Europe – SCCS – Final Opinion on Solubility of Synthetic Amorphous Silica (SAS)

The SCCS concludes the following:

1. Does the SCCS consider that Synthetic Amorphous Silica (SAS) are soluble (100
mg/L or higher) or degradable/non-persistent in biological systems, in light of the nanomaterial definition of the Cosmetic Regulation?

Having considered the data provided in this dossier and that available in published
literature, the SCCS concludes that:

i) the solubility values for hydrophilic SAS materials have been reported to range from
22 mg/L to 225 mg/L for the solubility tests performed in aqueous media, or following the enhanced OECD TG 105 (0.5% ethanol). The latter protocol has been noted to increase the solubility by a factor of 10 for some hydrophilic SAS materials.

ii) the solubility values of hydrophobic surface-treated SAS materials have been reported
to range from 0.4 to 180 mg/L for solubility tests performed in aqueous media, or following a modified enhanced OECD TG 105 protocol (i.e. using 10% ethanol).

The latter protocol has been noted to strongly increase the solubility of some hydrophobic SAS materials (by a factor up to 173)…