Synthetic amorphous magnesium silicate, with molar ratio (SiO2:MgO) range of 1.4-4

Endpoint summary

Additional information

The tested synthetic amorphous silicas showed no mutagenic or clastogenic activity in standard test systems under valid test conditions. In one non-standard test, the mutagenic potential was investigated following inhalation exposure to rats, as inhalation has to be considered to be the exposure route of highest toxicological significance for humans. For that purpose, the test design had to be modified and adjusted such as to meet relevant physiological needs: Therefore, the target cells were isolated after in-vivo exposure and cultivated ex vivo. Selection of possible mutants followed the standard method of the HPRT assay (see for details under 7.6.2: Johnston et al. 2000). This study gave no evidence of a mutagenic potential for Aerosil 200 when inhaled at a high exposure concentration of 50 mg/m³for 13 weeks.

Read-across based on the fact that synthetic magnesium silicate and silicon dioxide have similar basic physicochemical properties and are highly stable, inert substances can justify the use of silicon dioxide data in this endpoint. In addition, it will eliminate the need for further vertebrate studies that are unwarranted on ethical and animal welfare grounds.

Overview of the most relevant studies

Test	Test system	Substance/ Result	Reference
In-Vitro Assays
Ames	S. typh. (strains TA98, TA100, TA1535, TA1537, TA 1538)	Cab-O-Sil EH5 (pyrogenic): negative with and without metabolic activation	San and Springfield 1989 (Microbiol. Associates)
Ames	S. typh. TA 98, TA 100, TA 1535, TA 1537, TA 1538, E. coli WP 2	Silcron (silica gel): negative with and without metabolic	Mortelmans and Griffin 1981
Gene mutations (mammalian cell)	Chinese hamster ovary cells  / HGPRT assay	Cab-O-Sil EH5 (pyrogenic): negative with and without metabolic activation	Sigler and Harbell 1990 (Microbiol. Associates)
Chromosomal aberrations	Chinese hamster ovary cells /  cytogenetic assay	Cab-O-Sil EH5 (pyrogenic): negative with and without metabolic activation	Putman and Morris 1990 (Microbiol. Associates)
Chromosomal aberrations	Human embryonic lung cells (WI-38) / cytogenetic assay	Syloid 244 (silica gel): negative without metabolic activation	Litton Bionetics, Inc. 1974

Short description of key information:

The REACH data profile for this endpoint has been covered for synthetic amorphous silica:

Result: not mutagenic and not clastogenic in three valid in-vitro tests

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on experimental evidence, no classification for genotoxic potential is required under DPD (Directive 67/548/EEC) or CLP/GHS (Regulation 1272/2008) legislation.