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Diss Factsheets

Administrative data

Description of key information

There are no measured data on the skin sensitisation potential of triethoxypropylsilane, therefore the structural analogue substance trimethoxypropylsilane (CAS: 1067-25-0) has been used to assess its skin sensitisation potential.

Buehler test according to OECD TG 406: not sensitising

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
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.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Target: triethoxy(propyl)silane (2550-02-9)
Source: trimethoxy(propyl)silane (CAS 1067-25-0)

3. ANALOGUE APPROACH 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 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 for triethoxy(propyl)silane is evaluated point by point.

No skin sensitisation study is available for triethoxy(propyl)silane. A Buehler test is available for the analogous substance trimethoxy(propyl)silane. Trimethoxy(propyl)silane was not sensitising in guinea pigs. Both substances, triethoxy(propyl)silane (2550-02-9) and trimethoxy(propyl)silane (CAS 1067-25-0), have a medium dermal absorption potential (50%), corresponding to a dermal absorption of 0.01965 and 0.02810 mg/cm²/h, respectively. This prediction was calculated with Dermwin (2012) on the basis of molecular weight (206.35 and 164.27 g/mol), water solubility (280 and 9200 mg/L), and log Kow(3.2 and 1.7). Both substances could undergo hydrolysis, resulting in the common hydrolysis product, propylsilanetriol. The hydrolysis product is supposed to have a dermal absorption that is comparable to that of the parent substances. None of the parent substances and hydrolysis products showed a chemical structural feature indicative of sensitising potential (OECD Toolbox 2.3.0.1132). 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 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.
 
Reason / purpose for cross-reference:
read-across source
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
100% at induction, 25% at challenge
No. with + reactions:
0
Total no. in group:
20
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
100% at induction, 25% at challenge
No. with + reactions:
0
Total no. in group:
20
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0% at induction, 25% at challenge
No. with + reactions:
0
Total no. in group:
10
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0% at induction, 25% at challenge
No. with + reactions:
0
Total no. in group:
10
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
50%
No. with + reactions:
3
Total no. in group:
10
Interpretation of results:
other: CLP/EU GHS criteria are not met, no classification required according to Regulations (EC) No 1272/2008
Conclusions:
In a guinea pig skin sensitisation study (Buehler test), conducted according to OECD 406 and in compliance with GLP (reliability score 1) the structural analogue substance trimethoxypropylsilane (CAS: 1067-25-0) was not a skin sensitiser. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in acute inhalation toxicity potential.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Studies were chosen as key when the available study was of relevance and of sufficient quality for classification and labelling and for risk assessment.

There are no measured data available to assess the skin sensitisation potential of triethoxypropylsilane, therefore the structural analogue substance trimethoxypropylsilane (CAS: 1067-25-0) has been used to assess its skin sensitisation potential.

In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and following the Read across assessment framework (RAAF, ECHA 2017) read across from an analogue substance has been applied to support the human health hazard assessment of tritethoxypropylsilane. Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

In a key reliable Buehler test conducted according to OECD TG 406 and in compliance with GLP the structural analogue substance trimethoxypropylsilane (CAS: 1067-25-0) was found to be a non-sensitiser. 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 (Hüls AG, 1997). The same result is also considered for triethoxypropylsilane.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

No data available.


Justification for classification or non-classification

The available data on skin sensitisation of the structural analogue substance, trimethoxypropylsilane, do not meet the criteria for classification according to Regulation (EU) 1272/2008 and are therefore conclusive but not sufficient for classification of the registered substance.