Trioctylphosphine oxide

Endpoint summary

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:

From Oct. 29, 2014 to Nov. 24, 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/J

Sex:

female

Details on test animals and environmental conditions:

- Source: Janvier, Le Genest-Saint-Isle, France
- 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 controls for the animal room were set to maintain 18 to 24°C, a relative humidity of 40 to 70%, approximately 15 room air changes/hour, and a 12-h light/12-h dark cycle. Any variations to these conditions were maintained in the raw data and had no effect on the outcome of the study.

IN-LIFE DATES: From: 29 October - 24 November 2014

Vehicle:

methyl ethyl ketone

Concentration:

0, 5, 10, 25% w/w

No. of animals per dose:

5

Details on study design:

The vehicle was selected based on trial formulations performed at WIL Research Europe and on test substance data supplied by the sponsor.

RANGE FINDING TESTS:
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).

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 onClassification, Labelling and Packaging of substances and mixtures.

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 h prior to each treatment. No adjustment was made for specific gravity of the vehicle. Homogeneity was obtained to visually acceptable levels.
Rationale for vehicle: The vehicle was selected on the basis of maximizing the solubility using the test substance data provided by the sponsor and trial formulation results performed at WIL Research Europe. The vehicle was chosen from the vehicles specified in the test guideline: Acetone/Olive oil (4:1 v/v), N,N-dimethylformamide, methylethylketone, propylene glycol and dimethylsulfoxide.

Induction - Days 1, 2 and 3; Excision of nodes - 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 according to guidelines.

Necropsy: No necropsy for gross macroscopic examination was performed according to protocol.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Positive control results:

The six-month reliability check with Alpha-hexylcinnamicaldehyde indicates that the Local Lymph Node Assay as performed at WIL Research Europe is an appropriate model for testing for contact hypersensitivity. See attached document 'Reliability check'.

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 3481, 6207 and 7069 DPM, respectively. The mean DPM/animal value for the vehicle control group was 575 DPM.

Parameter:

SI

Value:

6.1

Test group / Remarks:

Substance concentration 5%

Parameter:

SI

Value:

10.8

Test group / Remarks:

substance concentration 10%

Parameter:

SI

Value:

12.3

Test group / Remarks:

substance concentration 25%

Results Pre-screen test:

No signs of systemic toxicity were observed in any of the animals examined. No erythema was observed in any of the animals examined except for the very slight erythema noted for both animals treated at 25% and 50% on Day 6. Scaliness was noted for all animals on Day 6. White staining of the dorsal surface of the ears by test substance remnants was noted for both animals treated at 25% and 50% between Days 1 and 3. The staining did not hamper the scoring of the ears. Thickened ears were noted for the animals treated at 25% between Days 4 and 6.

Variations in ear thickness during the observation period were less than 25% from Day 1 pre-dose values for the animals treated at 5%, 10% and 25% but more than 25% from Day 1 pre-dose values for the animals treated at 50%. Based on these results, the highest test substance concentration selected for the main study was a 25% concentration.

Other results - main study:

Skin reactions / Irritation:

No irritation of the ears was observed in any of the animals examined. Scaliness was noted for all animals treated at 10% and 25% on Day 6. Thickened ears were noted for all animals treated at 10% and 25% on Day 6. White staining of the dorsal surface of the ears by test substance remnants was noted for all animals treated at 25% on Days 1, 2 and 3. The staining did not hamper the scoring of the ears.

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.

Macroscopy of the auricular lymph nodes and surrounding area:

All auricular lymph nodes of the animals of the experimental groups were considered enlarged. No macroscopic abnormalities of the surrounding area were noted for any of the animals.

Interpretation of results:

sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test substance is a skin sensitzer (Latour JEHM, 2015).

Executive summary:

A study was conducted to assess the skin sensitizing potential of the test substance in mouse (Local Lymph Node Assay), according to OECD Guideline 429, EU method B42 and EPA, OPPTS 870.2600, in compliance with GLP. 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 at 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 (methyl ethyl ketone). Three days after the last exposure, all animals were injected with 3H-methyl thymidine and, after 5 h, 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. No irritation of the ears was observed in any of the animals examined. Scaliness was noted for all animals treated at 10 and 25% on Day 6. Thickened ears were noted for all animals treated at 10 and 25% on Day 6. All auricular lymph nodes of the animals of the experimental groups were considered enlarged. No macroscopic abnormalities of the surrounding area were noted for any of the animals. Mean DPM/animal values for the experimental groups treated at 5, 10 and 25% were 3481, 6207 and 7069 DPM, respectively. The mean DPM/animal value for the vehicle control group was 575. The SI values calculated for the substance concentrations of 5, 10 and 25% were 6.1, 10.8 and 12.3, respectively. These results show that the test substance elicits a SI ≥ 3. The data indicate a dose-response and the EC3 value (the estimated test substance concentration that will give a SI=3) was established to be between 0 and 5%. Under the study conditions, the test substance is a skin sensitiser (Latour JEHM, 2015).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

A study was conducted to assess the skin sensitizing potential of the test substance in mouse (Local Lymph Node Assay), according to OECD Guideline 429, EU method B42 and EPA, OPPTS 870.2600, in compliance with GLP. 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 at 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 (methyl ethyl ketone). Three days after the last exposure, all animals were injected with 3H-methyl thymidine and, after 5 h, 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. No irritation of the ears was observed in any of the animals examined. Scaliness was noted for all animals treated at 10 and 25% on Day 6. Thickened ears were noted for all animals treated at 10 and 25% on Day 6. All auricular lymph nodes of the animals of the experimental groups were considered enlarged. No macroscopic abnormalities of the surrounding area were noted for any of the animals. Mean DPM/animal values for the experimental groups treated at 5, 10 and 25% were 3481, 6207 and 7069 DPM, respectively. The mean DPM/animal value for the vehicle control group was 575. The SI values calculated for the substance concentrations of 5, 10 and 25% were 6.1, 10.8 and 12.3, respectively. These results show that the test substance elicits a SI ≥ 3. The data indicate a dose-response and the EC3 value (the estimated test substance concentration that will give a SI=3) was established to be between 0 and 5%. Under the study conditions, the test substance is a skin sensitiser (Latour JEHM, 2015).

Migrated from Short description of key information:
Under the study conditions, the test substance elicits a SI ≥ 3. The data showed a dose-response and the EC3 value (the estimated test substance concentration that will give a SI =3) was established to be between 0 and 5%.

Justification for selection of skin sensitisation endpoint:
Guideline-compliant study conducted according to GLP.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the results of a local lymph node assay, the test substance was found to be sensitising under the experimental conditions. The results suggest a classification as Skin sensitizer, Category 1 - H317 (may cause an allergic skin reaction) according to CLP (EC 1272/2008).