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Defining nanos

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Defining the term “nanos” – When the size defines the object

By the AVICENN team – last modification in March 2023

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 the physicochemical characteristics of nanos, others are regulatory definitions that change depending on the sector and country.

Some important concepts

Nanoparticle < Nano-object ≠ Nanomaterial

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

*When they have three nanometric dimensions, nano-objects are considered “nanoparticles”

Primary particle, agglomerate and aggregate

Nano-objects tend to group together to form larger sets called aggregates and 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
Fact sheet on the definition of nanomaterials, CIEL, ECOS, Öko-Institut e.V., November 2014
– Annex 2 “Review of existing nanomaterial definitions” of the report Evaluation des risques liés aux nanomatériaux – Enjeux et mise à jour des connaissances, ANSES, April 2014 (put online on May 15, 2014)
. As an example:

  • The International Organization for Standardization ( ISO ) defines a nanomaterial2Cf. ISO/TS 80004-1, ISO, 2015 as “a material of which at least one external dimension is at the nanoscale or which has an internal or surface structure at the nanoscale” (the nanoscale being presented as “approximately” between 1 and 100 nm). It adopted the term NOAA to encompass all “Nano-Objects, their Agglomerates and Aggregates greater than 100 nm”.
  • The European Commission’s 2022 definition recommendation is not legally binding, but it is intended to be included, like the 2011 recommendation it replaces, in several regulations at the European level ( REACH , Biocides and Medical devices) and French ( mandatory declaration R-nano ).
    It is more restrictive: unlike the ISO, it excludes internally structured nano- materials.
    While waiting for the finalization of a Joint European Research Center (JRC) guide for the 2022 recommendation, it is possible to refer to the guide published in 2020, “the NanoDefine Methods Manual“. In this document, the JRC provided terminological and methodological clarifications for determining whether or not a material falls within the 2011 definition.
  • The European regulation in the food industry defines a nanomaterial as a “intentionally produced material having one or more dimensions of the order of 100 nm or less, or composed of discrete functional parts, either internally 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 but retain properties typical of the nanoscale

What are the 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 in other European countries as well and at the EU level (Reach)
  • label them differently depending on the sector of use (cosmetics, biocides, food).

Nevertheless, the problems related to the coexistence of different definitions ultimately concern mainly the ingredient suppliers. Indeed, when the characterization of the substances is done in a complete and adequate way upstream and transmitted correctly to the downstream stakeholders, these can use the definition appropriate to their sector and implement the necessary labeling and notification(s).

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

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

Elsewhere on the web

Any questions or comments? This information sheet compiled by AVICENN is intended to be completed and updated. Please feel free to contribute.

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This sheet was originally created in April 2011

Notes and references

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