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Skin sensitisation

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skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-01-26 to 2010-03-08
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
24 April 2002
according to guideline
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Version / remarks:
30 May 2008
GLP compliance:
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Chemical structure
Reference substance name:
Succinic anhydride
EC Number:
EC Name:
Succinic anhydride
Cas Number:
Molecular formula:
Specific details on test material used for the study:
- White flakes with pungent odour.
- Solubility in water of 50 g/L (20° C, hydrolised)
- Density of 1.2340.
- Melting point of 119.6 C.
- Stable at room temperature.
- Name of test material (as cited in study report):succinic anhydride
- Substance type: dihydro-2,5-furandion cyclic acid anhydride
- Physical state: solid
- Analytical purity: 99.5%
- Purity test date: 22 October 2009
- Lot/batch No.: LEBA5A3070
- Expiration date of the lot/batch: 30 June 2010
- Stability under test conditions: stable
- Storage condition of test material: room temperature

In vivo test system

Test animals

Details on test animals and environmental conditions:
- Source: Harlan Italy, 1-33049 San Pietro all \latisone (UD).
- Females nulliparous and non-pregnant: yes
- Age at study initiation: About 8 weeks at the first administration.
- Weight at study initiation: 17.8 -22.2 g.
- Housing: Mice were individually housed in Makrolon cages type II, (22 cm x 16.S cm ground area, 15 cm high). Bedding material consisted of Aspen wood chips (Fa. ABEDD Dominik Mayr KEG, A-8580 Köflach). Germ reduction by autoclaving; Changed 1/week. Random samples of the bedding material are analysed for contaminants by the supplier. One sample is analysed also for contaminants in addition by an independent external laboratory. The limits of tolerance are the same as with the feed.
- Diet: Maintenance diet for rats and mice R/M-H (item V1534-300), autoclavable, ad libitum.
Random samples of the feed are analysed for contaminants by the manufacturer: Ssniff Spezialdiaten GmbH, D-59494 Soest. One sample is analysed also for contaminants in addition by an independent external laboratory. The limits of tolerance are derived from the "Deutsche Futtermittelverordnung" (German feed regulation).
- Water (e.g. ad libitum): Tap water from Makrolon-bottles with stainless steel canules, ad libitum.
Random samples of the water are analysed for contaminants and germ content by the "AGES", A-1226 Vienna. The limits of tolerance are identical with that used for drinking water for humans in Austria.
- Acclimation period: Mice were acclimated for 13 days
- Indication of any skin lesions: not specifed

- Temperature (°C): Average of 21.2°C (continuous monitoring and recording).
- Humidity (%): Average of 58.9 % (continuous monitoring and recording).
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): Only artificial light from 6.00 a.m. to 6.00 p.m.
- IN-LIFE DATES: From: 2010-01-13 To: 2010-02-01

Study design: in vivo (LLNA)

10, 25, and 31.3% (w/w) succinic anhydride
No. of animals per dose:
5 animals/ group (including spare animals). The spare animal of the low dose group died and therefore, the spare animals of other groups were not used. The number of animals/group used for lymph node examination was 4.
Details on study design:
Solubility testing of the test substance showed the highest concentration suitable for application of the test substance can be achieved with DMF (31.3%, w/w).

A range finding study was performed with 2 animals/concentration at 31.3 and 25% succinic anhydride. None of the animals showed overt systemic toxicity, excessive local skin irritation at the application sites or an important increase in ear thickness in the range finding study. Therefore, 31.3% was chosen as the highest test substance concentration and ear thickness measurement was not performed in the main study.

Main study: Test solutions were prepared fresh on each day of administration and administered in 3 concentrations to the dorsal surfaces of the ears of mice. One negative control group and one positive control group were treated with dimethylformamide (DMF) and hexyl cinnamic aldehyde (HCA), respectively. Each animal was treated for 3 consecutive days. 3 days after the last topical administration, each animal received 20 uCi 3HTdR by slow intravenous administration via the tail vein. Approximately 5 hours after 3HTdR injection, all animals were sacrificed by carbon dioxide asphyxiation and the draining auricular lymph nodes were rapidly excised. The proliferation of the lymphocytes of the draining auricular lymph node was measured by the determination of the amounts of incorporated 3HTdR.
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Stimulation Indices were calculated according to the standard method (see more details in section "Any other information on materials and methods incl. tables")

Results and discussion

Positive control results:
Application of 25% HCA in acetone:olive oil (4:1 v/v) resulted in an SI of 7.3.

In vivo (LLNA)

Resultsopen allclose all
Test group / Remarks:
negative control
Remarks on result:
other: dpm: 4733
Key result
Test group / Remarks:
low dose (10% test substance)
Remarks on result:
other: dpm: 43520
Key result
Test group / Remarks:
mid dose (25% test substance)
Remarks on result:
other: dpm: 54949
Key result
Test group / Remarks:
high dose (31.3% test substance)
Remarks on result:
other: dpm: 52036
Test group / Remarks:
positive control (25% HCA)
Remarks on result:
other: 34509
Cellular proliferation data / Observations:
- The SIs of the test substance groups were between 9.2 and 11.6.

- No abnormal behaviour or clinical signs were detected during the experiment in the animals.
- No local irritations were observed at the application sites of all animals of all test substance groups and the negative control group throughout the whole study. On Days 3 and 4 all animals of the positive control group had slight erythema on the application sites indicating slight irritative skin reactions.
- One animal (No. 10) of the low dosed group died on Day 6 near the application of 3H-methyl thymidine. Since this animal showed no adverse effects and no body mass loss during the study and the gross necropsy was without observation this death is assumed as random event which is not associated with the test substance application.

- Body masses and body mass gains of all animals were in the range to be expected from animals of the same strain, sex and age.

Any other information on results incl. tables

Table 1. Body mass index of animals on days 1 and 6

 Negative control           Low dose                    Mid dose        High dose              Positive control
  No.  b.m. day 1  b.m. day 6  b.m. gain   No. 1 6   b.m.gain No. 1 6   b.mgain   No. 1 6  b.m.gain    No. 1 6  b.m.gain 
 1  19.8 21.2  1.4   6  19.1 20.1  1.0   11 21.5  22.8  1.3   16 22.2  23.2  1.0   21 19.8  20.9  1.1 
 2  19.0 19.5  0.5  7 17.8   19.4 1.6   12 19.2  20.3  1.1   17  20.0 20.7  0.7   22  20.2 21.2  1.0 
 3  20.7 21.6  0.9   8  20.6 21.6  1.0   13  18.9 20.3  1.4   18  18.3 20.0  1.7   23  19.0 20.7  1.7 
 4  19.1 20.3  1.2   9  20.8 21.6  0.8   14 19.6  20.9  1.3   19  20.2 20.9  0.7   24  19.3 20.9  1.6 
 Mean  19.7 20.7  1.0  Mean   19.6 20.7  1.1  Mean  19.8  21.1  1.3  Mean  20.2  21.2  1.0  Mean  19.6  20.9  1.4 
 SD  0.8 0.9  0.4  SD  1.4  1.1  0.3  SD  1.2  1.2  0.1  SD  1.6  1.4  0.5  SD  0.5  0.2  0.4 
 n  4  4  4  n
    No. = Animal number; b.m.= body mass in g                                                     

Table 2. General observations and observations of the application sites on days 1 -6

 Finding  Group  No. of the affected animals  Observation time (day)
 General behavior normal  Negative control  1, 2, 3, 4  1 -6
   Low dose  6, 7, 8, 9  1 -6
   Mid dose  11, 12, 13, 14  1 -6
   High dose  16, 17, 18, 19  1 -6
   Positive control  21, 22, 23, 24  1 -6
 Application sites normal  Negative control  1, 2, 3, 4  1 -6
  Low dose   6, 7, 8, 9  1 -6
   Mid dose  11, 12, 13, 14  1 -6
   High dose  16, 17, 18, 19  1 -6
 Slight erythma  Positive control  21, 22, 23, 24  3 -4

Applicant's summary and conclusion

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
The results from this local lymph node assay (OECD 429) indicate that succinic anhydride is a skin sensitizer based on stimulation indices of 9.2, 11.6, and 11.0, calculated for the low(10%), mid (25%) and high dose (31.3%) groups, respectively.
No clear dose response relationship was observed. Potency categorisation for skin sensitisation according to ECHA Guidance R.8, Appendix R. 8 -10, Table R. 8 -23 was not possible, since no EC3 value could be calculated for succinic anhydride from the data obtained in this study.
Executive summary:

In a dermal sensitization study conducted according to OECD TG 429 with succinic anhydride (99.5%) in dimethlformamide, three groups of 4 female young adult CBA/CaOlaHsd mice/dose group were tested in the local lymph node assay.

Succinic anhydride was administered epicutaneously to the dorsal surface of both ears, once a day on three consecutive days, at concentrations of 10%, 25%, or 31.3% (w/w). The volume administered was 25 uL per ear. Positive (25% hexyl cinnamic aldehyde in acetone:olive oil) and negative control (dimethylformamide) groups were tested concurrently under identical conditions. Five days after topical administration, 3H-methyl thymidine was administered intravenously to all mice via a tail vein. Approximately 5 hours later, the draining auricular lymph nodes were excised, incorporation of radiolabelled 3HTdR was determined and compared with negative controls, and the SI index was calculated.

No adverse effects were noted in any animal. The SIs of the test substance concentrations were 9.2 (low dose), 11.6 (mid dose), and 11.0 (high dose). Although no clear dose response was observed, the SIs of all test substance concentrations were greater than 3 and succinic anhydride is regarded as a sensitizer in the LLNA.

Based on these results, classification of succinic anhydride as skin sensitizer Category 1 according to the CLP criteria set out in Regulation (EC) 1272/2008 is warranted.