Ferrosilicon - reaction mass of iron and iron disilicide and iron silicide and silicon

Endpoint summary

Additional information

Studies on FeSi have shown that the alloy surface restricts the release of the alloy components and thus affect the toxicity of the alloy. In the case of ferrosilicon containing >44% silicon, the silicon is the main element released from the alloy matrix. The release of iron from ferrosilicon containing up to 84% iron is very limited. It has been shown that the release of silicon, iron, aluminium, copper, manganese, titanium and zirconium from ferrosilicon and synthetic amorphous silica is very similar, although ferrosilicon contains significantly higher levels of many of these elements than synthetic amorphous silica. Therefore, synthetic amorphous silica can be used for read-across to cover the possible effects of these components to the mutagenicity of ferrosilicon. Since the surface of different ferrosilicon grades is composed of metal oxides and silicates, including calcium and aluminium silicates, the data on these silicates may also be used in the assessment of repeated dose toxicity of ferrosilicon. Some consideration is also given to barium and strontium, which may be released in higher amounts from certain grades of ferrosilicon. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

In vivo and in vitro studies on the mutagenicity of synthetic amorphous silica have not shown relevant positive responses. Also calcium silicate has shown negative results in vitro in cytogenetic and bacterial mutagenicity studies as well as in vivo in chromosomal aberration and dominant lethal studies. In one micronucleus study in vitro, the positive response has likely resulted from the reported high concomitant cytotoxicity. The contradictory results from in vitro Comet assays of synthetic amorphous silica require more positive backing from results obtained from other methods. The high sensitivity of the assay makes its reproducibility vulnerable to test conditions. Thus, based on weight of evidence, synthetic amorphous silica is non-genotoxic.

According to the comparative in vitro data on the dissolution kinetics of ferrosilicon and synthetic amorphous silica in different artificial biological fluids, dissolution of silicon from ferrosilicon particles in vitro is lower than from synthetic amorphous silica particles (pyrogenic silica). Thus, there is no reason to believe that ferrosilicon would cause higher mutagenic response due to its silicon part. Other main constituents, whose bulk concentration exceeds the classification cut-off limits of 0.1% (cat 1A and B) and 1% (cat 2) and which are dissolved at relevant amounts in artificial biological fluids during one-week incubation (strontium, barium) do not raise concerns for genotoxic effects. In vivo data on the mutagenicity of strontium was limited, but in vitro data supports non-mutagenicity. Strontium as well as barium have not been classified as mutagenic.

Short description of key information:
Negative data on amorphous silica in vitro and in vivo, negative in vitro data on calcium silicate.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

In vivo and in vitro studies on the mutagenicity of amorphous silicas and calcium silicate have not shown relevant positive responses. Other main constituents, whose bulk concentration exceeds the classification cut-off limits of 0.1% (cat 1A and B) and 1% (cat 2) and which are dissolved at relevant amounts in artificial biological fluids during one-week incubation (strontium, barium) are not classified as mutagenic, and according to available data do not raise concerns for genotoxic effects.