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Description of key information

No skin or eye irritation data are available for fused tungsten carbide. However, skin and eye irritation studies of sufficient quality and tested in accordance with standard methodology on tungsten carbide (WC), which were used for read-across, indicate a lack of irritating effects. In a semi-occlusive skin irritation study conducted on rabbits according to OECD TG 404, WC elicited no dermal irritation. In an eye irritation study conducted on rabbits according to OECD TG 405, instillation of WC into the rabbit eye elicited transient very slight to well-defined conjunctival irritation only. Based on the results of this study, fused tungsten carbide can be considered a non-irritant by virtue of read-across from WC.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin irritation: in vivo
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
1998-02-25 to 1999-09-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
ell documented, scientifically sound study that was conducted according to GLP and OECD guideline 404 with no deviations.
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Carbide
Target: Fused tungsten carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 404 (Acute Dermal Irritation / Corrosion)
GLP compliance:
yes
Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Harlan UK Ltd, Bicester, Oxon, England
- Age at study initiation: 10 to 11 weeks
- Weight at study initiation: 2.4 to 2.6 kg
- Housing: Individually in stainless steel cages with perforated floors.
- Diet (ad libitum): STANRAB (P) SQC Rabbit Diet-ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: Yes; time period not given.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 -22.5
- Humidity (%): 39-56%
- Air changes (per hr): 19
- Photoperiod (hrs dark / hrs light): 12 light (0700-1900 hrs)/12 dark

IN-LIFE DATES: From: 1998-02-25 To: 1998-02-28
Type of coverage:
semiocclusive
Preparation of test site:
shaved
Vehicle:
other: distilled water
Controls:
not required
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.5 g
- Approximately 0.5 g of test substance was applied under a 25 mm x 25 mm gauze pad which was moistened with 0.5 mL of distilled water, to one intact skin site on each animal.

VEHICLE
- Amount(s) applied (volume or weight with unit): 0.5 mL of distilled water
Duration of treatment / exposure:
4 hours
Observation period:
4 days
Number of animals:
3 males
Details on study design:
TEST SITE
- Area of exposure: 24 hours prior to application of test substance, hair was removed with electric clippers from the dorso-lumbar region of each rabbit.
- % coverage: Exposed an area of skin approximately 100 x 100 mm.
- Type of wrap if used: Each site was covered with "Elastoplast" elastic adhesive dressing for 4 hours.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): After 4 days, the semi-occlusive dressing and gauze pad were removed and the treatment site was washed with warm water to remove any residual test substance. The treated area was blotted dry with absorbent paper.


SCORING SYSTEM: Dermal irritation was scored according to Draize




Irritation parameter:
erythema score
Basis:
mean
Remarks:
for all three animals
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
edema score
Basis:
mean
Remarks:
for all three animals
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritant / corrosive response data:
No dermal response to treatment was observed in any animal throughout the study.
Other effects:
Clinical Signs: There were no signs of toxicity or ill health in any rabbit during the observation period.
Interpretation of results:
GHS criteria not met
Conclusions:
A single semi-occlusive application of Tungsten Carbide Powder- Pure to intact rabbit skin for four hours elicited no dermal irritation.

Executive summary:

No skin irritation data of sufficient quality are available for fused tungsten carbide (target substance). However, skin irritation data are available for tungsten carbide (source substance), which will be used for read-across. Due to similar water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate. In addition, read-across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in vivo
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
1998-03-02 to 1999-09-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that was conducted according to GLP and OECD Guideline 405 with no deviations.
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Carbide
Target: Fused tungsten carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 405 (Acute Eye Irritation / Corrosion)
Deviations:
no
GLP compliance:
yes
Species:
rabbit
Strain:
New Zealand White
Details on test animals or tissues and environmental conditions:
TEST ANIMALS
- Source: Harlan UK Ltd, Bicester, Oxon, England
- Age at study initiation: 13 to 15 weeks
- Weight at study initiation: 3.1 to 3.5 kg
- Housing:Individually in metal cages with perforated floors.
- Diet (ad libitum): ad libitum STANRAB (P) SQC Rabbit Diet
- Water (e.g. ad libitum): ad libitium
- Acclimation period: Yes, but no time span given.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 22
- Humidity (%): 34 - 65%
- Air changes (per hr): 19
- Photoperiod (hrs dark / hrs light): 12/12 (0700 - 1900 hours)

IN-LIFE DATES: From: 1998-03-02 To: 1998-03-08
Vehicle:
unchanged (no vehicle)
Controls:
no
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): Weight of 0.1 mL test material (100 mg); 579, 526, 590. Mean weight of 0.1 mL test substance: 565 mg.
Duration of treatment / exposure:
A single instillation
Observation period (in vivo):
3 days
Number of animals or in vitro replicates:
3
Details on study design:
REMOVAL OF TEST SUBSTANCE
- Washing (if done): Not rinsed

SCORING SYSTEM: Ocular irritation was scored according to Draize.

TOOL USED TO ASSESS SCORE: handheld light
Irritation parameter:
cornea opacity score
Basis:
mean
Remarks:
for all three animals
Time point:
24/48/72 h
Score:
0
Max. score:
8
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
iris score
Basis:
mean
Remarks:
for all three animals
Time point:
24/48/72 h
Score:
0
Max. score:
2
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Remarks:
No iridial iritation or damage was observed throughout the study
Irritation parameter:
chemosis score
Basis:
mean
Remarks:
for all three animals
Time point:
24/48/72 h
Score:
0
Max. score:
4
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
3
Reversibility:
fully reversible
Remarks on result:
no indication of irritation
Irritation parameter:
conjunctivae score
Basis:
animal #2
Time point:
24/48/72 h
Score:
0.3
Max. score:
3
Reversibility:
fully reversible within: 2 days
Remarks on result:
probability of weak irritation
Remarks:
Redness
Irritation parameter:
conjunctivae score
Basis:
animal #3
Time point:
24/48/72 h
Score:
0.3
Max. score:
3
Reversibility:
fully reversible within: 2 days
Remarks on result:
probability of weak irritation
Remarks:
Redness
Irritant / corrosive response data:
- No corneal damage or iridial inflammation was observed.
Other effects:
- A diffuse crimson colouration of the conjuctivae with or without slight swelling (grade 1 or 2) was seen in two animals up to 24 hours; in the remaining rabbit chemosis grade 1 was observed only 1 hour after instillation; 48 hours after instillation all ocular reactions had resolved. Tungsten carbide
showed only a transient very slight to well-defined conjunctival irritation.
- Transient hyperaemia of blood vessels was observed in the remaining rabbit. These reactions had resolved by either one or two days after instillation.
Interpretation of results:
GHS criteria not met
Conclusions:
Instillation of Tungsten Carbide Powder - Pure into the rabbit eye elicited transient very slight to well-defined conjunctival irritation only. Based on theresults of this study, tungsten carbide can be considered as non-irritant.
Executive summary:

No eye irritation data of sufficient quality are available for fused tungsten carbide (target substance). However, eye irritation data are available for tungsten carbide (source substance), which will be used for read-across. Due to similar water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate. In addition, read-across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

No skin or eye irritation data are available for fused tungsten carbide (target substance); however, data are available for tungsten carbide (source substance), which were used in the approach for read-across.

Due to similar bioaccessibility results for fused tungsten carbide (target substance) and tungsten carbide (source substance), the resulting toxicity potential would also be expected to be similar, so read-across is appropriate. In addition, read-across is justified because the classification and labelling, dose descriptors, and PBT/vPvB profiles are, or are expected to be, sufficiently similar for the target and source substances. For more details refer to the attached description of the read-across approach.

Justification for classification or non-classification

Skin Irritation:

A skin irritation study of sufficient quality and tested in accordance with standard methodology showed that tungsten carbide (WC) was not irritating to skin. Therefore, no classification is required for the skin irritation endpoint for fused tungsten carbide, based on read-across from WC.

Eye Irritation:

In an eye irritation study of sufficient quality and conducted in accordance with standard methodology on tungsten carbide (WC), the mean scores for all 3 animals were 0 for the cornea and iris. In 2 of the 3 animals, the average score for conjunctival redness over 24, 48, and 72 h was 0.3. The conjunctival redness reported in these 2 animals was only observed at 24 h and was fully reversible by 48 h. The average score at 24, 48, and 72 h for the remaining rabbit was zero for conjunctival effects. The cutoff value for eye irritation classification is a positive response of corneal opacity ≥ 3 and/or iritis > 1.5 calculated as the mean scores following grading at 24, 48, and 72 h after installation of the test material. Therefore, no classification is required for the eye irritation endpoint for fused tungsten carbide, based on read-across from WC.