Di-tert-butyl 1,1,4,4-tetramethyltetramethylene diperoxide

Endpoint summary

Description of key information

The results of guinea pig maximization studies with test substance CAS# 1068 -27 -5 (key study) and with test substance CAS# 2167-23-9 (supporting study), together with QSAR analysis results are used to support the conclusion that substance CAS# 78-63-7 is not skin sensitizing.

The key study is a Guinea Pig Maximisation Test (OECD GL No. 406) with test substance CAS# 1068-27-5 (unsaturated structural analog) 10 experimental animals were intradermally injected with a 50% concentration and epidermally exposed to a 100% concentration. Five control animals were similarly treated, but with vehicle alone (corn oil). Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle. No skin reactions were evident after the challenge exposure in the experimental and control animals. There was no evidence that the test article had caused skin hypersensitivity in the guinea pig, since no responses were observed in the experimental animals in the challenge phase.

In a supporting Guinea Pig Maximisation Test 10 males and 10 female animals were treated with test substance CAS# 2167-23-9 at a concentration of 25% w/w (intradermal injection) and undiluted (topical) in the induction phase and at a concentration of 50% (w/w) in the challenge phase. A control group (5 males/5 females) received treatment with vehicle only (corn oil). No clinical signs and no cutaneous reactions were observed at 24 and 48 hours after removal of the dressing in the challenge phase. Under the experimental conditions and according to the maximization method, test substance CAS# 2167-23-9 did not induce delayed contact hypersensitivity in guinea-pigs.

QSAR predictions indicate that organic peroxides like substance CAS# 78-63-7 in general are capable of forming reactive oxygen species that can bind to DNA or protein (QSAR Toolbox). However, for CAS# 78-63-7, nor for its structural analogues CAS# 1068-27-5 and CAS# 2167-23-9, no alert for protein binding is found (OECD toolbox).

Considering the QSAR results together with the in vivo studies conducted with structural analogues CAS# 1068-27-5 and CAS# 2167-23-9 it is concluded that the test substance CAS# 78-63-7 does not have to be classified and has no obligatory labelling requirement for skin sensitization according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2017) (including all amendments) and Regulation (EC) No 1272/2008 on classification, labelling and packaging of items and mixtures (including all amendments).

 

 

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

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:

other: Well-conducted and documented study performed under GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4100 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

while LLNA method was already available, OECD 406 was still an acceptable method at the time.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

Source: Charles River Deutschland, Kisslegg, Germany
Age: young adult animals (approx. 4 weeks old)
Identification: ear tattoo

Group housing of maximally 5 animals per labelled cage containing purified sawdust as bedding material. The acclimatization period was at least 5 days before the start of treatment.

A controlled environment was maintained in the room with optimal conditions considered as being approximately 15 air changes per hour, a temperature of 21 +/- 3 °C, a relative humidity of 30-70% and 12 hours artificial fluorescent light and 12 hours dark per day.

Free access to standard guinea pig diet. Certificates of analysis were examined and retained in the NOTOX archives. Pressed hay was provided twice a week. Free access to tap water. Certificates of quarterly analysis for tap water were examined and retained in the NOTOX archives.

Route:

intradermal

Vehicle:

corn oil

Concentration / amount:

50%

Day(s)/duration:

8

Route:

epicutaneous, semiocclusive

Vehicle:

corn oil

Concentration / amount:

50%

Day(s)/duration:

24 hrs (1 day)

No. of animals per dose:

10 animals per sex in the test group and 5 per sex in the control group.

Details on study design:

A preliminary irritation study was conducted in order to select test substance concentrations to be used in the main Study. The selection of concentrations was based on the following criteria:
- The concentrations are well-tolerated systemically by the animals.
- For the induction exposures: the highest possible concentration that produced mild to moderate irritation (grades 2 - 3).
- For challenge exposure: the maximum non-irritant concentration.
Series of test substance concentrations were tested. Practical feasibility of administration determined the highest starting-concentration for each route. The starting- and subsequent concentrations were taken from the series: 100% (undiluted), 50%, 20%, 10%, 5%, 2%, 1% and if needed, further lower concentrations using the same steps. The test system and procedures were identical to those used during the main study, unless otherwise specified. The four animals selected were between 4 and 9 weeks old. No body weights were determined.

Intradermal injections:
A series of four test substance concentrations was used, the highest concentration being the maximum concentration that could technically be injected. Each of two animals received two different concentrations in duplicate (0.1 ml/site) in the clipped scapular region. The injection sites were assessed for irritation 24 and 48 hours after treatment.

Epidermal application:
A series of four test substance concentrations was used, the highest concentration being the maximum concentration that could technically be applied. Two different concentrations were applied (0.5 ml each) per animal to the clipped flank, using Metalline patches° (2x3 cm) mounted on Medical tape# which were held in place with Micropore tape# and subsequently Coban elastic bandage°. The animals receiving intradermal injections were treated with the lowest concentrations and two further animals with the highest concentrations. After 24 hours, the dressing was removed and the skin cleaned of residual test substance using water. The treated skin areas were assessed for irritation 24 and 48 hours after exposure

Induction - Experimental animals:

Day 1: The scapular region was clipped and three pairs of intradermal injections (0.1 ml/site) were made in this area: (A), a 1:1 w/w mixture of Freunds' complete adjuvant withwater for injection; (B), the test substance at a 50% concentration; (C) a 1:1 w/w mixtureof the undiluted test substance and Freunds' complete adjuvant.

Day 3: The dermal reactions caused by the intradermal injections were assessed for irritation.

Day 8: The area between the injection sites was tereated with 0.5 ml of a 100% test substance concentration. The dressing was removed after 48 hours exposure, the the skin cleaned of residual test substance using water and the dermal reactions caused by the epidermal exposure were assessed for irritation.

Challenge:
Day 22: one flank of all animals was clipped and treated by epidermal application of a 50% test substance concentration and the vehicle (0.1 ml each) using patch test plasters. The dressing was removed after 24 hours exposure and the skin cleaned of residual test substance and vehicle using water. The treated sites were assessed for challenge reactions 24 and 48 hours after removal of the dressing.

MAIN STUDY

Initially, five control and ten experimental animals were treated. Since the animals declined in health due to unknown cause during the study, the results obtained so far were considered to be invalid and the study was intermediately terminated. A new main study was initiated with a new set of animals.
INDUCTION - Experimental animals
Day 1 The scapular region was clipped and three pairs of intradermal injections (0.1 ml/site) were made in this area as follows:
A) A 1:1 w/w mixture of Freunds' Complete Adjuvant (Difco, Detroit, U.S.A.) with water for injection (Fresenius AG, Bad Homburg, Germany).
B) The test substance at a 50% concentration.
C) A 1:1 w/w mixture of the undiluted test substance and Freunds' Complete Adjuvant.
Note: One of each pair was on each side of the midline and from cranial A) to caudal C).
Day 3 The dermal reactions caused by the intradermal injections were assessed for irritation.
Day 8 The area between the injection sites was treated with 0.5 ml of a 100% test substance concentration using a Metalline patch (2x3 cm) mounted on Medical tape, which was held in place with Micropore tape and subsequently Coban elastic bandage. The dressing was removed after 48 hours exposure, the skin cleaned of residual test substance using water and the dermal reactions caused by the epidermal exposure were assessed for irritation.
INDUCTION - Control animals
The control animals were treated as described for the experimental animals except that, instead of the test substance, vehicle alone was administered.
CHALLENGE - All animals
Day 22 One flank of all animals was clipped and treated by epidermal application of a 50% test
substance concentration and the vehicle (0.1 ml each), using Patch Test Plasters (Curatest®, Lohmann, Almere, The Netherlands). The patches were held in place with Micropore tape and subsequently Coban elastic bandage. The dressing was removed after 24 hours exposure and the skin cleaned of residual test substance and vehicle using water. The treated sites were assessed for challenge reactions 24 and 48 hours after removal of the dressing.

Challenge controls:

The control animals were treated as described for the experimental animals except that, instead of the test substance, vehicle alone was administered.

Positive control substance(s):

yes

Remarks:

alpha-hexylcinnamicaldehyde, at 20%

Positive control results:

A reliability check is carried out at regular intervals to check the sensitivity of the test system and the reliability of the experimental techniques as used by NOTOX. The skin reactions observed in five experimental animals in response to the 20% test substance

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none observed

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 50%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none observed.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

50%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

none observed

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 50%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none observed.

Interpretation of results:

not sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

There was no evidence that the test article had caused skin hypersensitivity in the guinea pig, since no responses were observed in the experimental animals in the challenge phase. This result indicates a sensitization rate of 0 per cent.

Based on these results, the test substance does not have to be
classified and has no obligatory labelling requirement for skin sensitization according to
the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the
United Nations (2017) (including all amendments) and Regulation (EC) No 1272/2008 on
classification, labelling and packaging of items and mixtures (including all amendments).

Executive summary:

Assessment for Contact Hypersensitivity to CAS# 1068 -27 -5 in the Albino Guinea Pig(Maximisation Test).

The study was carried out based on the guidelines described in: EC Commission Directive 96/54/EC, Part B.6, "Skin Sensitisation", OECD No. 406, "Skin Sensitisation", EPA OPPTS870.2600 "Skin Sensitisation", August 1998 and JMAFF: Japanese Test Guidelines (draft), July 2000 and based on the method described by Magnusson and Kligman, "Allergic ContactDermatitis in the Guinea Pig - Identification of Contact Allergens".

Test substance concentrations selected for the main study were based on the results of a preliminary study. In the main study, ten experimental animals were intradermally injected with a 50% concentration and epidermally exposed to a 100% concentration. Five control animals were similarly treated, but with vehicle alone (corn oil). Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle. No skin reactions were evident after the challenge exposure in the experimental and control animals.

There was no evidence that the test article had caused skin hypersensitivity in the guinea pig, since no responses were observed in the experimental animals in the challenge phase. This result indicates a sensitisation rate of 0 per cent.

Based on these results, the test item does not have to be classified and has no obligatory labelling requirement for skin sensitization according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2017) (including all amendments) and Regulation (EC) No 1272/2008 on classification, labelling and packaging of items and mixtures (including all amendments).

Reference 2

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

A Buehler test was performed on the registered substance CASA# 78 -63 -7. The results of this study were inconclusive and contradictory to those found for structural analogues. The results of a maximization study, on the read-across substance,1068 -27 -5, are used to support the conclusion that 78 -63 -7 is not sensitizing. In addition, another structural analog, CAS# 2167 -23 -9, was also negative in the guinea pig maximization study. (See section 13 for read-across justification).

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Results from guinea pig maximization studies, on analog substances, do not meet the criteria for classification.