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Description of key information

The substance S-10793 is a moderate skin sensitizer, having an EC3 value of 18.1% calculated from the results of the mouse local lymph node assay (LLNA).

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
25 January - 13 February 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Also complies with OECD GLP regulations.
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
2011-05-19
Type of study:
mouse local lymph node assay (LLNA)
Specific details on test material used for the study:
- Name of test material (as cited in study report): S-10793
- IUPAC nomenclature - Sodium diisobutyldithiophosphinate
- Lot S-20227-170B
- Appearance - White powder with lumps
- CAS No. 13360-78-6
- Molecular Formula - C8H18PS2.Na
- Molecular Weight - 232 g/mole
- Purity 93-94%
- Expiration date of the lot/batch: 16 December 2013
- Storage condition of test material: At room temperature in the dark
Species:
mouse
Strain:
CBA:J
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Janvier, Le Genest-Saint-Isle, France
- Females nulliparous and non-pregnant: yes
- Age at study initiation: Young adult animals (approx. 10 weeks old)
- Weight at study initiation: Body weight variation was within +/- 20% of the sex mean.
- Housing: Animals were group housed in labeld makrolon cages.
- Diet: Free access to pelleted rodent diet (SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany).
- Water: Free access to tap water.
- Acclimation period: At least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16.1 – 22.5ºC
- Humidity (%): 35 - 71%
- Air changes (per hr): approx 15
- Photoperiod (hrs dark / hrs light): 12/12

Cleaning procedures in the room might have caused the temporary fluctuations above the optimal maximum level of 70% for relative humidity. Based on laboratory historical data, these fluctuations were considered not to have affected the study integrity.

IN-LIFE DATES: From: 25 January - 13 February 2012
Vehicle:
dimethylformamide
Concentration:
0, 5, 10, 25%
No. of animals per dose:
5
Details on study design:
In the interest of animal welfare and to minimize any testing likely to produce severe responses in animals, a weight of evidence analysis was performed prior to start of this study. All available information was evaluated (e.g. existing human and animal data, literature, substance data supplied by the sponsor, analysis of structure activity relationships (SAR), physicochemical properties and reactivity (pH, buffering capacity).

PRE-SCREEN TESTS:
- Compound solubility: The vehicle was selected based on trial formulations performed at NOTOX and on test substance data supplied by the sponsor.
2 animals per concentration, 25 and 50% (maximum dose recommended in the guideline), treated on three consecutive days, ear thickness measured prior to dosing and on days 1, 3 and 6
- Irritation: slight irritation noted during the observation period
- Systemic toxicity: no
- Ear thickness measurements: varation < 25% for animals tested with 25% concentration, > 25% on Day 6 for animals tested with 50% concentration
- Erythema scores: 25%: 0 on days 1 and 2, 1 from day 3 through day 6; 50%: 0 on day 1, 1 from day 2 through day 6

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Local Lymph Node Assay
- Criteria used to consider a positive response: DPM values are presented for each animal and for each dose group. A Stimulation Index (SI) is calculated for each group. The SI is the ratio of the DPM/group compared to DPM/vehicle control group. If the results indicate a SI ≥ 3, the test substance may be regarded as a skin sensitizer. The results were evaluated according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (20011) and the Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures.
The EC3 value (the estimated test substance concentration that will give a SI =3) was determined, using linear interpolation

ANIMAL ASSIGNMENT
Three groups of five animals were treated with one test substance concentration per group. One group of five animals was treated with vehicle.

TREATMENT PREPARATION AND ADMINISTRATION:
Test substance preparation: The test substance formulations (w/w) were prepared within 4 hours prior to each treatment. Homogeneity was obtained to visually acceptable levels.

Induction (25 µl/ear) - Days 1, 2 and 3; Excision of nodes (the nodes were pooled for each animal) - Day 6; Tissue processing for radioacitivity - Day 6; Radioactivity measurements - Day 7; Performed according to test guidelines.

Observations:
Mortality/Viability: Twice daily.
Body weights: On Day 1 (pre-dose) and Day 6 (prior to necropsy).
Clinical signs: Once daily on Days 1-6 (on Days 1-3 between 3 and 4 hours after dosing).
Irritation: Once daily on Days 1-6 (on Days 1 - 3 immediately after dosing) according to the following numerical scoring system. Furthermore, a description of all other (local) effects was recorded

Necropsy: All animals surviving to the end of the study were sacrificed by intra-peritoneal injection with Euthasol® 20% (0.2 mL/animal).
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Not performed.
Positive control results:
The six-month reliability check with Alpha-hexylcinnamicaldehyde indicates that the Local Lymph Node Assay as performed at NOTOX is an appropriate model for testing for contact hypersensitivity. See attached document 'Reliability check'.
Parameter:
SI
Value:
1.4
Test group / Remarks:
5%
Parameter:
SI
Value:
1.1
Test group / Remarks:
10%
Parameter:
SI
Value:
4.6
Test group / Remarks:
25%
Parameter:
EC3
Value:
18.1
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: Mean DPM/animal values for the experimental groups treated with test substance concentrations 5, 10 and 25% were 676, 534 and 2283 DPM respectively. The mean DPM/animal value for the vehicle control group was 497 DPM.

Skin reactions / Irritation:

The slight irritation of the ears as shown by the animals treated at 25% was considered not to have a toxicologically significant effect on the activity of the nodes.

Systemic toxicity/Body weights:

No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The body weight loss noted for some animals across the dose groups was considered not toxicologically significant since the changes were slight in nature and no concentration-related incidence was apparent.

Macroscopy of the auricular lymph nodes and surrounding area:

The auricular lymph nodes of the highest dose group animals appeared larger in size as compared to the other treated groups. The other auricular lymph nodes were considered normal in size. No macroscopic abnormalities of the surrounding area were noted in any of the animals.

Interpretation of results:
Category 1B (indication of skin sensitising potential) based on GHS criteria
Conclusions:
The SI values calculated for the substance concentrations 5, 10 and 25% were 1.4, 1.1 and 4.6 respectively.
These results indicate that the test substance could elicit an SI ≥ 3. An EC3 value (the estimated test substance concentration that will give a SI =3) of 18.1% was calculated.
Executive summary:

Assessment of Contact Hypersensitivity to the test material was investigated in the Mouse (Local Lymph Node Assay) according to OECD TG 429 and under GLP conditions.

Test substance concentrations selected for the main study were based on the results of a pre-screen test. In the main study, three experimental groups of five female CBA/J mice were treated with test substance concentrations of 5, 10 or 25% w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with vehicle alone (Dimethyl formamide). Three days after the last exposure, all animals were injected with 3H-methyl thymidine and after five hours the draining (auricular) lymph nodes were excised and pooled for each animal. After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of Disintegrations Per Minute (DPM) and a stimulation index (SI) was subsequently calculated for each group.

The slight irritation of the ears as shown by the animals treated at 25% was considered not to have a toxicologically significant effect on the activity of the nodes. No mortality occurred and no clinical signs of systemic toxicity were observed in the animals of the main study. Body weights and body weight gain of experimental animals remained in the same range as controls over the study period. The body weight loss noted for some animals across the dose groups was considered not toxicologically significant since the changes were slight in nature and no concentration- related incidence was apparent. The auricular lymph nodes of the highest dose group animals appeared larger in size as compared to the other treated groups. The other auricular lymph nodes were considered normal in size. No macroscopic abnormalities of the surrounding area were noted in any of the animals.

Mean DPM/animal values for the experimental groups treated with test substance concentrations 5, 10 and 25% were 676, 534 and 2283 DPM respectively. The mean DPM/animal value for the vehicle control group was 497 DPM. The SI values calculated for the substance concentrations 5, 10 and 25% were 1.4, 1.1 and 4.6 respectively. These results indicate that the test substance could elicit an SI ≥ 3.

An EC3 value (the estimated test substance concentration that will give a SI =3) of 18.1% was calculated.

Based on this results, the substance should be regarded as a skin sensitizer, category 1B (accordng to GHS).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

In the LLNA, three groups of five animals were treated with one test substance concentration per group. One group of five animals was treated with vehicle. A Stimulation Index (SI) was calculated for each group. If the SI is greater than or equal to three, the substance may be regarded as a skin sensitizer. The SI values for substance concentrations 5, 10, and 25% were 1.4, 1.1, and 4.6, respectively. These results indicate the substance could elicit an SI greater than or equal to three. An EC3 value (the estimated test substance concentration that will give an SI = 3) was calculated to be 18.1%.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

In light of the LLNA study results presented above, S-10793 is classified as a moderate skin sensitizer (1B), and "May cause an allergic skin reaction" (H317).