[No public or meaningful name is available]

Endpoint summary

Description of key information

Skin Sensitisation (Read-across from ytterbium trifluoride, Richeux, 2017):

The test material was found not to be a skin sensitiser.

Skin Sensitisation (Read-across from ytterbium oxide, Weisz, 2016):

The test material was found not to be a skin sensitiser.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 December 2016 to 05 January 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

other: read-across target

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The rare earth substances are known to give false positives in the LLNA studies. The Maximisation study was therefore deemed to be more appropriate for investigating the skin sensitisation potential of this substance.

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Batch No.of test material: YBF1002/16
- Expiration date of the lot/batch: 17 October 2018

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature, darkness

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: the test material was used freshly prepared in physiological saline.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: 3 to 4 weeks old
- Weight at study initiation: 303 to 350 g
- Housing: In groups of 3
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: Minimum of 5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19 to 25°C
- Humidity: 30 to 70%
- Air changes: At least 10 per hour
- Photoperiod: twelve hours continuous light (07.00 to 19.00) and twelve hours darkness

Route:

other: Intradermal and Topical

Vehicle:

other: Physiological saline (Intradermal) and Distilled water (Topical)

Concentration / amount:

Intradermal: 20 %/ 0.1 mL
Topical: 80 %/ 0.5 mL

Day(s)/duration:

Intradermal induction took place on Day 0. On Day 8, animals received a topical induction application which was covered for 48 hours.

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

No.:

#1

Route:

other: Topical

Vehicle:

other: Distilled water

Concentration / amount:

80 and 40 % / 1 sample cup

Day(s)/duration:

On day 21 the challenge dose was applied for 24 hours

Adequacy of challenge:

not specified

No. of animals per dose:

5 in the negative control, 10 in the treated group.

Details on study design:

RANGE FINDING TESTS:
- Determination by intradermal injection of the Maximal Non Necrotizing Concentration (MNNC):
Two animals received a volume of 0.1 mL of the test material, on both sides of the spine, at 4 concentrations: diluted at 80%, 50%, 20% and 10% in physical saline in view to determine the MNNC. A macroscopic evaluation of the cutaneous reactions was conducted 24 hours after the injections.
- Determination by topical application of the Pre-Maximal Non Irritant Concentration (Pre-MNIC):
This test, which allowed evaluating the irritancy potential of the test material, defined whether an application of sodium lauryl sulphate would be needed during topical induction phase. The test material was applied on the dorso-lumbar zone of two guinea pigs shorn beforehand, with occlusive dressing for 24 hours, at 4 different concentrations: diluted at 80%, 50%, 20% and 10% in distilled water. After the removal of the occlusive dressing, the treated areas were rinsed with distilled water. A macroscopic evaluation of the cutaneous reactions was conducted 24 hours after removal of the dressing.
- Determination by topical application of the Maximal Non Irritant Concentration (MNIC):
Three guinea pigs were treated according to the same treatment as animals from group 1 (control) for the induction phase (i.e. physiological saline and distilled water). During the challenge phase, the animals were treated with the test material placed onto the selected treatment sites and covered with an occlusive dressing for a period of 24 hours at 4 different concentrations: diluted at 80%, 50%, 20% and 10% in distilled water. After the removal of the occlusive dressing, the treated areas were rinsed with distilled water. A macroscopic evaluation of the cutaneous reactions was conducted 24 and 48 hours after removal of the occlusive dressing.

MAIN STUDY

A. INDUCTION EXPOSURE
Intradermal Induction:
Day 0: After shearing the scapular zone, three pairs of intradermal injections (ID) of 0.1 mL were performed on the scapular zone in such a way as an injection on each pair is placed to either side of the spine as follows:
GROUP 1 (control):
-2 ID: Freund’s Complete Adjuvant diluted at 50 % in physiological saline
-2 ID: physiological saline
-2 ID: a mixture with equal volumes v/v: Freund’s Complete Adjuvant at 50% and physiological saline
GROUP 2 (Treated):
-2 ID: Freund’s Complete Adjuvant diluted at 50 % in physiological saline
-2 ID: test material at 20% in physiological saline
-2 ID: a test mixture in equal volumes v/v: Freund’s Complete Adjuvant at 50% and the test item at 40% in physiological saline

Topical Induction:
Day 7: The scapular zone of all the animals in each group, shorn beforehand, was brushed with a solution of sodium lauryl sulphate at 10% in thick Vaseline, in order to create a local irritation.
Day 8: A topical application under occlusive dressing (25mm x 25mm non-woven swab of 4-layer patch held in contact with the skin by means of 50 mm wide hypoallergenic adhesive tape) for 48 hours was performed on the injection sites of each animal.
GROUP 1 (control): 0.5 mL of distilled water.
GROUP 2 (treated): 0.5 mL of the test material at 80 % in distilled water.
Day 10: The occlusive dressing was removed and the treated areas were rinsed with distilled water.

REST PHASE
The animals of both groups were left for 10 days.

B. CHALLENGE EXPOSURE
Day 21: The experimental procedure of this phase was identical for both groups 1 (Control) and 2 (Treated) submitted to this experimentation: on the previously shorn dorso-lumbar zone, an application, under occlusive dressing, was performed during 24 hours:
1 sample cup containing the test material diluted at 80 % (MNIC) and 1 sample cup containing the test item diluted at 40 % in distilled water (1/2 MNIC).

Day 22: The occlusive dressing was removed and the treated areas were rinsed with distilled water.
Day 23: 1st reading time – 24 hours after the patch removal.
Day 24: 2nd reading time – 48 hours after the patch removal.

INTERPRETATION OF RESULTS
The test material will be regarded as a sensitiser if 30% or more of the test animals show a sensitisation response.

Challenge controls:

No, the experimental procedure of this phase was identical for both groups 1 (Control) and 2 (Treated).

Positive control substance(s):

yes

Remarks:

α-hexylcinnamaldehyde (HCA)

Positive control results:

The number of animals sensitised was ≥ 70%.
Therefore, under the experimental conditions, the reference substance a-Hexylcinnamaldehyde must be classified in category 1 “Skin sensitisation” sub-category 1B in accordance with the Regulation EC No. 1272/2008 on classification, labelling and packaging of substances and mixtures. The signal word “Warning” and hazard statement H317 “May cause an allergic skin reaction” are required.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

80 %

No. with + reactions:

1

Total no. in group:

10

Clinical observations:

Intense erythema was noted in three animals, moderate erythema was noted in five animals and discrete erythema was noted in two animals 24 hours after the first induction.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

40 %

No. with + reactions:

0

Total no. in group:

10

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

10

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

5

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

5

Preliminary studies

- MNNC determination:

Necrosis to slight necrosis was observed in the animals at the tested concentrations of 80 and 50%. 24 hours after the injections, moderate to discrete erythema was observed in the animals at the tested concentrations of 20 and 10 %. The first induction of the Group 2 has been carried out by intradermal injection at the maximal non necrosing concentration of 20 %.

- Pre MNIC determination:

24 hours after the removal of the occlusive dressings, no cutaneous reaction was noted whatever the tested concentration. In view of these results, the concentration selected was 80% for the 2nd induction of the Group 2 and the MNIC determination began at the concentration of 80%.

- MNIC determination:

24 and 48 hours after the removal of the occlusive dressings, no cutaneous reaction was noted whatever the tested concentration. In view of this result, the concentrations selected were 80% (MNIC) and 40% (1/2 MNIC).

 

Main study

- Induction phase Group 2:

Intense erythema was noted in three animals (3/10), moderate erythema was noted in five animals (5/10) and discrete erythema was noted in two animals (2/10) 24 hours after the first induction. Discrete erythema was noted in four animals (4/10) and dryness of the skin was noted in all the animals (10/10) 24 hours after the second induction.

- Induction phase Group 1:

No cutaneous reaction was noted during the induction phase.

- Challenge phase Groups 1 & 2:

Overall results of the challenge phase with the test material (readings at 24 and 48 hours) are given in Table 1. In the treated group (treatment dose of 80 %), a very slight erythema was noted in 10 % (1/10) of the treated animal 24 hours after the challenge phase. No macroscopic cutaneous reactions attributable to allergy were noted 48 hours after the challenge phase. In the control group (associated with the treatment dose of 80 %), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase.

In the treated group (treatment dose of 40%), no macroscopic cutaneous reactions attributable to allergy were noted after the challenge phase.

In the control group (associated with the treatment dose of 40%), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase.

-Weight evolution

No abnormality was recorded in the body weight gain of both groups.

- Mortality

No mortality was registered during the main test.

Table 1: Macroscopic evaluation (readings at 24 and 48 hours) of cutaneous reactions

Groups	Reading time	Concentrations	Incidence				% of positive responses≥1	% of animal sensitised
			0	1	2	3
Group 1 Control	24 h	80 %	5	0	0	0	0	-
	48 h	80 %	5	0	0	0	0	-
	24 h	40 %	5	0	0	0	0	-
	48 h	40 %	5	0	0	0	0	-
Group 2 Treated	24 h	80 %	9	1	0	0	10	10
	48 h	80 %	10	0	0	0	0	0
	24 h	40 %	10	0	0	0	0	0
	48 h	40 %	10	0	0	0	0	0

Interpretation of results:

other: Not sensitising in accordance with EU criteria

Conclusions:

Under the conditions of the study, the test material is not considered to be a skin sensitiser.

Executive summary:

The aim of the study was to evaluate the possible sensitisation of the test material using the guinea pig maximisation test. The study was performed in accordance with the standardised guidelines OECD 406 and EU method B.6 under GLP conditions.

According to the results of the pre-tests, the test material was applied to 10 Guinea pigs during the the induction phase (intradermic injection at 20% and topical application at 80%). Induction was followed by a 10-day rest phase.

On day 0 after shearing the scapular zone, three pairs of intradermal injections of 0.1 mL were performed on the scapular zone, including the test material at 20% in physiological saline. On day 7 the scapular zone was brushed with a solution of sodium lauryl sulphate at 10 % in thick Vaseline to create a local irritation and then on day 8 a topical application under occlusive dressing was applied for 48 hours on the injection sites of each animal. The occlusive dressing was removed on day 10 and the treated areas were rinsed with distilled water. The challenge phase was conducted under occlusive dressing for 24 hours and consisted of a single topical application of the test material diluted at 80 % and at 40 % in distilled water. The challenge was applied on day 21, removed on day 22 and then observed on days 23 and 24 (24 and 48 hours after removal respectively).

In the treated group (treatment dose of 80 %), a very slight erythema was noted in 10 % (1/10) of the treated animals 24 hours after the challenge phase.No macroscopic cutaneous reactions attributable to allergy were noted 48 hours after the challenge phase. In the control group (associated with the treatment dose of 80 %), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase. In the treated group (treatment dose of 40 %), no macroscopic cutaneous reactions attributable to allergy were noted after the challenge phase. In the control group (associated with the treatment dose of 40 %), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase.

Under the conditions of this study, the test material does not have to be classified in category 1 as a skin sensitiser, in accordance with the Regulation EC No. 1272/2008 on classification, labelling and packaging of substances and mixtures.

Reference 2

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The substances are structurally similar, both ytterbium compounds are in their +3 oxidation state. As the metal cation governs toxicity, it is concluded that the same effect will be observed.

Reason / purpose for cross-reference:

read-across source

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

80 %

No. with + reactions:

1

Total no. in group:

10

Clinical observations:

Intense erythema was noted in three animals, moderate erythema was noted in five animals and discrete erythema was noted in two animals 24 hours after the first induction.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

40 %

No. with + reactions:

0

Total no. in group:

10

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

10

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

5

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

40 / 80 %

No. with + reactions:

0

Total no. in group:

5

Interpretation of results:

other: Not sensitising in accordance with EU criteria

Conclusions:

Under the conditions of the study, the test material is not considered to be a skin sensitiser.

Executive summary:

The aim of the study was to evaluate the possible sensitisation of the test material using the guinea pig maximisation test. The study was performed in accordance with the standardised guidelines OECD 406 and EU method B.6 under GLP conditions.

According to the results of the pre-tests, the test material was applied to 10 Guinea pigs during the the induction phase (intradermic injection at 20% and topical application at 80%). Induction was followed by a 10-day rest phase.

On day 0 after shearing the scapular zone, three pairs of intradermal injections of 0.1 mL were performed on the scapular zone, including the test material at 20% in physiological saline. On day 7 the scapular zone was brushed with a solution of sodium lauryl sulphate at 10 % in thick Vaseline to create a local irritation and then on day 8 a topical application under occlusive dressing was applied for 48 hours on the injection sites of each animal. The occlusive dressing was removed on day 10 and the treated areas were rinsed with distilled water. The challenge phase was conducted under occlusive dressing for 24 hours and consisted of a single topical application of the test material diluted at 80 % and at 40 % in distilled water. The challenge was applied on day 21, removed on day 22 and then observed on days 23 and 24 (24 and 48 hours after removal respectively).

In the treated group (treatment dose of 80 %), a very slight erythema was noted in 10 % (1/10) of the treated animals 24 hours after the challenge phase.No macroscopic cutaneous reactions attributable to allergy were noted 48 hours after the challenge phase. In the control group (associated with the treatment dose of 80 %), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase. In the treated group (treatment dose of 40 %), no macroscopic cutaneous reactions attributable to allergy were noted after the challenge phase. In the control group (associated with the treatment dose of 40 %), no macroscopic cutaneous intolerance reactions were recorded after the challenge phase.

Under the conditions of this study, the test material does not have to be classified in category 1 as a skin sensitiser, in accordance with the Regulation EC No. 1272/2008 on classification, labelling and packaging of substances and mixtures.

 

Reference 3

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20 July 2016 to 13 August 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

other: read-across target

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Version / remarks:

2003

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Version / remarks:

2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The GPMT method (OECD 406) was preferred above LLNA (OECD 429) since previous experience with various rare earth compounds learned that there is an increased risk for false positive results when performing the LLNA. Additionally, insoluble inorganic substances, such as ytterbium oxide, are often not able to penetrate the skin.

Specific details on test material used for the study:

No correction for purity of the test material was applied.

Species:

guinea pig

Strain:

Hartley

Sex:

male

Details on test animals and environmental conditions:

TEST ANIMALS
- Age at study initiation: young adult, ~ 5 weeks old
- Weight at study initiation: 296 – 332 g
- Housing: Animals were housed in Macrolon cages size IV, with up to 5 animals/cage to allow socialisation; “Lignocel® 3/4-S Hygienic Animal Bedding” produced by J. Rettenmaier & Söhne GmbH & CO.KG (D-73494 Rosenberg, Germany) was available to animals during the study.
- Diet: ad libitum
- Water: tap water from municipal supply as for human consumption, containing at least 50 mg/100 mL ascorbic acid, ad libitum
- Acclimation period: 7 days
- Indication of any skin lesions: None

ENVIRONMENTAL CONDITIONS
- Temperature: 20.0 - 23.4 °C
- Humidity: 44 - 96%
- Air changes: 15-20 air exchange/hour
- Photoperiod: 12 hrs dark/12 hrs light

Route:

intradermal

Vehicle:

other: 1% methylcellulose

Concentration / amount:

5 % test material in vehicle

Day(s)/duration:

day 1 of treatment

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

0.5 g of test mayterial (as supplied, dampened with saline)

Day(s)/duration:

Day 8 of treatment; 48 hours of exposure

Adequacy of induction:

non-irritant substance, but skin pre-treated with 10% SDS

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100% test material (as supplied, dampened with saline)
(50% test material formulated in 1% methyl cellulose as a safeguard dose)

Day(s)/duration:

day 22 of treatment; 24 hours of exposure

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

Preliminary test: 8 animals
Main test: 10 in the test group, 5 in the control

Details on study design:

RANGE FINDING TEST
- A day prior to the test, the hair was removed from the right and left sides of the animals (approximately 5x5 cm). The hair removal was performed carefully to ensure animals are closely shaven.
- A series of test material concentrations was tested to identify the primary irritation following intradermal injection and dermal application: 0.05, 0.1, 0.5, 1, 2.5, and 5% (w/v) concentrations were used for intradermal injection and 25, 50, 75% (w/v) and 100% (as supplied, dampened with saline) for dermal application. Local effects were examined and scored 1, 24, 48 and 72 hours after the treatment or after patch removal. Skin effects were scored for erythema and oedema; any other observations of changes to the skin were recorded.
- For the intradermal application, 0.1 mL per concentration was injected intradermally into the hair free skin of the animals. Two concentrations were injected on the right side and another two concentrations on the left side of the animals. The highest concentration (5%) was also tested in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline solution. Each concentration was injected in duplicate. Two animals were used per concentration. The highest concentration (5%) formulated in the vehicle or in FCA:saline caused no more than mild-to-moderate erythema (score 1 or 2) during the observation period, therefore this concentration could be used in the main study.
- For the dermal application, the volume of the concentrations was 0.5 mL. For the 100% treatment, 0.5 g test material was dampened with saline, and then applied to the skin. A closed patch exposure was performed by means of an occlusive bandage using similar treatment procedures as for the main study. The time of exposure for the dermal application was 48 hours. One concentration was used on the right side and another concentration on the left side of the animals. Two animals per concentration were used. It was found that all the dermal treatments at the tested concentrations produced no reaction on the skin of guinea pigs.

MAIN STUDY
The dose levels for the main study were selected based on the results of the preliminary test.
Control animals were treated similarly to test animals, except that during the induction phase, the test material was omitted.

A1. INTRADERMAL INDUCTION EXPOSURE (day 1)
- No. of exposures: 3 pairs of injections per animal (0.1 mL/site)
- Test groups (the first listed nearest the head): 2 injections of Freund's Complete Adjuvant and physiological saline solution in a 1:1 (v/v) mixture; 2 injections of 5% test material in 1% methylcellulose; 2 injections of 5% test material, formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline solution.
- Control group (the first listed nearest the head): 2 injections of Freund's Complete Adjuvant and physiological saline solution in a 1:1 (v/v) mixture; 2 injections of 1% methylcellulose; 2 injections of 1% methylcellulose, formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline solution.
- Site: scapular region
- Frequency of applications: 1 application
- Skin reactions were observed and recorded as follows: 24 hours after the patch removal

A2. DERMAL INDUCTION EXPOSURE (day 8)
- Since the undiluted test material was not skin irritant in the dermal dose range-finding study, the test area was painted with 0.5 mL of 10% sodium dodecyl sulphate in Vaseline 24 hours prior to the topical induction application, in order to create a local irritation.
- Site: The same scapular region that received the intradermal injections, was used for dermal induction exposure.
- Test groups: Seven days after the intradermal injections, the same hair-free scapular area was treated. 0.5 g of the test material was placed on a 2.5x2.5 cm sterile gauze patch (4 layers of porous gauze pads) and dampened with saline, then applied over the injection sites. The gauze patches were kept in contact with the skin by a patch with a surrounding adhesive hypoallergenic plaster. The treated areas were covered for 48 hours with a fully occlusive foil (Closed Patch Test). After the patch removal any remaining test material was removed with a wet gauze swab. Following the dermal induction treatment, the animals were left untreated for 14 days prior to challenge applications.
- Control group: The control group was treated with 1% methylcellulose only.
- Frequency of applications: one application
- Skin reactions were observed and recorded as follows: 1, 24, 48 and 72 hours after patch removal

B. CHALLENGE EXPOSURE
Two weeks after the topical induction application, the animals were exposed to a dermal challenge dose. Approximately 24 hours before the treatment, the hair was removed from an area of approximately 5x5 cm on the left and right sides of each animal. 0.5 g of the test material was dampened with saline on a 5x5 cm patch of sterile gauze patch, then applied to the left side of all animals (both the test and the control). The right shaved side of all animals was treated with 50% dilution of the test material in 1% methylcellulose. The volume of formulated test material was 0.5 mL. Treatment was performed as described for the Closed Patch Test (see dermal induction exposure). The time of exposure was 24 hours. After the patch removal any remaining test material was removed with a wet gauze swab.

Terminal animals were sacrificed under pentobarbital anaesthesia.

OBSERVATIONS AND SCORING
- Body weight was recorded with a precision of 1 g at randomisation (Day -1), then at least weekly, including Day 25 prior to euthanasia. The mean values and the standard deviations were calculated and reported.
- Mortality/clinical signs: Daily recorded during the test.
- Detailed clinical observations were made on all animals outside the home cage in a standard arena before the first treatment (on the day of randomisation) and at least weekly thereafter. The dermal irritation scores (in case of dermal induction exposures) were evaluated according to the scoring system by Draize (1959).

Skin reactions were observed and recorded as follows:
- Preliminary study: 1, 24, 48 and 72 hours after the patch removal and/or treatment.
- Intradermal induction exposure: 24 hours after the treatment.
- Dermal induction exposure: 1, 24, 48 and 72 hours after the patch removal.
- Challenge exposure: 24 and 48 hours after the patch removal.

- Erythema and eschar formation:
0 = No erythema
1 = Very slight erythema (barely perceptible)
2 = Well defined erythema
3 = Moderate to severe erythema
4 = Severe erythema (beef redness) to slight eschar formation (injuries in depth)

- Oedema formation:
0 = No oedema
1 = Very slight oedema (barely perceptible)
2 = Slight oedema (edges of area well defined by definite raising)
3 = Moderate oedema (raised approx. 1 mm)
4 = Severe oedema (raised more than 1 mm and extending beyond area of exposure)

After the challenge exposure, each animal was examined and scored 24 and 48 hours after the end of the exposure period.

Grading was performed according to the following system (classification of skin sensitisation):
0 = no visible change
1 = discrete or patchy erythema
2 = moderate and confluent erythema
3 = intense erythema and swelling

Challenge controls:

0.5 g of test material was dampened with saline on a 5x5 cm sterile gauze patch, then applied to the left side of all animals. The right shaved side of all animals was treated with 50% dilution of the test material (w/v) in 1% methylcellulose.

Positive control substance(s):

yes

Remarks:

2-Mercaptobenzothiazole

Positive control results:

Challenge with reference item 2-mercaptobenzothiazole resulted in a positive response in test animals previously sensitised. The net response values at the 24 and 48 hours observations represented an incidence rate of 90% and 80% and net score values of 0.90 and 0.80 respectively. In the control animals no visible changes were found either at the 24 or 48 hours examinations following challenge with the reference item.

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

test chemical

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

negative control

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

negative control

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

9

Total no. in group:

10

Clinical observations:

discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Skin affects after the challenge exposure

- Test group: After the challenge with the test material at a concentration of 100% (undiluted, dampened with saline), no positive response was observed in the treated animals. The mean of the scores was 0.00 according to the 24 and 48-hours observations after patch removal. The right shaved side of all animals was treated with a test material concentration of 50% (w/v) as a safeguard dose and no reaction was noted.

- Control group: After the challenge with the test material at a concentration of 100% (undiluted, dampened with saline), no visible changes were found at the 24 and-48 hours examinations after patch removal. The right shaved side of control animals was treated with a test material concentration of 50% (w/v) as a safeguard dose and no reaction was noted.

 

Clinical observations/mortality 

- No signs of systemic or local toxicity were observed in any animal.

- No mortality was observed during the study.

 

Body weight

- There were no notable differences between the test animal group and the control group.

Interpretation of results:

other: not classified according to EU criteria

Conclusions:

Under the conditions of the present assay, the test material was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU regulations.

Executive summary:

A skin sensitisation study was performed in the guinea pig according to the Magnusson and Kligman method, using a maximisation method with Freund's Complete Adjuvant to evaluate the sensitisation potential of test material. The study was performed according to OECD Guideline No. 406 (adopted in 1992) and in compliance with GLP guidelines.

Based on the results of a preliminary test, ten test animals were subjected to sensitisation procedures in a two-stage process, named induction phase: i.e. an intradermal treatment and a 48-hour topical application (dermal treatment under an occlusive dressing). The test material was used at a concentration of 5% (w/v) for intradermal injections and at a concentration of 100% (undiluted, dampened with saline) for topical sensitisation treatment. Five control guinea pigs were simultaneously exposed to 1% methyl cellulose only during the sensitisation phase. Two weeks after the last induction exposure, a challenge dose at a concentration of 100% (undiluted, dampened with saline) was administered on the left side of all animals. The right side of the animals was treated with 50% dilution of the maximum dermal challenge dose as a safeguard dose (50% (w/v)). Challenge was performed by dermal application of the test item. Skin reactions were measured 24 and 48 hours after patch removal.

Challenge with test material (diytterbium trioxide) evoked no positive responses in the test animals previously sensitised with the test material or in the control group. The net response value represented an incidence rate of 0% and a net score value of 0.00.

Under the conditions of the present assay, the test material was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU regulations.

Reference 4

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The substances are structurally similar, both ytterbium compounds are in their +3 oxidation state. As the metal cation governs toxicity, it is concluded that the same effect will be observed.

Reason / purpose for cross-reference:

read-across source

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

test chemical

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

test chemical

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

no visible changes.

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

negative control

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

negative control

Dose level:

100% (undiluted, dampened with saline)

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

no visible changes

Remarks on result:

no indication of skin sensitisation

Key result

Reading:

1st reading

Hours after challenge:

48

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

9

Total no. in group:

10

Clinical observations:

discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Key result

Reading:

2nd reading

Hours after challenge:

72

Group:

positive control

Dose level:

50% w/v (2-mercaptobenzothiazole)

No. with + reactions:

8

Total no. in group:

10

Clinical observations:

discrete erythema (score 1) on the skin of the animals

Remarks on result:

positive indication of skin sensitisation

Interpretation of results:

other: not classified according to EU criteria

Conclusions:

Under the conditions of the present assay, the test material was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU regulations.

Executive summary:

A skin sensitisation study was performed in the guinea pig according to the Magnusson and Kligman method, using a maximisation method with Freund's Complete Adjuvant to evaluate the sensitisation potential of test material. The study was performed according to OECD Guideline No. 406 (adopted in 1992) and in compliance with GLP guidelines.

Based on the results of a preliminary test, ten test animals were subjected to sensitisation procedures in a two-stage process, named induction phase: i.e. an intradermal treatment and a 48-hour topical application (dermal treatment under an occlusive dressing). The test material was used at a concentration of 5% (w/v) for intradermal injections and at a concentration of 100% (undiluted, dampened with saline) for topical sensitisation treatment. Five control guinea pigs were simultaneously exposed to 1% methyl cellulose only during the sensitisation phase. Two weeks after the last induction exposure, a challenge dose at a concentration of 100% (undiluted, dampened with saline) was administered on the left side of all animals. The right side of the animals was treated with 50% dilution of the maximum dermal challenge dose as a safeguard dose (50% (w/v)). Challenge was performed by dermal application of the test item. Skin reactions were measured 24 and 48 hours after patch removal.

Challenge with test material (diytterbium trioxide) evoked no positive responses in the test animals previously sensitised with the test material or in the control group. The net response value represented an incidence rate of 0% and a net score value of 0.00.

Under the conditions of the present assay, the test material was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU regulations.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Read-across argument

The read across substances are structurally similar, both are ytterbium compounds that are in their +3 oxidation state. As the metal cation governs toxicity, it is concluded that the same effect will be observed for the read across substances as for the substance object of this registration.

An overview of the available information on the read across substances is provided below.

Skin Sensitisation (Read-across from ytterbium triflouride, Richeux, 2017):

The aim of the study was to evaluate the possible sensitisation of the test material using the guinea pig maximisation test. The study was performed in accordance with the standardised guidelines OECD 406 and EU method B.6 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

According to the results of the pre-tests, the test material was applied to 10 Guinea pigs during the the induction phase (intradermic injection at 20% and topical application at 80%). Induction was followed by a 10-day rest phase.

On day 0 after shearing the scapular zone, three pairs of intradermal injections of 0.1 mL were performed on the scapular zone, including the test material at 20% in physiological saline. On day 7 the scapular zone was brushed with a solution of sodium lauryl sulphate at 10 % in thick Vaseline to create a local irritation and then on day 8 a topical application under occlusive dressing was applied for 48 hours on the injection sites of each animal. The occlusive dressing was removed on day 10 and the treated areas were rinsed with distilled water. The challenge phase was conducted under occlusive dressing for 24 hours and consisted of a single topical application of the test material diluted at 80 % and at 40 % in distilled water. The challenge was applied on day 21, removed on day 22 and then observed on days 23 and 24 (24 and 48 hours after removal respectively).

In the treated group (treatment dose of 80 %), a very slight erythema was noted in 10 % (1/10) of the treated animals 24 hoursafter the challenge phase.No macroscopic cutaneous reactions attributable to allergy were noted 48 hours after the challenge phase.In the control group (associated with the treatment dose of 80 %), nomacroscopiccutaneous intolerance reactions were recorded after the challenge phase. In the treated group (treatment dose of 40 %), no macroscopic cutaneous reactions attributable to allergy were noted after the challenge phase.In the control group (associated with the treatment dose of 40 %), nomacroscopiccutaneous intolerance reactions were recorded after the challenge phase.

Under the conditions of this study, the test material was found not to be a skin sensitiser.

 

Skin Sensitisation (Read-across from ytterbium oxide, Weisz, 2016):

A skin sensitisation study was performed in the guinea pig according to the Magnusson and Kligman method, using a maximisation method with Freund's Complete Adjuvant to evaluate the sensitisation potential of test material. The study was performed according to OECD Guideline No. 406 (adopted in 1992) and in compliance with GLP guidelines.

The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).
Based on the results of a preliminary test, ten test animals were subjected to sensitisation procedures in a two-stage process, named induction phase: i.e. an intradermal treatment and a 48-hour topical application (dermal treatment under an occlusive dressing). The test material was used at a concentration of 5% (w/v) for intradermal injections and at a concentration of 100% (undiluted, dampened with saline) for topical sensitisation treatment. Five control guinea pigs were simultaneously exposed to 1% methyl cellulose only during the sensitisation phase. Two weeks after the last induction exposure, a challenge dose at a concentration of 100% (undiluted, dampened with saline) was administered on the left side of all animals. The right side of the animals was treated with 50% dilution of the maximum dermal challenge dose as a safeguard dose (50% (w/v)). Challenge was performed by dermal application of the test item. Skin reactions were measured 24 and 48 hours after patch removal.
Challenge with test material (diytterbium trioxide) evoked no positive responses in the test animals previously sensitised with the test material or in the control group. The net response value represented an incidence rate of 0% and a net score value of 0.00.
Under the conditions of the present assay, the test material was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU regulations.

 

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No 1272/2008, the substance does not require classification with respect to skin sensitisation.