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Description of key information

Skin sensitisation - in vitro

An in vitro or in chemico skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study (initiated before October 11th 2016) is available.

Skin sensitisation - in vivo

A reliable skin sensitisation study is available for ytterbium oxide (Weisz, 2016, GPMT study performed according to OECD guideline 406, scored Klimisch 1). In this study, no signs of contact sensitisation were detected after the challenge exposure in guinea pigs previously exposed to the test item during the experiment. In the control and treated animals, the mean of the scores was 0.00 according to the 24- and 48-hour observations after patch removal. Under the conditions of the present assay, ytterbium oxide was shown to have no skin sensitisation potential, and is classified as a non-sensitiser, according to current EU-regulations.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
20 July 2016 - 26 September 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Version / remarks:
17 July 1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. certificate)
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 was made for the purity/composition of the test item.
- The test item was formulated using 1% methylcellulose as vehicle.
- The formulations were used within 4 hours after adding the vehicle to the test item and the test item preparation was performed following approved procedures and documented in detail. The formulations were homogenised to visually acceptable levels and stirred up to finishing the treatment to ensure sufficient homogeneity.

Species:
guinea pig
Strain:
Hartley
Remarks:
LAL/HA/ BR
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: male albino guinea pigs (LAL/HA/ BR), LAB-ÁLL Bt., Budapest, 1174 Hunyadi u. 7, Hungary
- 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 (e.g. ad libitum): Animals received Cunigra Diet for Rabbits (produced by Bonafarm-Bábolna Takarmány Ltd., Hungary) (Batch number: NN16201718, expiry date: 24 August 2016), ad libitum.
- Water (e.g. ad libitum): Animals received tap water from municipal supply as for human consumption, containing at least 50 mg/100 mL ascorbic acid, ad libitum
- Acclimation period: 7 days before start of treatment under laboratory conditions
- Indication of any skin lesions: None

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.0 - 23.4 °C
- Humidity (%): 44 - 96%
- Air changes (per hr): 15-20 air exchange/hour
- Photoperiod (hrs dark / hrs light): 12 hrs dark/12 hrs light
Route:
intradermal
Vehicle:
other: 1% methylcellulose
Concentration / amount:
5%
Day(s)/duration:
day 1 of treatment
Route:
epicutaneous, occlusive
Vehicle:
unchanged (no vehicle)
Remarks:
dampened with saline
Concentration / amount:
100%
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)
Remarks:
dampened with saline
Concentration / amount:
amount: 0.5 g
Day(s)/duration:
day 22 of treatment; 24 hours of exposure
Adequacy of challenge:
highest non-irritant concentration
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
other: 1% methylcellulose
Concentration / amount:
volume applied: 0.5 mL
concentration: 50% (w/v)
Day(s)/duration:
day 22 of treatment; 24 hours of exposure
Adequacy of challenge:
other: safeguard dose
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 item 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 item 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 item 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 item in 1% methylcellulose; 2 injections of 5% test item, 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 item 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 item 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 item 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 item 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 item in 1% methylcellulose. The volume of formulated test item 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 item was removed with a wet gauze swab.

Terminal animals were sacrificed under pentobarbital anaesthesia.


BODY WEIGHT:
-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.

OBSERVATIONS
- Mortality/clinical signs: Daily during the test. As part of this observation, detailed clinical observationwas made weekly 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 cases of dermal induction exposure) were evalauted according to the scoring system of Draize (1959).

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).

- 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 item 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 item (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 group
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 group
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 EFFECTS AFTER THE CHALLENGE EXPOSURE

- Test group: After the challenge with the test item 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 item concentration of 50% (w/v) as a safeguard dose and no reaction was noted.

- Control group: After the challenge with the test item 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 item 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:
GHS criteria not met
Conclusions:
Challenge with test item (diytterbium trioxide) evoked no positive responses in the test animals previously sensitised with the test item or in the control group. The net response value represented an incidence rate of 0% and a net score value of 0.00. In conclusion, under the conditions of the present assay, the test item diytterbium trioxide was shown to have no skin sensitisation potential and is consequently classified as a non-sensitiser, according to current EU-regulations.
Endpoint:
skin sensitisation: in vitro
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Skin sensitisation - in vitro

An in vitro or in chemico skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study (initiated before October 11th 2016) is available.

Skin sensitisation - in vivo

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 the test item. The study was performed according to OECD guideline 406 and in compliance with GLP guidelines (Weisz, 2016, scored Klimisch 1). This skin sensitisation potential test method (OECD 406) was preferred above the 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.

Based on the results of a preliminary test, 10 test animals were subjected to sensitisation procedures in a two-stage process incorporating an induction phase using an intradermal treatment followed by a 48-hour topical application (dermal treatment under an occlusive dressing). The test item was used at a concentration of 5% (w/v) in 1% methylcellulose for intradermal injections, and at a concentration of 100% (as supplied, dampened with saline) for topical sensitisation treatment. Since the 100% formulation was not skin irritant in the dermal dose range-finding study, the test area was painted with 0.5 mL of 10% SDS in vaseline 24 hours prior to the topical induction application, in order to create local irritation. Five control guinea pigs were simultaneously exposed to 1% methylcellulose during the sensitisation phase (intradermal and dermal treatment). Two weeks after the last induction exposure, a challenge dose at a concentration of 100% (as supplied, dampened with saline) was dermally administered on the left side of all animals for 24 hours. The right side of the animals was treated with 50% (w/v) test item in 1% methylcellulose as a safeguard dose. Skin reactions were measured 24 and 48 hours after patch removal. No test item-related signs of systemic toxicity were observed in any animal. No signs of contact sensitisation were detected after the challenge exposure in guinea pigs previously exposed to the test item during the experiment. In the control and treated animals, the mean of the scores was 0.00 according to the 24- and 48-hour observations after patch removal. Under the conditions of the present assay, the test item was shown to have no sensitisation potential, and is 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

Skin sensitisation

The test item is considered to be non-sensitising, based on the results of a GPMT study (OECD guideline 406).

Respiratory sensitisation

No reliable study is available.