Vanadium carbide

Endpoint summary

Description of key information

Key studies demonstrate a lack of irritation/corrosion potential:

Data are read-across from a structural analogue, i.e. vanadium metal powder, based on inertness and similar solubility or lack thereof.

An in vitro skin irritation study (EpiSkinTM) was performed with vanadium metal powder (Heppenheimer, 2010), and results indicate that it is not irritant to skin.

An acute eye irritation / corrosion test according to OECD 405 (Leuschner, 2010) was performed with vanadium metal powder, and results indicate that it is not irritant to eyes.

Based on read-across (see discussion), it is assumed that vanadium carbide does also not cause respiratory irritation.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation / corrosion

Remarks:

other: validated "in vitro" test method

Type of information:

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

Adequacy of study:

key study

Study period:

2010-03-03 to 2010-03-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study reliable without restrictions

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EC) No. 440/2008 B.46 (draft)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ECVAM international validation study on in vitro tests for acute skin irritation (Altern Lab Anim. 2007 Dec; 35 (6):559-601)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: OECD Guideline for the Testing of Chemicals; Draft proposal for a new guideline, in vitro skin irritation: Reconstructed Human Epidermis (RhE) Test method, 11 December 2009, Vers. 4.

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-03-30

Details on test animals or test system and environmental conditions:

Not applicable - Since this is a in vitro study there is no information on test animals.

Vehicle:

water

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): Approx. 15 mg of the test item were applied to each of triplicate tissues.
No further information on the amount/concentration applied was stated.

Duration of treatment / exposure:

15+/- 1 min

Observation period:

not applicable

Number of animals:

not applicable

Details on study design:

CELL CULTURE
EpiSkin TM kits (Lot No.: 10-EKIN-007) are purchased from Skinethic Laboratories (06000 Nice, France). The EpiSkin TM tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organized basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiSkin TM tissues (surface 0.38 cm^2) are cultured on specially prepared cell culture inserts.
EpiSkin TM tissues were shipped with ice packs on medium-supplemented agarose gels in a 12-well plate. On day of experiment EpiSkin TM tissues were transferred to 12-well plates with maintenance medium.

TREATMENT:
The negative control (deionised water (lot no. 1.3.10, produced in-house; 15 µL were applied to each of triplicate tissues) and positive control (5% sodium lauryl sulphate (lot no. 1353471 51508322; Fluka, Sigma-Aldrich, 89555 Steinheim, Germany) solution in deionised water, prepared freshly prior to the performance of the experiment; 15 µL were applied to each of triplicate tissues), and the test item were added into the insert atop the concerning EpiSkin TM triplicate tissues. Additionally, the test item tissues were wetted with 15 µl of deionised water. The plates were placed into the incubator for 15+/- 1 min at 37 +/- 1.5 °C, 5 +/- 0.5 % CO2.
After the end of the treatment interval the inserts were removed immediately from the plate. Using a wash bottle the tissues were gently rinsed with PBS to remove any residual test material. Excess PBS was removed by gently shaking the inserts and blotting the bottom with blotting paper. The inserts were placed in the plates with 2 mL maintenance medium. The tissues were incubated for 42 +/- 1 hour at 37 +/- 1.5 °C, 5 +/- 0.5 % CO2.

MTT ASSAY:
Cell viability is measured by dehydrogenase conversion of MTT [(3-4, 5-dimethyl thiazole 2-yl) 2,5-diphenyl-tetrazoliumbromide], present in cell mitochondria, into a blue formazan salt that is quantitatively measured after extraction from tissues (Faller, C., Bracher, M., Dami, N., Roguet, R., 2002. Predictive ability of reconstructed human epidermis equivalents for assessment of skin irritation of cosmetics. Toxicology in vitro 16 (5), 557-552.).The percent reduction of cell viablity in comparison of untreated negative controls is used to predict skin irritation potential.
After the treatment procedure (42 hours) was completed for all tissues of each time point cell culture inserts were transferred from the holding plates to plates containing 2 mL assay medium containing 0.3 mg/mL MTT per well. After a 3 hour incubation period (37 +/- 1.5 °C, 5 +/- 0.5 % CO2) MTT solution was aspirated from the wells and wells were rinsed three times with PBS. Tissues samples were cut out of the inserts with a biopsy punch and transferred into plastic vials. The tissue samples were immersed into extractant solution by gently pipetting 0.5 mL extractant solution (isopropanol) into each vial. The tissue samples were completely covered by isopropanol. The vials were sealed to inhibit isopropanol evaporation. The formazan salt was extracted for approx. 72 hours in the refrigerator.
Per each tissue sample 2 X 200 µL aliquots of the formazan blue solution were transferred into a 96-well flat bottom microtiter plate. OD was read in a microplate reader (Versamax® Molecular Devices, D-85737 Ismaning, Germany) at 570 nm without reference filter. Mean values were calculated from the 2 wells per tissue sample.

EVALUATION OF RESULTS:
The mean OD of the three negative control tissues was calculated. This value corresponds to 100% tissue viability in the current test. For each individual tissue treated with the test item or the positive control the individual relative tissue viability is calculated according to the following formula:
Relative viability (%) = [OD test item/ OD negative control] * 100
For the test item and the positive control the mean relative viability +/- standard deviation of the three individual tissues are calculated and used for classification according to the following prediction model:
For the current test, an irritation potential of a test item according to EU classification R38 is predicted if the mean relative tissue viablity of three individual tissues is reduced below 50 % of the negative control.

ACCEPTABILITY OF THE ASSAY:
The absolute OD 570 nm of the negative control tissues in the MTT test is an indicator of tissue viability obtained after the shipping and storing procedure and under specific conditions of the assay. Tissue viability is meeting the acceptance criterion if the mean OD of the three tissues is ≥0.6 till ≤ 1.5.
An assay is meeting the acceptance criterion if mean relative tissue viability of the positive control is ≤ 40%.
The standard deviations in between tissues of the same treatment group should be ≤ 18%.

The data of the quality control (determined by Skinethic Laboratories, 06000 Nice, France) of the respecitve EpiSkin TM lot is mentioned below under "Attached background material" (the acceptance limit of the IC50 should be in the between 1.0 and 3.0 mg/L after 18 hours treatment with SLS).

TEST FOR DIRECT MTT REDUCTION.
For correct interpretation of results it was necessary to assess the ability of the test item to directly reduce MTT. To test for this ability approximately 15 mg of the test item were added to 1 mL of MTT solution and the mixture was incubated in the dark at room temperature for 60 minutes. Untreated MTT medium was used as control. If the MTT solution colour turned blue/purple, the test item was presumed to have reduced the MTT.
A colour change could not be observed.
No further information on the study design was stated.

Irritation parameter:

other: relative viability (%)

Basis:

mean

Time point:

other: after 15 min incubation

Score:

90.8

Max. score:

93

Reversibility:

no data

Irritant / corrosive response data:

After treatment with the test item Vanadium (metal) the relative absorbance values slightly decreased to 90.8%. This value is well above the treshold for irritancy of ≤ 50 %. Therefore, the test item is not considered to possess an irritant potential.

Results after treatment with vanadium (metal)

 

Dose group	Treatment Interval	Absorbance 570 nm Tissue 1	Absor-bance 570 nm Tissue 2	Absorbance 570 nm Tissue 3	Mean Absorbance of 3 Tissues	Absorbance [%] Tissue 1, 2 + 3	Rel. Standard Deviation	Rel. Absorbance [% of Negative Control]
Negative Control	15 min	0.878	0.819	0.873	0.857	102.5 95.6 101.9	3.8	100.0
Positive Control	15 min	0.293	0.209	0.203	0.235	34.2 24.4 23.7	5.9	27.4
Vanadium (metal)	15 min	0.752	0.786	0.797	0.778	91.7 93.0 83.6	2.7	90.8

Optical evaluation of the MTT-reducing capacity of the test item after 1 hour incubation with MTT-reagent did not show blue colour.

Historical data:

Positive Control		Negative Control
Number of Studies	73	Number of Studies	73
Period	July 2007 - March 2010	Period	July 2007 - March 2010
Mean Viability	16.5 %	Mean OD	1.081
Standard Deviation	11.0%	Standard Deviation	0.262
Range of Viabilities	3% - 36%	Range of ODs	0.7 – 1.6*

* The upper OD value is outside of the range of 0.6 - 1.5 recommended by the OECD guideline. Nevertheless since the OD value is only slightly above the required range, the historical data can still be considered as valid.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

After treatment with the test item vanadium (metal) the relative absorbance values slightly decreased to 90.8%. This value is well above the treshold for irritancy of ≤ 50 %. Therefore, the test item is not considered to possess an irritant potential.
The test item should not be classified and labeled as skin irritant according to Directive 67/548/EEC.
The test item should not be classified and labeled as skin irritant according to regulation (EC) No.: 1272/2008.

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:

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

Adequacy of study:

key study

Study period:

2010-05-18 to 2010-05-30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study reliable without restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Version / remarks:

2002-04-24

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-11-12

Species:

rabbit

Strain:

Himalayan

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Source: LPT Laboratory of Pharmacology and Toxicology GmbH & Co. KG, Branch Löhndorf, 24601 Löhndorf/Post Wankendorf, Germany
- Age at study initiation: Approx. 4 - 5 months
- Weight at study initiation: Animal 1: 2.4 kg; Animal 2: 2.0 kg; Animal 3: 2.5 kg
- Housing: For 8 hours following test item application, the animals were kept singly in restrainers which allowed free movement of the head but prevented a complete body turn, wiping of the eyes with the paws and excluded irritation of the eye by excrements and urine. During the acclimatisation period and after the 8-hour period in restrainers, the animals were kept singly in cages with dimensions of 380 mm x 425 mm x 600 mm (manufacturer: Dipl.Ing. W. EHRET GmbH, 16352 Schönwalde, Germany).
- Diet (ad libitum): Commercial diet, ssniff7 K-H V2333 (ssniff Spezialdiäten GmbH, 59494 Soest, Germany)
- Water (ad libitum before and after the exposure period): Tap water
- Acclimation period: At least 20 adaptation days

ENVIRONMENTAL CONDITIONS
- Temperature: 20 °C +/- 3 °C (maximum range)
- Relative humidity: 30% - 70% (maximum range; aim was 50% - 60%)
- Photoperiod (hrs dark / hrs light): 12/12
No further information on the test animals was stated.

Vehicle:

unchanged (no vehicle)

Controls:

no

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 100 mg of the test item were administered into one eye each of three animals. The test item was placed into the conjunctival sac of the right eye of each ani¬mal after gently pulling the lower lid away from the eyeball. The lids were then gently held together for about one second in order to prevent loss of the material. The left eye, which remained untreated, served as a control.
No further information on the amount/concentration applied was stated.

Duration of treatment / exposure:

1 hour (One hour after application the eyes were rinsed.)

Observation period (in vivo):

1, 24, 48 and 72 hours after the administration

Number of animals or in vitro replicates:

3 male rabbits

Details on study design:

It is explicitly note and in accordance with the guideline used, that the test was performed initially using one animal. As no corrosive or severe irritant effects were observed in this animal, 2 further animals were employed 24 hours after start of the initial test.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The eyes were rinsed with portions of 20 mL 0.9% aqueous NaCl solution, each.
- Time after start of exposure: 1 hour after administration

SCORING SYSTEM: Draize scoring system

TOOL USED TO ASSESS SCORE: The eyes were examined ophthalmoscopically with a slit lamp prior to the administration and 1, 24, 48 and 72 hours after the administration. The eye reactions were observed and registered.
24 hours after administration, fluorescein (Fluorescein SE Thilo drops (ALCON PHARMA GmbH, 79108 Freiburg, Germany) was applied to the eyes before being examined to aid evaluation of the cornea for possible lesions.

OTHER OBSERVATIONS: Any further lesions not covered by the scoring system were recorded. Body weight of all animals was measured at the beginning of the study and at the end of the study. Behaviour and food consumption were monitored.
No further information on the study design was stated.

Irritation parameter:

cornea opacity score

Basis:

mean

Remarks:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

iris score

Basis:

mean

Remarks:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

animal #1

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

cornea opacity score

Basis:

mean

Remarks:

animal #2

Time point:

other: 24, 48, and 72 hours

Score:

0

Max. score:

0

Irritation parameter:

iris score

Basis:

mean

Remarks:

animal #2

Time point:

other: 24, 48, and 72 hours

Score:

0

Max. score:

0

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

animal #2

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

cornea opacity score

Basis:

mean

Remarks:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

iris score

Basis:

mean

Remarks:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritation parameter:

conjunctivae score

Basis:

mean

Remarks:

animal #3

Time point:

24/48/72 h

Score:

0.33

Max. score:

1

Reversibility:

fully reversible within: 48 hours

Irritation parameter:

chemosis score

Basis:

mean

Remarks:

animal #3

Time point:

24/48/72 h

Score:

0

Max. score:

0

Irritant / corrosive response data:

Conjunctival redness (Grade 1: Some blood vessels hyperaemic (injected)) was observed in all animals 1 hour after instillation, in animal no. 3 until 24 hours after instillation. The mean score per animal, following grading at 24, 48 and 72 h after installation of the test material was calculated < 2. The effect was fully reversible within 48 h after application of the test material.
In addition, secretion was observed in animal no. one 1 hour after instillation.
The corneae and the irises were not affected by instillation of the test item.
The fluorescein test performed 24 hours after instillation did not reveal any changes.

Other effects:

There were no systemic intolerance reactions.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

According to the EC-Commission directive 67/548/EEC and its subsequent amendments on the approximation of the laws, regulations and administrative provision relating to the classification, packaging and labelling of dangerous substances and the results obtained under the present test conditions vanadium (metal) is non-irritating to eyes, hence, no labelling is required.
Also, according to the EC Regulation 1272/2008 and subsequent regulations, the test item is non-irritating to eyes; no classification and labelling of the substance is necessary.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Speciation:

Upon dissolution, vanadium substances transform in artificial body fluids, including PBS, sweat, gastric juice and lung fluid, predominantly to the pentavalent form,exceptin artificial lysosomal fluid; here, even pentavalent forms are converted almost completely totetravalent species already after a short period of time (for more information on in vitro bioaccessibility testing,please refer IUCLID section 7). Thus, it can be assumed that vanadium speciation in body fluids is controlled by the conditions of the respective medium but not by the vanadium source.

Read across concept:

The toxicity of vanadium carbide may reasonably be considered to be determined by the bioavailability of vanadium. As a first surrogate for bioavailability, the solubility of a test substance may be used. Under conditions of the transformation/dissolution test (T/D, OECD Series 29) with vanadium carbide powder at a loading of 1 mg/L, dissolved vanadium concentrations after 28d were 41.7 and 27.8 µg V /L at pH 8 and pH 6, respectively, while for vanadiun metal powder, dissolved vanadium concentrations after 28d were 38.4 and 39.6 µg V /L at pH 8 and pH 6, respectively. Vanadium carbide (2.1 mg/L; 20°C/pH 5.2) and vanadium metal (0.15 mg/L; 20°C/pH 5.8) are also poorly / sparingly soluble in water. In sum, read-across from a vanadium compound with similar water solubility, i.e. vanadium metal, is considered acceptable because kinetic data indicate a similar solubility potential.

Justification for selection of skin irritation / corrosion endpoint:

One reliable study conducted with vanadium is read-across to address this endpoint. Vanadium is not considered to be irritating to the skin. Consequently, vanadium carbide is also not considered to be irritating to the skin.

Justification for selection of eye irritation endpoint:

One reliable study conducted with vanadium is read-across to address this endpoint. Vanadium is not considered to be irritating to the eyes. Consequently, vanadium carbide is also not considered to be irritating to the eyes.

Justification for classification or non-classification

Skin and eye irritation:

Vanadium carbide does not possess an irritation potential and does not require classification as skin or eye irritant according to Directive 67/548/EEC and Regulation (EC) 1272/2008.

Respiratory irritation:

Vanadium carbide is only produced in briquette form. Based on the technical properties of a representative test material, the conduct of an acute inhalation toxicity test is neither technically feasible nor scientifically relevant for this type of compound. Due to the particle size, the low mobility and the negligible volatility, vanadium carbide in briquette form can safely be assumed to have avery low potential for human inhalation hazard during handling or application. In addition, vanadium carbide is poorly water soluble (1.7 mg/L at 20°C/5.2 pH) indicating inertness and a corresponding lack of potential to become bioavailable. Furthermore, pH-related effects do not need to be assumed upon contact with respiratory tract epithelia, and any lung overload associated with inert particles can be excluded. In sum, it is assumed that vanadium carbide does not cause respiratory tract irritation.