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Posted: Nov 24, 2010

International Council of Chemical Associations addresses key issues for nanomaterial definition

(Nanowerk News) The International Council of Chemical Associations (ICCA) has released a document addressing key issues that need to addressed when considering the definition of manufactured nanomaterials for regulatory purposes. It advocates five "Core Elements of a Regulatory Definition of Manufactured Nanomaterial".
Innovative technologies such as nanotechnology (the ability to engineer materials at the nanoscale) and manufactured nanomaterials have the potential to improve quality of life, providing benefits to the environment, and enabling societal advances. They are crucial to help answer some of the world's toughest environmental, energy and health challenges and provide a growing range of tools to improve product performance beyond what could normally be achieved using conventional non-nano technologies.
Most conventional nanomaterial manufacturing processes are "top down," in which the material is produced in bulk (large primary particles) and grinded or milled down to a smaller particle size (broken into smaller pieces). Depending on the process and the applied forces / energy the final content of particles at nano size can vary. Any top down process even if not intentionally manufactured is likely to result in a certain fraction of nano-objects and their aggregates and agglomerates. However, true manufactured nanomaterials are intentionally processed to achieve an intended functionality and therefore contain a significant weight percentage of nano-objects and their aggregates and agglomerates.
By contrast, "bottom up" nanomaterial manufacturing processes are those in which atoms are intentionally controlled during the manufacturing operation to result in nano-objects and their aggregates and / or agglomerates. These materials are synthesized from atomic or molecular species via chemical reactions, allowing for the precursor particles to grow in size.
A definition is required in order to provide increased clarity and consistency with respect to the term nanomaterial for use in regulations laying down provisions on substances. The definition should not prejudge nor reflect the scope or application within various legislations or of any provisions potentially determining requirements on nanomaterials, including those of a risk management nature. Any assessment of nanomaterials identified by the definition will vary on a material by material basis and will have to account for intrinsic properties of the substance as well as for potential of exposure.
The following key principles should be taken into consideration for the development of a regulatory definition of manufactured nanomaterials:
  • Existing regulations are generally based on substances, therefore in a regulatory context any definition should focus on solid particulate substances (as defined by chemical regulations) instead of materials in general.
  • The definition should cover nano-object as defined by ISO, their agglomerates and aggregates. The further specification on solid particulate substances containing nanoobjects and their aggregates and agglomerates ensures that any potential risk of disintegration of the larger structures are adequately addressed and at the same time avoids macroscopic (non-nano) substances having an internal nanostructure like e.g. activated carbon from inappropriately being included in the definition.
  • ICCA strongly advocates using weight concentration rather than particle number concentration to determine the cut of criterion for the definition of nanomaterials. Weight-% is generally used in all chemical legislation and test procedures and should therefore be the preferred choice instead of particle number concentration. In addition most identified modes of action in biological responses to nanomaterials suggest that the dose/response relationship is based on mass and not on particle number and hazard characterization is generally conducted in studies that meter out doses by weight.
  • A cut-off criterion is indispensable because all solid particulate substances will have a particle size distribution that is likely to have a certain fraction at the nanoscale. In addition the cut-off should reflect the current manufacturing processes (top down / bottom up) and should not limit the quantification to a specific measurement technique. Particle measurements at the nanoscale depend strongly on the use of the appropriate methods. Results vary based on the equipment, the dispersion unit, the dispersion energy, the media of dispersion, the concentration of the nanomaterials, and the stability of the generated aerosols.
  • Based on these key principles, five internationally harmonized core elements have been agreed by the global chemical industry and endorsed by ICCA for a definition of manufactured nanomaterials in a regulatory context:
    1. Solid, particulate substances
    2. Intentionally manufactured at the nano-scale
    3. Consisting of nano-objects with at least one dimension between 1 and 100nm on the basis of ISO
    4. And their aggregates and agglomerates
    5. With a weight based cut-off of either 10 wt.-% or more of nano-objects as defined by ISO or 50 wt % or more of aggregates / agglomerates consisting of nano-objects.
    The state of science around nanomaterials is constantly evolving and knowledge about potential and perceived risks and benefits related to nanomaterials continues to develop. The global chemical industry is at the forefront of international efforts to improve understanding towards the responsible development of nanotechnology and actively engages in research efforts focused on identifying, understanding and managing any potential risks.
    Source: ICCA
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