Registration Dossier

Administrative data

Description of key information

Skin Irritation:

The dermal irritation potential of target chemical 2,3-dimethylphenol (526-75-0) was assessed in various in- vitro and in-vivo experimental studies for test chemical and its structurally and functionally similar read across substances.Based on the available studies,it can be concluded that the test chemical is likely to cause skin irritation and considered as irritating to skin. Comparing the above annotations with the criteria of CLP regulation, it can be classified under the category “Category 2 (irritating to skin)''.

Eye Irritation:

The ocular irritation potential of target chemical 2,3-dimethylphenol (526-75-0) was assessed in in- vitro and in vivo experimental studies for test chemical and its structurally similar read across substances .Based on the available experimental studies,it can be concluded that the test chemical is likely to cause eye irritation and considered as irritating to eyes. 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:
May 05, 2017 to July 17, 2017
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 was to assess potential for the test article to be dermal irritants. The dermal irritation potential of test article may be predicted by measurement of their cytotoxic effect, as reflected in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, in the MatTek EpiDerm™ model (MatTek Corp., Ashland, MA).
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL- Source and 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/ASTABILITY 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 availableTREATMENT 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 availableFORM AS APPLIED IN THE TEST: SolidOTHER SPECIFICS: No data available
Test system:
human skin model
Source species:
human
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:
- 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 epidermis. 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 IdentificationAll of the EpiDerm™ 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 are included in this report. Tissue plates were appropriately labeled with study information.
Justification for test system used:
The 3-Dimensional Human Dermal Epithelial Model (EpiDerm™, MatTek, Ashland, MA) is made up of normal human keratinocytes in serum free medium. The cells form an epithelial tissue that consists of organized basal, spinous, granular, and cornified layers analogous to those found in vivo. The EpiDerm™ model also contains epidermis-specific differentiation markers such as pro-filaggrin, the K1/K10 cytokeratin pair, involucrin, and type I epidermal transglutaminase, as well as keratohyalin granules, tonofilament bundles, desmosomes, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns characteristic of in vivo epidermis. Each lot of tissues was Quality Assured by MatTek, Inc. according to specific QC standards including: histology (cell layers), tissue viability (MTT mean optical density) and reproducibility (SD). Tissue plates were appropriately labeled with study information. Bias was not a factor in this test system.
Vehicle:
unchanged (no vehicle)
Details on test system:
The tissues were exposed to the test article neat (undiluted) on June 28, 2017 (Run 1 of 1). EpiDerm™ 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 1 hour, with 35 minutes in an approximately 37°C, 5% CO2 humidified incubator and the remaining 25 minutes at room temperature. Following the exposure time, the tissues were rinsed and placed in fresh media for approximately 24 hours. The media was then changed again and the tissues were incubated in fresh media for another ~18 hours for a total of approximately 42 hour post-exposure recovery period. The tissue viability was then assessed by MTT assay. The tissue CoA was used instead of verification of barrier properties of the tissue.MTT and Color Pre-testsPretesting for MTT auto-reduction and coloring was not performed for this study but was based on the results obtained from another study (CYP1690_R1b).MTT AssayFollowing the rinsing period, the MTT assay was performed by transferring the tissues to 24-well plates containing 300 µL MTT medium (1.0 mg/mL). After 2 hours, 57 minute and 25 second 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 time was approximately 2 hours 04 minutes and 11 seconds with gentle shaking. The optical density of the extracted formazan (200 µL/well of a 96-well plate) was determined using a Synergy H4 spectrophotometer at 570 nm. Relative cell viability is 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 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) Controls30 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 ArticleFor 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 treatmentAfter 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: 6/08/2017TEMPERATURE USED FOR TEST SYSTEM- Temperature used during treatment / exposure: 37°C- Temperature of post-treatment incubation (if applicable): 37°CREMOVAL OF TEST MATERIAL AND CONTROLS-Volume and number of washing steps: TwiceMTT 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 dataNUMBER OF REPLICATE TISSUES: 3CALCULATIONS and STATISTICAL METHODSAll data were background subtracted before analysis. MTT data are presented as % viable compared to negative control. Data were generated as follows: MTT AssayBlanks:·        The optical density (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. 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. Tested compound :·        Calculate the blank corrected value ODTT= ODTTraw– ODblank. ·        The OD mean per tissue was calculated. ·        The viability per tissue was calculated: %TT = [ODTT/ mean ODNC] x 100. ·        The mean viability for all tissues was calculated: Mean TT = Σ %TT / number of tissues. ·        The standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated. Data Correction Procedure for MTT Interfering Compounds (if applicable)True viability = Viability of treated tissue – Interference from test article = ODtvt– ODktwhere ODkt= (mean ODtkt– mean ODukt).ODtvt= optical density of treated viable tissueODkt= optical density of killed tissuesODtkt= optical density of treated killed tissueODukt= optical density of untreated killed tissue (NC treated tissue) Data Correction Procedure for Colored Compounds (if applicable)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 mediaODvt= optical density of viable tissues incubated in media alone- Evaluation of data The results of the assay was evaluated and compared to negative control.  Table: Criteria for in vitro Interpretation: In VitroResults In VivoPredictionMean tissue viability ≤50% Irritant (I), R38Mean tissue viability >50% Non-irritant (NI)- 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): 25 mg - 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: noneNEGATIVE CONTROL- Amount(s) applied (volume or weight): 30 µL- Concentration (if solution): neatPOSITIVE CONTROL- Amount(s) applied (volume or weight): 30 µL- Concentration (if solution): 5% solution of sodium dodecyl sulfate
Duration of treatment / exposure:
The exposure times were approximately 1 hour, with ~35 minutes exposure in the incubator and ~25 minutes at room temperature.
Duration of post-treatment incubation (if applicable):
For a total of an approximately 42 hour post-exposure incubation.
Number of replicates:
3 tissues will be used per test compound and control.
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
Run 1
Value:
2.5
Vehicle controls validity:
not specified
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: mean of OD:0.058;Irritant
Interpretation of results:
other: irritating
Conclusions:
The dermal irritation potential of test article was determined according to the OECD 439 test guideline followed for this study. The mean of OD for test chemical was determined to be 0.058.The standard deviation of viabilities for test chemical were calculated to be 0.14.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 2.5%. Thus, test chemical was considered to be irritating to the human skin.
Executive summary:

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 0.058. The standard deviation of viabilities for test chemical were calculated to be 0.14.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 2.5%. Hence, under the current experimental test conditions it was concluded that test chemical was considered to be irritating to human skin.

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 by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, in the MatTek EpiOcular™ model.
GLP compliance:
no
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 IdentificationAll 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 applicabilityEpiOcularTM Eye Irritation (OCL) by MatTek In Vitro Life Science Laboratories, Bratislava, SlovakienThe 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 Lab. (Bratislava, Slovakia). 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, Inc. according to specific QC standards including: histology (cell layers), tissue viability (MTT mean optical density) and reproducibility (SD).
Vehicle:
unchanged (no vehicle)
Controls:
other: See ''Remark" for Control Samples used in the study
Amount / concentration applied:
TEST MATERIAL - Amount(s) applied (volume or weight with unit): 50 mg of solid 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: noneNEGATIVE CONTROL- Amount(s) applied (volume or weight): 50 µL- Concentration (if solution): neatPOSITIVE 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 6 hrs ± 15 min for solid test articles, 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 18 hrs for solid 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 usedThe 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 6 hrs ± 15 min for solid 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 25 min for solid test articles articles and controls. Following the washing step and the, the tissues were incubated at approximately 37°C, 5% CO2 in a humidified incubator for a post-exposure recovery time totaling ~2 hours for 18 hrs for solid 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 assessmentMTT Pre-testThe 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 TestApproximately 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 Solids: Inserts are removed from the 24-well plate after 3 hrs of incubation and the bottom of the insert is blotted on absorbent material, and then transferred to a pre-labeled 6-well plate containing 1 ml isopropanol in each well so that no isopropanol is flowing into the insert. At the end of the non-submerged extraction inserts and tissues are discarded without piercing and 1 ml of isopropanol is added into each well. The extract solution is mixed and the optical density of the extracted formazan (200 μL/well of a 96-well plate) was determined using aThermo Scientific Multiskan FC Microplate Photometer at 570 nm. Relative cell viability was calculated for each tissue as % of the mean negative control - Evaluation of Test Article in the cell Models1. 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: When a solid was tested, 50 mg of the solid were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 6 hrs ± 15 min. 3. Post exposure treatment:After the exposure, the tissues were rinsed 20 times with sterile of 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 solid 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 18 hrs overnight at approximately 37 degC, 5% CO2 in a humidified incubator.- Doses of test chemical and control substances usedTest Article: 50 mg of solid test article were added to the tissues. The tissues were placed into the ~37°C humidified incubator with 5% CO2 for the approximately 6 hrs 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 6 hrs exposure time. - Duration and temperature of exposure, post-exposure immersion and post-exposure incubation periods: Tissues were exposed for approximately 30 minutes for 6 hrs for solid 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 formazanThe 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 modelCalculations and Statistical MethodsMTT AssayBlanks: ·  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 CompoundsTrue 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 CompoundsTrue 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 VivoPredictionMean tissue viability ≤60% Irritant (I) – Category 1 or 2Mean 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:
15.7
Vehicle controls validity:
not specified
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: Mean of OD:0.340;irritant
Other effects / acceptance of results:
The MTT data show the assay quality controls were met.

The chemical of CAS No. 526-75-0 stck to the tissues after treatment, i.e. the chemical residue was still present after the washing and remained so until the end of the tests. However, the results seems not to have been affected since clear readings were recorded.

Interpretation of results:
other: irritating
Conclusions:
The ocular irritation potential of test article was determined according to the OECD 492 test guideline followed for this study. The mean of OD for test chemical was determined to be 0.340.The mean % tissue viability of test substance was determined to be 15.7%. Thus, test chemical was considered to be not 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 solid test articles and control for approx.6 hours, followed by a 25 minute post-soak and approximately 18 hours 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, and passing the acceptance criteria. The mean of OD for test chemical was determined to be 0.340.The mean % tissue viability of test chemical was determined to be 15.7%. Hence, under the experimental test conditions it was concluded that test chemical 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:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Skin Irritation:

In different studies, the test chemical 2,3-dimethylphenol (526-75-0) has been investigated for potential for dermal irritation. The studies are based on in- vitro data of target chemical and in-vivo data of structurally and functionally similar read across substances conducted in rabbits conducted which have been summarized as below:

In an in vitro study,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 0.058. The standard deviation of viabilities for test chemical were calculated to be 0.14.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 2.5%. Hence, under the current experimental test conditions it was concluded that test chemical was considered to be irritating to human skin.

In the another supporting in vivo study for structurally similar read across substance,a primary dermal irritation study was performed on 6 albino rabbits to assess the irritation potential of o-cresol. Undiluted o-cresol (volume not specified) was applied to the intact and abraded skin of rabbits and effects were observed till 72 hours.Erythema and edema were scored at 24 and 72 hours.Erythema and edema was observed in all rabbits. The Primary dermal irritation score of o-cresol was 8.0(maximum score = 8.0).Based on the scores and observations, o-cresol can be considered severely irritating to albino rabbit skin.

Both the above studies were further supported by another in vivo study for functionally similar read across substance,skin irritation study of test chemical Thymol (CAS no: 89-83-8) was conducted on rabbits to determine the relative local effects caused by the chemical.The chemical wasapplied in ether by flowing the ether solution on to the shaved back of the rabbits at a dose of 0.42 gm/kg and the skin reactions were scored according to the method of Draize, et al.The skin turned parchment-like within 24 hr. No apparent systemic effect. Complete necrosis of superficial layers after 10 days was noted.Thus on the basis of observed effects, the chemicalThymol (CAS no: 89-83-8) was considered to be severely irritating to the skin of treated rabbits.

Based on the available data for the target as well as read across substances,2,3-dimethyl phenol was irritant to skin.Comparing the above annotations with the criteria of CLP regulation, test chemical can be classified under the category “Category 2”. 

Eye Irritation:

In different studies, the test chemical 2,3-dimethylphenol (526-75-0) has been investigated for potential for ocular irritation. The studies are based on in- vitro data of target chemical and in-vivo data of structurally similar read across substances conducted in rabbits conducted which have been summarized as below:

In an in vitro study,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 solid test articles and control for approx.6 hours, followed by a 25 minute post-soak and approximately 18 hours 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, and passing the acceptance criteria. The mean of OD for test chemical was determined to be 0.340.The mean % tissue viability of test chemical was determined to be 15.7%. Hence, under the experimental test conditions it was concluded that test chemical 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.

In the another supporting in vivo study for structurally similar read across substance,the primary eye irritation potential of the test chemical was evaluated according to Draize method.3 female Japanese White rabbits (2.0-2.2 kg) were used for the study. The chemical (if solid= 100 mg, if liquid = 0.1ml) was instilled into the conjunctival sac of the left eye.Right eye (untreated eye) served as blank control.The eyes were examined and the grade of ocular lesions was recorded at 1, 24, 48, 72, 96 hours and 7, 14, 21 days after administration of test chemical.Corneal opacity, erythema, chemosis, secreta and iritis were recorded and classified under Draize method (Draize et.al, 1944).The sum of values, recorded for cornea, conjunctiva and iris was divided by the number of observation times and the average scores (Draize scores) were used as grades of ocular irritation potential of the chemical.The maximum value of Draize score are as follows: Cornea =80, Conjunctiva = 20 and Iris = 5.The average Draize scores after 21 days were as follows:CORNEA = 33.9/80, iris = 0.6, conjunctiva = 5.1.The test chemical caused moderate eye irritation recovering within 21 days of treatment.Hence,the test chemical can be considered irritating to eyes.

Both the above studies were further supported by another in vivo study for functionally similar read across substance,the primary eye irritation potential of the test chemical was evaluated according to Draize method.3 female Japanese White rabbits (2.0-2.2 kg) were used for the study. The chemical (if solid= 100 mg, if liquid = 0.1ml) was instilled into the conjunctival sac of the left eye.Right eye (untreated eye) served as blank control.The eyes were examined and the grade of ocular lesions was recorded at 1, 24, 48, 72, 96 hours and 7,14,21 days after administration of test chemical.Corneal opacity, erythema, chemosis, secreta and iritis were recorded and classified under Draize method (Draize et.al, 1944).The sum of values, recorded for cornea, conjunctiva and iris was divided by the number of observation times and the average scores (Draize scores) were used as grades of ocular irritation potential of the chemical.The maximum value of Draize score are as follows: Cornea =80, Conjunctiva = 20 and Iris = 5.The average Draize scores after 21 days were as follows:CORNEA = 54.1/80, iris = could not be determined, conjunctiva = 10.3/20.The test chemical induced severe eye irritation not recovering within 21 days of treatment.Hence the test chemical can be assessed as irritating to rabbit eyes.

Based on the available data for the target as well as read across substances,2,3-dimethyl phenol was irritating to eyes.Comparing the above annotations with the criteria of CLP regulation, test chemical can be classified under the category “Category 2”.

Justification for classification or non-classification

Available data for 2,3-dimethyl phenol suggests that it is likely to be irritant to eyes and skin.

2,3 -dimethyl phenol can be classified under the category “Category 2”as per CLP regulation.