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Carcinogenicity

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Description of key information

Human epidemiological data from ferrosilicon/silicon manufacturing do not show an increased incidence of cancer attributed to ferrosilicon exposure. Amorphous silica and calcium silicate have not shown carcinogenic responses in animal tests. Also other main constituents, which are dissolved from ferrosilicon in higher amounts than from synthetic amorphous silica particles in artificial biological fluids have not been classified as carcinogens.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Carcinogenicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Justification for classification or non-classification

Human epidemiological data from ferrosilicon/silicon manufacturing do not show increased incidences of cancer attributed to ferrosilicon exposure. Amorphous silica and calcium silicate have not shown carcinogenic responses in animal tests. Also other main constituents, which are dissolved from ferrosilicon in higher amounts than from synthetic amorphous silica particles in artificial biological fluids have not been classified as carcinogens.

Additional information

There are no animal studies on the carcinogenicity of ferrosilicon. Human epidemiological data from ferrosilicon/silicon manufacturing do not show increased incidence of cancer attributed to ferrosilicon exposure. Although this data supports the lack of carcinogenicity of ferrosilicon, it cannot be used as definitive proof of the non-carcinogenicity of ferrosilicon due to

the insensitivity of epidemiological studies.

Studies on FeSi show that the alloy surface restricts the release of the alloy components and thus, affect the toxicity of the alloy. For example, 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 carcinogenicity 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 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 significant amounts from certain grades of ferrosilicon. A detailed description of the justifications for read-across is available in Section 13 of the Iuclid dossier.

Some data on the carcinogenicity is available on the synthetic amorphous silica. A critical study is the two‑year rat and mouse feeding study with micronized silica gel (Syloid) by Takizawa et al. (1988), which showed no increased incidence of cancer. This conclusion is supported by negative in vitro and in vivo mutagenicity data (see Chapter 'Mutagenicity') and limited intrapleural/intratracheal studies on synthetic amorphous silica. Also a valid inhalation/intra-pleural study with calcium silicate did not produce tumours in rats. Thus, silicon ion released from ferrosilicon is not likely to cause carcinogenicity. The conclusion that silicon ion does not cause carcinogenicity is in line with the concusions made by OECD (2004) and the Cosmetic Ingredient Review panel (CIR 2003).

Other main constituents, which are dissolved from ferrosilicon in higher amounts than from synthetic amorphous silica particles in artificial biological fluids include strontium and barium. They are not classified as carcinogens. Available data summarized by WHO CICAD on strontium (2010) and ATSDR Toxicological Profile on barium (2004), barium and non-radioactive strontium do not raise concerns for carcinogenicity.


Justification for selection of carcinogenicity via oral route endpoint:
Read-across to silica.

Justification for selection of carcinogenicity via inhalation route endpoint:
Read-across to calcium silicate.

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