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

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

No studies available on ferrosilicon. Read-across to amorphous silicon dioxide is justified.

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

There are no substance-specific data on reproductive toxicity of ferrosilicon. Therefore the assessment has to be based on the data on surface composition, dissolution of the main components and the toxicity of these dissolved components.

Dissolution of main constituents from the ferrosilicon matrix is the main determinant affecting the systemic toxicity (including reproductive toxicity) of ferrosilicon. The surface of the ferrosilicon restricts the dissolution of many elements from ferrosilicon matrix. According to comparative dissolution studies with FeSi and synthetic amorphous silica, the release of silicon, iron, aluminium, copper, manganese, titanium and zirconium from both substances 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 reproductive effects of ferrosilicon. Since the surface of different ferrosilicon grades is composed of metal oxides (especially oxides of silicon) and silicates, including calcium and aluminium silicates, the data on these silicates can also provide important data for the assessment of reproductive toxicity of ferrosilicon. Some consideration also has to be given to barium and strontium which are released from certain grades of ferrosilicon in higher amounts than from amorphous silica. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

Synthetic amorphous silica was tested in a guideline two-generation study with rats. The study results indicated no effects on fertility. Furthermore, a dominant lethal study on calcium silicate did not show effects on male fertility.

Based on the acute and repeated dose toxicity data on synthetic amorphous silica, the silicon ion is virtually non-toxic, showing no systemic toxic effects even at very high oral doses (see Chapter Repeated Dose Toxicity). No harmful effects on reproductive organs have been described in repeated dose toxicity tests. After ingestion, synthetic amorphous silica is absorbed from the gastrointestinal tract, but it usually has very little effect on systemic silicon (H₃SiO₄)^- ion levels, i.e., the levels of silicon in blood, urine or tissues.

No indications of endocrine disrupting effects have been observed.

Silicon in different forms is ubiquitous in nature. Diet is the main factor affecting the blood/urine silicon levels. Diet also causes large inter-individual variability in blood/urine silicon levels. Silicon in different forms is a commonly used food additive, and EFSA (2009) has concluded that the use of silicon dioxide up to 1,500 mg SiO₂/day (equal to 700 mg/day) added to food supplements is of no safety concern. OECD (2004) concluded on the basis of weight of evidence that prolonged exposure to synthetic amorphous silica, applied before and during pregnancy at high doses, is not expected to produce harmful effects on the reproductive performance in experimental animals. The inherent physico-chemical properties and ubiquitous nature of amorphous silicas suggest that there is no structural alert to indicate any potential for reproductive toxicity.

Ferrosilicon contains some additional constituents, which are released from the matrix and which possible impact on reproductive toxicity should be assessed. Main impurities include strontium metal and barium metal, which are present in ferrosilicon at levels over 0.3% and released from it at levels higher than they are released from synthetic amorphous silica particles during one week incubation in synthetic biological fluids. Strontium or barium have not shown effects on fertility and are not classified for reprotoxicity. In addition, the dissolution and therefore the bioavailability of barium metal and strontium metal from ferrosilicon are limited.

No indications of endocrine disrupting effects have been observed.

Short description of key information:
A two-generation oral study with synthetic amorphous silica and a dominant lethal study with calcium silicate have failed to demonstrate any effects on fertility. The inherent physico-chemical properties and ubiquitous nature of silicon ion suggest that there is no structural alert to indicate any potential for reproductive toxicity. The main impurities of ferrosilicon, strontium metal and barium metal, are not classified for reprotoxicity. No indications of endocrine disrupting effects have been observed.

Justification for selection of Effect on fertility via oral route:
Read-across to guideline study performed with synthetic amorphous silica.

Effects on developmental toxicity

Description of key information

Animal data on developmental toxicity of synthetic amorphous silica, calcium silicate and sodium aluminium silicate, which can be used for read-across, do not suggest developmental toxicity or teratogenicity. The inherent physico-chemical properties and ubiquitous nature of silicon ion suggest that there is no structural alert to indicate any potential for developmental toxicity. The other main components of ferrosilicon have not shown any signs of causing developmental toxicity. No indications of endocrine disrupting effects have been observed.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

No studies available on ferrosilicon. Read-across to amorphous silicon dioxide and silicates is justified.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

There are no substance-specific data on reproductive toxicity of ferrosilicon. The assessment has therefore to be based on the data on surface composition, dissolution of the main components and the toxicity of these dissolved components.

Dissolution of main constituents from ferrosilicon matrix is the main determinant affecting the potential systemic toxicity (including reproductive toxicity) of ferrosilicon. The surface of the ferrosilicon restricts the dissolution of many elements from ferrosilicon matrix. According to comparative dissolution studies with ferrosilicon and synthetic amorphous silica, is the release of silicon, iron, aluminium, copper, manganese, titanium and zirconium from both substances fairly similar although ferrosilicon contains significantly higher levels of many of these elements than synthetic amorphous silica. Synthetic amorphous silica can be used for read-across to cover the possible effects of these components to the developmental toxicity of ferrosilicon. Since the surface of different ferrosilicon grades is composed of metal oxides (especially oxides of silicon) and silicates, including calcium and aluminium silicates, the data on these silicates can also provide important data for the assessment of reproductive toxicity of ferrosilicon. Some consideration also has to be given to barium metal and strontium metal, which may be released from certain grades of ferrosilicon in higher amounts than from synthetic amorphous silica. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

No treatment-related effects were observed in a guideline prenatal developmental toxicity stydy on synthetic amorphous silica. The data from studies on high-dose oral administration of hydrophilic silica gel, calcium silicate and sodium aluminium silicate support the conclusion that no toxic effects on development are expected. All tests showed negative results at high doses.

No indications of endocrine disrupting effects have been observed.

Also OECD (2004) concluded in its assessment on the hazards of synthetic amorphous silica that on the basis of weight of evidence prolonged exposure to synthetic amorphous silica is not expected to produce harmful effects on the embryonic/foetal development in experimental animals.

Main impurities of FeSi include strontium metal and barium metal, which are present in ferrosilicon at levels over 0.3% and released from it at levels higher than they are released from synthetic amorphous silica particles during one-week incubation in synthetic biological fluids. Studies reporting developmental toxicity of strontium have been conducted with soluble strontium compounds at very high dose levels (e.g., 1.5-2 g/kg bw/d). Thus, these effects are not considered relevant in the case of ferrosilicon. Strontium has not been classified as a developmental toxicant. Limited data is available on the developmental toxicity of barium metal and it is not classified as a developmental toxicant. In addition, the dissolution of barium and strontium from ferrosilicon are very limited.

Justification for selection of Effect on developmental toxicity: via oral route:
Read-across to oral studies with silicates and amorphous silica in several animal species.

Justification for classification or non-classification

No classification of ferrosilicon is suggested.

A two-generation oral study with synthetic amorphous silica, as well as subchronic studies with silicon, synhetic amorphous silica and a dominant lethal study with calcium silicate have not demonstrated any indications of fertility effects or histopathological changes or deleterious effects in the reproductive organs of treated animals.

Animal data on developmental toxicity of synthetic amorphous silica, calcium silicate and sodium aluminium silicate, which can be used for read-across, do not suggest developmental toxic effects.

The inherent physico-chemical properties and the ubiquitous nature of silicon ion suggest that there is no structural alert to indicate any potential for reproductive and developmental toxicity.

Other relevant components of ferrosilicon, i.e. strontium metal and barium metal, have not been classified as reproductive toxicants.