3-ethoxy-1,1,5-trimethylcyclohexane

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Remarks:

in vitro

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11-16 March 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study conducted according to OECD test Guideline No. 439 with minor deviation.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

historical data and skin model certificate are not reported

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

historical data and skin model certificate are not reported

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

UK GLP Compliance Programme (inspected on 7 June 2015 / signed on 24 September 2015)

Test material

Test material information

Constituent 1

Reference substance name:

3-ethoxy-1,1,5-trimethylcyclohexane

EC Number:

266-722-5

EC Name:

3-ethoxy-1,1,5-trimethylcyclohexane

Cas Number:

67583-77-1

Molecular formula:

C11H22O

IUPAC Name:

3-ethoxy-1,1,5-trimethylcyclohexane

Test material form:

liquid

Details on test material:

- Physical state/Appearance: Clear colorless liquid
- Storage condition of test material: Stored at room temperature in the dark
- Expiration date of the lot/batch: 09 July 2016

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

Regarding inconsistent results from available data, the EPISKIN™ Reconstructed Human Epidermis Model method was used to assess skin irritation as recommended in the OECD test guideline No. 439.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN™ Reconstructed Human Epidermis Model Kit, SkinEthic Laboratories, Lyon, France
- Tissue batch number(s): 16-EKIN-019
- Production date: not reported
- Shipping date: not reported
- Delivery date: not reported
- Expiry date: not reported
- Date of initiation of testing: 11 May 2016

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

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: not reported
At the end of the exposure period, each tissue was removed from the well using forceps and rinsed using a wash bottle containing DPBS with Ca++ and Mg++. Rinsing was achieved by filling and emptying each tissue insert for approximately 40 seconds using a constant soft stream of DPBS to gently remove any residual test item.
- Observable damage in the tissue due to washing: none reported
- Modifications to validated SOP: none reported

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL in DPBS
- Incubation time: 3 hours
- Spectrophotometer: Anthos 2001 microplate reader
- Wavelength: 562 nm (without a reference filter)
- Filter: not applicable
- Filter bandwidth: not applicable
- Linear OD range of spectrophotometer: no data reported

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: negative control OD values: 0.596, 0.642 and 0.610 (historical control not reported).
- Barrier function: not reported
- Morphology: The EPISKINTM model is a three-dimensional reconstructed human epidermis model consisting of adult human-derived epidermal keratinocytes seeded on a dermal substitute consisting of a collagen type I matrix coated with type IV collagen. A highly differentiated and stratified epidermis model is obtained after a 13 Day culture period comprising of the main basal, supra basal, spinous and granular layers and a functional stratum corneum.
- Contamination: : not reported
- Reproducibility: not reported

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
Not applicable

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

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be irritant to skin if the viability after the 15-min exposure period followed by the 42h post-exposure period is less or equal to 50%
- The test substance is considered to be non-irritant to skin if the viability after the 15-min exposure period followed by the 42h post-exposure period is greater than 50%

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 μL (26.3 μL /cm2) of the test item was applied to the epidermis surface.
- Concentration (if solution): Undiluted

VEHICLE
not applicable

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL of DPBS
- Concentration (if solution): undiluted

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL of SDS
- Concentration (if solution): 5% w/v aqueous solution

Duration of treatment / exposure:

Triplicate tissues were treated with the test item for an exposure period of 15 minutes at room temperature.
At the end of the exposure period, tissues were rinsed and incubated at 37 °C, 5% CO2 in air for 42 h.

Duration of post-treatment incubation (if applicable):

- On Day 3, at the end of the 42 h post-treatment incubation period: MTT test (MTT Loading/Formazan Extraction) was performed and tissues were incubated for 3 h at 37°C, 5 % CO2 in air.
- On Day 6, at the end of the formazan extraction period: The optical density was measured at 562 nm (without a reference filter) using the Anthos 2001 microplate reader.

Number of replicates:

Triplicate tissues for test item, negative and positive controls

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

15 minute exposure period and 42 h post-exposure incubation period.

Value:

95.8

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:

The relative mean viability of the test item treated tissues was 95.8% after a 15 minute exposure period and 42 h post-exposure incubation period. It was considered unnecessary to perform IL-1α analysis as the results of the MTT test were unequivocal.

- OTHER EFFECTS:
- Visible damage on test system: no
- Direct-MTT reduction: no
- Colour interference with MTT: not assessed because the solution containing the test item was colorless
DEMONSTRATION OF TECHNICAL PROFICIENCY: yes

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
- Range of historical values if different from the ones specified in the test guideline: not applicable

Any other information on results incl. tables

Table 7.3.1/1: Mean OD₅₆₂Values and Percentage Viabilities for the Negative Control Item, Positive Control Item and Test Item

Item	OD562of tissues	Mean OD562of triplicate tissues	±SDof OD562	Relative individual tissue viability (%)	Relative mean viability (%)	± SD of Relative mean viability (%)
Negative Control Item	0.596	0.616	0.024	96.8	100*	3.8
	0.642			104.2
	0.610			99.0
Positive Control Item	0.056	0.058	0.007	9.1	9.4	1.2
	0.052			8.4
	0.066			10.7
Test Item	0.579	0.590	0.021	94.0	95.8	3.4
	0.577			93.7
	0.615			99.8

OD=       Optical Density

SD=         Standard deviation

*=          The mean viability of the negative control tissues is set at 100%

 

Quality Criteria

The relative mean tissue viability for the positive control treated tissues was 9.4% relative to the negative control treated tissues and the standard deviation value of the percentage viability was 1.2%. The positive control acceptance criterion was therefore satisfied.

The mean OD562 for the negative control treated tissues was 0.616 and the standard deviation value of the percentage viability was 3.8%. The negative control acceptance criterion was therefore satisfied.

The standard deviation calculated from individual percentage tissue viabilities of the three identically test item treated tissues were 3.4%. The test item acceptance criterion was therefore satisfied.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the experimental conditions of this study, the test item is not classified according to Regulation (EC) No. 1272/2008 (CLP) and to the GHS.

Executive summary:

An in vitro skin irritation study was performed according to the OECD Guideline 439 and in compliance with GLP, using the EPISKIN^TM reconstructed human epidermis model.

 

Triplicate tissues were treated with the test item for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for 42 h. At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labeled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT-loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues. At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 μL samples were transferred to the appropriate wells of a pre-labeled 96-well plate. The optical density was measured at 562 nm. Data are presented in the form of percentage viability (MTT reduction in the test item treated tissues relative to negative control tissues).

 

The relative mean viability of the test item treated tissues was 95.8% after the 15 minute exposure period and 42 h post-exposure incubation period.

 

The relative mean tissue viability for the positive control treated tissues was 9.4% relative to the negative control treated tissues and the standard deviation value of the percentage viability was 1.2%. The mean OD562 for the negative control treated tissues was 0.616 and the standard deviation value of the percentage viability was 3.8%. The positive and negative controls acceptance criterion were therefore satisfied. The standard deviation calculated from individual percentage tissue viabilities of the three identically test item treated tissues were 3.4%. The test item acceptance criterion was therefore satisfied.

 

Under the experimental conditions of this study, the test item is not classified according to Regulation (EC) No. 1272/2008 (CLP) and to the GHS.