Define nanos

Defining nanos – When size defines the object

By AVICENN Team – last edited Jul 2022

Nanoparticles, nano-objects, nanomaterials: the terms referring to the nano world are multiple, complex, but not always interchangeable! It is important not to confuse them. While some refer to physico-chemical characteristics nanos, others are regulatory definitions, which change according to sectors and countries.

Some important concepts

Nanoparticle < Nano-object ≠ Nanomaterial

A “nanomaterial” (which has different scientific and regulatory definitions) is distinguished from a “nano-object”, a material having one, two or three* dimensions at the nanometric scale.

When they have three nanometric dimensions, nano-objects are considered “nano-particles”:

Primary particle, agglomerate and aggregate

Nano-objects may tend to group together to form larger sets called aggregates et agglomerates.

Several definitions for nanomaterials

Coexistence of different regulatory definitions

At the international level, several definitions of nanomaterials co-exist with different criteria (ISO, OECD, Scenihr, SCCP, European Regulations, ACC, etc.)¹See more details in the following publications:
- Comparative assessment of nanomaterial definitions and safety evaluation considerations, Boverhof DR et al., Regul Toxicol Pharmacol., 73(1):137-50, October 2015
- Factsheet on the definition of nanomaterials, CIEL, ECOS, Öko-Institut eV, November 2014
– Appendix 2 “Review of existing definitions of nanomaterials” of the report Assessment of the risks associated with nanomaterials – Issues and update of knowledge, ANSES, April 2014 (online May 15, 2014). By way of illustration:

• theInternational Organization for Standardization (ISO) defines a nanomaterial²See ISO/TS 80004-1 standard, ISO, 2015 as " a material of which at least one external dimension is in the nanoscale or which has an internal or surface structure in the nanoscale” (the nanometric scale being presented as comprised “approximately” between 1 and 100 nm). She adopted the term NOAA to encompass all of the Nano-Objects, their Agglomerates and Aggregates greater than 100 nm”.

• la recommendation European Commission's 2022 definition, is not legally binding, but it is intended to be taken up, as that of 2011 that it replaces, in several regulations at European level (REACH, Biocides et Medical devices) and French (mandatory declaration R-nano).
  It is more restricted: unlike that of the ISO, it excludes internally nanostructured materials.
  Pending the finalization of a guide from the Joint European Research Center (the JRC) for the 2022 recommendation, it is possible to refer to the guide published in 2020, “ the NanoDefine Methods Manual“, in which the JRC provided terminological and methodological clarifications to determine whether or not a material fell within the 2011 definition.

• la European regulations in the cosmetics sector has yet another specific definition: an insoluble or bio-persistent material, intentionally made and characterized by one or more external dimensions, or internal structure, on a scale of 1 to 100 nm« ³View notes published in July 2021 by the DGCCRF and the ANSM ; this regulation is currently being revised, with uncertainty about the definition that will be used ultimately⁴See our article “Towards a new nano definition in the future Cosmetics Regulation… yes, but which one? », WatchNanos, July 2022.

• European food regulations defines a nanomaterial as a " intentionally produced material having one or more dimensions of the order of 100 nm or less, or composed of distinct functional parts, either internal or on the surface, many of which have one or more dimensions of the order of 100 nm or less, including structures, agglomerates or aggregates that may be larger than 100 nm in size but retain typical nanoscale properties« 

Summary table :

What consequences?

The co-existence of different definitions complicates the work of producers / importers / distributors who must:

• declare their nanomaterials to the health authorities, as is the case in France (r-nano register) and also in other European countries and at Community level (Reach)
• and label differently depending on the sectors of use (cosmetics, biocides, food).

Nevertheless, the problems linked to the coexistence of different definitions ultimately concern mainly the suppliers of ingredients. Indeed, when substance characterization is done in a complete and adequate manner upstream and transmitted correctly to downstream actors, the latter can apply the appropriate definition to their sector and apply the necessary measures: labeling and notification(s), if applicable. 

This situation could have been avoided if the European register project nanomaterials with a harmonized definition at Community level had not been hindered by the European Commission under pressure from industrial federations.

In the meantime, the temptation is great for many industrialists to adopt avoidance strategies, with the use of nanomaterials whose size and number distribution can flirt with the set thresholds (with less than 50% of particles exceeding 100 nm for example) in order to escape the regulations, while retaining the desired properties...