Developing a pragmatic approach to material nanoforms under REACH - Part II

Usage of (eco)toxicological data for bridging data gaps between and grouping of nanoforms of the same substance. Part II: Justifying grouping and the implementation of cross references for nanomaterials. 

Applying established risk analysis for a nanoparticular substance (source substance) to a different nanometric form derived from the same material (target substance) must be scientifically justified and substantiated. In 2008, ECHA published a guide for establishing cross references between chemical products. Specific points relating to nanomaterials were added later.

A complete review of available data and how missing data was identified was compiled in a matrix. In the case of a REACH submission including nanometric substances, this matrix must identify the different forms covered by the submission.

A strategy has been developed to establish cross references to apply the risk analysis conducted on one or several "source" nanomaterials to another nanometric form produced from the same substance and referred to as "target".

This strategy involves six steps:

  1. Identification of the nanometric forms of a given substance based on their physicochemical properties.
  2. Grouping of nanoforms based on similarities between physicochemical properties and establishment of clear thresholds between groups based on these parameters. Over subsequent steps, collection of further data can result in reconsideration of group limits an even in the creation of subgroups. 
  3. Identification of available and missing data. This involves compiling an inventory of available information per REACH-required risk criterion in order to identify missing data.
  4. Identification of potential nanoparticular "source" substances. For each missing datum, it is essential to identify, within the group, source materials whose characteristics may be used to create cross references with target nanoforms. This stage includes the scientific justification (based on a hypothesis) of the pertinence of chosen sources. 
  5. Substantiating the hypothesis. When cross references are to be established between nanomaterials, it may be necessary to reassess the initial grouping and to collect new data in order to at least partially bridge the data gap. 
  6. Evaluation of new data: Iterative interpretation of available information in order to decide whether or not it sufficiently confirms the hypothesis and justifies cross references. 
    The justification provided by informants is assessed by ECHA to ensure its conformity with legal requirements.
    An illustrated example of this strategy can be found at:


  • Usage of (eco)toxicological data for bridging data gaps between and grouping of nanoforms of the same substance : elements to consider ECHA (March 2016).