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

Usage of (eco)toxicological data for bridging data gaps between and grouping of nanoforms of the same substance. Part I: Specific measures applying to nanomaterials. 

Nanomaterials can be produced in different forms and sizes and can be subjected to a vast range of surface treatments. Particle modifications can proffer them with new functions, but can also influence their (eco)toxicological behaviour. As such, it appears necessary to develop a pragmatic approach in order to ensure the safe use of varying nanoforms of a given substance under REACH. In 2015, ECHA (the European Chemicals Agency), in association with the RIVM (Dutch National Institute for Public Health and the Environment) and the JRC-IRMM (Joint Research Center Institute for Reference Materials and Measurements) conducted a vast project aimed at scientifically justifying when and how to extend (eco)toxicological results of a study conducted on one nanoform to another of the same substance.

The publication that resulted from the project focuses, in particular, on two methods acknowledged as offering valid approaches with regard to regulations in order to fill the gap in existing data on risk characterisation, by basing study on the availability of results obtained on similar substances. The first method consists in grouping together substances, and the second in establishing cross references between them.  The use of these procedures demands for extremely solid scientific justification.  

Structurally similar substances that present similar physicochemical, toxicological or environmental properties can be considered as a group of substances. Application of the concept of grouping substances implies that the information required by REACH (physicochemical properties, effects on human health and the environment, etc.) can be drawn from tests conducted on reference substances (source substances) within the group, by interpolation with other substances in the group (target substances).

In certain cases, the information required by REACH is insufficient for identifying a nanomaterial. The study of the nanoparticular forms of a material includes size and granulometric distribution, surface chemistry, identification of crystalline phases, etc.

Indeed, these properties affect their (eco)toxicological behaviour and their environmental impact. Furthermore, in certain cases, such as the case of a high risk of inhalation (fibres), specific parameters such as the material's rigidity and hardness can play an important role in risk assessment. 

During its life cycle, the characteristics of a nanomaterial can be modified through, for example, ageing processes, agglomeration or disagglomeration processes, chemical reactions, etc. These modifications are potentially likely to affect its behaviour in terms of toxicity. As such, it is of great importance that we assess the impact of these changes on (eco)toxicological properties in order to ensure that data applying to one nanomaterial also apply to another.

The decision to attribute to one nanometric form of a substance the same data as those of another nanomaterial, along with the scientific justification for such an approach, remains the responsibility of the informant. 

Source

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