Reaction mass of 4-methylpentane-2,2-diyl dihydroperoxide, dioxybis-4-methylpentane-2,2-diyl dihydroperoxide and methylisobutylketon

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 1999-04-20

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:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Version / remarks:

1996

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 GPMT was an internationally accepted and recommended method to assess sensitising properties.

Test material

Test material information

Constituent 1

Reference substance name:

2-[(2-hydroperoxy-4-methylpentan-2-yl)peroxy]-4-methylpentane-2-peroxol; 4-methylpentan-2-one; 4-methylpentane-2,2-diperoxol

EC Number:

942-932-9

Cas Number:

37206-20-5

Molecular formula:

Reaction mass of C6H14O4 and C12H26O6 and C6H12O

IUPAC Name:

2-[(2-hydroperoxy-4-methylpentan-2-yl)peroxy]-4-methylpentane-2-peroxol; 4-methylpentan-2-one; 4-methylpentane-2,2-diperoxol

additive 1

Reference substance name:

Diisobutyl phthalate

EC Number:

201-553-2

EC Name:

Diisobutyl phthalate

Cas Number:

84-69-5

Molecular formula:

C16H22O4

IUPAC Name:

diisobutyl phthalate

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: Individual body weights did not exceed 500 grams
- Housing: Group housing of 5 animals per labelled metal cage with wire-mesh floors and equipped with an automatic drinking system (ITL, Bergen, The Netherlands).
- Diet: Free access to standard guinea pig diet, including ascorbic acid (1600 mg/kg); LC 23-B, pellet diameter 4mm (Hope farms, Woerden, The Netherlands).
- Water: Free access to tap-water, diluted with decalcified water.
- Acclimation period: At least 5 days before the start of treatment under laboratory conditions

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21
- Humidity (%): 50
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (non-LLNA)

Induction

Route:

intradermal and epicutaneous

Vehicle:

propylene glycol

Concentration / amount:

2 %

Challenge

Route:

epicutaneous, semiocclusive

Vehicle:

propylene glycol

Concentration / amount:

0.5 %

No. of animals per dose:

Experimental group: 10 females
Control group: 5 females

Details on study design:

RANGE FINDING TESTS: 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.

MAIN STUDY
A. INDUCTION EXPOSURE (Intradermal and epidermal)
- No. of exposures: 6 intradermal injections (2 injections each of 0.1 mL Freund's adjuvant without the test substance emulsified with water in ratio 1:1; 2 injections 0.1 mL each containg 2 % of the test substance; 2 injections each of 0.1 mL Freund's adjuvant/water (1:1) with test substance). After one week percutaneous induction was carried out (single 48 hours application under occlusive conditions).
- Exposure period: 48 hours
- Test groups: 10 animals
- Control group: 5 animals: Were treated as described for the experimental animals, except that instead of the test substance, vehicle alone was administered.
- Site: clipped flank
- Frequency of applications: 6 simultaneous intradermal injections, one week later, single percutaneous administration
- Duration: one week before percutaneous challenge; 48 hours exposure; ca. 14 days later the first challenge.
- Concentrations: 2 % of test substance

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: On day 21
- Exposure period: 24 hours
- Test groups: 10 animals
- Control group: 5 animals (Treated like test group)
- Site: intact clipped flank
- Concentrations: 0.5 % of test substance
- Evaluation (hr after challenge): 24 h and 48 h after removal of dressing

Challenge controls:

Challenge control group was treated like test group.

Positive control substance(s):

no

Results and discussion

In vivo (non-LLNA)

Results

Results 1

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

0.5 %

No. with + reactions:

5

Total no. in group:

10

Results 2

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

0.5 %

No. with + reactions:

5

Total no. in group:

10

Clinical observations:

scaliness and necrosis

Results 3

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

0.5 %

No. with + reactions:

0

Total no. in group:

5

Results 4

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

0.5 %

No. with + reactions:

0

Total no. in group:

5

Results 5

Group:

positive control

Remarks on result:

not measured/tested

Applicant's summary and conclusion

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Conclusions:

The skin sensitizing potential of the test item was determined in a study according to OECD guideline 406. The test item 45 % in diisobutyl phtalate indicate a sensitisation rate of 50 %.

Executive summary:

Assessment for Contact Hypersensitivity to the test item 45% in Diisobutyl Phtalate 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" and OECD No. 406, "Skin Sensitisation", and based on the method described by Magnusson and Kligman, "Allergic Contact Dermatitis 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 2% concentration and epidermally exposed to a 2% concentration. Five control animals were similarly treated, but with vehicle alone (propylene glycol). Two weeks after the epidermal application all animals were challenged with a 0.5% test substance concentration and the vehicle.

Skin reactions varying between grades 1 and 3 were observed in nine experimental animals in response to the 0.5% test substance concentration. Skin reactions of grade 1 were observed in two control animals in response to the 0.5% test substance concentration and the vehicle.

Scaliness or signs of necrosis were seen in some treated skin sites among the experimental animals.

The skin reactions grade 1 were considered to be non specific skin reactions. The skin reactions observed in the vehicle treated skin-site in two control animals were unexpected, but were considered to have occurred by accident. Leakage from adjacent treated sites may possibly have occurred. Taking into account the intensity of the responses and comparing these with the skin reactions seen in the control animals, it was considered that hypersensitivity to the test item had been induced in five (of the ten) experimental animals. These results indicate a sensitisation rate of 50 %.