tert-butyl peroxypivalate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1998-10-19 to 1998-11-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Version / remarks:

1996

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The study was conducted in 1999 when the LLNA was not yet an established testing alternative.

Test material

Test material information

Constituent 1

Reference substance name:

tert-butyl peroxypivalate

EC Number:

213-147-2

EC Name:

tert-butyl peroxypivalate

Cas Number:

927-07-1

Molecular formula:

C9H18O3

IUPAC Name:

tert-butyl 2,2-dimethylpropaneperoxoate

additive 1

Reference substance name:

2,2,4,6,6-pentamethylheptane

EC Number:

236-757-0

EC Name:

2,2,4,6,6-pentamethylheptane

Cas Number:

13475-82-6

Molecular formula:

C12H26

IUPAC Name:

isododecane

Test material form:

liquid

In vivo test system

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River, Germany
- Age at study initiation: approx. 4 weeks old
- Weight at study initiation: mean 337 g
- Housing: group housing of 5 animals per labelled metal cage with wire-mesh floors
- Diet: Free access to standard guinea pig diet (including ascorbic acid)
- Water: Free access to tap-water, diluted with decalcified water.
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 21 °C
- Humidity: 50 %
- Air changes: 15 air changes per hour
- Photoperiod: 12 hours artificial fluorescent light and 12 hours dark per day

Study design: in vivo (non-LLNA)

Induction

Route:

intradermal and epicutaneous

Vehicle:

corn oil

Concentration / amount:

Induction (intradermal): 10%
Induction (epicutaneous): undiluted test item

Challenge

Route:

epicutaneous, semiocclusive

Vehicle:

corn oil

Concentration / amount:

Challange (epicutanous): 20 %

No. of animals per dose:

- Experimental group: 10 females
- Control group: 5 females

Details on study design:

RANGE FINDING TESTS: A prelminary irritation study was conducted in order to select test substance concentrations to be used in the Main study. the test substance concentrations used were from the series: Undiluted (if a liquid), 50 %, 20 %, 10 %, 5 %, 2 %, 1 % and, if needed, further lower concentrations using steps.

MAIN STUDY
A. INDUCTION EXPOSURE
a) First induction (intradermal)
- No. of exposures: 1
- Exposure period: single treatment on day 1
- Test groups: A) A 1:1 w/w mixture of Freunds` Complete adjuvant with water for injection. B) The test substance at a 10 % concentration. C) A 1:1 w/w miture of the test substance, at twice the concentration used in (B) and Freunds`Complete Adjuvant.
- Control group: treated with adjuvant and the vehicle
- Site: scapular region
- Frequency of applications: once
- Concentrations: 10 %

b) Second induction (epicutanous), 7 days after first induction
- No. of exposures: 1
- Exposure period: 48 hours
- Test groups: The scapular area was treated with 0.5 mL of the undiluted test substance using a Metalline patch mounted on Medical tape.
- Control group: treated with adjuvant and the vehicle
- Site: scapular region
- Frequency of applications: once
- Concentrations: undiluted

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 13 days after the epidermal exposure
- Exposure period: 24 hours
- Test groups: single treatment
- Control group: single treatment
- Site: flank
- Concentrations: 20 %
- Evaluation: 24, 48 hours

Challenge controls:

No

Positive control substance(s):

yes

Remarks:

alpha-hexylcinnamicaldehyde (10 %)

Results and discussion

Positive control results:

A reliability check is carried out at regular intervals to chek the sensitivity of the test system and the reliability of the experimental techniques as used by the lab. The results lead to a sensitisation rate of 100 per cent to the 10 % concentration. From these results, it was concluded that the female guinea pig of the albino Dunkin Hartley strain is an appropriate animal model for the performance of studies designed to evalute the sensitising potential of a substance in a Maximisation type of test.

In vivo (non-LLNA)

Results

Results 1

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

20 %

No. with + reactions:

0

Total no. in group:

5

Results 2

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

20 %

No. with + reactions:

1

Total no. in group:

5

Results 3

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

20 %

No. with + reactions:

8

Total no. in group:

9

Clinical observations:

One animal was found dead on day 8.

Results 4

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

20 %

No. with + reactions:

6

Total no. in group:

9

Clinical observations:

One animal was found dead on day 8.

Results 5

Key result

Group:

positive control

Remarks on result:

other: not applicable

Applicant's summary and conclusion

Interpretation of results:

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

Conclusions:

Taking into account the occurrence and intensity of the responses and comparing these with the skin reactions seen in the control animals, it was considered that hypersensitivity to tert-butyl peroxypivalate had been induced in eight (of nine) the experimental animals. The response seen in the control animal was considered to be a non specific skin reaction. These results indicate a sensitisation rate of 89 %.

Executive summary:

Tert-butyl peroxypivalate was tested in a Maximisation Test in albino guinea pig according to EU method B.6 and OECD guideline no. 406.

The test item concentrations selected for the main study were based on the results of a preliminary study. In the main study, experimental animals were intradermally injected with a 10 % concentration (1. induction). The test animals were epidermally exposed to the undiluted test substance seven days after the first induction. Control animals were similarly treated, but with the vehicle (Corn oil) only. Two weeks after the epidermal application all animals were challenged with a 20 % test item concentration and the vehicle. Skin reactions varying between grades 1 and 2 were observed in eight experimental animals in response to the 20 % test item concentration, 24 and/or 48 hours after exposure.

A skin reaction of grade 1 was observed in one control animal in response to the 20 % test item, 48 hours after exposure.

One experimental animal was found dead on day 8. Macroscopic post-mortem examination of the animal showed dark red discolouration of the lungs and haemorrhages in the lungs and a reduction in size of the thymus. It was considered that the death of this animal was incidental and that the study outcome, based on healthy surviving animals, was not adversely affected.

No further mortality occurred and no further symptoms of systemic toxicity were observed in any of the animals of the main study.

Taking into account the occurrence and intensity of the responses and comparing these with the skin reactions seen in the control animals, it was considered that hypersensitivity to tert-butyl peroxypivalate had been induced in eight (of nine) experimental animals. The response seen in the control animal was considered to be a non specific skin reaction. These results indicate a sensitisation rate of 89 %. Thus, the test item TBPPI is considered to be skin sensitising.