2-methylpropane-2-thiol

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 May to 23 June 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

2-methylpropane-2-thiol

EC Number:

200-890-2

EC Name:

2-methylpropane-2-thiol

Cas Number:

75-66-1

Molecular formula:

C4H10S

IUPAC Name:

2-methylpropane-2-thiol

Constituent 2

Reference substance name:

tertiobutylmercaptan

IUPAC Name:

tertiobutylmercaptan

Test material form:

other: liquid

In vivo test system

Test animals

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Janvier (France)
- Age at study initiation: 8 weeks
- Weight at study initiation: 20.1 to 23.4 g
- Housing: 2 or 4 in polycarbonate cages (Techniplast 1145T) and then individually in disposable crystal polystyrene cages
- Diet (ad libitum): SSNIFF R/M-H pelleted maintenance diet (SSNIFF Spezialdiaten, Germany)
- Water (ad libitum): facility tap water
- Acclimation period: 13 or 14 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 24
- Humidity (%): 30 to 70
- Air changes (per hr): approximately 12
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES:
From: 8 June 2011
To: 20 June 2011

Study design: in vivo (LLNA)

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

10, 25, 50 or 100% preliminary test
5, 10 25, 50 or 100% main test

No. of animals per dose:

2 females preliminary test
4 females main test

Details on study design:

RANGE FINDING TESTS:
- Compound solubility: solution obtained at 50% concentration of test substance.
- Irritation: no local reaction noted
- Ear thickness response: no increase in ear thickness noted

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response: SI >= 3 together with dose-response relationship

TREATMENT PREPARATION AND ADMINISTRATION:
The test item was administered as a solution in the vehicle. The test item was mixed by vortex with the required quantity of vehicle. The test item concentrations were expressed in % (v/v). The positive control was prepared at the concentration of 25% (v/v) a mixture of Acetone/Olive Oil (4/1; v/v) (AOO). Dosage forms preparations were prepared extemporaneously on the day of each administration. The dosage forms were stored at room temperature and delivered to the study room in stoppered plastic tubes.

On days 1, 2 and 3, a dose-volume of 25 μL of the appropriate dosage form preparation was applied to the dorsal surface of one or both ears, using an adjustable pipette fitted with a plastic tip. In order to avoid licking, to ensure an optimized application of the test materials and to facilitate ear thickness measurement, the animals were placed under light isoflurane anaesthesia during the administration. No massage was performed but the tip was used to spread the preparation over the application site. No rinsing was performed.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

The EC3 value (theoretical concentration resulting in a SI value of 3) was determined by linear interpolation of points on the dose-response curve, immediately above and below the 3-fold threshold. The equation used for calculation of EC3 was:

EC3 = c + [(3 - d)/(b - d)] x (a - c)

Where a = the lowest concentration giving Stimulation Index > 3; b = the actual Stimulation Index caused by a; c = the highest concentration failing to produce a Stimulation Index of 3; d = the actual Stimulation Index caused by c.

Group means and Standard deviations calculated where appropriate.

Results and discussion

Positive control results:

The positive control Stimulation Index was 12.66, therefore, the experiment was considered valid.

In vivo (LLNA)

Results

Results 1

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: Group mean dpm increased with increasing concentration in treated groups - see table.

Results 2

Parameter:

SI

Value:

1.73

Test group / Remarks:

5 % 2-methylpropane-2-thiol

Results 3

Parameter:

SI

Value:

1.77

Test group / Remarks:

10 % 2-methylpropane-2-thiol

Results 4

Parameter:

SI

Value:

3.62

Test group / Remarks:

25 % 2-methylpropane-2-thiol

Results 5

Parameter:

SI

Value:

4.26

Test group / Remarks:

50 % 2-methylpropane-2-thiol

Results 6

Parameter:

SI

Value:

30.43

Test group / Remarks:

100 % 2-methylpropane-2-thiol

Results 7

Parameter:

SI

Value:

12.66

Test group / Remarks:

25 % HCA (positive control)

Results 8

Parameter:

EC3

Value:

20

Test group / Remarks:

An EC3 value of 20% was calculated from the results and presented in the study report

Any other information on results incl. tables

Mortality

There were no unscheduled deaths during the study.

Clinical Signs

There were no remarkable clinical signs noted during the study.

Body weight

There was no effect on body weight.

Ear thickness measurement and local reactions

No local reactions were noted in any animals and no notable increase in ear thickness was noted at any tested concentration.

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

2-Methylpropane-2-thiol was found to be sensitising in a mouse local lymph node assay, resulting in a Stimulation Index of greater than 3 at concentrations of 25% and above (3.62, 4.26 and 30.43 at substance concentrations of 25, 50% and 100% respectively). The EC3 value was calculated to be 20%.