Triethylsilane

Endpoint summary

Description of key information

No sensitisation data are available for the registered substance. Data are available for the structural analogue, tetramethylsilane (CAS 75-76-3), from a skin sensitisation study, conducted in accordance with OECD 406 (Buehler method) and in compliance with GLP.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

There are no measured data available to assess the skin sensitisation potential of triethylsilane. Therefore data for the structural analogue substance tetramethylsilane (CAS 75-76-3) has been used to assess its skin sensitisation potential.

Tetramethylsilane was not sensitising (Hüls, 1998) when tested in the guinea-pig Buehler assay (OECD 406). Undiluted test substance was applied to 20 animals in both the induction and challenge phases. No irritation was observed in the preliminary irritation test or in the induction or challenge phases, and no skin reactions were observed at challenge. Historical positive controls demonstrated the sensitivity of the test and concurrent negative controls showed no skin reactions.

To reduce animal testing REACH recommends to make use of a read-across approach where appropriate based on the high accordance in properties relevant for the specific endpoint. In the case of sensitisation, the relevant properties are physicochemical properties and structural similarity. In the following paragraphs the proposed read-across from tetramethylsilane to trimethylsilane is discussed.

Read-across hypothesis

The hypothesis is that source and target substances have similar toxicological properties because they are structurally similar and have similar physicochemical properties. The substances are hydrolytically stable (triethylsilane and tetramethylsilane have half-lives in water of days) so reaction products do not need to be considered for the human health hazard assessment of these substances.

See Section 'repeated dose toxicity' for further justification of the read-across.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

There are no skin sensitisation data on triethylsilane, so good quality data on the structurally-related substance, tetramethylsilane have been used for read-across.

In a key guinea pig skin sensitisation study (Buehler test), conducted in compliance with GLP and according to OECD TG 406, tetramethylsilane was found to be a non-sensitiser. No irritation was observed so undiluted test substance was used in both the induction and challenge phases. The sensitisation index was calculated to be 0% for the test group following challenge. Appropriate positive and solvent controls were included and gave expected results.

In the absence of measured data for triethylsilane, it is considered appropriate to use this result in support of the skin sensitisation endpoint. The both registered substance and read-across substance are moderately lipophilic (log K_ow 3.6 and 2.7 respectively) for which dermal uptake is favourable. The substances are hydrolytically stable (triethylsilane and tetramethylsilane have half-lives in water of days) so reaction products do not need to be considered for the human health hazard assessment of these substances and read-across based on similarity of parent is appropriate.

Justification for classification or non-classification

Based on a reliable in vivo study on tetramethylsilane, triethylsilane is not classified as a skin sensitiser according to Regulation (EC) No 1272/2008.

There are no data to suggest that triethylsilane is a respiratory sensitiser.