Registration Dossier

Diss Factsheets

Administrative data

Description of key information

No irritation data are available for the registered substance. Data are available for the structural analogue, triethylsilane (CAS 617-86-7), from skin and eye irritation studies conducted in accordance with OECD 404 and 405 respectively and in compliance with GLP. Triethylsilane was not irritant in rabbits.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

There are no data available to assess the skin and eye irritation potential of trimethylsilane, and testing is not technically feasible because the substance is a gas. Therefore data for the structural analogue substance triethylsilane (CAS 617-86-7) have been used to assess its skin and eye irritation potential. Triethylsilane was found to be not irritating to rabbit skin and eyes.

Information on triethylsilane is included for completeness only.

Read-across justification

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 irritation the relevant properties are structural similarity as well as physical-chemical properties in the same range. In the following paragraphs the proposed read-across from triethylsilane to trimethylsilane is discussed. A report considering read across for all endpoints is attached in Section 13.

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. Trimethylsilane has a half-life in water of days and triethylsilane is hydrolytically stable, so reaction products do not need to be considered for the human health hazard assessment of these substances. 

Read-across justification

(a) Structural similarity

The registration and read-across substances are structurally similar and are members of an analogue group of alkylsilanes. The substances contain a silicon atom to which is attached three alkyl (methyl/ethyl) groups. For the registered substance the alkyl groups are methyl, for the read-across substance they are ethyl. It is not considered likely that decreasing the carbon chain length by one carbon would be likely to confer additional irritation properties on the registration substance; however, this cannot be demonstrated experimentally due to the physical state of trimethylsilane at ambient temperature and pressure.

(b) Similar physicochemical characteristics

The key physicochemical parameters are summarised below.

Table: Key physicochemical parameters  

CAS number



EC number



Chemical Name



Molecular weight (gmol-1)



log Kow (parent)



Water solubility (parent)

1400 mg/l (QSAR), limited by condensation reactions following abiotic reaction to silanol

6 mg/l

Vapour pressure (parent)

not applicable (substance is a gas)

2700 Pa

Justification for classification or non-classification

Based on available information for the read-across substance triethylsilane, the registered substance, trimethylsilane, does not require classification for skin and eye irritation according to Regulation (EC) No 1272/2008.

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