Registration Dossier

Administrative data

Description of key information

No data about skin sensitisation is available with the trimethoxy(2,4,4 -trimethylpentyl)silane. Reliable read across data from triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) was used.

Skin sensitisation (OECD 406 / GPMT with CAS 35435 -21 -3): not sensitising

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

No information about skin sensitisation is available for the registered substance, however, reliable data is available for the closely related substance, triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3). The silicon-containing products of hydrolysis are close structural analogues: both trimethoxy(2,4,4-trimethylpentyl)silane (CAS 34396-03-7) and triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) hydrolyse to (2,4,4-trimethylpentyl)silanetriol. Both substances hydrolyse very rapidly: hydrolysis is expected to occur during testing and following exposure. The further products of hydrolysis are methanol and ethanol, respectively. It is therefore considered appropriate to read-across the skin sensitisation results from triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) to the registered substance.

Guinea Pig Maximization Test:

In the available key study (Bioservice, 2007) the test item triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) was tested for skin sensitising properties according to the OECD TG 406 and in compliance with GLP. 10 Hsd Poc: DH Guinea pigs of the test group were used for this study. During the induction phase the animals were intradermally injected with 5% test item (diluted in cotton seed oil) and, after treatment with sodium lauryl sulphate, topically treated with 100% test material. After a latency of 14 days (to allow a potential reaction with the immune system) the animals were challenged with 100% test material on the flank. The grade of skin reactions was compared to those of the 5 control animals, which were treated with cotton seed oil during the induction phase and, during the challenge phase, with the test item, respectively. The sensitisation rate after application of the test item was 0%. Under the test conditions described, the test item showed no sensitising effects. Normal weight gain as compared to both historical data and control animals was reported for the test animals. No other signs of clinical toxicity were reported.


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 skin sensitisation relevant properties are structural similarity as well as physical-chemical and basic toxicological parameters in the same range. In the following paragraphs the read-across approach fortrimethoxy(2,4,4-trimethylpentyl)silaneis evaluated point by point.

Read-across hypothesis

One skin sensitisation study (GPMT according OECD 406) is available for the analogue substancetriethoxy(2,4,4-trimethylpentyl)silane. No sensitisation was observed in the guinea pigs. Both substances,trimethoxy(2,4,4-trimethylpentyl)silane(CAS 34396-03-7) andtriethoxy(2,4,4-trimethylpentyl)silane(CAS 35435-21-3) have a moderate to low dermal absorption potential (50 and 10%, respectively), corresponding to a dermal absorption of 5.39E-03 and <1.60E-04 mg/cm²/h, respectively. This prediction was calculated with Dermwin (2012) on the basis of molecular weight (234.4 and 276.5 g/mol), water solubility (110 and <0.1 mg/l), and log Kow(4.0 and >6.5). Both substances could undergo hydrolysis resulting in the same hydrolysis product,(2,4,4-trimethylpentyl)silanetriol. The hydrolysis product is supposed to have a dermal absorption that is higher than that of the parent substances. None of the parent substances and the hydrolysis product showed a chemical structural feature indicative of sensitising potential (OECD Toolbox Since skin penetration is one essential step during skin sensitisation, and in the absence of any chemical structural features indicative of sensitising potential, it is considered appropriate to read-across this result to the other members of the alkyl alkoxysilane analogue group. This is supported by a larger data set of skin sensitisation studies for alkyl alkoxysilanes (PFA, 2013t). In addition the hydrolysis products methanol and ethanol are not sensitising to skin.


Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

No data available.

Migrated from Short description of key information:
No data available.

Justification for classification or non-classification

The available data is reliable and suitable for classification. Based on this data, classification for skin sensitisation according to 67/584/EEC and EC/1272/2008 is not warranted.