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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001-06-27 to 2001-08-07
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Certificate from the Swiss GLP Monitoring Authorities
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The Murine Local Lymph Node Assay (LLNA) is the first-choice method for in vivo testing according to the REACH Regulation. However, this reliable GPMT test was performed before entry into force of the REACH Regulation.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Details on test material:
- Name of test material (as cited in study reports): T002102
- Physical state: solid
- Appearance: white (SDS)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: RT002102G4A311
- Expiration date of the lot/batch: 25 March 2002 (retest date)
- Purity: 99.4%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: In the original container, at room temperature (range 20 ± 3°C), away from direct sunlight
- Solubility and stability of the test substance in the solvent/vehicle: Stable at 20% (w/v) in PEG 300 for at least 7 days at room temperature.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test item and vehicle or auxillary compound were placed into a glass beaker on a tared Mettler PM 460 balance and a weight dilution was prepared. Homogeneity of the test item preparation was ensured and maintained during treatment using a magnetic stirrer and/or Ultra-Turrax. The preparations were made immediately prior to dosing.


In vivo test system

Test animals

Species:
guinea pig
Strain:
other: Ibm: GOHI guinea pigs (synonym: Himalayan spotted)
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: SPF-Quality, RCC Ltd., Biotechnology & Animal Breeding Division, Switzerland
- Females (if applicable) nulliparous and non-pregnant: not specified
- Age at study initiation: 4-6 weeks at pretest start/beginning of acclimatization period, 5-7 weeks at main study start
- Weight at study initiation: 346-362 g (pretest group) at pretest start, 308-380 g (control and test groups) at beginning of acclimatization period.
- Housing: individually in Makrolon type-4 cages with standard softwood bedding
- Diet (e.g. ad libitum): Pelleted standard Provimi Kliba 3418, batch nos. 90/01 and 91/01, guinea pig breeding/maintenance diet, containing Vitamin C, ad libitum
- Water (e.g. ad libitum): Community tap water from Fűllinsdorf, ad libitum
- Acclimation period: One week for the control and test group under test conditions after health examination. No acclimatization for the animals of the pretest. Only animals without any visible signs of illness were used for the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30-70%
- Air changes (per hr): approx 10-15 air changes per hour
- Photoperiod (hrs dark / hrs light ):12 hours light and 12 hours dark. Music was played during the light period

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal
Vehicle:
polyethylene glycol
Concentration / amount:
volume: 0.1 mL/site
test group: 5% test item in PEG 300 or 5% test item in a 1/1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline
Day(s)/duration:
day 1
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Route:
epicutaneous, occlusive
Vehicle:
polyethylene glycol
Remarks:
PEG 300
Concentration / amount:
concentration: 75% test item in bi-distilled water
volume applied: 0.3 mL
Day(s)/duration:
day 8 - 48 hours
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Challenge
Route:
epicutaneous, occlusive
Vehicle:
polyethylene glycol
Concentration / amount:
volume: 0.2 g
test item: 75%: applied to the left flank
vehicle only (bi-distilled) applied to the right flank
Day(s)/duration:
day 22 - 24 hours
Adequacy of challenge:
highest non-irritant concentration
No. of animals per dose:
1 for intradermal pretest, 2 for epidermal pretest, 5 for control group, 10 for the test group.
Details on study design:
RANGE FINDING TESTS:
- Intradermal injections: Four intradermal injections (0.1 mL/site) of a 1:1 (v/v) mixture of Freund's Complete Adjuvant/physiological saline were made into the shaved neck of one guinea pig. One week later intradermal injections (0.1 mL/site) were made into the clipped flank of the same guinea pig at concentrations of A=10%, B=5%, and C=3% of the test substance in PEG 300. The three concentrations were determined during non-GLP formulation trials performed prior to the pretest. Dermal reactions were assessed 24 hours later. Based on the results, the test substance concentration of 10% was selected for intradermal induction in the main study.
-Epidermal application: Four intradermal injections (0.1 mL/site) of a 1:1 (v/v) mixture of Freund's Complete Adjuvant/physiological saline were made into the shaved neck of two guinea pigs. One week later both flanks of each of the guinea pigs were clipped and shaved just prior to the application. Thereafter, 4 patches of filter paper (3 x 3 cm) were saturated with the test substance at D=50%, E=25%, F=15%, and G=10% in PEG 300 and applied to the clipped and shaved flanks. The volume of the test substance preparation applied was approximately 0.2 mL. The patches were covered by a strip of aluminum foil and firmly secured by elastic plaster wrapped around the trunk and covered with impervious adhesive tape. The dressings were removed after an exposure period of 24 hours. Twenty-four hours after removal of the dressing, the application site was depilated with an approved depilatory cream for 3-5 minutes in order to visualize any resulting erythema. The cream was then thoroughly washed off with water. The reaction sites were assessed 24 and 48 hours after removal of the bandage according to the method of Magnusson and Kligman. Based on the results obtained, the concentration selected for induction and challenge in the main study was 50% and 15%, respectively.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2
- Exposure period: Intradermal injections were performed on test Day 1; Epidermal applications were performed on test Day 8.
- Test groups:
intradermal injections (day1):
An area of dorsal skin from the scapular region (approximately 6 x 8 cm) was clipped free of hair. Three pairs of intradermal injections (0.1 mL/site) were made at the border of a 4 x 6 cm area in the clipped region as follows:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline,
2) the test substance at 10% in PEG 300, and
3) The test substance at 10% in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
epidermal applications (day 8)
One week after the injection, the scapular area (approximately 6 x 8 cm) was again clipped and shaved free of hair prior to application. A 2 x 4 cm patch of filter paper was saturated with approximately 0.3 mL of the test substance (50% in PEG 300) and placed over the injection sites of the test animals. The patch was covered with aluminum foil and firmly secured by an elastic plaster wrapped around the trunk of animal and secured with impervious adhesive tap. The occlusive dressing was left in place for 48 hours. The reaction sites were assessed 24 and 48 hours after removal of the bandage for erythema and oedema according to the method of Magnusson and Kligman.
- Control group: Three pairs of intradermal injections (0.1 mL/site) as follows:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline,
2) PEG 300, and
3) 1:1 (v/v) mixture of PEG 300 in a 1:1 (v/v) mixture Freund's Complete Adjuvant and physiological saline. For the epidermal exposure, approximately 0.3 mL of PEG 300 was applied.
- Site: Intradermal injection: an area of dorsal skin from the scapular region; epidermal induction: scapular area.
- Frequency of applications: one time intradermal, one time epidermal
- Duration: one time intradermal injection, and 48 hours for epidermal exposure
- Concentrations: 10% for intradermal injection; 50% for epidermal application

B. CHALLENGE EXPOSURE
- No. of exposures: one exposure
- Day(s) of challenge: Test Day 22
- Exposure period: 24 hours
- Test groups: Test substance (15% in PEG 300; 0.3 mL) was applied to the shaved left flank. 21 hours after removal of the dressing the test sites treated with the test substance were depilated as described in the epidermal pretest.
- Control group: PEG 300 (0.3 mL) was applied to the right flank.
- Site: left (test item) and right (control group) flank
- Concentrations: 15%
- Evaluation (hr after challenge): The reaction sites were assessed 24- and 48-hours after removal of the bandage for erythema and oedema according to the method of Magnusson and Kligman.
The scoring system was performed by visual scoring of erythema, oedema and other clinical changes of skin conditions. They were assessed using the following Magnusson and Kligman grading scale:
0 = no visible change
1 = discrete or patchy erythema
2 = moderate and confluent erythema
3 = intense erythema and swelling
Grading of all animals was done by positioning the animal under true-light.

OTHER:
Rating of allergenicity according to Magnusson and Kligman
Based on the percentage of animals sensitized (24- and 48-hour readings), the test substance was assigned to one of five grades of allergenic potency according to Magnusson and Kligman.
Challenge controls:
A patch of filter paper saturated with the vehicle only (PEG 300) was applied to the right flank.
Positive control substance(s):
yes
Remarks:
2-mercaptobenzothiazole

Results and discussion

Positive control results:
The study was performed with 15 (10 test and 5 control) male albino guinea pigs. The intradermal induction of sensitization in the test group was performed in the nuchal region with a 5% dilution of the test item in mineral oil and in an emulsion of Freund's Complete Adjuvant (FCA) / physiological saline. The epidermal induction of skin sensitization was conducted for 48 hours under occlusion with the test item at 50% in mineral oil one week after the intradermal induction. The animals of the control group were intradermally induced with mineral oil and FCA/physiological saline and epidermally induced with mineral oil under occlusion. Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test item at 0.5% in mineral oil and mineral oil alone under occlusive dressing. Cutaneous reactions were evaluated at 24 and 48 hours after removal of the dressing. No toxic symptoms were evident in the guinea pigs of the control or test group. No deaths occurred.
All 10 test animals showed discrete/patchy to intense erythema and swelling at the 24-and 48-hour reading after the challenge treatment with 2-mercaptobenzothiazole at 0.5% (w/w) in mineral oil.
No skin effect was observed in the control group.
Based on these findings, 2-mercaptobenzothiazole has to be classified and labelled as a skin sensitizer.

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
15% in PEG 300 (left flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
no signs of systemic toxicity were observed in the animals
Remarks on result:
positive indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
Dose level:
15% in PEG 300 (left flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
no signs of systemic toxicity were observed in the animals
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
PEG 300 (right flank)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no signs of systemic toxicity were observed in the animals
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
PEG 300 (right flank)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no signs of systemic toxicity were observed in the animals
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
0.5 % in mineral oil (left flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
no toxic symptoms were evident in the guinea pigs
Remarks on result:
positive indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
28
Group:
positive control
Dose level:
0.5 % in mineral oil (left flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
no toxic symptoms were evident in the guinea pigs
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
Mineral oil only (right flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
no toxic symptoms were evident in the guinea pigs
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
Mineral oil only (right flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No toxic symptoms were evident in the guinea pigs
Remarks on result:
no indication of skin sensitisation

Any other information on results incl. tables

Skin effects after intradermal induction - performed on test day 1:

The expected and common findings were observed in the control and test groups after the different applications using FCA intradermally and consisted of erythema, oedema, necrotizing dermatitis, encrustation and exfoliation of encrustation.

Skin effects after epidermal induction - performed on test day 8:

No erythematous or oedematous reactions were observed in the animals treated with PEG 300 only in the control group. Discrete/patchy erythema was observed in all animals at the 24 -hour reading, and in 9 out of 10 animals at the 48 -hour reading after treatment with the test substance at 50% in PEG 300 in the test group.

Skin effects after the challenge - performed on test day 22:

No skin reactions were observed in the animals when treated with either PEG 300 only, or when treated with the test substance at 15% in PEG 300. In the test group, discrete/patchy erythema was observed in all animals at the 24- and 48 -hour readings after treatment with the test substance at 15% in PEG 300, and no skin reactions were observed in the animals when treated with PEG 300 only.

There were no deaths during the course of the study. No signs of systemic toxicity were observed in any animals. The body weights of the animals were within the normal range for animals of this strain and age.

Applicant's summary and conclusion

Interpretation of results:
Category 1B (indication of skin sensitising potential) based on GHS criteria
Conclusions:
Based on the above mentioned findings in an adjuvant sensitization test in guinea pigs and in accordance to Commission Directive 96/54/EEC, the test substance does have to be classified and labelled as an extreme skin sensitizer. With a response of > 30% at >1% intradermal induction dose, the substance is classified as a skin sensitiser category 1B according to the criteria of the CLP Regulation.