Niobium hydride

Endpoint summary

Description of key information

Skin Corrosion. Groot (2018)

Under the conditions of this study, the test material is not corrosive in the in vitro skin corrosion test.

Skin Irritation. Groot (2019)

Under the conditions of the study, the test material showed 93% cell viability compared to the control and is therefore considered as not irritating.

Eye Irritation, BCOP. Groot (2018)

Under the conditions of this study, since the test material induced an IVIS ≤ 3 in 5 out of 6 corneas, no classification is required for eye irritation or serious eye damage.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 September 2018 to 14 September 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Version / remarks:

2016

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Method B.40 Bis "In Vitro Skin Corrosion: Human Skin Model Test"

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: No correction was made for the purity/composition of the test material. The solid test material was crushed and ground in a mortar with pestle to improve the consistency.

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

Recommended in international guidelines.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm Skin Model (EPI-200)
- Tissue Lot no.: 29404 Kit J
- Source: MatTek Corporation, Ashland MA, U.S.A.
- The model 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 EpiDerm tissues (surface 0.63 cm²) were cultured on polycarbonate membranes of 10 mm cell culture inserts.

TEST FOR COLOUR INTERFERENCE BY THE TEST MATERIAL
- The test material was checked for possible colour interference before the study was started. Some non-coloured test materials may change into coloured materials in aqueous conditions and thus stain the skin tissues during the 1-hour exposure. To assess the colour interference, at least 25 mg of the test material or 50 μL Milli-Q water as a negative control were added to 0.3 mL Milli-Q water. The mixture was incubated for approximately 1 hour at 37.0 ± 1.0 °C in the dark. At the end of the exposure time the mixture was shaken and it was checked if a blue/ purple colour change was observed.

TEST FOR REDUCTION OF MTT BY THE TEST MATERIAL
- The test material was checked for possible direct MTT reduction before the study was started. To assess the ability of the test material to reduce MTT, at least 25 mg of the test material or 50 μL Milli-Q water as a negative control were added to 1 mL MTT (Sigma, Zwijndrecht, The Netherlands) solution (1 mg/mL) in phosphate buffered saline. The mixture was incubated for approximately 1 hour at 37.0 ± 1.0 °C. At the end of the exposure time it was checked if a blue/ purple colour change or a blue/ purple precipitate was observed.

TEST SYSTEM
- Application/Treatment of the Test Material: The skin tissues were kept in the refrigerator the day they were received. The next day, at least 1 hour before the assay was started the tissues were transferred to 6-well plates containing 0.9 mL DMEM per well. The level of the DMEM was just beneath the tissue. The plates were incubated for approximately 3 hours at 37.0 ± 1.0 °C. The medium was replaced with fresh DMEM just before the test material was applied. The test was performed on a total of 4 tissues per test material together with a negative control and positive control. Two tissues were used for a 3-minute exposure to the test material and two for a 1-hour exposure. The skin was moistened with 25 μL Milli-Q water (Millipore Corp., Bedford, Mass., USA) to ensure close contact of the test material to the tissue and 51.66 to 71.80 mg of the solid test material was added into the 6-well plates on top of the skin tissues. The test material was applied directly on top of the skin tissue and spread to match the size of the tissue. For the negative and positive controls, 2 tissues were treated with 50 μL Milli-Q water (negative control) and 2 tissues were treated with 50 μL 8N KOH (positive control) for both the 3-minute and 1-hour time point.

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: Room temperature
- Temperature of post-treatment incubation: 37 °C with MTT

REMOVAL OF TEST MATERIAL AND CONTROLS
- After the exposure period, the tissues were washed with phosphate buffered saline (Invitrogen Corporation, Breda, The Netherlands) to remove residual test material. The skin inserts were carefully dried. Rinsed tissues were kept in 24 well plates on 300 μL DMEM until 6 tissues (= one application time) were dosed and rinsed.

CELL VIABILITY MEASUREMENT
- The DMEM was replaced by 300 μL MTT-medium and tissues were incubated for 3 hours at 37 °C in air containing 5 % CO2. After incubation the tissues were washed with PBS and formazan was extracted from top and bottom with 2 mL isopropanol (MatTek corporation) over night at room temperature. The amount of extracted formazan was determined spectrophotometrically at 570 nm in triplicate with the TECAN Infinite® M200 Pro Plate Reader (calibrated with a linear range of 0.09 -2.3).

ACCEPTABILITY CRITERIA
The in vitro skin corrosion test is considered acceptable if it meets the following criteria:
a) The absolute mean OD570 of the two tissues of the negative control should reasonably be within the laboratory historical control data range.
b) The mean relative tissue viability following 1-hour exposure to the positive control should be <15 %.
c) In the range 20 – 100 % viability, the Coefficient of Variation (CV) between tissue replicates should be ≤ 30 %.

INTERPRETATION
A test material is considered corrosive in the in vitro skin corrosion test if:
a) The relative mean tissue viability obtained after 3-minute treatment compared to the negative control tissues is decreased below 50 %.
b) In addition, a test material considered non-corrosive (viability ≥ 50 %) after the 3-minute treatment is considered corrosive if the relative tissue viability after 1-hour treatment with the test material is decreased below 15 %.
A test material is considered non corrosive in the in vitro skin corrosion test if:
a) The relative mean tissue viability obtained after the 3-minute treatment compared to the negative control tissues is not decreased below 50 %.
b) In addition, the relative tissue viability after the 1-hour treatment is not decreased below 15 %.

STEP 1
< 50 % viability after 3 minute exposure = Corrosive
≥ 50 % viability after 3 minute exposure AND < 15 % viability after 1 hour exposure = Corrosive
≥ 50 % viability after 3 minute exposure AND ≥ 15 % viability after 1 hour exposure = Non-corrosive

STEP 2 (for substances/mixtures identified as Corrosive in step 1)
< 25 % viability after 3 minute exposure = Optional Sub-category 1A
≥ 25 % viability after 3 minute exposure = A combination of optional Sub-categories 1B and 1C

ANALYSIS
- Calculation of Cell Viability: Optical Density readings were transferred into Microsoft Excel to allow further calculations to be performed.
- The corrected OD (ODc) for each sample or control was calculated by subtracting the value of the blank mean (ODbl) from each reading (ODraw).

ODc = ODraw – ODbl

- The OD value representing 100 % cell viability is the average OD of the negative controls (ODlt_u+MTT).

- The %Viability for each sample and positive control is calculated as follows:

% Viability = (ODc/mean ODlt_u+MTT) * 100

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied: 51.66 to 71.80 mg

NEGATIVE CONTROL
- Amount(s) applied: 50µL

POSITIVE CONTROL
- Amount(s) applied: 0 µL
- Concentration: 8 N

Duration of treatment / exposure:

3 minutes and 1 hour

Duration of post-treatment incubation (if applicable):

3 hours with MTT

Number of replicates:

2 per treatment time

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3-minute application

Value:

98

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1-hour application

Value:

97

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- The test material was checked for colour interference in aqueous conditions and possible direct MTT reduction by adding the test material to MTT medium. Because the solutions did not turn blue / purple nor a blue / purple precipitate was observed it was concluded that the test material did not interfere with the MTT endpoint.
- Skin corrosion is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after the 3-minute and 1-hour treatments with the test material compared to the negative control tissues was 98 and 97 % respectively. Because the mean relative tissue viability for the test material was not below 50 % after 3 minutes treatment and not below 15 % after 1 hour treatment the test material is considered to be not corrosive.
The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the acceptance limits of OECD 431 (lower acceptance limit ≥0.8 and upper acceptance limit ≤2.8) and the laboratory historical control data range. The mean relative tissue viability following the 1-hour exposure to the positive control was 7.2 %.
- In the range of 20 – 100 % viability the Coefficient of Variation between tissue replicates was ≤ 13 %, indicating that the test system functioned properly.

Table 1: Mean Tissue Viability in the in vitro Skin Corrosion Test with The Test Material

Treatment	3-Minute Application Viability (Percentage of Control)	1-Hour Application Viability (Percentage of Control)
Negative Control	100	100
Test Material	98	97
Positive Control	8.5	7.2

 

Table 2: Coefficient of Variation between Tissue Replicates

Treatment	3 Minutes	1 Hour
Negative Control	1.3	2.2
Test Material	7.5	1.6
Positive Control	36	9.6

CV (%) = 100 - [(lowest OD570/highest OD570) x 100 %]

Interpretation of results:

other: Not classified in accordance with EU criteria

Conclusions:

Under the conditions of this study, the test material is not corrosive in the in vitro skin corrosion test.

Executive summary:

The skin corrosion potential of the test material was investigated in accordance with the standardised guidelines OECD 431 and EU method B.40 BIS, under GLP conditions.

The objective of this study was to evaluate the test material for its ability to induce skin corrosion on a human three dimensional epidermal model (EpiDerm (EPI-200)). The possible corrosive potential of the test material was tested through topical application for 3 minutes and 1 hour.

The test material was a silver grey solid. Skin tissue was moistened with 25 μL of Milli-Q water and at least 25 mg of the test material was applied directly on top of the skin tissue.

The positive control had a mean relative tissue viability of 7.2 % after the 1-hour exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the acceptance limits of OECD 431 (lower acceptance limit ≥0.8 and upper acceptance limit ≤2.8) and the laboratory historical control data range. In the range of 20 – 100 % viability the Coefficient of Variation between tissue replicates was ≤ 13 %, indicating that the test system functioned properly.

Skin corrosion is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after 3-minute and 1-hour treatments with the test material compared to the negative control tissues was 98 and 97 %, respectively. Because the mean relative tissue viability for the test material was not below 50 % after the 3-minute treatment and not below 15 % after the 1-hour treatment the test material is considered to be not corrosive.

Under the conditions of this study, the test material is not corrosive in the in vitro skin corrosion test.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 October 2018 to 22 October 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

2015

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

2012

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Final preparation of a solid: The solid test material was crushed and ground in a mortar with pestle to improve the consistency and was applied directly on top of the skin tissue.
- No correction was made for the purity/composition of the test material.

Test system:

human skin model

Remarks:

EPISKIN™-SM

Cell type:

non-transformed keratinocytes

Justification for test system used:

In the interest of sound science and animal welfare, a sequential testing strategy is recommended to minimize the need of in vivo testing. One of the validated in vitro skin irritation tests is the EPISKIN test, which is recommended in international guidelines (e.g. OECD and EC).

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN™-SM
- Tissue batch number(s): 8-EKIN-042

TEST SYSTEM SET UP
- On the day of receipt the tissues were transferred to 12-well plates and pre-incubated with pre-warmed Maintenance Medium for approximately 22 hours at 37 °C.
- All incubations, with the exception of the test material incubation of 15 minutes at room temperature, were carried out in a controlled environment, in which optimal conditions were a humid atmosphere of 80 – 100 % (actual range 69 – 85 %), containing 5.0 ± 0.5 % CO2 in air in the dark at 37.0 ± 1.0 °C (actual range 36.8 - 37.4 °C). Temperature and humidity were continuously monitored throughout the experiment. The CO2 percentage was measured once on each working day. Temporary deviations from the temperature, humidity and CO2 percentage may occur due to opening and closing of the incubator door. Based on laboratory historical data these deviations are considered not to affect the study integrity.


APPLICATION / TREATMENT OF THE TEST MATERIAL
- The test was performed on a total of 3 tissues per test material together with negative and positive controls. The skin was moistened with 5 μL Milli-Q water (Millipore Corp., Bedford, Mass., USA) to ensure close contact of the test material with the tissue, and the solid test material (36.8 to 54.7 mg) was added into 12-well plates on top of the skin tissues.
- The test material was spread to match the size of the tissue.
- Three tissues were treated with 25 μL PBS (negative control) and 3 tissues with 25 μL 5 % SDS (positive control) respectively. The positive control was re-spread after 7 minutes contact time.


TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 °C
- Temperature of post-treatment incubation: 37 °C


REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: After the exposure period of 15 ± 0.5 minutes at room temperature, the tissues were washed with phosphate buffered saline to remove residual test material.
- After rinsing, the cell culture inserts were each dried carefully and moved to a new well on 2 mL pre-warmed maintenance medium until all tissues were dosed and rinsed. Subsequently the skin tissues were incubated for 42 hours at 37 °C.


MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT Medium: MTT concentrate (Sigma Aldrich, Zwijndrecht, The Netherlands; 3 mg/mL in PBS) diluted (10x) in Assay medium.
- MTT concentration: Final concentration 0.3 mg/mL.


NUMBER OF REPLICATE TISSUES
- Three tissues per test material, three per positive control and three per negative control.


CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
- A test material may interfere with the MTT endpoint if it is coloured and/or it is able to directly reduce MTT. The cell viability measurement is affected only if the test material is present on the tissues when the MTT viability test is performed.
The test material was checked for possible direct MTT reduction and colour interference in the Skin corrosion test using EpiDerm as a skin model (Test Facility Study No. 20154269). Because solutions did not turn blue / purple and a blue / purple precipitate was not observed it was concluded that the test material did not interfere with the MTT endpoint.


CELL VIABILITY MEASUREMENT
- After incubation, cell culture inserts were dried carefully to remove excess medium and were transferred into a 12-wells plate prefilled with 2 mL MTT-solution (0.3 mg/mL in PBS). The tissues were incubated for 3 h at 37 °C. After incubation the tissues were placed on blotting paper to dry the tissues. Total biopsy was made by using a biopsy punch. Epidermis was separated from the collagen matrix and both parts were placed in pre-labelled microtubes and extracted with 500 μL isopropanol (Merck, Darmstadt, Germany). Tubes were stored refrigerated and protected from light for approximately 69 hours. The amount of extracted formazan was determined spectrophotometrically at 570 nm in duplicate with the TECAN Infinite® M200 Pro Plate Reader (calibrated with a linear range of 0.09 - 2.3).


PREDICTION MODEL / DECISION CRITERIA
- A test material is considered irritant in the skin irritation test if: The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test material and 42 hours of post incubation is ≤ 50 % of the mean viability of the negative controls.
- A test material is considered non-irritant in the in vitro skin irritation test if: The relative mean tissue viability of three individual tissues after 15 minutes of exposure to the test material and 42 hours of post incubation is > 50 % of the mean viability of the negative controls.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied: 36.8 to 54.7 mg

NEGATIVE CONTROL
- Amount(s) applied: 25 μL PBS

POSITIVE CONTROL
- Amount(s) applied: 25 μL 5% SDS

Duration of treatment / exposure:

15 ± 0.5 minutes

Duration of post-treatment incubation (if applicable):

42 h

Number of replicates:

Three tissues per test material, three per positive control and three per negative control.

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Mean

Value:

93

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

The test material was checked for possible direct MTT reduction and colour interference in the Skin corrosion test using EpiDerm as a skin model (Test Facility Study No. 20154269). Because no colour changes were observed it was concluded that the test material did not interact with the MTT endpoint.
Skin irritation is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test material compared to the negative control tissues was 93 %. Since the mean relative tissue viability for the test material was above 50 % the test material is considered to be non-irritant.
The positive control had a mean cell viability of 6.5 % after 15 ± 0.5 minutes exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three tissues treated with the test material or positive control was < 6 %, indicating that the test system functioned properly.

Interpretation of results:

other: Not classified according to EU criteria.

Conclusions:

Under the conditions of the study, the test material showed 93% cell viability compared to the control and is therefore considered as not irritating.

Executive summary:

The skin irritation potential of the test material was assessed in accordance with the standardised guidelines OECD 439 and EU Method B.46, under GLP conditions, using a human three dimensional epidermal model (EPISKIN Small model (EPISKIN-SM™)).

The possible skin irritation potential of the test material was tested through topical application for 15 minutes.

The test material was a silver grey solid. Skin tissue was moistened with 5 μL of Milli-Q water and at least 10 mg of the test material was applied directly on top of the skin tissue for 15 ± 0.5 minutes. After a 42 hour post-incubation period, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT at the end of the treatment.

Skin irritation is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test material compared to the negative control tissues was 93 %. Since the mean relative tissue viability for the test material was above 50 % after 15 ± 0.5 minutes treatment the test material is considered to be non-irritant.

The positive control had a mean cell viability of 6.5 % after 15 ± 0.5 minutes exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three tissues treated with the test material or positive control was < 6 %, indicating that the test system functioned properly.

Under the conditions of the study, the test material showed 93 % cell viability compared to the control and is therefore considered as not irritating.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 July 2018 to 14 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Version / remarks:

2017

Deviations:

no

GLP compliance:

yes

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: Bovine eyes from young cattle were obtained from the slaughterhouse.
- The eyes were excised by a slaughterhouse employee as soon as possible after slaughter.
- Storage, temperature and transport conditions of ocular tissue: Eyes were collected and transported in physiological saline in a suitable container under cooled conditions.

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied: 310.0 to 367.8 mg

VEHICLE
- Amount applied: Since no workable suspension of the test material in physiological saline could be obtained, the test material was used as delivered and added pure on top of the corneas.

Duration of treatment / exposure:

240 ± 10 minutes

Duration of post- treatment incubation (in vitro):

90 ± 5 minutes with Sodium Fluorescein

Number of animals or in vitro replicates:

Three corneas were selected at random for each treatment group.

Details on study design:

SELECTION AND PREPARATION OF CORNEAS
- The eyes were checked for unacceptable defects, such as opacity, scratches, pigmentation and neovascularisation by removing them from the physiological saline and holding them in the light. Those exhibiting defects were discarded.
- The isolated corneas were stored in a petri dish with cMEM (Earle’s Minimum Essential Medium (Life Technologies, Bleiswijk, The Netherlands) containing 1 % (v/v) L-glutamine (Life Technologies) and 1 % (v/v) Foetal Bovine Serum (Life Technologies)). The isolated corneas were mounted in a corneal holder (one cornea per holder) of BASF (Ludwigshafen, Germany) with the endothelial side against the O-ring of the posterior half of the holder. The anterior half of the holder was positioned on top of the cornea and tightened with screws. The compartments of the corneal holder were filled with cMEM of 32 ± 1 °C. The corneas were incubated for the minimum of 1 hour at 32 ± 1 °C.


QUALITY CHECK OF THE ISOLATED CORNEAS
- After the incubation period, the medium was removed from both compartments and replaced with fresh cMEM. Opacity determinations were performed on each of the corneas using an opacitometer (BASF-OP3.0, BASF, Ludwigshafen, Germany). The opacitometer was calibrated using reference holders before use. The opacity of each cornea was read against a cMEM filled chamber, and the initial opacity reading thus determined was recorded. Corneas that had an initial opacity reading higher than 7 were not used.


NUMBER OF REPLICATES: 3


NEGATIVE CONTROL USED: Physiological saline


POSITIVE CONTROL USED: 20 % (w/v) Imidazole prepared in physiological saline.


APPLICATION DOSE AND EXPOSURE TIME: 310.0 to 367.8 mg for 240 ± 10 minutes.


TREATMENT METHOD:
- The medium from the anterior compartment was removed and 750 µL of the negative control and 20 % (w/v) Imidazole solution (positive control) were introduced onto the epithelium of the cornea. The test material was weighed in a bottle and applied directly on the corneas using the open-chamber method in such a way that the cornea was completely covered (310.0 to 367.8 mg). The holder was slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the solutions over the entire cornea. Corneas were incubated in a horizontal position for 240 ± 10 minutes at 32 ± 1 °C.


REMOVAL OF TEST SUBSTANCE
- After the incubation the solutions and the test material were removed and the epithelium was washed at least three times with MEM with phenol red (Earle’s Minimum Essential Medium Life Technologies).


METHODS FOR MEASURED ENDPOINTS:
- Possible pH effects of the test material on the corneas were recorded.

- Corneal opacity: Each cornea was inspected visually for dissimilar opacity patterns. The medium in the posterior compartment was removed and both compartments were refilled with fresh cMEM and the opacity determinations were performed. The opacity of a cornea was measured by the diminution of light passing through the cornea. The light was measured as illuminance (I = luminous flux per area, unit: Lux) by a light meter. The opacity value (measured with the device OP-KIT) was calculated according to:

Opacity = [(I0 / I) − 0.9894 ] / 0.0251

With I0 the empirically determined illuminance through a cornea holder but with windows and medium, and I the measured illuminance through a holder with cornea. The change in opacity for each individual cornea (including the negative control) was calculated by subtracting the initial opacity reading from the final post-treatment reading. The corrected opacity for each treated cornea with the test material or positive control was calculated by subtracting the average change in opacity of the negative control corneas from the change in opacity of each test material or positive control treated cornea. The mean opacity value of each treatment group was calculated by averaging the corrected opacity values of the treated corneas for each treatment group.

- Corneal permeability: Following the final opacity measurement, permeability of the cornea to Na-fluorescein (Sigma-Aldrich, Germany) was evaluated. The medium of both compartments (anterior compartment first) was removed. The posterior compartment was refilled with fresh cMEM. The anterior compartment was filled with 1 mL of 5 mg Na-fluorescein/mL cMEM solution (Sigma-Aldrich Chemie GmbH, Germany). The holders were slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the sodium-fluorescein solution over the entire cornea. Corneas were incubated in a horizontal position for 90 ± 5 minutes at 32 ± 1 °C. After the incubation period, the medium in the posterior compartment of each holder was removed and placed into a sampling tube labelled according to holder number. 360 µL of the medium from each sampling tube was transferred to a 96-well plate. The optical density at 490 nm (OD490) of each sampling tube was measured in triplicate using a microplate reader (TECAN Infinite® M200 Pro Plate Reader). Any OD490 that was 1.500 or higher was diluted to bring the OD490 into the acceptable range (linearity up to OD490 of 1.500 was verified before the start of the experiment). OD490 values of less than 1.500 were used in the permeability calculation. The mean OD490 for each treatment was calculated using cMEM corrected OD490 values. If a dilution has been performed, the OD490 of each reading of the positive control and the test material was corrected for the mean negative control OD490 before the dilution factor was applied to the reading.


SCORING SYSTEM: In Vitro Irritancy Score (IVIS)

- The mean opacity and mean permeability values (OD490) were used for each treatment group to calculate an in vitro score:

In vitro irritancy score (IVIS) = mean opacity value + (15 x mean OD490 value)

- Additionally the opacity and permeability values were evaluated independently to determine whether the test material induced irritation through only one of the two endpoints.

- The IVIS cut-off values for identifying the test materials as inducing serious eye damage (UN GHS Category 1) and test materials not requiring classification for eye irritation or serious eye damage (UN GHS No Category) are given hereafter:
IVIS ≤ 3: No Category
IVIS > 3; ≤ 55: No prediction can be made
IVIS >55: Category 1

Irritation parameter:

in vitro irritation score

Run / experiment:

First experiment

Value:

1.8

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Since the results from the three corneas were spread over 2 categories (-0.5, -0.9 and 6.8 respectively), the test was inconclusive and a repeat experiment was performed.

Irritation parameter:

in vitro irritation score

Run / experiment:

Second experiment

Value:

-0.6

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

FIRST EXPERIMENT
- In the first experiment, the individual in vitro irritancy scores for the negative controls ranged from 0.9 to 2.0. The corneas treated with the negative control material were clear after the 240 minutes of treatment. The individual positive control in vitro irritancy scores ranged from 137 to 173. The corneas treated with the positive control were turbid after the 240 minutes of treatment.
- The corneas treated with the test material showed opacity values ranging from -2.5 to 0.3 and permeability values ranging from 0.106 to 0.436. The corneas were clear after the 240 minutes of treatment with the test material. No pH effect of the test material was observed on the rinsing medium. Hence, the in vitro irritancy scores ranged from -0.9 to 6.8 after 240 minutes of treatment with the test material.
- The mean in vitro irritancy score was 1.8 after 4 hours of treatment with the test material. Since the results were spread over 2 categories (-0.5, -0.9 and 6.8 respectively), the test was inconclusive and a repeat experiment was performed.

SECOND EXPERIMENT
- In the second experiment, the individual in vitro irritancy scores for the negative controls ranged from 2.7 to 2.9. The corneas treated with the negative control material were clear after the 240 minutes of treatment. The individual positive control in vitro irritancy scores ranged from 166 to 185. The corneas treated with the positive control were turbid after the 240 minutes of treatment.
- The corneas treated with the test material showed opacity values ranging from -2.3 to -1.2 and permeability values ranging from 0.013 to 0.139. The corneas were clear after the 240 minutes of treatment with the test material. No pH effect of the test material was observed on the rinsing medium. Hence, the in vitro irritancy scores ranged from -1.9 to 0.9 after 240 minutes of treatment with the test material.


ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas.
- Acceptance criteria met for positive control: The mean in vitro irritancy score of the positive control (20 % (w/v) Imidazole) was 159 and 176 in the first and second experiment, respectively and within two standard deviations of the current historical positive control mean.
- It was concluded that the test conditions were adequate and that the test system functioned properly.

Table 1: Summary of Opacity, Permeability and In Vitro Scores

Experiment	Treatment	Mean Opacity	Mean Permeability	Mean IVIS*
1	Negative Control	1.5	0.006	1.6
	Positive Control	123	2.387	159
	Test Material	-1.4	0.217	1.8
2	Negative Control	2.3	0.029	2.8
	Positive Control	128	3.175	176
	Test Material	-1.9	0.086	-0.6

* Calculated using the negative control mean opacity and mean permeability values for the positive control and test material. In vitro irritancy score (IVIS) = mean opacity value + (15 x mean OD490 value).

Interpretation of results:

other: Not classified in accordance with EU criteria

Conclusions:

Under the conditions of this study, since the test material induced an IVIS ≤ 3 in 5 out of 6 corneas, no classification is required for eye irritation or serious eye damage.

Executive summary:

The eye hazard potential of the test material was investigated in accordance with the standardised guideline OECD 437, under GLP conditions.

The objective of this study was to evaluate the eye hazard potential of the test material as measured by its ability to induce opacity and increase permeability in an isolated bovine cornea using the Bovine Corneal Opacity and Permeability test (BCOP test). The eye damage of the test material was tested through topical application for approximately 240 minutes. Since no workable suspension in physiological saline could be obtained, the test material was used as delivered and added pure on top of the corneas.

In the first experiment, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20 % (w/v) Imidazole) was 159 and within two standard deviations of the current historical positive control mean. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

The mean in vitro irritancy score was 1.8 after 4 hours of treatment with the test material. Since the results were spread over 2 categories (-0.5, -0.9 and 6.8 respectively), the test was inconclusive and a repeat experiment was performed.

In the second experiment, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20 % (w/v) Imidazole) was 176 and within two standard deviations of the current historical positive control mean. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

The test material did not induce ocular irritation through both endpoints, resulting in a mean in vitro irritancy score of 1.8 and -0.6 after 4 hours of treatment in the first and second experiment, respectively.

Under the conditions of this study, since the test material induced an IVIS ≤ 3 in 5 out of 6 corneas, no classification is required for eye irritation or serious eye damage.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin Corrosion. Groot (2018)

The skin corrosion potential of the test material was investigated in accordance with the standardised guidelines OECD 431 and EU method B.40 BIS, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The objective of this study was to evaluate the test material for its ability to induce skin corrosion on a human three dimensional epidermal model (EpiDerm (EPI-200)). The possible corrosive potential of the test material was tested through topical application for 3 minutes and 1 hour.

The test material was a silver grey solid. Skin tissue was moistened with 25 μL of Milli-Q water and at least 25 mg of the test material was applied directly on top of the skin tissue.

The positive control had a mean relative tissue viability of 7.2 % after the 1-hour exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the acceptance limits of OECD 431 (lower acceptance limit ≥0.8 and upper acceptance limit ≤2.8) and the laboratory historical control data range. In the range of 20 – 100 % viability the Coefficient of Variation between tissue replicates was ≤ 13 %, indicating that the test system functioned properly.

Skin corrosion is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after 3-minute and 1-hour treatments with the test material compared to the negative control tissues was 98 and 97 %, respectively. Because the mean relative tissue viability for the test material was not below 50 % after the 3-minute treatment and not below 15 % after the 1-hour treatment the test material is considered to be not corrosive.

Under the conditions of this study, the test material is not corrosive in the in vitro skin corrosion test.

Skin Irritation. Groot (2019)

The skin irritation potential of the test material was assessed in accordance with the standardised guidelines OECD 439 and EU Method B.46, under GLP conditions, using a human three dimensional epidermal model (EPISKIN Small model (EPISKIN-SM™)). The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The possible skin irritation potential of the test material was tested through topical application for 15 minutes.

The test material was a silver grey solid. Skin tissue was moistened with 5 μL of Milli-Q water and at least 10 mg of the test material was applied directly on top of the skin tissue for 15 ± 0.5 minutes. After a 42 hour post-incubation period, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT at the end of the treatment.

Skin irritation is expressed as the remaining cell viability after exposure to the test material. The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test material compared to the negative control tissues was 93 %. Since the mean relative tissue viability for the test material was above 50 % after 15 ± 0.5 minutes treatment the test material is considered to be non-irritant.

The positive control had a mean cell viability of 6.5 % after 15 ± 0.5 minutes exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the laboratory historical control data range. The standard deviation value of the percentage viability of three tissues treated with the test material or positive control was < 6 %, indicating that the test system functioned properly.

Under the conditions of the study, the test material showed 93 % cell viability compared to the control and is therefore considered as not irritating.

Eye Irritation, BCOP. Groot (2018)

The eye hazard potential of the test material was investigated in accordance with the standardised guideline OECD 437, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The objective of this study was to evaluate the eye hazard potential of the test material as measured by its ability to induce opacity and increase permeability in an isolated bovine cornea using the Bovine Corneal Opacity and Permeability test (BCOP test). The eye damage of the test material was tested through topical application for approximately 240 minutes. Since no workable suspension in physiological saline could be obtained, the test material was used as delivered and added pure on top of the corneas.

In the first experiment, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20 % (w/v) Imidazole) was 159 and within two standard deviations of the current historical positive control mean. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

The mean in vitro irritancy score was 1.8 after 4 hours of treatment with the test material. Since the results were spread over 2 categories (-0.5, -0.9 and 6.8 respectively), the test was inconclusive and a repeat experiment was performed.

In the second experiment, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20 % (w/v) Imidazole) was 176 and within two standard deviations of the current historical positive control mean. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

The test material did not induce ocular irritation through both endpoints, resulting in a mean in vitro irritancy score of 1.8 and -0.6 after 4 hours of treatment in the first and second experiment, respectively.

Under the conditions of this study, since the test material induced an IVIS ≤ 3 in 5 out of 6 corneas, no classification is required for eye irritation or serious eye damage.

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No 1272/2008, the substance does not require classification with skin or eye irritation.