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May 7, 2014

ECHA Biocidal Products Committee Issues Opinion on HeiQ AGS-20

Lynn L. Bergeson

The European Chemicals Agency (ECHA) Biocidal Products Committee (BPC) adopted an opinion on April 10, 2014, concerning HeiQ AGS-20 (AGS-20). The European Commission (EC) requested an opinion on the following questions:

  1. With regard to the biocidal product AGS-20, should silver or silver adsorbed on silicon dioxide be considered as the active substance?
  2. Would this active substance meet the definition of a nanomaterial, as provided in Article 3(1)(z) of the Biocidal Products Regulation (BPR)?
  3. Finally, if this active substance meets the definition of a nanomaterial what should be its specifications?

According to the opinion, HeiQ’s claims include:

  1. The biocidal product AGS-20 is a composite material consisting of micrometer sized silicon dioxide powder with physically bound elemental silver crystallites. The elemental silver crystallites span from sub 100 nanometer (nm) range to larger than 100 nm. AGS-20 is a composite of two chemically and physically distinct phases (silver and silicon dioxide).
  2. The composite is not a reaction mass nor is it a simple mixture. It is a complex multi-component structure — a composite material.
  3. The composite material should be regarded as the active substance.
  4. As AGS-20 must be considered as a composite, it is currently not covered by the scope of the EC’s October 18, 2011, recommendation on the definition of nanomaterial with reference to recital 14. Recital 14 outlines that “. . . materials with internal structure or surface structure in the nanoscale such as complex nano-component nano-materials including nano-porous and nano-composite materials . . .” are currently not covered by the definition.
  5. AGS-20 should not be classified as a nanomaterial.  The elemental metallic silver contained in AGS-20 is not manufactured separately and so fundamentally cannot be characterized alone without its inert silica support.  The composite must be assessed as a whole.

The BPC reached the following conclusions with respect to the three questions in the request for an opinion:

1.  The material AGS-20 should be regarded as the biocidal active substance as it is the result of a combustion synthesis process and not just a simple mixing of the two components. It is agreed that the chemical name for the active substance should be silver adsorbed on silicon dioxide. A range for the silver content (and silicon dioxide content) should be added.

2. AGS-20 meets the definition of a nanomaterial as provided in Article 3(1)(z) of the BPR as it is a stable aggregate with primary particles complying with the number size distribution provision.

It is proposed that the derogation in recital 14 to Commission Recommendation 2011/696/EU does not apply to AGS-20 as the purpose of recital 14 is to outline that more complex heterogeneous nanomaterials are currently not covered by the definition.

3. It is premature to discuss a possible (nano) specification of AGS-20 prior to the evaluation phase of the active substance under the Review Regulation. However, as for the approval of (nano) silicon dioxide under the BPR (Implenting Regulation (EU) No 408/2014), it could be outlined that AGS-20 is a stable aggregate with primary particles in the nanoscale with additional specification of particle size and volume specific surface area.