dimethyl 1,2-benzenedicarboxylate;reaction mass of: 1,2-dimethylpropylidene dihydroperoxide

Endpoint summary

Description of key information

A GPMT was peformed with the substance. In the main study, ten experimental animals were intradermally injected with a 1% concentration and epidermally exposed to a 5% 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 2% test substance concentration and the vehicle. A second challenge was performed one week later with a 2% test substance concentration and the vehicle.

Based on the results of a GPMT a sensitization rate of 30% was concluded since three of the ten animals showed a positive skin reaction (grade 1) at the first challenge. The skin reactions observed in the first challenge phase in response to a 2% test substance concentration in six (of the ten) experimental animals were confirmed in the second challenge phase and were therefore considered indicative of sensitisation, based on the absence of any response in the control animals. These results indicate a sensitisation rate of 60 per cent a 1% intradermal induction dose.

The substance is a skin sensitizer.

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

Study period:

11 February 2002 - 28 March 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Qualifier:

according to guideline

Guideline:

other: "Allergic Contact Dermatitis in the Guinea-Pig: Identification of Contact Allergens" Magnusson B. Kligman A.M., 1970 published by C.C. Thomas, Springfield, Illinois, USA.

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

study was commissioned before LLNA method was adopted

Species:

guinea pig

Strain:

Himalayan

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Biotechnology & Animal Breeding Division (RCC Ltd.), Fullinsdorf, Switzerland.
- Age at study initiation: approx. 5 weeks old
- Weight at study initiation: mean ±358g
- Housing: Group housing of 5 animals per labelled metal cage with wire-mesh floors.
- Diet (e.g. ad libitum): Free access to standard guinea pig diet, including ascorbic acid (1000 mg/kg); (Charles River Breeding and Maintenance Diet for Guinea Pigs, Altromin, Lage, Germany). Certificates of analysis were examined and retained in the NOTOX archives. Hay (B.M.I., Helmond, The Netherlands) was provided twice a week.
- Water (e.g. ad libitum): Free access to tap water. Certificates of quarterly analysis for tap-water were examined and retained in the NOTOX archives
- Acclimation period:The acclimatisation period was at least 5 days before the start of treatment under laboratory conditions.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 3
- Humidity (%): 30-70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: 11 February 2002 - 28 March 2002

Route:

intradermal and epicutaneous

Vehicle:

corn oil

Concentration / amount:

Induction:
intradermal;
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 1% concentration.
C) A 1:1 w/w mixture of the test substance, at twice the concentration used in (B) and Freunds' Complete Adjuvant.
epicutaneous; 5%
Challenge:epicutaneous; 2%

Route:

epicutaneous, occlusive

Vehicle:

corn oil

Concentration / amount:

Induction:
intradermal;
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 1% concentration.
C) A 1:1 w/w mixture of the test substance, at twice the concentration used in (B) and Freunds' Complete Adjuvant.
epicutaneous; 5%
Challenge:epicutaneous; 2%

No. of animals per dose:

Control group: 5
Test group: 10

Details on study design:

RANGE FINDING TESTS:
A preliminary irritation study was conducted in order to select test substance concentrations to be used in the main study.

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 1% concentration.
C) A 1:1 w/w mixture of the test substance, at twice the concentration used in (B) 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 scapular area between the injection sites was clipped and subsequently treated with 0.5 ml of a 5% 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 2% 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.

Day 29 A re-challenge was conducted approximately one week after the first challenge, to clarify the results in the first challenge. The contralateral flank of all animals was similarly treated.

Positive control substance(s):

no

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

2%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 2%. No with. + reactions: 0.0. Total no. in groups: 5.0.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

2%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 2%. No with. + reactions: 0.0. Total no. in groups: 5.0.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

2%

No. with + reactions:

1

Total no. in group:

10

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 2%. No with. + reactions: 1.0. Total no. in groups: 10.0.

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

2%

No. with + reactions:

2

Total no. in group:

10

Clinical observations:

scaliness was observed in 6 animals

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 2%. No with. + reactions: 2.0. Total no. in groups: 10.0. Clinical observations: scaliness was observed in 6 animals.

Key result

Reading:

rechallenge

Hours after challenge:

192

Group:

negative control

Dose level:

2%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: rechallenge. . Hours after challenge: 192.0. Group: negative control. Dose level: 2%. No with. + reactions: 0.0. Total no. in groups: 5.0.

Key result

Reading:

rechallenge

Hours after challenge:

216

Group:

test chemical

Dose level:

2%

No. with + reactions:

4

Total no. in group:

10

Remarks on result:

other: Reading: rechallenge. . Hours after challenge: 216.0. Group: test group. Dose level: 2%. No with. + reactions: 4.0. Total no. in groups: 10.0.

Key result

Reading:

rechallenge

Hours after challenge:

216

Group:

test chemical

Dose level:

2%

No. with + reactions:

7

Total no. in group:

10

Clinical observations:

scaliness was observed in 7 animals

Remarks on result:

other: Reading: rechallenge. . Hours after challenge: 216.0. Group: test group. Dose level: 2%. No with. + reactions: 7.0. Total no. in groups: 10.0. Clinical observations: scaliness was observed in 7 animals.

PRELIMINARY IRRITATION STUDY

Based on the results, the test substance concentrations selected for the main study were a 1% concentration for the intradermal induction and a 5% concentration for the epidermal induction exposure. A 2% test substance concentration was selected for the challenge phase.

For further details on results see attached tables.

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Remarks:

Migrated information

Conclusions:

Based on the results the substance is classified as skin sensitizing category 1.

Executive summary:

Assessment for Contact Hypersensitivity 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" and EPA OPPTS 870.2600 "Skin Sensitisation", August 1998 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 1% concentration and epidermally exposed to a 5% 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 2% test substance concentration and the vehicle. A second challenge was performed one week later with a 2% test substance concentration and the vehicle.

In the first challenge phase skin reactions of grade 1, were observed in three experimental animals in response to the 2% test substance concentration. No skin reactions were evident in the control animals. Scaliness was seen in some treated skin sites of among the experimental

animals.

To confirm the results of the first challenge, a second challenge was performed one week later. In the second challenge phase skin reactions varying between grades 1 and 2, were observed in seven experimental animals in response to the 2% test substance concentration. No skin reactions were evident in the control animals. Scaliness was seen in some treated skin sites among the experimental animals.

Since scaliness was not observed in control animals, it may be indicative of sensitisation in the experimental animals. Therefore, scaliness was taken into account for the establishment of the sensitisation rate.

The skin reactions observed in the first challenge phase in response to a 2% test substance concentration in six (of the ten) experimental animals were confirmed in the second challenge phase and were therefore considered indicative of sensitisation, based on the absence of any response in the control animals. These results indicate a sensitisation rate of 60 per cent a 1% intradermal induction dose.

2018 Evaluation

The study was conducted in a proper way and the selection of the highest concentrations that could be used for the main study were performed in accordance with the test guidelines. For the evaluation of the first challenge results, the report states that “Since scaliness was not observed in control animals, it may be indicative of sensitization in the experimental animals”. This statement is scientifically sound by itself, but the guidelines and literature for proper interpretation of the data indicate that only positive skin reactions (grade 1 or more) and not scaliness should be considered as signs of sensitization, provided that such reactions are not observed or are less persistent in the control group. Applying this interpretation to the results of the first challenge, a sensitization rate of 30% would have been concluded since three of the ten animals showed a positive skin reaction (grade 1). This means that the first challenge was conclusive and hence there was no need to clarify or confirm the responses. It should be mentioned however that the responses were not strong, were observed at one time point for each animal and only 3 animals responded (which is exactly on the 30% threshold for classification). The strong positive response during the second challenge confirms that the compound has sensitizing capability in the guinea pig but no relevance for the sensitizing potential or potency for humans should be attached to this second challenge. Firstly, this challenge was performed while there was no need to clarify the response to the first challenge and secondly, the first challenge may have further induced the animals thereby significantly enhancing the response.

In conclusion, only the results of the first challenge should be used for interpretation and classification and although the results were not strong and exactly on the borderline for classification, the results suggest that MIPKP may act as a weak sensitizer in humans (Category 1B according to Regulation (EC) No 1272/2008).

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:

adverse effect observed (sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

MIKP is classified as a sensitizer based on the results of a GPMT. Therefore it is classified for Skin Sensitization cat. 1.