Benzyl isovalerate

Endpoint summary

Description of key information

Skin irritation

The dermal irritation potential of test chemical was assessed in various experimental studies conducted for test chemical. Also the predicted data for target chemical using the Danish QSAR database has also been compared with the experimental data. Based on the available data for the key and supporting studies, it can be concluded that the test chemical is unable to cause skin irritation and thus considered as not irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Not Classified”.

 

Eye irritation

The ocular irritation potential of target chemical was assessedin various in- vitro and in-vivo experimental studies which were conducted for test chemical and its structurally similar read across substances.Based on the available key data and supporting studies,it can be concluded thatchemical is able to cause eye irritation and considered as irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Category 2 (irritating to eyes)”.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 04, 2017 to March 13, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Data is from experimental study report

Qualifier:

according to guideline

Guideline:

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

Principles of method if other than guideline:

The purpose of this study is to provide classification of dermal irritation potential of a chemical by using a three-dimensional human epidermis model, according to the OECD Test Guideline No. 439, “In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”. The EpiDerm™ SIT allows discrimination between irritants of Category 2 and non-irritants, according to the UN Globally Harmonized System of Classification and Labeling of Chemicals (GHS).

GLP compliance:

yes

Specific details on test material used for the study:

IUPAC name : benzyl 3-methylbutanoate
molecular formula : C12H16O2
molecular weight : 192.2564 g/mol
InChI:1S/C12H16O2/c1-10(2)8-12(13)14-9-11-6-4-3-5-7-11/h3-7,10H,8-9H2,1-2H3
Smiles: c1(COC(CC(C)C)=O)ccccc1
- Source : Otto Chemie Pvt Ltd
- Expiration date of the lot/batch:
- Purity : 98.05%

RADIOLABELLING INFORMATION (Not applicable)
- Radiochemical purity: N/A
- Specific activity: N/A
- Locations of the label: N/A
- Expiration date of radiochemical substance: N/A

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature or Fridge storage
- Stability under test conditions: No data available
- Solubility and stability of the test substance in the solvent/vehicle: No data available
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No data available

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Test articles is tested as provided (neat).
- Preliminary purification step (if any): No data available
- Final dilution of a dissolved solid, stock liquid or gel: No data available
- Final preparation of a solid: No data available

FORM AS APPLIED IN THE TEST: liquid

OTHER SPECIFICS: No data available

Test system:

other: MatTek EpiDerm™ Tissue Model (EPI-200-SIT) kit

Source species:

other: no data

Cell type:

non-transformed keratinocytes

Cell source:

other: EpiDerm™ 3-dimensional human tissues used in this study

Source strain:

other: Not applicable

Details on animal used as source of test system:

EpiDerm™ tissues, Lot No. 27646 Kits I and J, were received from MatTek on 12 Dec 2017, and Lot No. 27654 Kits O and P, were received from MatTek on 19 Dec 2017. See Appendix C for EpiDerm™ tissue Quality Control report. All tissues were refrigerated at 2-8°C upon receipt. Before use, the tissues were incubated (37±1°C, 5±1% CO2) with assay medium (MatTek) for a one-hour equilibration. The tissues were then moved to new wells with fresh medium for an additional overnight equilibrium, for 18±3 hours. Equilibration medium was replaced with fresh medium before dosing.

Justification for test system used:

The EpiDerm™ Skin Model closely parallels human skin, thus providing a useful in vitro means to assess dermal irritancy and toxicology

Vehicle:

unchanged (no vehicle)

Details on test system:

EpiDerm™ Tissue Samples
EpiDerm™ tissues, Lot No. 27646 Kits I and J, were received from MatTek on 12 Dec 2017, and Lot No. 27654 Kits O and P, were received from MatTek on 19 Dec 2017. See Appendix C for EpiDerm™ tissue Quality Control report. All tissues were refrigerated at 2-8°C upon receipt. Before use, the tissues were incubated (37±1°C, 5±1% CO2) with assay medium (MatTek) for a one-hour equilibration. The tissues were then moved to new wells with fresh medium for an additional overnight equilibrium, for 18±3 hours. Equilibration medium was replaced with fresh medium before dosing.

Mesh Compatibility
Five of the test articles supplied were liquids. These test articles were assessed for compatibility with
pre-cut nylon mesh supplied with the tissues. The mesh was placed on a slide and 30 μl of a liquid test articles or PBS (negative control) were applied. After 60 minutes of exposure, the mesh was checked microscopically. If no damage or other interaction was observed, indicating that the mesh was compatible with the test article, the mesh was used as a spreading aid.

Tissue Viability (MTT Reduction)
At the end of the incubation period, each EpiDerm™ tissue was rinsed with PBS and transferred to a 24-well plate containing 300 μl of MTT solution (1 mg/ml MTT in DMEM). The tissues were then returned to the incubator for a three-hour MTT incubation period. Following the MTT incubation period, each EpiDerm™ tissue was rinsed with PBS and then treated with 2.0 ml of extractant solution (isopropanol) per well for at least two hours, with shaking, at room temperature. Two aliquots of the extracted MTT formazan were measured at 540 nm using a plate reader (μQuant Plate Reader, Bio-Tek Instruments, Winooski, VT).
For several tissues, the test article had stained the tissues. Therefore, the tissues were extracted with only 1.0 ml, allowing extraction to occur only through the bottom of the insert. After the extraction period, the tissue insert was removed and discarded and 1.0 ml of extraction solution were added to each well, bringing the volume to a total of 2.0 ml.

Quality Controls
The assay meets the acceptance criteria if the mean OD540 of the negative control tissues is between 1.0 and 2.5, inclusive, and the mean viability of positive control tissues, expressed as percentage of the negative control tissues, is at least 20%. In addition, the standard deviation (SD) calculated from individual percent tissue viabilities of the three identically-treated replicates must be less than 18%.
Note: Chemicals that provide tissue viabilities in a range of 30% to 70% may provide high SD. If the high SD (above acceptance limits) is typical for the chemical and the classification of the chemical is consistent in all independent runs, MatTek recommends that this result be accepted, although it did not meet the Assay Acceptance Criterion.

Analysis of Data
See Table 1 for Experimental Data. The mean absorbance value for each time point was calculated from the optical density (OD) of the duplicate samples and expressed as percent viability for each sample using the following formula:
% viability = 100 X (OD sample/OD negative control)

Skin Irritation Prediction
According to the EU1,2 and GHS3 classification (R38 / Category 2 or no label), an irritant is predicted if the mean relative tissue viability of three individual tissues exposed to the test substance is 50% or less of the mean viability of the negative controls.

In vitro result In vivo Classification
Mean tissue viability ≤ 50% Category 2
Mean tissue viability > 50% Non-irritant (NI)


Assessment of direct MTT reduction and assessment of coloring or staining materials was not performed. Therefore, it cannot be fully assessed if the test articles interfered with MTT viability measurements.

Retention of Data
Upon signing the final report, all raw data, supporting documentation and reports are submitted to the Archivist by the Study Director. The raw data are filed at MB Research by project number. The final report is filed at MB Research by Sponsor name and MB project number.
All data generated during the conduct of this study will be archived at MB Research for at least one year from the date of the final report and optionally longer at additional cost. The Sponsor will be contacted in writing to determine final disposition of the records.
Any remaining test article will be discarded upon submission of the report.

Amendment to the Protocol
There were no amendments to the protocol. See Appendix C for the protocol in its entirety
Evaluation of Test Article in the Cell Models:
1. Cell system: Upon receipt, the MatTek EpiDerm™ tissue cultures were placed in 0.9 mL of fresh Maintenance medium (in a 6-well plate). The culture inserts are incubated for ~one hour. The tissues were then transferred to 6-well plates containing 0.9 mL fresh Maintenance medium and they were incubated overnight at ~37°C, 5% CO2 in a humidified incubator.

2. Control and Test Article Exposures: On the day of dosing, the tissues are then removed from the incubator and the controls and the test article are applied topically to tissues by pipette. Tissues were exposed to controls and the test articles for one hour, with ~35 minutes in a 37°C, 5% CO2 humidified incubator and the remaining 25 minutes at room temperature.

a) Controls
30 µL of negative control DPBS, positive control 5% SDS was applied topically to the tissue and gently spread by placing a nylon mesh on the apical surface of each tissue, if necessary.

b)Test Article
For solid test article, the tissues were moistened with 25 μL of ultrapure water to improve contact of the tissue surface with the test article. Approximately 25 mg of each test article was evenly applied to the apical surface of each tissue (n=3). All the tissues were placed into the ~37°C incubator with 5% CO2. The exposure times were approximately 1 hour, with ~35 minutes exposure in the incubator and ~25 minutes at room temperature.

3.Post-exposure treatment
After the 1 hour exposure, the tissues were rinsed 20 to 25 times with 1 mL of DPBS. The apical surface was gently blotted with a cotton swab. The tissues were placed in 0.9 mL of fresh Maintenance medium (6-well plate) for either 25 hours, 38 minutes and 23 seconds or for 24 hours, 10 minutes and 09 seconds (as there were numerous tissues, they had to be broken down into 2 sets to complete dosing in a timely manner). After this initial ~24 hour incubation, the tissues were placed in 6-well plates containing 0.9 mL fresh Maintenance medium and incubated for another 17 hours, 03 minutes and 34 seconds prior to performing the MTT assay, for a total of an approximately 42 hour post-exposure incubation.

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: The EpiDerm™ 3 dimensional human tissue model
- Tissue Lot number(s): 26459
- Date of initiation of testing: 6/08/2017

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

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: Twice

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 300 µL MTT medium (1.0 mg/mL).
- Incubation time: After 2 hours, 57 minute and 25 second MTT incubation
- Spectrophotometer: Synergy H4 spectrophotometer
- Wavelength: 570 nm
- Filter: No data
- Filter bandwidth: No data
- Linear OD range of spectrophotometer: No data

NUMBER OF REPLICATE TISSUES: 3

CALCULATIONS and STATISTICAL METHODS
All data were background subtracted before analysis. MTT data are presented as % viable compared to negative control. Data were generated as follows:

MTT Assay
Blanks:
·        The optical density (OD) mean from all replicates for each plate (ODblank).

Negative Controls (NC):
Identity: Phosphate-Buffered Saline (PBS), Lot No. AC10239794
Provided by:MatTek
Date Received:12 Dec 2017 and 19 Dec 2017
Expiration Date:18 Jul 2018
Storage:Room temperature and humidity
Description:Clear colorless liquid
Sample Preparation:Used as received

Positive Control (PC):
Identity: 5% Sodium Dodecyl Sulfate (SDS), Lot No. 071817MAB
Provided by:MatTek
Date Received:12 Dec 2017 and 19 Dec 2017
Expiration Date:18 Jul 2018
Storage:Room temperature and humidity
Description:Clear colorless liquid
Sample Preparation:Used as received

- Assay quality controls
- Negative Controls (NC)
The Dulbecco’s phosphate buffered saline (DPBS) was used as a NC. The assay passed all acceptance criteria if the ODs of the negative control exposed tissues were between ≥0.8 and ≤2.8.
 
- Positive Controls (PC)
5% solution of sodium dodecyl sulfate was used as a PC. The assay is meeting the acceptance criteria if the viability of the PC is ≤20% of the negative control.
 
- Standard Deviation (SD)
The standard deviation (SD) calculated from individual percent tissue viabilities of the test article exposed replicates was ≤18.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 30 μl
- Concentration (if solution): neat (undiluted)

VEHICLE (Not used)
- Amount(s) applied (volume or weight with unit): none
- Concentration (if solution): none
- Lot/batch no. (if required): none
- Purity: none

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL
- Concentration (if solution): neat

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL
- Concentration (if solution): 5% solution of sodium dodecyl sulfate

Duration of treatment / exposure:

Tissues will be topically exposed to the test article and control articles for 60 minutes.

Duration of post-treatment incubation (if applicable):

After dosing, the tissues will be returned to the incubator for 35 ±1 minute, and then returned to the sterile hood for the remainder of the 60-minute exposure period.

Number of replicates:

All treatments with test articles and controls will be dosed in triplicate EpiDerm™ tissues.

Duration of treatment / exposure:

The duration of the EpiDerm™ Skin Irritation Test (SIT) is approximately five days

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Run 1

Value:

82.5

Vehicle controls validity:

not specified

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

All treatments with test articles and controls will be dosed in triplicate EpiDerm™ tissues.

In vitro result In vivo Classification
Mean tissue viability ≤ 50% Category 2
Mean tissue viability > 50% Non-irritant

Interpretation of results:

other: Non-Irritant

Conclusions:

The dermal irritation potential of test article was determined according to the OECD 439 test guideline followed for this study. The Mean % tissue viability compared to negative control (n=3) of the test substance was determined to be 82.5%. Thus, the test chemical was considered to be not irritating to the human skin.

Executive summary:

The dermal irritation potential of test article was determined according to the OECD 439 In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. The objective of this study was to assess the dermal irritation potential of test article Tissues were exposed to test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay.  The MTT data shows that the assay quality controls were met, as the OD of the negative control tissues was between 1.195 and 1.430. Also, the positive control, 5% sodium dodecyl sulfate (SDS), reduced tissue viability to 4.5% of negative control. The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 82.5%. Hence, under the experimental test conditions it was concluded that test chemical was considered to be not irritating to the human skin and being classified as “Not Classified'' as per CLP Regulation.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Data is from experimental study report.

Qualifier:

according to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Principles of method if other than guideline:

The purpose of this study was to assess potential for the test article to be ocular irritants. The ocular irritation potential of a test article may be predicted by measurement of its cytotoxic effect, as reflected inthe 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, in the MatTek EpiOcular™ model

GLP compliance:

no

Specific details on test material used for the study:

Specific details on test material used for the study
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material:
- Lot/batch No.of test material:
- Expiration date of the lot/batch:
- Purity test date:

RADIOLABELLING INFORMATION (Not applicable)
- Radiochemical purity: N/A
- Specific activity: N/A
- Locations of the label: N/A
- Expiration date of radiochemical substance: N/A

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature / Fridge storage
- Stability under test conditions: No data available
- Solubility and stability of the test substance in the solvent/vehicle: No data available
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No data available

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The test article tested as provided neat (undiluted).
- Preliminary purification step (if any): No data available
- Final dilution of a dissolved solid, stock liquid or gel: No data available
- Final preparation of a solid: No data available

FORM AS APPLIED IN THE TEST: Liquid

Species:

human

Strain:

other: Not applicable

Details on test animals or tissues and environmental conditions:

- Description of the cell system used:
The normal human-derived keratinocytes were cultured at the air-liquid interface in a chemically defined medium on a permeable polycarbonate insert (surface 0.5 cm2). They were cultured in chemically defined serum free medium to form a multi-layered epithelium similar to that found in native corneal mucosa. Each lot of tissues was Quality Assured by MatTek according to specific QC standards including: histology, tissue viability (MTT mean optical density), reproducibility (SD) and tissue thickness.

- Test System Identification
All of the EpiOcular™ 3-dimensional human tissues used in this study were identified by the date of arrival and the lot number. Certificate of Analysis for the tissues is included in this report. Tissue plates were appropriately labeled with study information. Bias was not a factor in this test system.

- Justification of the test method and considerations regarding applicability
EpiOcularTM Eye Irritation (OCL) by MatTek In Vitro Life Science Laboratories, Bratislava, Slovakien.
The test articles and controls were evaluated for potential ocular irritancy using the EpiOcular™ 3 dimensional human tissue model purchased from MatTek In Vitro Life Science Laboratories, Bratislava, Slovakien.
The EpiOcular tissue construct is a nonkeratinized epithelium prepared from normal human keratinocytes (MatTek). It models the cornea epithelium with progressively stratified, but not cornified cells. These cells are not transformed or transfected with genes to induce an extended life span in culture. The “tissue” is prepared in inserts with a porous membrane through which the nutrients pass to the cells. A cell suspension is seeded into the insert in specialized medium. After an initial period of submerged culture, the medium is removed from the top of the tissue so that the epithelial surface is in direct contact with the air. This allows the test material to be directly applied to the epithelial surface in a fashion similar to how the corneal epithelium would be exposed in vivo. Each lot of tissues was Quality Assured by MatTek In Vitro Life Science Laboratories according to specific QC standards including: histology (cell layers), tissue viability (MTT mean optical density) and reproducibility (SD)

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 50 μL of liquid test article
- Concentration (if solution): neat (undiluted)

VEHICLE (no vehicle)
- Amount(s) applied (volume or weight with unit): none
- Concentration (if solution): none
- Lot/batch no. (if required): none
- Purity: none

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 50 μL
- Concentration (if solution): neat

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 50 μL
- Concentration (if solution): neat

Duration of treatment / exposure:

Tissues were exposed for approximately 30 minutes for liquid test article and controls, at approximately 37°C, 5% CO2 in a humidified incubator.

Observation period (in vivo):

Not applicable

Duration of post- treatment incubation (in vitro):

Following the washing step and the post-soak, the tissues were incubated at approximately 37°C, 5% CO2 in a humidified incubator for a post-exposure recovery time of ~2 hours for liquid test articles , or 18 hrs for solid test articles, and controls.

Number of animals or in vitro replicates:

2 tissues were used for test compound and control.

Details on study design:

- Details of the test procedure used
The tissues were exposed to the test article neat (undiluted). EpiOcular™ tissues were purchased from MatTek. Quality control of the tissues was performed by MatTek and the Certificate of Analysis (CoA) for the tissues is provided and is kept in the study binder. Tissues were exposed for approximately 30 minutes for liquid test articles and controls, at approximately 37°C, 5% CO2 in a humidified incubator. After the exposure, the test article was rinsed off the tissues and the tissues were soaked in media for ~12 minutes for liquid test articles and controls. Following the washing step and the post-soak, the tissues were incubated at approximately 37°C, 5% CO2 in a humidified incubator for a post-exposure recovery time of ~2 hours for liquid test articles and controls. Tissue viability was assessed by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

- MTT Auto reduction and colouring assessment
MTT Pre-test
The test article was assessed for the potential to interfere with the assay. Approximately 50 µL of liquid test article was added to 1 mL of MTT media (~1 mg/mL) and incubated in a humidified incubator at approximately 37°C and approximately 5% CO2 for 3 hours. 50 µL of ultrapure water was used as a negative control.

- Test Article Color Test
Approximately 50 µL of liquid test article was added to 1.0 mL of ultrapure water and 2.0 mL isopropanol and incubated in a humidified incubator at approximately 37°C and approximately 5% CO2 for 2 hours, 04 minutes and 35 seconds. Samples were then added to the wells of a clear 96-well plate and the plate was read on a Thermo Scientific Multiskan FC Microplate Photometer to 570 nm. Test articles that tested positive for excessive coloration (OD >0.08) were assessed on living-tissue controls that were incubated in both culture media and MTT media as well (n=3 for both conditions).

- MTT Assay:
After the recovery period, the MTT assay was performed on run 1 tissues by transferring the tissues to 24-well plates containing 300 µL MTT medium (1.0 mg/mL). After 3 hours of MTT incubation at approximately 37°C, approximately 5% CO2 in a humidified incubator.The blue formazan salt was extracted by submerging tissues in 2 mL isopropanol in a 24-well plate. The extraction for liquid exposed tissues was overnight incubation. The optical density of the extracted formazan (200 µL/well of a 96-well plate) was determined using a Thermo Scientific Multiskan FC Microplate Photometer at 570 nm. Relative cell viability was calculated for each tissue as % of the mean negative control tissues

- Evaluation of Test Article in the cell Models
1. Cell System:
Upon receipt, the MatTek EpiOcular™ tissue cultures were placed in 1.0 mL of fresh Maintenance medium (in a 6-well plate) for 60 minutes. After the 60 minutes incubation, the Maintenance medium was exchanged with fresh medium and the tissues were incubated overnight (16-24 hrs) at approximately 37°C, approximately 5% CO2 in a humidified incubator.
2. Control and Test Article Exposures:
20 µL of calcium and magnesium free DPBS was added to each tissue and the tissues placed back into the incubator for 30 minutes. The controls and the test article will be applied topically to tissues by pipette. Three tissues will be used per test compound and control.
a)Controls: 50 µL of negative control sterile ultrapure water and positive control methyl acetate were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 30 minute exposure time.
b)Test Article: 50 µL of liquid test article were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 30 minute exposure time.
3. Post exposure treatment:
After the exposure, the tissues were rinsed 20 times with sterile DPBS to remove test material. The apical surface was gently blotted with a cotton swab and cultures were immediately transferred to a 12-well plate containing 5 mL of media per well. Tissues exposed to liquid test articles (and the respective control) were incubated, submerged in the media for ~12 minutes at room temperature.For liquid test articles, tissues, Tissuses were then transferred to 6-well plates containing 1.0 mL fresh Maintenance medium per well and incubated for a post-exposure recovery period for 2 hours at approximately 37 degC, 5% CO2 in a humidified incubator.
- Doses of test chemical and control substances used
Test Article:
50 µL of liquid test article were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 30 minute exposure time.
Controls: 50 µL of negative control sterile ultrapure water, positive control methyl acetate were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 30 minute exposure time.
- Duration and temperature of exposure, post-exposure immersion and post-exposure incubation periods: Tissues were exposed for approximately 30 minutes for liquid test articles and controls, at approximately 37°C, 5% CO2 in a humidified incubator. Following the washing step and the, the tissues were rinsed and incubated at approximately 37°C, 5% CO2 in a humidified incubator for a post-exposure recovery time totaling ~2 hours for liquid test articles and controls.
- Justification for the use of a different negative control than ultrapure H2O (Not applicable
- Justification for the use of a different positive control than neat methyl acetate (Not applicable)
- Number of tissue replicates used per test chemical and controls: 2 tissues were used for test compound and control.
- Description of the method used to quantify MTT formazan
The blue formazan salt was extracted by submerging tissues in 2 mL isopropanol in a 24-well plate. The extraction for liquid exposed tissues was overnight incubation with a 20 minute 24 second shake the following morning. The optical density of the extracted formazan (200 µL/well of a 96-well plate) was determined using a Thermo Scientific Multiskan FC Microplate Photometer at 570 nm. The blue formazan salt was extracted by placing the tissue insterts in 1 mL isopropanol in a 6-well plate. The extraction for solid exposed tissues was 3 hrs incubation. After an addition of 1 ml isopropanol and mixing, the optical density of the extracted formazan (200μL/well of a 96-well plate) was determined using a Thermo Scientific Multiskan FC Microplate Photometer at 570 nm.

- Description of evaluation criteria used including the justification for the selection of the cut-off point for the prediction model
Calculations and Statistical Methods
MTT Assay
Blanks:
· The OD mean from all replicates for each plate (ODblank).
Negative Controls (NC):
· The blank corrected value was calculated: ODNC= ODNCraw– ODblank.
· The OD mean per NC tissue was calculated.
· The mean OD for all tissues corresponds to 100% viability.
· The mean, standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated.
ODblank= optical density of blank samples (isopropanol alone).
ODNCraw= optical density negative control samples.
ODNC= optical density of negative control samples after background subtraction.
Positive Control (PC):
· Calculate the blank corrected value: ODPC= ODPCraw– ODblank.
· The OD mean per PC tissue was calculated.
· The viability per tissue was calculated: %PC = [ODPC/ mean ODNC] x 100.
· The mean viability for all tissues was calculated: Mean PC = Σ %PC / number of tissues.
· The standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated.
ODPCraw= optical density positive control samples.
ODPC= optical density of positive control samples after background subtraction.
Tested Articles:
· Calculate the blank corrected value ODTT= ODTTraw– ODblank.
· The OD mean per tissue is calculated.
· The viability per tissue is calculated: %TT = [ODTT/ mean ODNC] x 100.
· The mean viability for all tissues is calculated: Mean TT = Σ %TT / number of tissues.
· The standard deviation (SD) and the percent coefficient of variation (% CV)for the controls and the test articles will be calculated.
ODTTraw= optical density test article samples.
ODPC= optical density of test article samples after background subtraction.
Data Correction Procedure for MTT Interfering Compounds
True viability = Viability of treated tissue – Interference from test article = ODtvt – ODkt where ODkt = (mean ODtkt – mean ODukt).
ODtvt = optical density of treated viable tissue
ODkt = optical density of killed tissues
ODtkt = optical density of treated killed tissue
ODukt = optical density of untreated killed tissue (NC treated tissue)

Data Correction Procedure for Colored Compounds
True viability = Viability of treated tissue incubated in MTT media – Viability of treated tissue incubated in media without MTT = ODtvt – ODvt.
ODtvt = optical density of treated viable tissue incubated in MTT media
ODvt = optical density of viable tissues incubated in media alone.
Proposed Statistical methods
The mean, standard deviation (SD) and the percent coefficient of variation (% CV) for the controls and the test article will be calculated.
- Evaluation of data
The results of the assay was evaluated and compared to negative control.
Table: Irritancy Prediction
In VitroResults In VivoPrediction
Mean tissue viability ≤60% Irritant (I) – Category 1 or 2
Mean tissue viability >60% Non-irritant (NI) – No Category
- Assay quality controls
- Negative Controls (NC)
The assay is meeting the acceptance criterion if the mean viability of the NC in terms of Optical Density (OD570) of the NC tissues (treated with sterile ultrapure water) in the MTT assay are >0.8 to <2.5. This is an indicator of tissue viability following shipping and conditions under use.
- Positive Controls (PC)
Methyl acetate was used as a PC and tested concurrently with the test article. The assay is meeting the acceptance criteria if the viability of the PC is <50% of the negative control.
- Standard Deviation (SD)Each test of ocular irritancy potential is predicted from the mean viability determined on 3 single tissues. The assay meets the acceptance criteria if SD calculated from individual percent tissue viabilities of the replicates is <18% for three replicate tissues.

Irritation parameter:

other: mean % tissue viability

Run / experiment:

Run 1

Value:

48.6

Vehicle controls validity:

not specified

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

positive irritation observed

Other effects / acceptance of results:

The MTT data show the assay quality controls were met.

Table:

	mean	Dif.	mean of	Dif.	Dif./2
	of OD	of OD	viabilities [%]	of viabilities
103-38-8	1.428	0.085	48.6	2.90	1.45

 

Code N°	Tissue	Raw data		Blank corrected data		mean of OD	% of viability
	n	Aliq. 1	Aliq. 2	Aliq. 1	Aliq. 2
103-38-8	1	1.4112	1.433	1.374	1.396	1.385	47.2
	2	1.5208	1.4938	1.484	1.457	1.470	50.1

 

Interpretation of results:

Category 2 (irritating to eyes) based on GHS criteria

Conclusions:

The ocular irritation potential of test article was determined according to the OECD 492 test guideline followed for this study. The mean % tissue viability of test substance was determined to be 48.6%. Thus, the test substance was considered to be irritating to the human eyes.

Executive summary:

The ocular irritation potential of test article was determined according to the OECD 492 test guideline for this study. The MatTek EpiOcular™ model was used to assess the potential ocular irritation of the test articles by determining the viability of the tissues following exposure to the test article via MTT. Tissues were exposed to liquid test articles and controls for ~30 minutes, followed by a ~12 minute post-soak and approximately 2 hour recovery after the post-soak. The viability of each tissue was determined by MTT assay.

The MTT data show the assay quality controls were met, passing the acceptance criteria.

The mean % tissue viability of test substance was determined to be 48.6%. Hence, under the experimental test conditions it was concluded that test substance was considered to be irritating to the human eyes and can thus be classified as ‘’Irritating to eyes in Category 2” as per CLP Regulation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin Irritation:

Various studieshas been investigated for the test chemical to observe the potential for dermal irritation to a greater or lesser extent. The studies are based on in-vitro and in-vivo experiments conducted for target chemicaland its structurally similar read across substances.Also the predicted data for target chemical using the Danish QSAR database has also been compared with the experimental data that have been summarized as below;

 

The dermal irritation potential of test article was determined according to the OECD 439 In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method”. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. The objective of this study was to assess the dermal irritation potential of test article Tissues were exposed to test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay.  The MTT data shows that the assay quality controls were met, as the OD of the negative control tissues was between 1.195 and 1.430. Also, the positive control, 5% sodium dodecyl sulfate (SDS), reduced tissue viability to 4.5% of negative control. The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 82.5%. Hence, under the experimental test conditions it was concluded that test chemical was considered to be not irritating to the human skin and being classified as “Not Classified'' as per CLP Regulation.

 

 

Another in-vitro study was conducted for test chemical to assess the dermal irritation potential of test article was determined according to the OECD 439 test guideline for this study. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. Tissues were exposed to the test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay. The MTT data show the assay quality controls were met and passed the acceptance of criteria. The mean of OD for test chemical was determined to be 1.180.The standard deviation of viabilities for test chemical were calculated to be 8.83.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 52.5 %.Hence, under the current experimental test conditions it was concluded that test chemical was considered to be not irritating to human skin.

 

The above results were supported by another skin irritation study conducted in humans to evaluate the irritation potential of test chemical. The test chemical was tested at a concentration of 4 % in petrolatum in a 48-hr closed-patch test in 25 human subjects. The test chemical produced no irritation in 25 human subjects. Hence, the test chemical was considered to be not irritating to human skin.

 

Further, a dermal irritation test was conducted in rabbits to evaluate the irritation potential of test chemical. The test chemical was applied full strength to intact or abraded rabbit skin for 24 hr under occlusion and the effects were observed. The test chemical was observed to slightly irritating to intact or abraded rabbit skin after 24 hours. Hence test chemical can be considered to be slightly irritating to rabbit skin.

 

The above results were further supported by the acute Dermal Irritation/corrosion Study conducted for read across chemical as per OECD guideline No. 404. Three healthy young adult female rabbits were used for conducting acute dermal irritation study. Body weights were re­corded on day 0 (prior to application) and at termination. Rabbits with good intact skin were selected for the study. The hairs of all the rabbits were clipped at contralateral sites, approximately 24 hours prior to treatment. A dose of0.5 ml of test item (as such) was applied to the skin, over an area of approximately 6 x 6 cm clipped of hair on one side of rabbits. The other untreated side was kept as control area and 0.5 ml of distilled water was applied at this site. At the end of 4 hours, the gauze patch was removed and test item application site was wiped with water without altering the integrity of the epidermis. Initially, the test item was applied to the clipped area of skin of one rabbit. The test site was covered with gauze patch. After 4 hours of exposure in Animal No. 1, there was no erythema and oedema observed at 1, 24, 48 and 72 hours observation. Hence the confirmatory test was conducted on additional two rabbits (No. 2 and 3)to confirm the non-irritant nature of the test item. In Animals No. 2 and 3 after post patch removal, revealed no erythema and oedema at 1, 24, 48 and 72 hours observation. The patch was removed after 4 hours and rabbits were observed for erythema and oedema at 1, 24, 48 and 72 hours after patch removal, evaluated and graded as per Draize method. The individual mean score at 24, 48 and 72 hours for Animal Nos. 1, 2 and 3 were 0.00, 0.00, 0.00 and 0.00, 0.00, 0.00, for erythema and oedema formation, respectively. Hence, it was concluded that the test chemical was Non-Irritating to the skin of Female New Zealand White rabbits under the experimental conditions tested. 

 

The overall studies were supported by the Preliminary irritation study conducted for read across chemical performed in guinea pigs to determine the suitable challenge concentration for the sensitization study. The animals received a single dermal application of 10%, 25% or 50% test chemical in acetone using 8 mm saturated filter paper and 11 mm aluminum patch test cups which were applied to the shaved flank for 24 h. Reactions were assessed for irritation at 24 and 48 h after patch removal. Barely perceptible erythema was observed at all concentrations. Since the test chemical did not induce any cutaneous effects at concentration of 10%, the test chemical was considered to be not irritating to the skin of male albino Dunkin/Hartley guinea pigs.

 

Even though one study suggests that the chemical might cause slight irritation but the potential of causing skin irritation is not sufficient to classify the test chemical as skin irritant. Thus on the basis of available dataand majority of results obtained in various studies, the test chemical can be considered as not irritating to the skin . Hence, comparing the above annotations with the criteria of CLP regulation, Test chemical can be classified under the category “Not Classified”.

 

 

Eye Irritation:

In different studies, the test chemical has been investigated for potential for ocular irritation to a greater or lesser extent. The studies are based onin- vitro and in-vivo experimental conductedin rabbits conducted which have been summarized as below;

 

The ocular irritation potential of test article was determined according to the OECD 492 test guideline for this study. The MatTek EpiOcular™ model was used to assess the potential ocular irritation of the test articles by determining the viability of the tissues following exposure to the test article via MTT. Tissues were exposed to liquid test articles and controls for ~30 minutes, followed by a ~12 minute post-soak and approximately 2 hour recovery after the post-soak. The viability of each tissue was determined by MTT assay. The MTT data show the assay quality controls were met, passing the acceptance criteria. The mean % tissue viability of test substance was determined to be 48.6%. Hence, under the experimental test conditions it was concluded that test substance was considered to be irritating to the human eyes and can thus be classified as ‘’Irritating to eyes in Category 2” as per CLP Regulation.

 

Another in-vitro eye irritation study was conducted to assess the ocular irritation potential of test article according to the OECD 492 test guideline. The MatTek EpiOcular™ model was used to assess the potential ocular irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. The objective of this study was to assess the ocular irritation potential of test article. Tissues were exposed to test article and controls for ~6 hours, followed by a ~25 minute post-soak and approximately 18 hour recovery after the post-soak. The viability of each tissue was determined by MTT assay. The MTT data show the assay quality controls were met, as the OD of the negative control tissues was between 0.8 to 2.5 in run 1. Also, the positive control, methyl acetate, reduced tissue viability to be below 50% of negative control (for 6 hour exposures with solids) in run one and the standard deviation (SD) calculated from individual percent tissue viabilities of the test article exposed replicates was passing the acceptance criteria. The mean % tissue viability of test substance was determined to be 58.3%. Hence, under the experimental test conditions it was concluded that test substance was considered to be irritating to the MatTek EpiOcular Tissue Model OCL-200 and being classified as ‘’Irritating to eyes in Category ”

 

This in-vitro result was supported by the experimental study conducted for similar read across chemical. An eye irritation study was conducted in rabbits to determine the eye irritation potential of test chemical. The 0.1 ml of 2.5% test chemical in EtOH was instilled into the eyes of each rabbit which caused moderate to severe conjunctival irritation in all treated rabbits. Hence the test chemicalwas considered to be irritating to the eyes of rabbits.

 

The above results were further supported by another ocular irritation study carried out for similar read across chemical in rabbits. The ocular irritation potential of the test chemical was assessed by performing rabbit eye test. Neat (100%) of test chemical was applied to the center of the cornea while the lids were retracted. One minute later the lids were released. The eyes were examined 18–24 h later in strong diffuse daylight and then stained with fluorescein. The test chemical had given a grade 1 (iritis and slight internal congestion) after 24 hours of observation. Based on this rating, the test chemical can be considered as an eye irritant.

 

Based on the above summarized studies for target chemical and its structurally similar read across substances,it can be concluded that the testchemical is able to cause eye irritation and considered as irritating. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Category 2 (irritant)”.

Justification for classification or non-classification

The skin and eye irritation potential of test chemical and its structurally and functionally similar read across substances were observed in various studies. The results obtained from these studies indicate that the chemical is not likely to cause skin irritation but can cause eye damage. Hence the test chemical can be classified under the category “Not Classified” for skin and “Category 2 (irritant)” for eye as per CLP.