Zinc isodecyl phosphorodithioate

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 August 2017 to 18 August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Human Skin Model Test)

Version / remarks:

Adopted 29 July 2016

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Zinc isodecyl phosphorodithioate

EC Number:

246-618-6

EC Name:

Zinc isodecyl phosphorodithioate

Cas Number:

25103-54-2

Molecular formula:

C20H43O2PS2.1/2Zn

IUPAC Name:

zinc bis[O,O-bis(8-methylnonyl) dithiophosphate]

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: Keratinocyte strain 00267

Source strain:

other: All cells used to produce EpiDerm tissue are purchased or derived from tissue obtained from accredited institutions, from the donor or the donor's legal next of kin for use of the tissues or derivatives of the tissue for research purposes

Details on animal used as source of test system:

Not applicable

Justification for test system used:

The test is based on the experience that corrosive chemicals show cytotoxic effects following short-term exposure to the stratum corneum of the epidermis. The test is designed to predict and classify the skin corrosion potential of a test item by assessment of its effect on a three-dimensional human epidermis model.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm Skin Model (EPI-200)
- Source: MatTek Corporation, USA
- Tissue batch number(s): Lot no. 26767
- Production date: Certificate of analysis dated 16th August 2017
- Date of initiation of testing: One day after receipt of the tissues

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: All incubations, with the exception of the test item incubation of 3 minutes at room temperature, were carried out in a controlled environment at 37.0 ± 1.0°C (actual range 36.8 - 37.5°C).
- Temperature of post-treatment incubation (if applicable): 37.0°C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: After the exposure period, the tissues were washed with phosphate buffered saline to remove residual test item.
- Observable damage in the tissue due to washing: None noted
- Modifications to validated SOP: None

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 5 mg/ml diluted (1:5) with MTT diluent (supplemented DMEM).
- Incubation time: 3 hours
- Spectrophotometer: TECAN Infinite® M200 Pro Plate Reader
- Wavelength: 570nm

NUMBER OF REPLICATE TISSUES: 2

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be corrosive to skin if the viability after 3 minutes exposure is less than 50%, or if the viability after 3 minutes exposure is greater than or equal to 50 % and the viability after 1 hour exposure is less than 15%.
- The test substance is considered to be non-corrosive to skin if the viability after 3 minutes exposure is greater than or equal to 50% and the viability after 1 hour exposure is greater than or equal to 15%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 50 μl
- Concentration (if solution): Test material was applied neat.

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 50 μl
- Concentration (if solution): Milli-Q water, concentration not applicable.

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 50 μl
- Concentration (if solution): Potassium hydroxide, 8.0 normal solution

Duration of treatment / exposure:

3 minutes and 1 hour

Duration of post-treatment incubation (if applicable):

3 hours

Number of replicates:

Two test replicates each for the 3 minute and 1 hour exposures

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 minute exposure

Value:

81

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: No indication of skin corrosion

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minute exposure

Value:

84

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: No indication of skin corrosion

Other effects / acceptance of results:

ACCEPTANCE OF RESULTS:
The quality criteria to deem the results of the assay to be considered acceptable are:

Negative Control

The absolute OD570 of the negative control treated tissues in the MTT-test is an indicator of tissue viability obtained in the testing laboratory after the shipping and storing procedure and under specific conditions of the assay. The mean OD570 of the two negative control tissues should be ≥ 0.8 and ≤ 2.8 for each exposure time. The mean OD570 of the negative control was within this range and within the historical control range, therefore this criterion was met.

Positive Control

Potassium Hydroxide 8.0N solution was used as a positive control. An assay meets the acceptance criterion if the mean relative tissue viability of the 60 minute positive control is <15%. The mean relative tissue viability was 6.4% therefore this criterion was met.

Any other information on results incl. tables

Table 1 Mean Absorption in thein vitroSkin 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	2.030	2.037	2.034	±	0.005	2.061	1.950	2.006	±	0.078
Test item	1.678	1.608	1.643	±	0.050	1.615	1.764	1.690	±	0.106
Positive control	0.149	0.179	0.164	±	0.021	0.141	0.114	0.128	±	0.019

SD = Standard deviation

Duplicate exposures are indicated by A and B.

In this table the values are corrected for background absorption (0.0430). Isopropanol was used to measure the background absorption.

Table 2  Mean Tissue Viability in thein vitroSkin Corrosion Test with the test item

	3-minute application viability (percentage of control)	1-hour application viability (percentage of control)
Negative control	100	100
Test item	81	84
Positive control	8.1	6.4

Table 3 data interpretation and sub-categorisation of test items

Viability measured after 3-minutes and 1 hour	Prediction to be considered
Step 1
< 50% after 3 minute exposure	Corrosive
≥ 50% after 3 minute exposure AND < 15% after 1 hour exposure	Corrosive
≥ 50% after 3 minute exposure AND ≥ 15% after 1 hour exposure	Non-corrosive
Step 2 (for substances/mixtures identified as Corrosive in step 1)
< 25% after 3 minute exposure	Optional Sub-category 1A
≥ 25% after 3 minute exposure	A combination of optional Sub-categories 1B and 1C

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The test item is a not corrosive based on the results from an OECD guideline 431 study.

Executive summary:

The skin corrosion potential of the test item was assessed in an in vitro skin corrosion study.The study is assigned a reliability score of 1 (reliable without restrictions) as it followed OECD Guideline 431: In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method and as it is compliant with GLP. 50 µL of the test item was applied undiluted to the EpiDerm tissue for 3 minutes and 1 hour. Negative and positive controls were also tested. All validity criteria for the study were met. The test item had a mean tissue viability of 81% after a 3-minute application and a mean tissue viability of 84% after a 1-hour application. The test item is therefore non-corrosive to the skin.