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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 404 (Acute Dermal Irritation / Corrosion)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 2,4,4-trimethylpentene (also known as diisobutylene and diisobutene)
- Physical state: clear, colourless liquid
- Analytical purity: 95.19%
- Lot/batch No.: Batch No. 2 (a 50:50 mixture of two original batches of 2,4,4-trimethylpentene - Batch No. R11 supplied by Shell and Batch No. 155833 supplied by Erdolchemie).
- Expiration date of the lot/batch: 29 April 1997
- Storage condition of test material: Under nitrogen, protected from light, in a cool store.

Test animals

Species:
rabbit
Strain:
New Zealand White
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Froxfield SPF Rabbits, Broadway Farm, Froxfield, Hampshire, England
- Age at study initiation: Approximately 3 months
- Weight at study initiation: 2.23-2.52 kg
- Housing: Individually housed in suspended stainless steel cages
- Diet: Standard pelleted rabbit diet (STANRAB (P) SQC - Special Diets Services Ltd., Witham, Essex, England) ad libitum
- Water: Tap water ad libitum
- Acclimation period: Not reported

ENVIRONMENTAL CONDITIONS
- Temperature: 18-25°C
- Humidity: 40-68%
- Air changes: at least 10/hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 28 May 1996 To: 12 June 1996

Test system

Type of coverage:
semiocclusive
Preparation of test site:
shaved
Vehicle:
unchanged (no vehicle)
Controls:
no
Amount / concentration applied:
TEST MATERIAL
Amount(s) applied: 0.5 mL
Duration of treatment / exposure:
4 hours
Observation period:
16 days
Number of animals:
3
Details on study design:
TEST SITE
- Day prior to application, the dorsum between the limb girdles was clipped
- Two areas 6 cm x 6 cm on either side of dorsum were marked
- Area of exposure: 3 cm x 2 cm on left dorsum
- Type of wrap: gauze patch (3 cm x 2 cm) held in place by strips of Blenderm. Pads of cotton wool and elasticated bandage used to protect patches and ensure good contact between skin and test substance
- Control site: 3 cm x 2 cm on right dorsum was covered by similar semi-occlusive dressing but otherwise remained untreated

REMOVAL OF TEST SUBSTANCE
- Washing: skin sites gently washed with warm water and dried with paper tissues
- Time after start of exposure: 4 hours

SCORING SYSTEM: Draize, 1959

Results and discussion

In vivo

Resultsopen allclose all
Irritation parameter:
erythema score
Basis:
mean
Time point:
other: 24, 48 and 72 hours after removal of dressings
Score:
1.6
Max. score:
2
Reversibility:
fully reversible within: 13 days
Irritation parameter:
edema score
Basis:
mean
Time point:
other: 24, 48 and 72 hours
Score:
0
Max. score:
0
Irritant / corrosive response data:
Very slight/ well defined erythema, spreading beyond test site, was present during first 7-10 days after application. Eschar formation was apparent in all animals 24 hours after dressing removal, resolving in one rabbit at 48 hours and in others by day 7. Exfoliation was evident at all test sites during the 2nd week and was still present in one animal at termination on day 16.

Any other information on results incl. tables

 Skin irritation scores according to the Draize scheme

Time

Erythema (Test/Control sites)

Oedema (Test/Control sites)

 Animal number

837

847

766

837

847

766

after 1 hour

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

0 / 0

after 24 hours

2*s/ 0

2*s/ 0

2*s/ 0

0 / 0

0 / 0

0 / 0

after 48 hours

1*/ 0

1*s/ 0

2*s/ 0

0 / 0

0 / 0

0 / 0

after 72 hours

1*/ 0

1*s/ 0

2*s/ 0

0 / 0

0 / 0

0 / 0

mean scores 24-72h

1.3

1.3

2

0

0

0

Overall mean score (24-72 h)

1.6

0

*   lesion spread beyond test site

s    eschar formation

Applicant's summary and conclusion

Interpretation of results:
not irritating
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Mean values for erythema and oedema (at 24, 48 and 72 hours after application) did not equal or exceed EU limit values. Therefore, 2,4,4-trimethylpentene does not require classification for skin irritation.
Executive summary:

Skin irritation was assessed in a group of New Zealand white rabbits by applying 0.5 mL undiluted 2,4,4-trimethylpentene to the shaved skin under a semi-occlusive dressing for 4 hours. Very slight/ well defined erythema, spreading beyond test site, was present during first 7-10 days after application. Eschar formation was apparent in all animals 24 hours after dressing removal, resolving in one rabbit at 48 hours and in others by day 7. Exfoliation was evident at all test sites during the 2nd week and was still present in one animal at termination on day 16. Mean values for erythema and oedema (at 24, 48 and 72 hours after application) did not equal or exceed EU limit values. Therefore, 2,4,4-trimethylpentene does not require classification for skin irritation.