Reaction mass of 1-(2,6,6-trimethylcyclohex-2-en-1-yl)hepta-1,6-dien-3-one and 1-(2,6,6-trimethylcyclohex-1-en-1-yl)hepta-1,6-dien-3-one

Endpoint summary

Description of key information

Skin corrosion: Not corrosive based on absence of skin and eye irritation.

Skin irritation (OECD TG 439): not irritating
Eye irritation (OECD TG 438): not irritating

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:

15 March, 2016 - 21 March, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2015)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

(2012)

Deviations:

no

GLP compliance:

yes

Test system:

human skin model

Species:

other: EPIKSIN in vitro Reconstructed Human Epidermis (RHE) Model

Strain:

other: Not applicable

Details on test animals or test system and environmental conditions:

EPISKIN Small ModelTM
Supplier : SkinEthic Laboratories, Lyon, France
EpiSkin-SMTM Tissues (0.38cm^2) batch number : 16-EKIN-011

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 36.3 - 37.3
- Humidity (%): 67 - 87

Type of coverage:

other: None; Twenty five μL of the undiluted test substance was added into 12-well plates on top of the skin tissues.

Preparation of test site:

other: The test item was applied topically to the corresponding tissues ensuring uniform covering.

Vehicle:

unchanged (no vehicle)

Controls:

other: 3 Tissues were treated with 25 μL PBS (negative control) and 3 tissues with 25 μL 5% SDS (positive control) respectively.

Amount / concentration applied:

Test material
- Applied volume: 25 μL

Duration of treatment / exposure:

15-Minute exposure period and 42 hours post-exposure incubation period.

Number of animals:

A total of 9 tissues were used: Triplicate tissues were treated with: test substance, positive control or negative control.

Details on study design:

PRE-TEST PROCEDURE:
Assessment of Direct Test Item Reduction of MTT
MTT Salt Metabolism, Cell Viability Assay

The MTT assay, a colorimetric method of determining cell viability, is based on reduction of the yellow tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a blue formazan salt by mitochondrial succinate dehydrogenase in viable cells.

One limitation of the assay is possible interference of the test item with MTT. A test item may directly reduce MTT, thus mimicking dehydrogenase activity of thecellular mitochondria. This property of the test item is only a problem, if at the time of the MTT test (after rinsing) there are still sufficient amounts of the test item present on or in the tissues. In this case, the true metabolic MTT reduction and the false direct MTT reduction can be differentiated and quantified.

Test for Direct MTT Reduction and colour interference:
The test substance (multi-constituent) was checked for possible direct MTT reduction and colour interference before the study was started. Some non-coloured test items may change into coloured items in aqueous conditions and thus stain the skin tissues during the exposure. To assess the colour interference, 10 μL of the test substance (multi-constituent) was added to 90 μL Milli-Q water. The mixture was mixed for approximately 15 minutes. A negative control, 10 μL Milli-Q water was tested concurrently. At the end of the shaking period a colour check was performed.
To assess the ability of the test item to reduce MTT, 25 μL of the test item was added to 2 mL MTT solution (0.3 mg/mL in PBS). The mixture was incubated for 3 hours at 37°C. A negative control, sterile Milli-Q water was tested concurrently. At the end of the incubation period a colour check was performed.

PRE-INCUBATION:
On the day of receipt the tissues were transferred to 12-well plates and preincubated with prewarmed Maintenance Medium for approximately 22 hours at 37°C. Maintenance medium and Assay medium were supplied by Skinethic Laboratories, Lyon, France.

APPLICATION/TREATMENT OF TEST SUBSTANCE:
The test was performed on a total of 3 tissues per test item together with negative and positive controls. Twenty five μL of the undiluted test item was added into 12-well plates on top of the skin tissues. Three tissues were treated with 25 μL PBS (negative control) and 3 tissues with 25 μL 5% SDS (positive control) respectively. The positive control was re-spread after 7 minutes contact time. After the exposure period of 15 ± 0.5 minutes at room temperature, the tissues were washed with phosphate buffered saline to remove residual test item. After rinsing, the cell culture inserts were each dried carefully and moved to a new well on 2 mL pre-warmed maintenance medium until all tissues were dosed and rinsed. Subsequently the skin tissues were incubated for 42 hours at 37°C.

CELL VIABILITY MEASUREMENT:
After incubation, cell culture inserts were dried carefully to remove excess medium and were transferred into a 12-wells plate prefilled with 2 mL MTT-solution (0.3 mg/mL in PBS). The tissues were incubated for 3 h at 37°C. After incubation the tissues were placed on blotting paper to dry the tissues. Total biopsy was made by using a biopsy punch. Epidermis was separated from the collagen matrix and both parts were placed in prelabeled microtubes and extracted with 500 μL isopropanol (Merck, Darmstadt, Germany). Tubes were stored refrigerated and protected from light for 70 hours. The amount of extracted formazan was determined spectrophotometrically at 570 nm in duplicate with the TECAN Infinite® M200 Pro Plate Reader.
Cell viability was calculated for each tissue as a percentage of the mean of the negative control tissues. Skin irritation potential of the test item was classified according to remaining cell viability following exposure of the test item.

Irritation / corrosion parameter:

% tissue viability

Remarks:

Mean

Run / experiment:

Time point: 15 minutes exposure.

Value:

97

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

The relative mean tissue viability compared to the negative control tissues (100%).

Irritant / corrosive response data:

The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test substance (multi-constituent) compared to the negative control tissues was 97%. Since the mean relative tissue viability for the test substance (multi-constituent) was above 50% the test substance (multi-constituent) is considered to be non-irritant.

Direct MTT Reduction

The test substance (multi-constituent) was checked for colour interference in aqueous conditions and possible direct MTT reduction by adding the test item to MTT medium. Because no colour changes were observed it was concluded that the test substance (multi-constituent) did not interact with the MTT endpoint.

Test Item, Positive Control Item and Negative Control Item

The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test substance (multi-constituent) compared to the negative control tissues was 97%. Since the mean relative tissue viability for the test substance (multi-constituent) was above 50% the test substance (multi-constituent) is considered to be non-irritant.

Quality Criteria

The positive control had a mean cell viability after 15 ± 0.5 minutes exposure of 44%. The positive control meets the validity criterion meets the validity criterion even though it is just outside the historical control range, which has not affected the result of the results for the test substance.The absolute mean OD570 of the negative control tissues was within the laboratory historical control data range. The positive control had a mean cell viability after 15 ± 0.5 minutes exposure of 44%. The positive control meets the validity criterion meets the validity criterion even though it is just outside the historical control range, which has not affected the result of the results for the test substance.The absolute mean OD570 of the negative control tissues was within the laboratory historical control data range.

Mean OD570 Values and Percentage Viabilities for the Negative Control Item, Positive Control Item and Test Item:

Item	OD570 of tissues	Mean OD562 of triplicate tissues	± SD of OD570	Relative individual tissue viability (%)	Relative mean viability (%)
Negative Control Item	1.066	1.047	0.022		100
	1.052
	1.024
Positive Control Item	0.398	0.462	0.078	37	44
	0.549			52
	0.437			43
Test Item	0.815	1.018	0.176	76	97
	1.116			106
	1.123			110

SD = Standard deviation

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

Interpretation of results:

other: Not a skin irritant

Remarks:

in accordance with EU CLP (1272/2008 and its updates)

Conclusions:

The relative mean tissue viability obtained after 15 ± 0.5 minutes treatment with the test substance (multi-constituent) compared to the negative control tissues was 97%. Since the mean relative tissue viability for the test substance (multi-constituent) was above 50% the test substance (multi-constituent) is considered to be non-skin irritant.

Executive summary:

The possible skin irritation potential of the test substance (multi-constituent) was tested in vitro using a human skin model through topical application for 15 minutes. The study procedures described in this report were according to OECD TG 439 guideline and GLP principles. Skin tissue was treated by topical application of 25 µL undiluted test substance. After 42 hours incubation period, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) MTT at the end of treatment. Skin irritation is expressed as the remaining cell viability after exposure to the test substance. Reliable negative and positive controls were included. The positive control had a mean cell viability of 44% after 15 minutes exposure. The standard deviation value of the percentage viability of three tissues treated identically was less than 5%, indicating that the test system functioned properly. The relative mean tissue viability obtained after 15 minutes treatment with the substance compared to the negative control tissue was 97%. Since the mean relative tissue viability for the test substance (multi-constituent) was above 50% after 15 minutes treatment the substance is considered to be not a skin irritant.

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:

15-03-2016 to 15-04-2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 438 (Isolated Chicken Eye Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

GLP compliance:

yes (incl. QA statement)

Remarks:

Triskelion, Utrechtseweg 48, 3700 AV, Zeist

Species:

other: eyes of male or female chickens (ROSS, spring chickens)

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: Slaughterhouse v.d. Bor, Nijkerkerveen, The Netherlands
- Characteristics of donor animals: Approximately 7 weeks old, male or female chickens, body weight range approximately 1.5-2.5 kg, were used as eye donors.
- Storage, temperature and transport conditions of ocular tissue: Heads of the animals were cut off immediately after sedation of the animals by electric shock and incision of the neck for bleeding, and before they reached the next station on the process line. The heads were placed in small plastic boxes on a bedding of paper tissues moistened with isotonic saline. Next, they were transported to the testing facility. During transportation, the heads were kept at ambient temperature.
- Time interval prior to initiating testing: Within 2 hours after kill, eyes were carefully dissected and placed in a superfusion apparatus.
- indication of any existing defects or lesions in ocular tissue samples: No
- Indication of any antibiotics used: No

Vehicle:

unchanged (no vehicle)

Details on study design:

SELECTION AND PREPARATION OF ISOLATED EYES
Within 2 hours after kill, eyes were carefully dissected and placed in a superfusion apparatus using the following procedure: First the eye-lids were carefully removed without damaging the cornea and a small drop of Fluorescein sodium 2.0% w/v was applied to the corneal surface for a few seconds and subsequently rinsed off with isotonic saline at ambient temperature. Next, the head with the fluorescein-treated cornea was examined with a slit-lamp microscope (Slit-lamp 900 BP, Haag-Streit AG, Liebefeld-Bern, Switzerland) to ensure that the cornea was not damaged. If undamaged (e.g., fluorescein retention and corneal opacity scores of ≤ 0.5), the eye was further dissected from the head without damaging the eye or cornea. Care was taken to remove the eye-ball from the orbit without cutting off the optical nerve too short. The enucleated eye was placed in a stainless steel clamp with the cornea positioned vertically and transferred to a chamber of the superfusion apparatus. The clamp holding the eye was positioned in such a way that the entire cornea was supplied with isotonic saline from a bent, stainless steel tube, at a target rate of 0.10-0.15 mL/min. The chambers of the superfusion apparatus as well as the saline were temperature controlled at approximately 32 °C (water pump set at 36.4 °C). After placing in the superfusion apparatus, the eyes were examined again with the slit-lamp microscope to ensure that they were not damaged. An accurate measurement was taken at the corneal apex of each eye. Eyes with a corneal thickness deviating more than 10% of the average corneal thickness of the eyes, eyes showing opacity (score higher than 0.5), or were unacceptably stained with fluorescein (score higher than 0.5) indicating the cornea to be permeable, or eyes that showed any other signs of damage, were rejected as test eyes and replaced.

EQUILIBRATION AND BASELINE RECORDINGS
Each eye provided its own baseline values for corneal swelling, corneal opacity and fluorescein retention. For that purpose, after an equilibration period of 45-60 minutes, the corneal thickness of the eyes was measured again to determine the zero reference value for corneal swelling calculations.

NUMBER OF REPLICATES
Negative control: 1
Positive control: 3
Test group: 3

NEGATIVE CONTROL USED
Physiological saline

POSITIVE CONTROL USED
Benzalkonium Chloride 5%

APPLICATION DOSE AND EXPOSURE TIME
30 μL for 10 seconds

OBSERVATION PERIOD
240 minutes

REMOVAL OF TEST SUBSTANCE
- Volume and washing procedure after exposure period: 20 mL saline. After rinsing, each eye in the holder was returned to its chamber.
- Indicate any deviation from test procedure in the Guideline: none

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: Slit-lamp microscope examination
- Damage to epithelium based on fluorescein retention: Slit-lamp microscope examination
- Swelling: measured with optical pachymeter on a slit-lamp microscope; slit-width setting: set at 0.095 mm
- Others: After the final examination, the test substance treated eyes, the negative and positive control eyes were preserved in a neutral aqueous phosphate-buffered 4% solution of formaldehyde. The corneas were embedded in paraffin wax, sectioned at ca 4 μm and stained with PAS (Periodic Acid-Schiff). The microscopic slides were subjected to histopathological examination.

SCORING SYSTEM:
Defined scoring scales were used for each parameter to define the severity of effects into four categories (I-IV).
- Mean corneal swelling (%): According to OECD 438 guideline. Examination of the eyes after 0, 30, 75, 120, 180, and 240 minutes
- Mean maximum opacity score: According to OECD 438 guideline. Examination of the eyes after 0, 30, 75, 120, 180, and 240 minutes
- Mean fluorescein retention score at 30 minutes post-treatment: According to OECD 438 guideline.

DECISION CRITERIA: According to OECD 438 guideline

Irritation parameter:

percent corneal swelling

Run / experiment:

slit-lamp examination

Value:

1

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: maximum mean values

Irritation parameter:

cornea opacity score

Run / experiment:

slit-lamp examination

Value:

0.2

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: maximum mean values

Irritation parameter:

fluorescein retention score

Run / experiment:

slit-lamp examination

Value:

0

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

Slit-lamp examination: The test substance caused corneal effects consisting of very slight corneal swelling (mean of 1%), no or very slight opacity (mean score of 0.2) and no fluorescein retention (mean score of 0.0). The negative control eye did not show any corneal effect and demonstrated that the general conditions during the tests were adequate. The positive control BAC 5% caused severe corneal effects and demonstrated the ICE test valid to detect severe eye irritants.

Microscopic examination: Microscopic examination of the corneas treated with the test substance revealed very slight erosion of the epithelium in one cornea. Microscopic examination of the cornea treated with the negative control (saline) did not reveal any abnormalities. Microscopic examination of the corneas treated with the positive control BAC 5% revealed moderate or severe erosion and slight vacuolation of the epithelium, the epithelium partly detached from the basement membrane, and endothelial necrosis (two corneas).

Interpretation of results:

other: Not an eye irritant

Remarks:

according to EU CLP (1272/2008 and its amendments)

Conclusions:

Under the test conditions (OECD 438 and GLP) the test substance is not considered to be an eye irritant

Executive summary:

In accordance to OECD guideline 438 and GLP, the test substance was examined for its in vitro eye irritating potential using the Isolated Chicken Eye (ICE) Test. In the ICE test, 3 eyes were exposed to 30 µL test substance for 10 seconds. In addition, one negative control eye (30 µL saline) and three positive control eyes (30 µL Benzalkonium Chloride (BAC)) were tested. After the exposure the eyes were rinsed with 20 mL saline and were examined at approximately 0, 30, 75, 120, 180, and 240 minutes after treatment. The test substance caused corneal effects consisting of very slight corneal swelling (mean of 1%), no or very slight opacity (mean score of 0.2) and no fluorescein retention (mean score of 0.0). The negative control eye did not show any corneal effect and demonstrated that the general conditions during the tests were adequate. The positive control BAC 5% caused severe corneal effects and demonstrated the ICE test valid to detect severe eye irritants. Microscopic examination of the corneas treated with the test substance revealed very slight erosion of the epithelium in one cornea. Microscopic examination of the cornea treated with the negative control (saline) did not reveal any abnormalities. Microscopic examination of the corneas treated with the positive control BAC 5% revealed moderate or severe erosion and slight vacuolation of the epithelium, the epithelium partly detached from the basement membrane, and endothelial necrosis (two corneas). Based on these results, the test substance is considered to be not eye irritating.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Skin corrosion: The substance is not considered corrosive based on absence of skin and eye irritation.

Skin irritation:

The possible skin irritation potential of the test substance (multi-constituent) was tested in vitro using a human skin model through topical application for 15 minutes. The study procedures described in this report were according to OECD TG 439 guideline and GLP principles. Skin tissue was treated by topical application of 25 µL undiluted test substance. After 42 hours incubation period, determination of the cytotoxic (irritancy) effect was performed. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) MTT at the end of treatment. Skin irritation is expressed as the remaining cell viability after exposure to the test substance. Reliable negative and positive controls were included. The positive control had a mean cell viability of 44% after 15 minutes exposure. The standard deviation value of the percentage viability of three tissues treated identically was less than 5%, indicating that the test system functioned properly. The relative mean tissue viability obtained after 15 minutes treatment with the substance compared to the negative control tissue was 97%. Since the mean relative tissue viability for the test substance (multi-constituent) was above 50% after 15 minutes treatment the substance is considered to be not a skin irritant.

Eye irritation:

In accordance to OECD guideline 438 and GLP, the test substance was examined for its in vitro eye irritating potential using the Isolated Chicken Eye (ICE) Test. In the ICE test, 3 eyes were exposed to 30 µL test substance for 10 seconds. In addition, one negative control eye (30 µL saline) and three positive control eyes (30 µL Benzalkonium Chloride (BAC)) were tested. After the exposure the eyes were rinsed with 20 mL saline and were examined at approximately 0, 30, 75, 120, 180, and 240 minutes after treatment. The test substance caused corneal effects consisting of very slight corneal swelling (mean of 1%), no or very slight opacity (mean score of 0.2) and no fluorescein retention (mean score of 0.0). The negative control eye did not show any corneal effect and demonstrated that the general conditions during the tests were adequate. The positive control BAC 5% caused severe corneal effects and demonstrated the ICE test valid to detect severe eye irritants. Microscopic examination of the corneas treated with the test substance revealed very slight erosion of the epithelium in one cornea. Microscopic examination of the cornea treated with the negative control (saline) did not reveal any abnormalities. Microscopic examination of the corneas treated with the positive control BAC 5% revealed moderate or severe erosion and slight vacuolation of the epithelium, the epithelium partly detached from the basement membrane, and endothelial necrosis (two corneas). Based on these results, the test substance is considered to be not eye irritating.

Respiratory irritation:

There are no human data indicating respiratory irritation. In addition, the substance is not corrosive or causing eye damage with irreversible effect and therefore respiratory irritation is not anticipated either.

Justification for classification or non-classification

In view of the information above and in accordance with to EU CLP (1272/2008 and its updates) the substance does not have to be classified as skin and eye irritant and not for respiratory irritation either.