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Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-01-28 to 2013-04-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report date:
2013

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
A LLNA was performed showing ambiguous results (Hargitai 2015). As it is known that the LLNA might be indefinite for certain metals, the present guinea pig study was performed.

Test material

Constituent 1
Reference substance name:
tantalum pentoxide
IUPAC Name:
tantalum pentoxide
Constituent 2
Chemical structure
Reference substance name:
Ditantalum pentaoxide
EC Number:
215-238-2
EC Name:
Ditantalum pentaoxide
Cas Number:
1314-61-0
Molecular formula:
O5Ta2
IUPAC Name:
ditantalum(5+) pentaoxidandiide
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): Ditantalum Pentaoxide
- CAS number: 1314-61-0
- Lot/batch No.: 20110415
- Physical state: solid
- Appearance: white powder
- Storage condition of test material: Room temperature
- Purity: > 99.8 % Ta2O5
- Expiration date of the lot/batch: 2013-04-12

In vivo test system

Test animals

Species:
guinea pig
Strain:
other: LAL/HA/BR
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: LAB-ÁLL Bt. Budapest, 1174 Hunyadi u. 7., Hungary
- Age at study initiation: young adults, 5 weeks
- Weight at study initiation: 256 - 297 g
- Housing: macrolon cages size IV, with 5 animals per cage
- Diet: CuniFort Diet for Rabbits (Bonafarm-Bábolna Takarmány Ltd., Hungary), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19.3 - 23.5
- Humidity (%): 28 - 53
- Air changes (per hr): 15-20
- Photoperiod (hrs dark / hrs light): 12/12

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal and epicutaneous
Vehicle:
other: 1 % methylcellulose
Concentration / amount:
- Range-Finding Test
Intradermal - 0.5, 1, 2.5, 5 % (w/v) in 1% methylcellulose
Epicutaneous - 25, 50, 75, 100 % (w/v) in 1 % methylcellulose

- Main Test
Main Study I (Intradermal induction): 5 % (w/v) in 1% methylcellulose
Main Study II (Epicutaneous induction): 100 % (w/v) in 1% methylcellulose
Main Study III (Epicutaneous challenge): 100 % (w/v) in 1% methylcellulose (left flank); 50 % (w/v) in 1% methylcellulose (right flank)
Challengeopen allclose all
Route:
intradermal and epicutaneous
Vehicle:
other: 1 % methylcellulose
Concentration / amount:
- Range-Finding Test
Intradermal - 0.5, 1, 2.5, 5 % (w/v) in 1% methylcellulose
Epicutaneous - 25, 50, 75, 100 % (w/v) in 1 % methylcellulose

- Main Test
Main Study I (Intradermal induction): 5 % (w/v) in 1% methylcellulose
Main Study II (Epicutaneous induction): 100 % (w/v) in 1% methylcellulose
Main Study III (Epicutaneous challenge): 100 % (w/v) in 1% methylcellulose (left flank); 50 % (w/v) in 1% methylcellulose (right flank)
No. of animals per dose:
Range-Finding Test: 2

Main Test: 10 animals per treatment group; 5 animals per control group
Details on study design:
RANGE FINDING TESTS
- Intradermal Range-Finding: Two animals each received intradermal injections of test material at concentrations of 0.5, 1, 2.5 and 5% (w/v). Following intradermal administration, the treatment sites were covered for approximately 24 hours with porous gauze. Skin reactions were observed 1, 24, 48 and 72 hours following administration.
- Epicutaneous Range-Finding: Two animals each received a single 0.5 mL dermal application of test material at 25, 50, 75 or 100 % (w/v) in 1 % methlcellulose. One concentration was used on the right side and another concentration on left side of the animals. Two animals were used per concentration. Occlusive exposure was for approximately 24 hours. Skin reactions were observed at 1, 24, 48 and 72 hours.

MAIN STUDY
A. INDUCTION EXPOSURE
Induction involved two main procedures: intradermal treatment (Main Study I) and epicutaneous (occlusive) exposure (Main Study II).
- Main Study I: Intra-dermal Induction Exposure
Approximately 24 hours before the treatment, an area of 5 x 5 cm² on the scapular region of animals was clipped free of hair and shaved.

Test group:
A series of three injections was administered on each side of the scapular region of treatment group animals, as follows, resulting in six injections per animal:
> 2 injections with 0.1 mL of Freund's Complete Adjuvant mixed with physiological saline (1:1) (v/v)
> 2 injections with 0.1 mL of the test material in 1 % methylcellulose at 5 % (w/v) concentration
> 2 injections with 0.1 mL of test material in 5 % (w/v), formulated in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline

Control group:
The control animals were treated with the vehicle without test material, as follows:
> 2 injections with 0.1 mL mix of Freund's Complete Adjuvant and physiological saline (NaCl 0.9 %) (1:1) (v/v)
> 2 injections with 0.1 mL of 1 % methylcellulose
> 2 injections with 0.1 mL of 50 % formulation of 1% methylcellulose in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline

- Main study II: Dermal Induction Exposure
The same inter-scapular region which received the intradermal injections, were used for dermal induction exposure.
Since the test material caused very slight erythema only at 1 hour after the patch removal in the 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.
The test animals were treated with approximately 0.5 mL of 100 % (w/v) test material in 1 % methylcellulose. This was the highest possible dose; and it was determined to be not irritating to the skin of the guinea pigs in the range-finding test. Control animals were treated with 1 % methylcellulose. The exposed areas were covered for 48 hours with 4 layers of porous gauze pads covered with a fully occlusive foil fasteneing (Closed Patch Test). After the patch removal, any remaining test material was removed with a gauze swab.
Following the dermal induction treatment, the animals were left untreated for 14 days prior to challenge applications.


B. CHALLENGE EXPOSURE
Two weeks after the topical induction application, the animals were exposed to a dermal challenge dose. Twenty four hours before treatment, the hair was removed from an area of approximately 6x8 cm² on the left and right flank of each animal. A 2.5x2.5 cm² patch of sterile gauze was saturated with the test material at 100 % (w/v) in 1 % methylcellulose concentration and applied to the left flank of all animals (both test and control groups). The right shaved flank area of all animals was treated with a 50 % dilution of the maximum dermal challenge dose (i.e. 50 (w/v) % in 1 % methylcellulose).

The volume of formulated test material was approximately 0.5 mL. The time of the exposure was 24 hours. After patch removal any remaining test material was removed with a gauze swab.

Challenge controls:
N.A.
Positive control substance(s):
yes
Remarks:
2-Mercaptobenzothiazole

Results and discussion

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 80 % and 70 % and net score values of 1.00 and 0.70 respectively. In the control animals no visible changes were found either at the 24 or 48 hours examinations following challenge with the reference item.

On the basis of the results of the reliability check study, the reference item 2-Mercaptobenzothiazole was classified as a skin sensitiser. This demonstrated that the experimental procedure and the test system were appropriate.

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
50 % (w/v)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 50 % (w/v). No with. + reactions: 0.0. Total no. in groups: 5.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
100 % (w/v)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 100 % (w/v). No with. + reactions: 0.0. Total no. in groups: 5.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
50 % (w/v)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 50 % (w/v). No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
100 % (w/v)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 100 % (w/v). No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
50 % (w/v)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 50 % (w/v). No with. + reactions: 0.0. Total no. in groups: 5.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
100 % (w/v)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 100 % (w/v). No with. + reactions: 0.0. Total no. in groups: 5.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
50 % (w/v)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 50 % (w/v). No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
100 % (w/v)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 100 % (w/v). No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
50 % (w/v)
No. with + reactions:
8
Total no. in group:
10
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
50 % (w/v)
No. with + reactions:
7
Total no. in group:
10

Any other information on results incl. tables

RANGE-FINDING TEST

Intradermal Exposure

It was found that concentrations of 5 and 1% (w/v) in 1% methylcellulose caused very slight erythema at the 1 hour observation. The concentration of 5% (w/v) caused very slight erythema also at the 24, 48 and 72 hours observations, while 0.5 and 2.5% (w/v) in 1% methylcellulose produced no reaction (scores 0-0) in the skin of guinea pigs.

 

Epicutaneous Exposure

It was found that approximately 0.5 mL of the test material formulations at concentrations of 100 and 50 % (w/v) caused very slight erythema at the 1 hour observation and produced no reaction (scores 0-0) on the skin of guinea pigs at the 24, 48 and 72 hour observations.

 

On the basis of results of the Range-Finding Test, the 5 % (w/v) concentration was used for intradermal induction and 100 % (w/v) formulation was used for dermal induction treatment in the main test. Control animals were treated with the vehicle, 1 % methylcellulose. For the challenge exposure, all animals of the treatment and control group were treated with the 100 % (w/v) concentration as a challenge dose and at a concentration of 50 % (w/v) as a safeguard dose.

MAIN TEST

Skin Effects after the Challenge Exposure

 - Test group

After the challenge with the test material at a concentration of 100 % (w/v) in 1 % methylcellulose, no positive response was observed in the treated animals. The mean of the scores was 0.00 according to the 24 and 48-hours results. The right shaved flank area of all animals was treated with a test material concentration of 50 % (w/v) in 1 % methylcellulose as a safeguard dose and no reaction was noted.

 - Control group

After the challenge with the test material at a concentration of 100 % (w/v) in 1 % methylcellulose no visible changes were found at the 24 and 48 hours examinations. The right shaved flank area of control animals was treated with a test material concentration of 50 % (w/v) in 1 % methylcellulose as a safeguard dose and no reaction was noted.

 

Clinical Observations

There were no overt signs of an adverse clinical response to treatment with the test material during the course of the study. During the induction period very slight erythema was observed in 3 test animals 24 hours after the intradermal treatment. No further local skin effects were observed in either the test group or in the control group.

 

Mortality

There were no moribund or dead animals during the study.

 

Body weight

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

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
In conclusion, under the conditions of the study, tantalum pentoxide is considered to be not a dermal sensitizer.
Executive summary:

In a dermal sensitization study (OECD 406) with Tantalum pentoxide (>99.8 %) in 1 % methylcellulose, young adult male LAL/HA/BR guinea pigs (10 animals per treatment group and 5 animals per control group) were tested using the method of Magnusson and Kligman. No signs of systemic toxicity were observed in any animal. During the induction period very slight erythema was observed in three test animals 24 hours after the intradermal treatment. No further local skin effects were observed in either the test or control group. In the control and treatment groups the mean score for dermal reactions was 0 at 24 and 48 hours after challenge. In this study, tantalum pentoxide is not a dermal sensitizer.