Ethyl isovalerate

Endpoint summary

Description of key information

In a weight of evidence approach, three in vitro assays were carried out, namely DPRA, LuSens and h-CLAT for 3 -methylbutyl isovalerate as a read-across substance.

The DPRA study was inconclusive due to the insolubility of the test compound in the peptides. The h-CLAT assay was positive regarding the sensitization as the substance activated dendritic cells. All data obtained in the LuSens assay compiled with acceptance evaluation criteria, and showed a negative result regarding sensitizing.

Based on the overall inconclusive result of the three in vitro assays an in vivo test (guinea pig maximization test) using the read across substance 3 -methylbutyl isovalerate was conducted. Based on the in vivo data the substance is considered not to be sensitizing to skin.

Using this read across approach, the test item is considered not to be sensitizing to skin.

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:

weight of evidence

Study period:

24.3.2016 - 07.07.2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

It is suspected that false positive LLNA results could be caused by some kind of detergent effect. Seeing that "emulsion formation" was the cause of the inconclusive output of the in vitro test battery, no LLNA test was conducted.

Species:

guinea pig

Strain:

Hartley

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Microbiological status of animals, when known: SPF
- Age at study initiation: 5 weeks
- Weight at study initiation: 337–395 g
- Housing: (during the study) stainless wire mesh cages, 210W×350D×180H (mm), one animal per cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 12 days
- Indication of any skin lesions: no

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.0–23.8°C (permissible range: 18.0-24.0°C)
- Humidity (%): 33.9–52.1% (permissible range: 30.0-70.0%)
- Air changes (per hr):10–15 times/hour
- Photoperiod (hrs dark / hrs light):12 hour light/dark cycle

Route:

intradermal and epicutaneous

Vehicle:

olive oil

Concentration / amount:

25% / 0.1 mL (intradermal), 100 % / 0.2 mL (topical application)

Day(s)/duration:

Day 0 Intradermal; Day 7 topical application for 48 h

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100% / 0.1 mL

Day(s)/duration:

24 h

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

10 (5 for control)

Details on study design:

RANGE FINDING TESTS: Based on the results of the preliminary test the concentrations for the main study was determined

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (first induction: intradermal exposure; second induction: epicutaneous exposure)
- Exposure period: 20 days
- Test groups: 1
- Control group: 1
- Site: Six sites, three each on the left and right sides of the midline of the shoulder region for injection and two sites, one on the left and one on the right sidesfor application (region of the first induction sites)
- Frequency of applications: once
- Duration: 48 h
- Concentrations: 25%

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: Day 21
- Exposure period: 3 days
- Test groups: 1
- Control group: 1
- Site: two sites, one on the left (for test substance) and one on the right (for vehicle) sides (region of the induction sites)
- Concentrations: 100%
- Evaluation (hr after challenge): 24 and 48 hours

Positive control substance(s):

yes

Remarks:

CDNB (1-Chloro-2,4- dinitrobenzene)

Positive control results:

The sensitization rate of CDNB was 100% and the sensitization grade was classified to be ‘V (Extreme)’ according to the classification of skin sensitization grade of Magnusson & Kligman. Consequently, the study was considered to be valid.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

100%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

100%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no

Remarks on result:

no indication of skin sensitisation

Interpretation of results:

GHS criteria not met

Conclusions:

The test item did not produce skin sensitization under the conditions of this study.

Executive summary:

A Guinea pig maximization test was performed (OECD 406). In the test substance group, the 25% test substance was injected intradermally for the first induction. The second induction was concluded with the 100% test substance occluded for 48 hours. The challenge was conducted with the 100% test substance and olive oil occluded for 24 hours. As a result, no skin reactions such as redness or swelling were observed in any animal at 24 and 48 hours after challenge patch removal. Based on the results, isoamyl isovalerate item did not produce skin sensitization under the conditions of this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Using this read across approach and based on the available in vivo result, the target substance is not classified as sensitising under CLP (according to Regulation (EC) No 1272/2008).