Reaction mass of [3-(trimethoxysilyl) propyl]urea, [3-(dimethoxyethoxysilyl) propyl]urea, [3-(methoxydiethoxysilyl) propyl]urea and [3-(triethoxysilyl) propyl]urea.

Endpoint summary

Description of key information

Buehler test according to OECD TG 406 and in compliance with GLP regulations: 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:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

adopted 1992

Deviations:

no

GLP compliance:

yes

Type of study:

Buehler test

Justification for non-LLNA method:

The current accepted and preferred method for skin sensitisation testing according to the REACH legislation (EC no 1907/2006) and CLP Regulation (EC No 1272/2008) is the murine local lymph node assay (LLNA). A validated test method, OECD TG 429 (OECD 2002) is available for the LLNA. The guideline acknowledges the limits of the LLNA, and states that there are instances where test substance classes or substances containing functional groups shown to act as potential confounders make the use of guinea pig tests more appropriate. It is concluded that the LLNA is not applicable where the properties of the test material cause interference in the accuracy of the LLNA (OECD 2002). The statement in the OECD TG 429 is given with reference to the findings of Basketter et al. (2009a), who demonstrated false positives in silicone based substances which had previously been demonstrated to be non-sensitisers in the guinea pig maximisation test (GPMT). The importance of available evidence from guinea pig results, consideration of chemical reactivity, epidermal bioavailability and clinical and experimental human data are emphasised as central to reaching appropriate regulatory decisions for substances which have been shown to fall outside the specificity of the LLNA (Basketter et al., 2009b). The non-applicability of the LLNA for silicone based substances has also been demonstrated by Petry et al. (2012). The sensitisation potential of polyfunctional silicone materials was tested in a comparative study investigating the GPMT and the LLNA assays, which found the five tested substances to be negative in the GPMT whereas they were concluded to be weak to moderate skin sensitisers in the LLNA (Petry et al., 2012).

Species:

guinea pig

Strain:

Himalayan

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Biotechnology and animal breeding division (RCC Ltd.), Fuellinsdorf, Switzerland
- Age at study initiation: approx. 4 weeks
- Weight at study initiation: 294 ± 14 g (control group), 308 ± 16 g (experimental group)
- Housing: 5 animals per metal cage
- Diet: Standard guinea pig diet including ascorbic acid (1000 mg/kg); Charles River breeding and maintenance diet for guinea pigs, Altromin, Lage, Germany, ad libitum
- Water: Tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 3
- Humidity (%): 30-70
- Air changes (per hr): 15
- Photoperiod: 12 hrs dark / 12 hrs light

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100% (0.5 ml of undiluted test substance (experimental group); 0.5 ml of water (control group))

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100% (0.15 ml of undiluted test substance (experimental group); 0.15 ml of water (control group))

No. of animals per dose:

Control group: 10 animals
Experimental group: 20 animals

Details on study design:

RANGE FINDING TESTS:
In a range finding test the application of undiluted test substance to 2 animals did not reveal any erythema or edema findings 24 and 48 h after exposure.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3 (day 1, 8, and 15)
- Exposure period: 6 h
- Test groups: 0.5 ml undiluted test substance
- Control group: 0.5 ml water
- Site: left side of the scapular region
- Frequency of applications: every 7 days
- Duration: day 1-15
- Concentrations: 100%

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day of challenge: 28
- Exposure period: 6 h
- Test groups: 0.15 ml undiluted test substance + 0.15 mL water
- Control group: 0.15 ml undiluted test substance + 0.15 mL water
- Site: right flank
- Concentrations: 50%
- Evaluation (hr after challenge): 24, 48

Challenge controls:

The control group is actually a challenge control.

Positive control substance(s):

no

Remarks:

The sensitivity of the test system was checked at least every 6 months.

Positive control results:

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).

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

20

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

20

Group:

positive control

Remarks on result:

positive indication of skin sensitisation

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulation (EC) No 1272/2008

Conclusions:

In a Buehler Test conducted to GLP and OECD 406 (reliability score 1) ureidopropyltrialkoxysilane, mixed methoxy and ethoxy esters was not sensitising to the skin.

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, labelling and for risk assessment.

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, 2000b). 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).

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study 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.