On 3 July the Europan Commission Scientific Committee on Consumer Safety (SCCS) published their Opinion on the Solubility of of synthetic amorphous silica (SAS)

The opinion explains what the SCCS considers 'soluble' with regard to nanomaterials used in cosmetics. The SCCS assessed dossiers provided to them on SAS where the solubility values for hydrophilic SAS materials are in the range from 22 mg/L to 225 mg/L, and the solubility values of hydrophobic surface-treated SAS materials are reported to range from 0.4 to 180 mg/L. 

The SCCS concludes that both the hydrophilic and hydrophobic SAS materials are regarded as “insoluble” (i.e. below 100 mg/L) to “very slightly soluble” (i.e. 100 mg/L to 1000 mg/L) by the SCCS based upon the terminology used in USP38 and USP 38 NF33' (USP USP 38 and USP 38 – NF 33: The Pharmacopeia of the United States of America (USP

The SCCS goes on to state 'In regard to the nanomaterial definition in the Cosmetic Regulation, none of the SAS materials (hydrophilic or hydrophobic) included in the dossier can be regarded as soluble.' The SCCS also notes that 'the protocols used for solubility tests have a strong influence on the solubility of SAS materials.'