p-benzoquinone dioxime

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Remarks:

in vitro

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19-02-2018 to 23-02-2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study performed under GLP. All relevant validity criteria were met.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Deviations:

yes

Remarks:

Minor deviation in environmental conditions (humidity minimum 41% and temperature minimum 35.0°C) which does not affect the reliability of the study

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: EU Method B.40 BIS : In Vitro Skin Corrosion: Human Skin Model Test

Deviations:

yes

Remarks:

Minor deviation in environmental conditions (humidity minimum 41% and temperature minimum 35.0°C) which does not affect the reliability of the study

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

p-benzoquinone dioxime

EC Number:

203-271-5

EC Name:

p-benzoquinone dioxime

Cas Number:

105-11-3

Molecular formula:

C6H6N2O2

IUPAC Name:

N-[(1Z,4Z)-4-(hydroxyimino)cyclohexa-2,5-dien-1-ylidene]hydroxylamine

Test material form:

solid

Details on test material:

- Physical state: Solid
- Storage condition of test material: In refrigerator (2-8°C) container flushed with nitrogen
- Other: Brown powder

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

foreskin from a single donor

Vehicle:

unchanged (no vehicle)

Details on test system:

EpiDerm Skin Model (EPI-200, Lot no.: 27958 kit F). The test consists of topical application of the test item on the skin tissue for 3-minute and 1-hour. After exposure the skin tissue is thoroughly rinsed to remove the test item followed by immediate determination of the cytotoxic (corrosive) effect.
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 the treatment. The EpiDerm Skin Model 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) were cultured on polycarbonate membranes of 10 mm cell culture inserts.

Preincubation:
On the day of receipt the tissues were kept on agarose and stored in the refrigerator. On the next day, at least one hour before starting the assay the tissues were transferred to 6-well plates with 0.9 ml DMEM.

Application of test item and rinsing:
The solid test item was applied directly on top of the skin tissue. The test item was spread to match the size of the tissue. The plates were incubated for approximately 2 hours at 37.0 ± 1.0ºC. The medium was replaced with fresh DMEM just before the test item was applied. The test was performed on a total of 4 tissues per test item together with a negative control and positive control. Two tissues were used for a 3-minute exposure to the test item and two for a 1-hour exposure. The skin was moistened with 25 µL Milli-Q water to ensure close contact of the test item to the tissue and 39.5 to 50.1 mg of the solid test item was added into the 6-well plates on top of the skin tissues. Negative Control: similarly treated with 50 µl Milli-Q water only. Positive control: 50 µl 8N KOH (potassium hydroxide 8 normal solution). After the exposure periods (3 minutes and 1 hour, respectively), the tissues were washed with phosphate buffered saline to remove residual test item. The skin inserts were carefully dried. Rinsed tissues were kept in 24 well plates on 300 µl DMEM until 6 tissues (= one application time) were dosed and rinsed.

All incubations, with the exception of the test item incubation of 3 minutes at room temperature, were carried out in a controlled environment, in which optimal conditions were a humid atmosphere of 80 - 100% (actual range 41 - 80%), containing 5.0 ± 0.5% CO2 in air in the dark at 37.0 ± 1.0°C (actual range 35.0 - 37.3°C). Temperature and humidity were continuously monitored throughout the experiment. The CO2 percentage was monitored once on each working day. Temporary deviations from the temperature, humidity and CO2 percentage may occur due to opening and closing of the incubator door. Based on testing laboratory historical data these deviations are not considered significant.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): Solid: ca. 39.5 to 50.1 mg + 25 µL H2O (guideline requires 25 mg + 25 µL H20, more test item if necessary).
- Concentration (if solution): undiluted

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 50 μl H2O
- Concentration (if solution): Not applicable

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 50 μl
- Concentration (if solution): 8N KOH(aq) (pre-diluted)

Duration of treatment / exposure:

Observations are made 3-minutes and 1-hour post-test item application

Duration of post-treatment incubation (if applicable):

The DMEM was replaced by 300 µl MTT-medium and tissues were incubated for 3 hours at 37°C in air containing 5% CO2. After incubation the tissues were washed with PBS and formazan was extracted with 2 ml isopropanol (MatTek corporation) over night at room temperature.

Number of replicates:

Duplicate; used for a 3-minute exposure to the test substance and two for a 1-hour exposure.

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Remarks:

3 minute exposure

Value:

104

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Basis: mean. Time point: 3 minute exposure. Remarks: n=2 ; CV = 9.6% ; Score in terms of percentage of negative control.

Results 2

Irritation / corrosion parameter:

% tissue viability

Remarks:

1 hour exposure

Value:

85

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: Basis: mean. Time point: 1 hour exposure. Remarks: n=2 ; CV = 22% ; Score in terms of percentage of negative control.

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: None reported.
- Direct-MTT reduction: Screened prior to test. Not applicable.
- Colour interference with MTT: Screened prior to test. Not applicable.

DEMONSTRATION OF TECHNICAL PROFICIENCY:

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: Historic Control Data: Negative Control OD570: 3-minutes (n=111): 1.258 – 2615 ; 1-hour (n=110): 1.371 – 2.371. Positive Control HCD data are presented within the full study report and the concurrent PC was within the specified ranges.

Any other information on results incl. tables

Table 1. Mean absorption and tissue viability in the in vitro skin corrosion test with the test item

	3-minute application				1-hour application
	A (OD570)	B (OD570)	Mean (OD570)	SD	A (OD570)	B (OD570)	Mean (OD570)	SD
Negative control	1.579	1.706	1.643	±0.090	1.749	1.834	1.792	±0.060
Test Item	1.788	1.616	1.702	±0.122	1.718	1.337	1.527	±0.270
Positive control	0.153	0.146	0.149	±0.005	0.135	0.148	0.142	±0.009

Values are corrected for background absorption (0.0423). Isopropanol was used to measure the background absorption.

SD = Standard deviation

Duplicate exposures are indicated by A and B.

CV (%) = 100 - [(lowest OD570/highest OD570) x 100%]

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Remarks:

EU criteria not met

Conclusions:

Under the conditions of this in vitro study, the test item is not considered to be corrosive to the skin.

Executive summary:

The study was performed to OECD TG 431 and EU Method B.40 BIS to assess the skin corrosion potential of the test item in accordance with GLP using a human three dimensional epidermal model (EpiDerm (EPI-200)). The test was performed on a total of 4 tissues per test item together with a negative control and positive control. Two tissues were used for a 3-minute exposure to the test item and two for a 1-hour exposure. 50 μl of the undiluted test item was added (with a pipette) into the 6-well plates on top of the skin tissues. The remaining tissues were treated with 50 μl Milli-Q water (negative control) and with 50 μl 8N KOH (positive control), respectively. The positive control had a mean relative tissue viability of 7.6% after 1 hour exposure. The absolute mean OD570 (optical density at 570 nm) of the negative control tissues was within the laboratory historical control data range. In the range of viability 20 - 100% the Coefficient of Variation between tissue replicates was less than 11%, indicating that the test system functioned properly. Skin corrosion is expressed as the remaining cell viability after exposure to the test item. The relative mean tissue viability obtained after 3-minute and 1-hour treatments with the test item compared to the negative control tissues was 112% and 103%, respectively. Because the mean relative tissue viability for the test item was not below 50% after the 3-minute treatment and not below 15% after the 1-hour treatment the test item is considered to be not corrosive. Under the conditions of this study, the test item is not corrosive in the in vitro skin corrosion test.