The EC’s Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) has published its opinion on the most recent developments in the risk assessment of nanomaterials.

The Opinion was developed under a new mandate from the European Commission, which tasked SCENIHR to answer the question’ What have been the developments between the SCENIHR Opinion of 2006 and early 2008’.

Entitled ‘Opinion on: Risk Assessment of Products of nanotechnologies', it builds on and confirms earlier opinions published in 2006 (cf. ‘The appropriateness of existing methodologies to assess the potential risks associated with engineered and adventitious products of nanotechnologies’) and 2007 (‘Opinion on the appropriateness of the risk assessment methodology in accordance with the technical guidance documents for new and existing substances for assessing the risks of nanomaterials’, and ‘Opinion on the scientific aspects of the existing and proposed definitions relating to products of nanoscience and nanotechnologies’).

In this latest opinion, SCENIHR draws the following conclusions:

• Characterisation: For the characterisation of manufactured nanomaterials several issues are important: (a) characterisation as produced by manufacturers, (b) characterisation as/if used in biological systems, (c) state of agglomeration/aggregation, and (d) characterisation as used in products.
• Solubility: For (partially) soluble nanomaterials the toxicity may be governed at least in part by the soluble species released from the nanomaterial. [...]
  The solubility of the nanomaterials is an important property that needs to be addressed. Knowledge of the extent to which nanomaterials dissolve and the rate at which this takes place is essential in two respects: (i) it is a direct control of the concentrations of nanomaterials in the environment and of the time that the nanomaterials reside in the environment and in organisms, and (ii) it determines the concentrations of dissolved species that originate from the nanomaterials. It is doubtful whether currently available standard methods for measuring the (rate of) dissolution can adequately deliver this knowledge. [...]
  Unlike in the assessment of exposure concentrations of conventional (dissolved) chemical substances, the octanol-water partition coefficient K_ow is likely to have a limited role in predicting water-solids partitioning.
• Reference material: There is a need for reference nanomaterials since this would allow the assessment of fate and behaviour as well as effects, which could then be related to the material’s properties and characteristics.
• Definition: Currently the definition of what is “nano” is still under debate. Generally nanomaterials are defined as being smaller than about 100 nm in at least one dimension. The currently proposed definitions use the size of the primary particle/structure as a starting point. [...] when describing a nanomaterial it is important to describe not only the mean particle size but also the size of the primary particles. [...] extending the current definition based on physical size by the addition of a limit of the specific surface area to be above 60 m²/g of material volume (the value of 60 m²/g corresponds to the specific surface area of 100 nm solid spheres of unit density) should be considered.
• Environmental Fate: Of major importance is the estimation of nanoparticle release and fate, and exposures within the environment.
• Ecotoxicology: The common endpoints used in ecotoxicology such as mortality, growth, feeding, and reproduction can also be used for the evaluation of ecotoxicity by nanomaterials.
• Toxicity: [...] it should be noted that not all nanomaterials induce toxic effects.
  The hypothesis that smaller means more reactive and thus more toxic cannot be substantiated by the published data. In this respect nanomaterials are similar to normal substances in that some may be toxic and some may not. As there is not yet a generally applicable paradigm for nanomaterial hazard identification, a case by case approach for the risk assessment of nanomaterials is recommended.

NOTE: Unlike former SCENIHR Opinions, this latest Opinion did not undergo public consultation. However, DG SANCO announced that the Opinion will be made subject of a hearing that is to be held later this year.

Follow these links find out more about the latest SCENIHR Opinion, or todownload the full Opinion.

Registered NIA Members can download the full meeting noted of the Workshop of the REACH Competent Authorities subgroup on Nanomaterials, where a sneak preview of the SCENIHR Opinion was presented (download the meeting note from the ‘Members only’-area on the NIA website, by following the link to ‘Meeting Reports (from the NIA delegate)’).