Definition of nanomaterial


In the EU, nanomaterials are covered by the same regulations that ensure the safe use of all chemicals and mixtures. This means that the hazardous properties of nanoforms of substances must be assessed to make sure they are used safely.

A standard and commonly agreed definition helps regulators identify and take decisions on these materials.

The European Commission has adopted a recommendation on the definition of a nanomaterial.

The recommendation defines a nanomaterial as:

A natural, incidental, or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm-100 nm.

In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50 % may be replaced by a threshold between 1 and 50 %.

By derogation, fullerenes, graphene flakes and single wall carbon nanotubes with one or more external dimensions below 1 nm should be considered as nanomaterials.

In this context, ‘unbound state’ refers to particles that are produced. ‘Aggregate’ refers to strongly bound or fused particles and ‘agglomerate’ refers to weakly bound particles or aggregates that have a surface area similar to the total surface area of individual components. Aggregate and agglomerates occur as a result of particle interactions or with their surrounding environments, for example, with organic matter.

Different focus, different definitions

Different EU agencies and bodies have used the Commission's definition and adapted it to fulfil specific regulatory needs.

Here are some examples:  

  • The Biocidal Products Regulation applies the definition to active and non-active substances and extends it to specific materials with external dimensions below 1 nm, keeping the recommended definition’s threshold of ≥50 % for size distribution. As the regulation focuses on exposure and risk of marketed products, its nanomaterial definition explicitly states that where nanomaterials are used in a product, the risk to human health, animal health and the environment must be assessed separately, covering both active and non-active substances.
  • REACH applies the European Commission definition but introduces the term nanoforms instead of nanomaterial. The regulation follows the ‘one substance, one registration’ principle where all nanomaterials of a substance must be registered together. As properties, such as the size and shape of each nanomaterial, influence their hazard potential, a separate assessment of all forms of a substance is needed. Nanoform was introduced to clarify that all nanomaterial variations of a substance need to be independently assessed.
  • The European Food Safety Authority (EFSA), only considers manufactured nanomaterials, regardless of their distribution, as they focus on the Food and Feed Additives Regulation where nanomaterials are always intentionally added.


  • Regulation - ECHA (
  • Nanomaterials - ECHA (
  • BPR
  • EC Recommendation