulators around the world have generated nano-definitions with several elements: size ranges, cut-offs, intention, size-specific properties and/or properties such as solubility. But particulate materials, both conventional and engineered, exhibit a distribution of particle sizes, are often polymorph. The number metrics metrics employed for size distributions and cut-off criteria is a game-changing decision. Confronted with huge existing portfolios of particulate materials, a substance- and method-specific decision-tree and measurement strategy is of urgency, such as those developed by the NanoDefine FP7 project (by 2017). Some very first modifications to be implemented by a revision or technical guidance are addressed in this talk, and supported by experiments, including the practical value of sector-specific ‘best possible dispersion’ protocols to resolve the inconsistent treatment of aggregates and nanoporous materials and to enable the wider use of techniques other than EM and VSSA, including further the general validity ranges of methods for powders and for suspensions, the concepts of grouping and of tiered measurement strategies with integrated validity checks. see also: Environ Health Perspect (2013), DOI: 10.1289/ehp.1306957; J Nanopart Res (2012) 14:1300.