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Description of key information

Skin sensitisation - in vitro

Compatibility testing indicated that the test item tungsten zirconium (hydroxide) oxide is not compatible with the in vitro test methods. Therefore, an in vivo test was performed.

Skin sensitisation - in vivo

A reliable skin sensitisation study is available for tungsten zirconium (hydroxide) oxide (Tarcai, 2018, GPMT study performed according to OECD guideline 406, scored Klimisch 1). In this study, no signs of contact sensitisation were detected after the challenge and rechallenge exposure in guinea pigs previously exposed to the test item during the experiment. In the control and treated animals, after the first challenge, the mean of the scores was 0.00 according to the 24- and 48-hour observations after patch removal. At rechallenge evoked erythema score 1 in the test animals previously sensitised to the test item, however, the control group produced the same reaction. The mean of the scores was 1.00 according to the 24- and 48-hour observations after patch removal. The dermal reactions of the test group animals were not different from the reactions in the animals of the control group, therefore the test result was considered to be negative. Under the conditions of the present assay, the test item was shown to have no skin sensitisation potential.

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:
from 2018-05-03 to 2018-07-17
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)
Version / remarks:
30 May 2008
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Version / remarks:
March 2003
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 learned that this method is the most suitable method for testing insoluble inorganic substances, which are often not able to penetrate the skin.
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature.
- Stability under test conditions: The formulations were freshly formulated at appropriate concentrations in the vehicle on the day of administration and used within 4 hours after adding the vehicle to the test item.
- Solubility and stability of the test substance in the solvent/vehicle: The selection of the vehicle was based on trial formulations with the test item. It is preferred to use aqueous vehicles whenever possible, therefore physiological saline solution (saline) should be the first choice whenever possible (as distilled water is not compatible with intradermal treatments). However, saline was not tested as previous information from a different study (study code: 17/232-001P) showed that the test item was insoluble in distilled water (the formulation separated immediately to different phases). 1% methylcellulose (1% MC) was tested as a second option. During the Preliminary Compatibility Test, 1% MC was found to be suitable as a vehicle for the study.

FORM AS APPLIED IN THE TEST
The formulations were prepared with mortar and pestle. The concentrations were applied as suspensions. The test item was weighed and formulations were prepared daily on a weight by volume basis (as % (w/v).
No correction for the purity of the test item was applied.
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, ~ 8 weeks old
- Weight at study initiation: 499 – 611 g
- Housing: Animals were housed in Macrolon cages size IV, with up to 3 animals/cage to allow socialisation. The bedding used was Lignocel® 3/4-S Hygienic Animal Bedding.
- Diet (e.g. ad libitum): Animals in the first preliminary test received Cunigra Diet for Rabbits ad libitum. Animals in the second preliminary test and main study received ssniff® "Complete feed for Guinea pigs – maintenance", ad libitum.
- Water (e.g. ad libitum): Animals in the first preliminary test received tap water from municipal supply as for human consumption, containing at least 50 mg/100 mL ascorbic acid, ad libitum. Animals in the second preliminary test and main study received tap water from municipal supply without addition of ascorbic acid, as the food contained the necessary level of ascorbic acid for guinea pigs.
- Acclimation period: At least 28 days before the start of treatment under laboratory conditions.
- Indication of any skin lesions: Health inspection was performed at arrival of the animals. Only healthy animals were used for the test. The health status was certified by the staff Veterinarian.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18.0–25.9
- Humidity (%): 22–89
- 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:
concentration: 2.5% (w/v)
volume: 0.1 mL

Day(s)/duration:
day 1 of treatment
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Route:
epicutaneous, occlusive
Vehicle:
other: 1% methylcellulose
Concentration / amount:
concentration: 100% (w/v)
amount: 0.5 mL
Day(s)/duration:
day 8 of treatment; 48 hours of exposure
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
other: 1% methylcellulose
Concentration / amount:
50% (w/v)
Day(s)/duration:
day 22 of treatment; 24 hours of exposure
Adequacy of challenge:
other: highest non irritant concentration based on preliminary study results
No.:
#2
Route:
epicutaneous, occlusive
Vehicle:
other: 1% methylcellulose
Concentration / amount:
100% (w/v)
Day(s)/duration:
day 38 of treatment; 24 hours of exposure
Adequacy of challenge:
other: highest non irritant concentration based on dermal induction and 1st challenge results (main test)
No. of animals per dose:
Preliminary studies: 8 animals
Main study: 10 in the test group, 5 in the control group

Details on study design:
RANGE FINDING TESTS:
- 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: 1, 2.5 and 5% (w/v) concentrations in 1% MC were used for intradermal injection and 25, 50, 75 and 100% (w/v) in 1% MC for dermal application. Local effects were examined and scored 1, 24, 48 and 72 hours after the treatment (in case of intradermal injection) or after patch removal (in case of topical application). Skin effects were scored for erythema and oedema; any other observations of changes to the skin were recorded if present.
- For the intradermal application, 0.1 mL per concentration was injected intradermally into the hair free skin of the animals where the formulation properties made it possible. Two concentrations were injected on the right side and another two concentrations on the left side of the animals. The highest concentration of 5% (w/v) for intradermal treatment was also tested in a 1:1 mixture (v/v) of Freund's Complete Adjuvant (FCA) and physiological saline solution (saline). Each concentration was injected in duplicate where applicable. Two animals were used per concentration. 1 hour to 72 hours after intradermal injections of concentrations of 5% (w/v) with and without FCA:saline, very slight to well defined erythema was observed. The erythema was high enough and persistent for the main study. However, the injections of the 5% (w/v) concentrations with and without FCA were feasible but difficult, therefore the use of 5% (w/v) concentration was not advisable for the main study, as there was a risk that these formulations could not be injected as a whole. A concentration of 2.5% (w/v) caused very slight erythema which was observed from 1 hour to 48 hours after injection and 1% (w/v) caused only very slight erythema at 24 hours, therefore 2.5 % (w/v) was considered appropriate for the main study.
- For the topical application, the volume of the concentrations was 0.5 mL. 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 topical application was approximately 48 hours. One concentration was used on the right side and another concentration on the left side of animals. Two animals per concentrations were used. Very slight erythema was observed in the 100% (w/v) concentration groups at the 1-hour and 24-hour observation and 75% (w/v) at 1 hour after patch removal. No effects were observed at concentrations of 25 and 50% (w/v).

MAIN STUDY
On the basis of results of the Preliminary Dose Range Finding Study, the following treatments were chosen for the main study:
- Intradermal induction: 2.5% (w/v) test item formulated in 1% MC was used in the test group. For the control group, injections of the vehicle (1% MC) were chosen.
- Dermal induction: 100% (w/v) test item formulated in 1% MC. For control animals, 1% MC. Considering the irritation observed in the preliminary study at the chosen concentration, sodium dodecyl sulphate was considered to be unnecessary before topical treatment.
- Challenge phase: All animals of the treatment and control groups were treated with 50% (w/v) test item in 1% MC on the left side (highest concentration which caused no irritation) and with 1% MC on the right side.

A. INDUCTION EXPOSURE
- No. of exposures: once
- Test groups:
2 injections of Freund's Complete Adjuvant and physiological saline solution in a 1:1 (v/v) mixture,
2 injections of 2.5% (w/v) test item in 1% MC,
2 injections of 2.5% (w/v) test item, formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline solution.

- Control group:
2 injections of Freund's Complete Adjuvant and physiological saline solution in a 1:1 (v/v) mixture,
2 injections of 1% MC,
2 injections of vehicle (1% MC), formulated in a 1:1 mixture (v/v) of Freund's Complete Adjuvant and physiological saline solution.

- Site: scapular region
- Time of observation: 24 (± 2) hours after treatment

B. DERMAL INDUCTION EXPOSURE
- No. of exposures: once
- Exposure period: 48 +/- 2 hours
- Site: same scapular region which received the intradermal injections
- Time of observations: 1(+/- 5 min), 24(+/- 2), 48(+/- 2) and 72 (+/- 2) hours after the patch removal
- Concentrations:
test group: 100% (w/v) test item formulated in 1% methylcellulose
control group: 1% methylcellulose

C. CHALLENGE EXPOSURE
- No. of exposures: once
- Day(s) of challenge: on day 22
- Exposure period: 24 +/- 2 hours
- Site: left and right sides
- Evaluation (hr after challenge): 24 (+/- 2) and 48 (+/- 2) hours after the patch removal
- Concentrations: 50% w/v (in 1% methylcellulose) applied to the left side of animals and 1% methylcellulose applied to the right side

D. RECHALLENGE EXPOSURE
- No. of exposures: once
- Day(s) of challenge: on day 38
- Exposure period: 24 +/- 2 hours
- Site: left and right sides
- Evaluation (hr after challenge): 24 (+/- 2) and 48 (+/- 2) hours after the patch removal
- Concentrations: 100% w/v (in 1% methylcellulose) applied to an untreated area of the left flank of each animal animals and 1% methylcellulose applied to an untreated area of the right flank
Challenge controls:
Control animals were treated with the test item at a concentration of 100% (w/v) formulated in 1% MC on the left side during challenge. The right side was treated with the vehicle only.
No naive control animals were used for the rechallenge, as the animals were symptom-free during the challenge phase.
Positive control substance(s):
yes
Remarks:
2-mercaptobenzothiazole
Positive control results:
Challenge with the test item 2-mercaptobenzothiazole elicited discrete erythema (score 1) on the skin surface of previously sensitised guinea pigs. The mean of the scores were 0.80 (80% of animals) at the 24-hour observation and 0.70 (70% of animals) at the 48-hour observation. In the control group the mean of the scores was 0.00.
On the basis of the results of the present study, the test item 2-mercaptobenzothiazole was classified as a skin sensitiser. This demonstrates that the Magnusson and Kligman method (OECD 406) in this laboratory is considered to be reliable.
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test group
Dose level:
50% (w/v) (in 1% methylcellulose)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
no signs of systemic toxicity observed
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
Dose level:
50% (w/v) (in 1% methylcellulose)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
no signs of systemic toxicity observed
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
50% (w/v) (in 1% methylcellulose)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no signs of systemic toxicity observed
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
50% (w/v) (in 1% methylcellulose)
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
no signs of systemic toxicity observed
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
1st reading
Hours after challenge:
24
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)
Remarks on result:
positive indication of skin sensitisation
Remarks:
In the control group of this study the mean of the scores was 0.00.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
50% (w/v) (2-mercaptobenzothiazole)
No. with + reactions:
7
Total no. in group:
10
Clinical observations:
discrete erythema (score 1)
Remarks on result:
positive indication of skin sensitisation
Remarks:
In the control group of this study the mean of the scores was 0.00.
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
negative control
Dose level:
100 % (w/v) in 1% methylcellulose
No. with + reactions:
5
Total no. in group:
5
Clinical observations:
discrete or patchy erythema (score 1)
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
negative control
Dose level:
100 % (w/v) in 1% methylcellulose
No. with + reactions:
5
Total no. in group:
5
Clinical observations:
discrete or patchy erythema (score 1)
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
test group
Dose level:
100 % (w/v) in 1% methylcellulose
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
discrete or patchy erythema (score 1)
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
test group
Dose level:
100 % (w/v) in 1% methylcellulose
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
discrete or patchy erythema (score 1)
Remarks on result:
no indication of skin sensitisation

Skin effect during induction phase

Intradermal

No test item-related signs of erythema, local reactions or systemic toxicity were observed in any animal during the intradermal induction phase.

 

Topical

No test item-related signs of systemic toxicity were observed in any animal during the topical induction phase. Slight erythema (score 1) was observed on 2 out of 10 animals after 24 hours in the test group. The animals were symptom-free at 48- and 72-hour observations. No erythema was observed in the control group during the topical induction phase.

Skin effects after the challenge exposure

Test group

After the challenge with the test item at a concentration of 50% (w/v) formulated in 1% MC, no positive response was observed in the treated animals on the left flank. The mean of the scores was 0.00 according to the 24- and 48-hour results. The right shaved side of test animals was treated with 1% MC and no reaction was noted.

 

After the rechallenge with the test item at a concentration of 100% (w/v) formulated in 1% MC, positive responses were observed (erythema score 1) in 10 out of 10 treated animals on the left flank. The mean of the score was 1.00 according to the 24- and 48-hour results. The right shaved side of test animals was treated with 1% MC and no reaction was noted.

Control group

After the challenge with the test item at a concentration of 50% (w/v) formulated in 1% MC, no visible changes were found at the 24- and 48-hour examinations on the left flank. The right shaved side of control animals was treated with 1% MC and no reaction was noted.

 

After the rechallenge with the test item at a concentration of 100% (w/v) formulated in 1% MC, positive responses were observed (erythema score 1) in 5 out of 5 animals on the left flank. The mean of the scores was 1.00 according to the 24- and 48-hour results. The right shaved side of control animals was treated with 1% MC and no reaction was noted.

Scores of erythema after treatment of challenge and rechallenge exposure

 

Groups

Animal
Number

Day 24

Day 25

Day 40

Day 41

Left side

Right side

Left side

Right side

Left side

Right side

Left side

Right side

1. Control group

11

0

0

0

0

1

0

1

0

8

0

0

0

0

1

0

1

0

3

0

0

0

0

1

0

1

0

15

0

0

0

0

1

0

1

0

4

0

0

0

0

1

0

1

0

2. Dosed group

5

0

0

0

0

1

0

1

0

12

0

0

0

0

1

0

1

0

1

0

0

0

0

1

0

1

0

20

0

0

0

0

1

0

1

0

19

0

0

0

0

1

0

1

0

14

0

0

0

0

1

0

1

0

16

0

0

0

0

1

0

1

0

17

0

0

0

0

1

0

1

0

13

0

0

0

0

1

0

1

0

2

0

0

0

0

1

0

1

0

0 = no visible change

1 = discrete or patchy erythema

2 = moderate and confluent erythema

3 = intense erythema and swelling

Based on the scores measured after challenge and rechallenge, the dermal reactions of the test group animals were not different from the reaction in the animals of the control group, therefore the test result was considered to be negative.

Clinical observations/mortality

No signs of systemic toxicity were observed during induction, challenge or rechallenge.

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 the test item (tungsten zirconium hydroxide oxide) evoked no positive responses in the test animals previously sensitised with the test item or in the control group. In the control and treated animals, the mean of the scores were 0.00 according to the 24- and 48-hour results after the first challenge.

Rechallenge with the test item (tungsten zirconium hydroxide oxide) evoked erythema score 1 in the test animals previously sensitised with the test item, however the control group produced the same reaction. In the control and treated animals, the mean of the scores were 1.00 according to the 24- and 48-hour results after the rechallenge.

The dermal reactions of the test group animals were not different from the reaction in the animals of the control group, therefore the test result was considered to be negative.

Under the conditions of the present assay the test item tungsten zirconium hydroxide oxide was shown to have no sensitisation potential and is classified as a non- sensitiser, according to current GHS criteria and EU-regulations.
Endpoint:
skin sensitisation: in vitro
Data waiving:
study technically not feasible
Justification for data waiving:
an in vitro skin sensitisation study does not need to be conducted because the available in vitro test methods are not applicable for the substance and therefore an in vivo skin sensitisation study was conducted
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

A skin sensitisation study was performed with tungsten zirconium (hydroxide) oxide 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 (Tarcai, 2018, scored Klimisch 1). This skin sensitisation potential test method was preferred above the LLNA (OECD 429) since previous experience learned that this method is the most suitable method for testing this kind of substances, since insoluble inorganic compounds are often not able to penetrate the skin.

Based on the results of preliminary studies, 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 2.5% (w/v) for intradermal injections and at a concentration of 100% (w/v) for topical sensitisation treatment, both formulated in 1% methylcellulose (1% MC). Five control guinea pigs were simultaneously exposed to 1% MC during the sensitisation phase (intradermal and dermal treatment).  

Two weeks after the last induction exposure, a challenge dose at a concentration of 50% (w/v) in 1% MC was administered on the left side of all animals. The right side of the animals was treated with 1% MC. Challenge was performed by dermal application of the test item for 24 hours with a fully occlusive foil (Closed Patch Test). Skin reactions were measured 24 and 48 hours after patch removal.

Due to the absence of skin irritation effects following the dermal induction and challenge phase, a rechallenge (second challenge) at a higher concentration (100% w/v) was performed 16 days after the last treatment of the first challenge.  

At the induction phase, no test item-related signs of erythema, local reactions or systemic toxicity were observed in any animal during the intradermal phase. At the topical phase, slight erythema (score 1) was observed in 3 out of 10 animals at the 24-h observation in the test group. The animals were symptom-free at 48- and 72-h observations. No erythema was observed in the control group.

No signs of contact sensitisation were detected after the first challenge in guinea pigs previously exposed to the test item during the experiment. After the rechallenge, at 100% (w/v) on an untreated area of the left flank, erythema (score 1) was observed 24 and 48 hours after application in both treatment (10 animals out of 10) and control (5 out of 5) group. No reaction was noted on the right flank of any animals. The dermal reactions of the test group animals were not different from the reaction in the animals of the control group, therefore the test result was considered to be negative.

Under the conditions of the present assay the test item tungsten zirconium hydroxide oxide was shown to have no skin sensitisation potential and is classified as a non-sensitiser, according to current GHS criteria and EU regulations.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Skin sensitisation

Based on the test results of a guinea pig maximisation test performed with tungsten zirconium (hydroxide) oxide, the substance was concluded not to be classified as a skin sensitiser.

Respiratory sensitisation

No reliable study is available.