Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route
Endpoint conclusion:
no study available
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

According to REACH information requirements, a two-generation reproduction toxicity study is the standard information requirement at above 1,000 t/year. No such test has been conducted with silicon or related substances (amorphous silica or silicates). However, the REACH guidelines do not require reproduction toxicity testing if, e.g., all of the following circumstances exist: substance exhibits a) low toxicological activity and b) negligible systemic absorption and c) no or no significant human exposure. In addition, before any specific reproductive toxicity testing is suggested, a detailed review of all existing toxicological data to identify any specific alerts and testing requirements should be conducted. If this kind of weight-of-evidence analysis shows that there is sufficient data to permit a robust conclusion on reproductive toxicity potential, no further testing is required.

Based on the acute and repeated dose toxicity data on synthetic amorphous silica, 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, amorphous silica is absorbed from the gastrointestinal tract but it usually has very little effect on systemic silicon ion levels i.e. the levels of silicon in blood, urine or tissues. 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. This conclusion is based on the information that subchronic studies with amorphous silica and a dominant lethal study with calcium silicate have failed to demonstrate any histopathological changes or deleterious effects in the reproductive organs of treated animals. Calcium silicate can be used for the read across in the case of both amorphous silica and silicon since it is also a sparingly soluble silicon compound which releases silicon in the body. In addition, the inherent physico-chemical properties and ubiquitous nature of synthetic amorphous silicas suggest that there is no structural alert to indicate any potential for reproductive toxicity.

According to available comparativein vitro dissolution data, the dissolution of silicon from elemental silicon and synthetic amorphous silica (Aerosil Ox50) is similar, Aerosil Ox50 showing somewhat better release than elemental silicon. Thus, the bioaccessibility (and bioavailability) of silicon is likely to be similar or lower than that of synthetic amorphous silica. In circulation, silicon exists in the form of moniosilicic acid in both cases. Thus, the reproductive hazards are likely to be the same, which means that exposure to silicon is not expected to produce harmful effects on the reproductive performance. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

Main impurities, present in silicon at levels over 0.3% and released from it, include aluminium, iron and calcium. Iron is an essential mineral, with no reproductive toxic properties, and widely used dietary supplement also during pregnancy. Same applies to calcium. Soluble species of aluminium are widely used as antacidal drugs and they have not been shown to exert effects on reproduction or development and are therefore indicated also during the pregnancy. In addition, the dissolution of these elements from silicon matrix is restricted because of the protective silicon oxide layer and has been shown not to differ significantly from the release of these elements from pyrogenic amorphous silica. Thus, it can be concluded that the known impurities are unlikely to have any impact on silicon reproductive toxicity.

Conclusion: Silicon is regarded not to cause fertility effects. No classification or further testing of fertility effects is suggested.


Short description of key information:
Subchronic studies with silicon and amorphous silica and a dominant lethal study with calcium silicate have failed to demonstrate any histopathological changes or deleterious effects in the reproductive organs of treated animals. 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.

Effects on developmental toxicity

Description of key information
Available 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.
Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
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

Thereareonly limited data available on the developmental toxicity of amorphous silica. In these studies, high-dose or long-term oral administration of hydrophilic silica gel did not induce developmental toxicity in several species.However, the teratogenic effects of calcium silicate and sodium aluminium silicate have also been tested in different animal species. All tests showed negative results at high doses.Thesedata support the conclusion that amorphous silica has no toxic effect on development

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.

The comparative in vitro data on the dissolution kinetics of silicon and amorphous silica in different artificial biological fluids shows that the dissolution of silicon from silicon particles in vitro is similar or lower than from amorphous silica particles (pyrogenic silica Aerosil Ox50). In blood, silicon exists in the form of monosilicic acid regardless of the source. Thus, based on the read-across from synthetic amorphous silica, calcium silicate and sodium aluminium silicate, silicon is not likely to exert developmental toxicity. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

Conclusion: Silicon is regarded not to cause developmental toxicity. No classification or further testing of developmental toxicity is suggested.



Justification for selection of Effect on developmental toxicity: via oral route:
Read-across to oral studies with silicates an synthetic amorphous silicon dioxide.

Justification for classification or non-classification

Subchronic studies with amorphous silica and a dominant lethal study with calcium silicate have failed to demonstrate any histopathological changes or deleterious effects in the reproductive organs of treated animals. 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.

Available 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. Silicon contains no reprotoxic impurities.