[3-(triethoxysilyl)propyl]urea

Endpoint summary

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 Ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2). The read-across is justified as follows:

 

READ-ACROSS JUSTIFICATION

No data on skin sensitisation are available for the registered substance [3-(triethoxysilyl)propyl]urea (CAS 23779-32-0). However, 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 parameters in the same range. In the following paragraphs the read-across approach for [3-(triethoxysilyl)propyl]urea (CAS 23779-32-0) is evaluated point by point.

 

Read-across hypothesis

Read-across was performed from ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2), which was not sensitising in guinea pigs (Buehler Test). The read-across substance ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2) is a multi constituent substance, with the submission substance [3-(triethoxysilyl)propyl]urea (CAS 23779-32-0) being one of the constituents. All constituents (including the submission substance) have a low to moderate dermal absorption potential (20-50%), corresponding to a dermal absorption of 0.01453, 0.00833, 0.00481, and 00272 mg/cm²/h, respectively for [3-(trimethoxysilyl)propyl]urea, [3-(dimethoxyethoxysilyl)propyl]urea, [3-(methoxydiethoxysilyl)propyl]urea, and [3-(triethoxysilyl)propyl]urea (DERMWIN, 2012). This prediction was calculated on the basis of molecular weight (222.31, 236.34, 250.36, and 264.39 g/mol), water solubility (240 000, 74 000, 23 000, and 7 000 mg/l), and log Kow (0.2, 0.3, 0.8, and 1.3). All compounds are known to undergo hydrolysis, producing the common hydrolysis product [3-(trihydroxysilyl)propyl]urea, which exhibits a very low dermal absorption (0.00069 mg/cm²/h, 10%). However, hydrolysis is considered to be of minor importance due to the low presence of water on the skin surface.

The parent substances and the common hydrolysis product were evaluated for their skin sensitising potential by means of the OECD Toolbox (version 2.3.0.1132). The databases Protein binding by OASIS, Protein binding by OECD and Protein Binding Potency contain structural alerts (e.g. a functional group) that indicate a protein binding potential. A structural alert is an indication that a substance may have the potential to cause skin sensitisation. By comparing a substance (the molecular structure) with the list of alerts, a potential skin sensitiser may be identified. The modelling results from the OASIS and OECD databases for the parent substances and the hydrolysis products were given as 'no binding'. For the Protein Binding Potency database, the result was N/A, 'not applicable', because the substance did not comply with the application domain of the model.

In the absence of any chemical structural features indicative of a sensitising potential for the submission substance and all constituents of the read-across substance, read-across from ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters (CAS 116912-64-2) and [3-(trimethoxysilyl)propyl]urea (CAS 23843-64-3) to the registered substance [3-(triethoxysilyl)propyl]urea (23779-32-0) for acute oral and dermal toxicity is considered to be appropriate.

Additional information is given in a supporting report (PFA, 2013a) attached in Section 13 of the IUCLID 5 dossier.

 

 

In a key guinea pig Buehler test, conducted in compliance with GLP and according to OECD TG 406, ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters was found to be a non-sensitiser. Induction was performed thrice (day 1, 8, and 15) with 0.5 ml of the undiluted test substance for 6 h under occlusive conditions(NOTOX, 2000a). Directly after the third induction erythema grade 1 (9/20) and grade 2 (2/20) but no edema were observed. After the challenge with 0.3 ml test substance solution (50%; day 28) no erythema or edema were observed 24 and 48 h after challenge treatment. In conclusion ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters was found to be a non-sensitizer as no skin reactions were observed after the challenge period, neither in the control (0/10) nor in the test group (0/20). No positive control was used with this study, but data are available showing that a reliability check is carried out at regular intervals. The positive control substance (Alpha-hexylcinnamic aldehyde) was used for a reliability check, and induced positive reactions in 60% of the animals, thus meeting the reliability criteria for the Buehler test (≥15% positive response).

 

Migrated from Short description of key information:
Buehler test according to OECD TG 406 and in compliance with GLP regulations (NOTOX, 2000): not sensitising.

Justification for selection of skin sensitisation endpoint:
The key study was selected for assessment.

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 on skin sensitisation of the registered substance do not meet the criteria for classification according to Regulation 1272/2008 or EU Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.