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Diss Factsheets

Administrative data

Description of key information

The substance is not irritating to skin and eye.

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:
2017-07-17 - 2017-10-06 (experimental phase)
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:
OECD Guideline for the testing of Chemicals 439: In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method (Original Guideline adopted July 28, 2015), and as described in detail in the Protocol for: In Vitro EpiDermTM Skin Irritation Test (EPI-200-SIT) for use with MatTek Corporation’s Reconstructed Human Epidermal Model EpiDerm (EPI-200).
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)
Version / remarks:
Based on a “Statement on the Scientific Validity of In Vitro Tests for Skin Irritation” of the European Commission (November 2008), official acceptance of the test method in the EU was achieved and implemented in EU, 2008a, Council Regulation (EC) No 440/2008 of 30 May 2008 laying down test methods pursuant to EC Regulation No 1907/2006 of the European Parliament and of the Council on REACH; 1st ATP 2009: EC Regulation No 761/2009 of 23 July 2009 amending, for the purpose of its ATP, EC Regulation No 440/2008 laying down test methods pursuant to EC Regulation No 1907/2006 of the European Parliament and of the Council on REACH, section B46.
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Cell source:
other: not stated
Source strain:
other: not applicable
Details on animal used as source of test system:
SOURCE ANIMAL
human donors
Justification for test system used:
Dermal irritation is generally defined as "the production of reversible inflammatory changes in the skin". The potential for chemical induced skin irritation is an important consideration in establishing procedures for the safe handling, packing and transport of chemicals. It is usually determined in vivo in the Draize rabbit skin irritation test as described in OECD guideline 404. Because systemic reactions play a minor role in modulating local skin toxicity potential of chemicals, skin irritation potential may be predicted by in vitro systems, provided they are sufficiently complex to mimic human skin barrier and cell reactivity. In an international prevalidation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiDerm™ and EpiSkin™ and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.
Vehicle:
unchanged (no vehicle)
Details on test system:
RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: Epi-200 SIT kits and MTT-100 assay diluent were purchased from MatTek Corporation (82105 Bratislava, Slovakia). The EpiDerm™ tissue consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multilayered, highly differentiated model of the human epidermis. It consists of organized basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDerm™ tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELLs, 10 mm diameter).
- Tissue batch number(s): 25847
- Production date: 2017-10-03
- Delivery date: EpiDerm™ tissues were shipped with cool packs on medium-supplemented agarose gels in a 24-well plate and reached on 04 October 2017.
- Date of initiation of testing: On day of receipt the pre-incubation phase of the EpiDerm™ tissues started.

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 20 – 25 °C (treatment); 37 ± 1.5 °C (incubator)

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: After the end of the treatment interval the inserts were removed immediately from the 6-well plate and tissues were gently rinsed with DPBS at least 15 times in order to remove any residual test material.
- Observable damage in the tissue due to washing: none stated
- Modifications to validated SOP: none stated; but the following deviation from study plan occurred: The pre-incubation phase was shortened to 1 hour instead of 1 + 18 hours as described in the study plan. The quality of the tissues was not affected, because the acceptance criteria for the test method were clearly fulfilled, positive and negative controls gave the appropriate response, and the OD values were within the historically established boundaries.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: On the day of testing the MTT concentrate was diluted with the MTT diluent (1 mg/mL). The 24-well plates were prepared before the end of the tissue pre-warming period. A volume of 300 µL of the MTT solution was added to each well and the plates were kept in an incubator (37 ± 1.5 °C, 5 ± 0.5 % CO2) until further use.
- Incubation time: After the approximately 42-hours incubation period was completed for all tissues and exposure groups, culture inserts were transferred from the holding plates to the MTT-plates. After a 3-hour incubation period (37 ± 1.5 °C, 5 ± 0.5 % CO2), the tissues were rinsed three times with DPBS, and carefully dried with blotting paper. The tissues were transferred into new 24-well plates containing 2 mL of extractant solution (isopropanol) in each well ensuring that the tissues are completely covered. The 24-well plate was sealed to inhibit the isopropanol evaporation.
The formazan salt was extracted for about 2 hours while shaking at room temperature.
After the extraction period was completed, the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken. Afterwards the insert was discarded. The 24-well plates were placed on a shaker for 15 minutes until the solution was homogeneous in colour.
- Spectrophotometer / Wavelength / Filter: Per each tissue, 3 x 200 µL aliquots of the blue formazan solution were transferred into a 96-well flat bottom microtiter plate from the 15 minutes exposure. OD was read in a microplate reader (Versamax® Molecular Devices, Softmax Pro Enterprise, version 4.7.1) with a 570 nm filter. Mean values were calculated from the 3 wells per tissue.

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: See below, historical control data; 1.311 ± 0.083 (1.0 – 3.0)
- Barrier function: 8.10 h (4.77 – 8.72 h)
- Contamination: sterile

NUMBER OF REPLICATE TISSUES: triplicates

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
Since the MTT solution did not turn blue/purple in the Test for Direct MTT Reduction and Colour Interference, the test item was not considered to reduce MTT and an additional test with freeze-killed tissues did not have to be performed.

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: 1

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
An irritation potential of a test item leading to H315 (according to regulation (EC) 1272/2008), and GHS category 2 according to UN GHS (published 2003, last (6th) revision 2015) is recommended if the mean relative tissue viability of three individual tissues is reduced ≤ 50% of the negative control after incubation with the test item for 60 min in total.
Control samples:
yes, concurrent negative control
other: yes, concurrent positive control
Amount/concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 30 μL (47 μL/cm² according to guideline) of the undiluted test item was dispensed directly atop the EpiDerm™ tissue and spread to match the surface of the tissue for a complete treatment time of 60 minutes.
- Concentration (if solution): undiluted

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µl DPBS (Gibco)

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µl 5% SLS solution in deionised water (MatTek)
Duration of treatment / exposure:
60 min
Duration of post-treatment incubation (if applicable):
After the end of the treatment interval the inserts were removed immediately from the 6-well plate and tissues were gently rinsed with DPBS at least 15 times in order to remove any residual test material. After the rinsing the inserts were submerged in DPBS at least three times. Afterwards the inserts were once again rinsed with sterile DPBS from the inside and the outside. Excess DPBS was removed by gently shaking the inserts and blotting the bottom with sterile blotting paper. The tissues were then transferred into new 6-well plates with 0.9 mL of fresh assay medium in the upper row. The inserts were placed in the prepared holding plate. Tissues were incubated for about 24 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. After incubation medium will be changed (0.9 mL of pre-warmed fresh medium). Thereafter tissues were incubated for another 18 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. The complete incubation time was about 42 hours.
Number of replicates:
1 run, each three replicate tissues
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
mean of three replicates
Value:
103.8
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Other effects / acceptance of results:
- OTHER EFFECTS:
- Visible damage on test system:
- Direct-MTT reduction: none
- Colour interference with MTT: none
The optical pre-experiment (colour interference pre-experiment) to investigate the test item’s colour change potential in water did not led to a change in colour.
Optical evaluation of the MTT-reducing capacity of the test item after 1 hour incubation with MTT-reagent did not show blue/purple colour.
The test item passed the MTT- and the Colour Interference pre-tests.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes

The relative standard deviations between the % variability values of the test item, the positive and negative controls in the main test were below 11% (threshold of the "OECD Guideline for the Testing of Chemicals 439: In vitro Skin Irritation: Reconstructed Human Epidermis Test Method”: < 18%), thus ensuring the validity of the study.
Interpretation of results:
GHS criteria not met
Conclusions:
The study was conducted under GLP according to OECD guideline 439 on the registered substance itself. The method is to be considered scientifically reasonable with no deficiencies in documentation or any deviations, the validity criteria are fulfilled, positive and negative controls gave the appropriate response. Hence, the results can be considered as reliable to assess the irritating potential of the test substance to the skin in vitro. The relative mean tissue viability obtained after 60 minutes treatment with the test item compared to the negative control tissues was 103.8%. Since the mean relative tissue viability for the test item was above 50% the test item is considered to be non-irritant. It is concluded that this test is valid and that 3,5-Diethyltoluene-2,4-diisocyanate is non-irritant in the in vitro skin irritation test under the experimental conditions described in this report and should not be classified according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) of the United Nations.
Executive summary:

This in vitro study was performed according to OECD 439 under GLP to assess the irritation potential of 3,5-Diethyltoluene-2,4-diisocyanate by means of the Human Skin Model Test.

The test item did not reduce MTT (test for direct MTT reduction), and it did not change colour when mixed with deionised water (test for colour interference). Also its intrinsic colour was not intensive. Consequently, additional tests with freeze-killed or viable tissues were not necessary.

Each three tissues of the human skin model EpiDerm™ were treated with the test item, the negative control (DPBS) or the positive control (5% SLS) for 60 minutes.

After treatment with the negative control the absorbance values were well within the required range of the acceptability criterion of mean OD³0.8 and ≤ 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.

Treatment with the positive control induced a sufficient decrease in the relative absorbance as compared to the negative control for the 60 minutes treatment interval, and thus assuring the validity of the test system.

After treatment with the test item 3,5-Diethyltoluene-2,4-diisocyanate the mean relative absorbance value was 103.8% compared to the relative absorbance value of the negative control. This value is above the threshold for irritancy of ≤ 50%. Therefore, the test item is not considered to possess an irritant potential.

In conclusion, it can be stated that in this study and under the experimental conditions reported, 3,5-Diethyltoluene-2,4-diisocyanate is not irritant to skin.

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:
2017-07-14 (experimental phase)
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:
OECD Guideline for Testing of Chemicals 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 (July, 2013).
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU method B.47 (Bovine corneal opacity and permeability test method for identifying ocular corrosives and severe irritants)
Version / remarks:
Commission Regulation (EU) No 1152/2010: B. 47. Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants (Official Journal of the European Union, L 324, 9.12.2010).
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room Temperature
Species:
cattle
Strain:
not specified
Details on test animals or tissues and environmental conditions:
SOURCE OF COLLECTED EYES
- Source: AB Schlachthof GmbH & Co. KG, 63739 Aschaffenburg, Germany
- Characteristics of donor animals (e.g. age, sex, weight): at least 9 month old donor cattle
- Storage, temperature and transport conditions of ocular tissue (e.g. transport time, transport media and temperature, and other conditions): Excess tissue was removed from the excised eyes. The isolated eyes were stored in HBSS containing 1% (v/v) Penicillin/Streptomycin (100 units/mL penicillin and 100 µg/mL streptomycin) in the cooled slaughter-house until transportation on the same morning to the laboratory using a Styrofoam box. The corneae were isolated on the same day after delivery of the eyes.
- Time interval prior to initiating testing: same day
- indication of any existing defects or lesions in ocular tissue samples: All eyes were carefully examined macroscopically for defects. Those presenting defects such as vascularization, pigmentation, opacity and scratches were discarded.
- Indication of any antibiotics used: isolated eyes were stored in HBSS containing 1% (v/v) Penicillin/Streptomycin (100 units/mL penicillin and 100 µg/mL streptomycin)
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): 0.75 mL
- Concentration (if solution): undiluted
Duration of treatment / exposure:
The incubation time lasted ten minutes.
Duration of post- treatment incubation (in vitro):
further two hours
Number of animals or in vitro replicates:
3 cornea for each test item, negative and positive control
Details on study design:
SELECTION AND PREPARATION OF CORNEAS
All eyes were carefully examined macroscopically for defects. Those presenting defects such as vascularization, pigmentation, opacity and scratches were discarded. The cornea was carefully removed from the eye using scalpel and rounded scissors. A rim of about 2 mm of tissue (sclera) was left for stability and handling of the isolated cornea.
Each isolated cornea was mounted in a specially designed cornea holder according to the description given in OECD guideline 437, which consists of anterior and posterior compartments, which interface with the epithelial and the endothelial sides of the cornea, respectively. The endothelial side of the cornea was positioned against the sealing ring (O-ring) of the posterior part of the holder. The cornea was gently flattened over the O-ring but stretching was avoided. The anterior part of the holder was positioned on top of the cornea and fixed in place with screws. Both compartments of the holder were filled with incubation medium. The posterior compartment was filled first to return the cornea to its natural convex position. Care was taken to assure that no air bubbles were present within the compartments.
For equilibration, the corneae in the holder were incubated in a vertical position for about one hour at 32 ± 1 °C in a water-bath.

QUALITY CHECK OF THE ISOLATED CORNEAS
At the end of the incubation period, the basal opacity was determined (t0).
The basal opacity of all corneae was recorded. Each cornea with a value of the basal opacity > 7 was discarded.

NUMBER OF REPLICATES
Sets of three corneae were used for treatment with the test item and for the negative and positive controls.

NEGATIVE CONTROL USED
0.75 mL Saline (0.9% NaCl in deionised water)

POSITIVE CONTROL USED
0.75 mL 2-Ethoxyethanol (purity: 99%)

APPLICATION DOSE AND EXPOSURE TIME
The anterior compartment received the test item or the negative or positive controls at a volume of 0.75 mL on the surface of the corneae, respectively. The corneae were incubated in a horizontal position at 32 ± 1 °C in the water-bath.
The incubation time lasted ten minutes.

REMOVAL OF TEST SUBSTANCE
- Number of washing steps after exposure period: After the test item or control items, respectively, were rinsed off from the application side with saline, fresh cMEM was added into the anterior compartment.
- POST-EXPOSURE INCUBATION: Then the corneae were incubated at 32 ± 1 °C for further two hours in a vertical position, followed by a second opacity reading (t130). In the second step of the assay, permeability of the corneae was determined.

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: The opacitometer determines changes in the light transmission passing through the corneae, and displays a numerical opacity value. This value was recorded in a table. The opacitometer OP_KiT opacitometer (Electro Design, 63-Riom France) was calibrated as described in the manual and the opacity of each of the corneae was determined by reading each holder placed in the photoreceptor compartment for treated cornea.
After exposure of the corneae to the test groups, after rinsing and further incubation of the corneae for two hours, the opacity value was determined again (t130).
The change of opacity value of each treated cornea or positive and negative control corneae is calculated by subtracting the initial basal opacity from the post treatment opacity reading (t130 – t0).
The average change in opacity of the negative control corneae is calculated and this value is subtracted from the change in opacity of each treated cornea or positive control to obtain a corrected opacity.
- Corneal permeability: Following the opacity readings, the permeability endpoint was measured as an indication of the integrity of the epithelial cell sheets. After the final opacity measurement was performed, the complete medium was removed from the anterior compartment and replaced by 1 mL of a 0.4% (w/v) sodium fluorescein solution in HBSS. Corneae were incubated again in a horizontal position for 90 ± 5 minutes in a water-bath at 32 ± 1 °C. Complete medium from the posterior compartment was removed, well mixed and transferred into a 96 well plate.
The optical density was measured with a microplate reader (Versamax® Molecular Devices) at 490 nm (OD490). The absorbance values were determined using the software SoftMax Pro Enterprise (version 4.7.1).
The corrected OD490 value of each cornea treated with positive control or test item is calculated by subtracting the average negative control cornea value from the original permeability value for each cornea.

SCORING SYSTEM: In Vitro Irritancy Score (IVIS)
The following formula is used to determine the IVIS of the negative control:
IVIS = opacity value + (15 x OD490 value)
The following formula is used to determine the IVIS of the positive control and the test item:
IVIS = (opacity value – corrected opacity value mean negative control) + (15 x corrected OD490 value)
The mean IVIS value of each treated group is calculated from the IVIS values.
Depending on the score obtained, the test item is classified into the following category according to OECD guideline 437:
IVIS UN GHS
≤ 3 No Category
> 3; ≤ 55 No prediction can be made
> 55 Category 1

DECISION CRITERIA: please specify if the decision criteria as indicated in the TG was used. --> yes
Criteria for Determination of a Valid Test
The test will be acceptable if
- the positive control gives an IVIS that falls within two standard deviations of the current historical mean (updated every three months), and if
- the negative control responses result in opacity and permeability values that are less than the established upper limits for background opacity and permeability values for bovine corneae treated with the respective negative control.
Irritation parameter:
in vitro irritation score
Run / experiment:
mean value
Value:
2.83
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Remarks:
Not categorized
Irritation parameter:
in vitro irritation score
Run / experiment:
cornea 1
Value:
2.22
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
in vitro irritation score
Run / experiment:
cornea 2
Value:
3.21
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Irritation parameter:
in vitro irritation score
Run / experiment:
cornea 3
Value:
3.07
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Interpretation of results:
GHS criteria not met
Conclusions:
Testing was performed via a GLP OECD 437 guideline study on the registered substance itself. It is hence sufficiently reliable to assess the eye irritating potential of the test item. The present in vitro method is recommended in a bottom up approach. The present in vitro method allows the identification of corrosive chemical substances and mixtures or of substances which do not require classification. The test item 3,5-Diethyltoluene-2,4-diisocyanate was tested undiluted. Relative to the negative control, the test item 3,5-Diethyltoluene-2,4-diisocyanate did not cause a relevant increase of the corneal opacity or permeability. The calculated mean IVIS was 2.83 (threshold for serious eye damage: IVIS > 55). According to OECD 437, the test item is not categorized.
This test may hence serve as a stand-alone test, no further testing is required, and the test item does not need to be classified as eye irritant.
Executive summary:

This in vitro study was performed to assess the corneal damage potential of 3,5-Diethyltoluene-2,4-diisocyanate by means of the BCOP assay using fresh bovine corneae in a OECD 437 study under GLP.

After a first opacity measurement of the fresh bovine corneae (t0), the neat test item, the positive, and the negative controls were applied to corneae fixed in an incubation chamber in horizontal position for 10 minutes at 32 ± 1 °C. The posterior chamber contained incubation medium. After the incubation phase the test item, the positive, and the negative controls were each rinsed from the corneae. Further, the corneae were incubated for another 120 minutes at 32 ± 1 °C in a vertical position, while the anterior chamber contain incubation medium as well. Afterwards, opacity was measured a second time (t130).

After the opacity measurements permeability of the corneae was determined by measuring spectrophotometrically the transfer of sodium fluorescein after incubation in a horizontal position for 90 minutes at 32 ± 1 °C.

With the negative control (0.9% (w/v) NaCl solution in deionised water) neither an increase of opacity nor permeability of the corneae could be observed.

The positive control (2-Ethoxyethanol) showed clear opacity and distinctive permeability ofthe corneae corresponding to a classification as serious eye damaging (CLP/EPA/GHS (Cat 1)).

 

Relative to the negative control, the test item 3,5-Diethyltoluene-2,4-diisocyanate did not cause a relevant increase of the corneal opacity or permeability. The calculated mean in vitro irritancy score was 2.83. According to OECD 437 the test item is not categorized (GHS).

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

Additional information

Justification for classification or non-classification