November 24, 2010 by Rhiannon Smith
Nano, from the Greek for “dwarf”, is the prefix for 10-9. There is a general consensus that nanomaterials contain particles in the order of 10-9 metres, which is the length of only ten hydrogen atoms (Institute of Nanotechnology). However, despite the development of nanotechnology in the 1980’s, there is still an ongoing discussion on an EU-wide definition for nanomaterials. This post describes some of these discussions and proposed definitions.
There is a range of previously proposed definitions, which are in general agreement:
- The ISO, OECD, cosmetics directive, Novel foods directive, RoHS/WEEE andbiocides directive have all indicated nanomaterials to cover the range 1-100 nm;
- The Soil Association proposes an upper cut-off of 125 nm or a mean upper limit of 200 nm;
- Friends of the Earth have an upper limit of 300 nm, suggesting that up to this size, the risks are similar to those from less than 100 nm materials.
These definitions generally agree with the definition agreed by the European Commission’s Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR): “any form of a material that is composed of discrete functional parts, many of which have one or more dimensions of the order of 100 nm or less”.
In July 2010 SCENHIR indicated that there was a need for upper and lower limits to be set and validated, with standardised methods to determine size and size distribution. They recommended that nanomaterials should be defined as consisting of more than 0.15% of a material, based on number concentration, below the upper size limit. SCENHIR added that specific surface area may be applicable to dry solid powders as an identification criterion. The Committee stated that the nanomaterials definition should be broad enough to cover all three types of nanoscale materials (natural, man-induced, and manufactured), but that each combination of a nanomaterial with a coating has to be considered individually for safety evaluation.
Based on these considerations, SCENHIR concluded that:
- For materials with a median size of >500 nm or substances with less than 0.15% of materials below 100 nm, a classical risk assessment should be produced;
- For materials with a median size of between 1 and 100 nm or substances with greater than 0.15% material below 100 nm, a nano-specific risk assessment should be produced.
However, SCENHIR, in contrast with the SRC Reference Report of July 2010, suggested that there was no scientific evidence for an upper limit of 100 nm and the use of a fixed limit may be too limiting, with a tiered approach based on a relatively high upper threshold being more appropriate.
There is as yet no agreed definition for nanomaterials under REACH. As of the 21st October 2010, the European Commission recommendation on the definition of the term “nanomaterials” indicated that nanomaterials must meet at least one of the following criteria:
- Consisting of particles (minute piece of matter with defined physical boundaries – ISO 146446:2007) with one or more external dimensions in the range of 1-100 nm for more than 1% of their number size distribution;
- Having internal or surface structures in one or more dimensions in the size range of 1-100 nm; or
- Having a specific surface area by volume greater than 60 m2 cm-3, excluding materials consisting of particles with a size less than 1 nm.
As indicated by the lack of an EU definition, there are no direct provisions under REACH for nanomaterials as a class of substances. Nanomaterials are considered as substances and therefore may be subject to a whole range of REACH requirements. Each substance should be reviewed individually to determine which parts of the regulations are applicable.
Nanomaterial registration under REACH
The European Commission has confirmed that nanoparticles should be considered as substances. Although no reference is made to particle size, REACH is applicable to “a chemical element and its compounds in the natural state or obtained by any manufacturing process”. As of 2008, the decision on the inclusion or exclusion of nanomaterials under the registration of their bulk forms is based on substance identification: namely whether the nanoform has a separate EINECS number.
Issues with current nanoparticles registrations:
- Much of the nanotechnology industry is not comfortable with performing nanomaterial risk assessments under current regulations;
- The registration of nanoparticles under bulk substances, especially when nanoparticles have different properties from the bulk substance, makes little scientific sense;
- Nanomaterials have different properties, which are not always caught adequately using current risk assessment tools;
- Human health issues may be a concern, especially as many filters on respirators are not reliable for filtering nanomaterials;
- There could be greater ecotoxic effects from nanomaterials, due to their enhanced surface area to volume ratio;
- Bulk substance testing and measurement methods are not always applicable to nanomaterials, as discussed in our report to Defra.
The tonnage limit, whether and in what conditions bulk- and nano-forms can be considered the same substance, and whether test requirements and risk assessment methodologies for bulk materials are applicable to nanoforms may also raise problems for REACH registrations.
The majority of nanoparticles, being imported or manufactured below 1 tonne, are not subject to REACH registration. However if the substance is registered under the bulk form, it is subject to registration of the combined tonnage, as well as the deadlines applicable to the bulk substance.
If both bulk and nanoform data are required for a registration, there may be issues with differences in the data requirements and test methods applicable to nanomaterials. This leads to questions about whether the properties of the nanomaterial should be included in the registration of the bulk substance if they are different, and whether the two sets of data are comparable if nano- and bulk substances are tested with different test methods. The inclusion of nano- and bulk form data may lead to contrasting properties and even conflicting classifications within the same dossier.
The differences in properties could be the basis for an argument in favour of separate registrations; however this may lead to data sharing problems when the properties for the bulk and nano- forms are the same. Considering the bulk and nano- forms to be different would also have implications for communications, with the need for formation of a separate REACH SIEF and subsequent issues for data sharing. The separation or unification of nano- and bulk form substance SEIFs can be challenged by ECHA and separate registrations may prove problematic, as this could appear to be multiple registrations of the same substance.
ECHA guidance on sameness
This subject is not dealt with specifically under REACH but it is expected that current ECHA guidance documents will be modified after the Commission acknowledged that further clarification was needed on the sameness issue. As of 2008, the decision on the inclusion or exclusion of nanomaterials under the registration of their bulk forms is based on substance identification, namely whether the nanoform has a separate EINECS number. The registration of nanomaterials together with or separate from their bulk form is also being discussed by the RIP-oN (REACH Implementation Plan on Nanomaterials) and may be addressed at a later date.
In theory, if properly run, a risk assessment under the current regulations should be adequate for nanomaterials. However, current risk assessment methodologies are being looked into as the Commission has indicated that nano-specific properties are not being adequately addressed.
It is expected that ECHA will base further evaluation of the requirements of nanomaterials under REACH on the registration of the 11 nanomaterials expected to be registered this year under the same submissions as their bulk forms. It has been suggested that the REACH Scope Review in 2012 may bring nanomaterials into the scope of REACH by lowering the 1 tonne threshold, possibly to the 10 kg threshold required under the Dangerous Substance Directive, with the subsequent Research and Development exemptions reintroduced.
The European Commission is expected to recommend that nanomaterials consist of more than 1% particles or internal or external structures with at least one dimension in the range of 1-100 nm or have a specific surface area by volume greater than 60 m2cm-3, excluding particles with a size less than 1 nm. Although nanomaterials should be considered as substances, if the nanoform does not have separate EINICs number from the bulkform, both forms should considered the same and subject to combined registration. The combined registrations may have implications for tonnage limits and test and risk assessment methodologies and raises questions regarding the extent to which forms with differing properties can be considered the same substance.