Opinion on the Scientific Aspects of the Existing and Proposed Definitions Relating to Products of Nanoscience and Nanotechnol

This Opinion is concerned with the development of a conceptual framework for definitions in the areas of nanoscience and nanotechnologies. It is recognised that there is a need for an overarching framework for such definitions. This framework is based on an analysis of existing definitions in these areas, taking into account the need to avoid the promulgation of unnecessary terms and the requirements that it should be based on sound principles of lexicology. In view of the mandate of SCENIHR, this framework has been developed in the context of risk assessment procedures. Most of the concepts and behaviour patterns seen at the very small dimensions associated with nanotechnology are not new, and can be described by the existing terminology used at larger scales. It is recognised that it is impossible to stop individuals producing new words and definitions, but it is crucial that a new language is not adopted unnecessarily by the scientific community, and that on those occasions where it is required, it is consistent with established terminology. The framework takes into account a number of key factors. First, the selection of the size limits associated with the prefix ‘nano’ in all aspects of nanoscience and the nanotechnologies is somewhat arbitrary, and there does not appear to be any sharp change in either toxicokinetic or toxicodynamic properties of substances at any particular size. Secondly, many of the terms used in nanoscience are based on commonly used words such as ‘substance’, ‘matter’ and ‘material’ and terms in nanoscience should not conflict with the general meaning of such words. Thirdly, certain physico-chemical properties of the products of nanotechnologies are anticipated to have a major impact on their behaviour in the environment. Some of these properties of substances may be size dependent and, therefore, determinants for both exposure and interactions with living systems and the environment. Fourthly, it is recognised that certain forms of substances that have characteristics with very small dimensions are found naturally in the environment such that exposure of man and other species is inevitable. However, there has been, and will continue to be, a significant increase in the use of manufactured and engineered products of nanotechnologies, and it is this increased production which requires consideration of potential new words and definitions. Finally, with respect to small individual components, as size decreases, it may be necessary to distinguish between different sizes of particles and molecules for a variety of reasons. This does not imply, however, that there is, a priori, any greater toxicological, public health, or environmental health concern associated with any one size range. The existing and proposed definitions relating to products of nanotechnologies 4 The majority of terms that need to be considered in the context of nanoscience and nanotechnology are those that start with the prefix ‘nano-’, which specifically means a measure of 10 units, the nature of this unit being determined by the word that follows. There is absolutely no need to change the meaning of any scientific term, such as metre or material just because it is pre-fixed by ‘nano-’. The majority of terms used in nanotechnology are broadly self-explanatory. There are, however, some situations in which explanations are required in the development of a suitable framework for this terminology, especially for risk assessment purposes. The framework involves a hierarchy of terms, principal of which is ‘nanoscale’, which is considered here to be characterised by dimensions of the order of 100 nm or less. The framework builds on this concept of the nanoscale and develops series of definitions, appropriate for risk assessment purposes, based on considerations of size, shape and properties.