Registration Dossier

Administrative data

Description of key information

No skin sensitisation data are available for trimethoxy(octy)lsilane, therefore good quality data for the related substance triethoxy(2,4,4-trimethylpentyl)silane have been read-across. In a guinea pig maximisation test conducted in compliance with OECD Test Guideline 406 and in compliance with GLP, there were no positive skin responses in 10/10 test group animals following challenge with 100% test substance. There were no clinical signs of toxicity during the study.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
An LLNA study was not performed because there is an existing reliable study for skin sensitisation using the Guinea Pig Maximisation test method. Furthermore, the LLNA test method is not considered to be suitable for substances that contain silicon. Please refer to the attached document for further details.
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan Winkelmann GmbH
- Age at study initiation: No data
- Weight at study initiation: 300-500 g
- Housing:Groups in Terluran cages
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Described as 'adequate'


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ±3
- Humidity (%): 55 ±10
- Air changes (per hr): At least 10
- Photoperiod (hrs dark / hrs light): 12/12

Route:
intradermal and epicutaneous
Vehicle:
cotton seed oil
Concentration / amount:
Induction: Intradermal injection of 5% test substance
Induction: Topical exposure to 100% test substance
Challenge: 100% test substance
Route:
epicutaneous, occlusive
Vehicle:
cotton seed oil
Concentration / amount:
Induction: Intradermal injection of 5% test substance
Induction: Topical exposure to 100% test substance
Challenge: 100% test substance
No. of animals per dose:
Ten in test groups and five in negative control.
Details on study design:
RANGE FINDING TESTS: For the justification of the dose levels a preliminary test was performed. Four animals were topically treated with 25%, 50% or 100% of the test substance in cotton seed oil. No signs of irritation or systemic toxicity were recorded after a contact period of 48 hours after application of 100% concentration. Therefore the 100% concentration was chosen as the concentration for the topical and challenge exposures. For the justification of the first stage of the induction three animals were intradermally treated with 1%, 2.5% or 5% test substance. Slight erythema was found in the animals treated with 5%, until 48 hours after application. No signs were recorded at 72 hours. Therefore the concentration of 5% was chosen for the intradermal induction injection.

MAIN STUDY
A. INDUCTION EXPOSURE: intradermal injection
- No. of exposures: One
- Exposure period: Single injection
- Test groups: Injection 1: Freund's Adjuvant complete, 1+1 (v/v) diluted with isotonic saline (FCA). Injection 2: Test substance (5%). Injection 3: Prepared test substance at a concentration of 50% (v/v) in FCA, 1+1 (v/v) diluted with isotonic saline.
- Control group: Injection 1: FCA. Injection 2: Cotton seed oil. Injection 3: cotton seed oil at a concentration of 50% (v/v) FCA.
- Site: Shoulder region (Injections 1 and 2 close to each other and nearest the head. Injection 3 towards the caudal part of the test region).

B. INDUCTION EXPOSURE: topical application
- On Day 6, approximately 24 hours before the topical induction the test area, after close clipping, was painted with 0.5 ml of 10% sodium lauryl sulfate in vaseline, to create a local irritation.
- On Day 7, a patch saturated with either 0.5 ml 100% test substance (test group) or 0.5 ml of cotton seed oil (control group) was applied to the test site and held in contact by an occlusive dressing for 48 hours.

C. CHALLENGE EXPOSURE: topical
A patch saturated with 0.5 ml of the test substance (100%) was applied to the left flank of the animals. A patch saturated with 0.5 ml cotton seed oil was applied to the right flank. The patches were held in place with an occlusive dressing for 24 hours. At the end of the challenge period the skin was cleaned with moistened gauze patches. Skin reactions were assessed 24, 48 and 72 hours after removal of the dressings.
Challenge controls:
POSITIVE CONTROLS: Mercaptobenzothiazole (three animals): 2% for intradermal induction, 25% or topical induction and 15% for challenge.
NEGATIVE CONTROLS: cotton seed oil.
Positive control substance(s):
yes
Remarks:
Mercaptobenzothiazole
Positive control results:
Three of three animals gave a positive result.
Reading:
1st reading
Hours after challenge:
72
Group:
test group
Dose level:
100% test substance
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No clinical signs of toxicity
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
72
Group:
negative control
Dose level:
cotton seed oil
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
No clinical signs of toxicity
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
72
Group:
positive control
Dose level:
15% Mercaptobenzothiazole
No. with + reactions:
3
Total no. in group:
3
Remarks on result:
positive indication of skin sensitisation
Interpretation of results:
GHS criteria not met
Conclusions:
In a good quality Guinea-pig Maximisation Test conducted according to OECD 406 and GLP, Wacker BS 1701 was not sensitising to the skin of Dunkin-Hartley guinea-pigs.
Executive summary:

Triethoxy(2,4,4-trimethylpentyl)silane has been tested in a Guinea-Pig Maximisation test conducted according to OECD Test Guideline 406. During the induction phase the Dunkin-Hartley guinea-pigs (10 test group and 5 control group, all females) were injected intradermally with 5% test substance (in cotton seed oil) and, after treatment with sodium lauryl sulfate, topically treated with 100% test substance. After a latency of 14 days, to allow a potential reaction of the immune system, the animals were challenged with 100% test substance on the flank. The grade of the skin reactions was compared to control animals, which were treated with cotton seed oil during the induction phase and, with the test substance during challenge phase. The animals had normal weight gain and there were no clinical signs of toxicity. The sensitisation rate for

triethoxy(2,4,4-trimethylpentyl)silane was 0%.

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

The key study is the only sensitisation test available for the analogue substance, triethoxy(2,4,4-trimethylpentyl) silane, which is similar to the registered substance but contains a branched octyl group rather than a linear octyl group.

Triethoxy(2,4,4-trimethylpentyl)silane has been tested in a Guinea-Pig Maximisation test conducted according to OECD Test Guideline 406. During the induction phase the Dunkin-Hartley guinea-pigs (10 test group and 5 control group, all females) were injected intradermally with 5% test substance (in cotton seed oil) and, after treatment with sodium lauryl sulfate, topically treated with 100% test substance. After a latency of 14 days, to allow a potential reaction of the immune system, the animals were challenged with 100% test substance on the flank. The grade of the skin reactions was compared to control animals, which were treated with cotton seed oil during the induction phase and, with the test substance during challenge phase. The animals had normal weight gain and there were no clinical signs of toxicity. The sensitisation rate for

triethoxy(2,4,4-trimethylpentyl)silane was 0%.


Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the available read-across data, trimethoxy(octyl)silane does not require classification as a skin sensitiser according to Regulation (EC) No 1272/2008.