Molybdenum zinc tetraoxide

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 May 2018 - 17 May 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Molybdenum zinc tetraoxide

EC Number:

237-377-8

EC Name:

Molybdenum zinc tetraoxide

Cas Number:

13767-32-3

Molecular formula:

MoO4Zn

IUPAC Name:

molybdenum(6+) zinc(2+) tetraoxidandiide

Test material form:

solid: particulate/powder

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

This study was performed in order to evaluate the skin corrosion potential of Zinc molybdate to human skin in an in vitro study. The principle of the human skin model assay is based on the hypothesis that corrosive chemicals are able to penetrate the stratum corneum by diffusion or erosion and are cyto-toxic to the underlying cell layers and its use is recommended by the relevant OECD guideline for corrosion testing (OECD No. 431).

Vehicle:

water

Remarks:

Demineralised water

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDermTM
- Tissue batch number(s): 28610
- Production date: MatTek In Vitro Life Science Laboratories, Brati-slava
- Delivery date: 15 May 2018
- Date of initiation of testing: 15 May 2018

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1°C (and 5.0 ± 0.5% CO2)
- Temperature of post-treatment incubation: 37 ± 1°C (and 5.0 ± 0.5% CO2)

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: DPBS, once
- Observable damage in the tissue due to washing: No.
- Modifications to validated SOP: No.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 300 μL (1 mg/mL in DPBS)
- Pre-incubation time: 1h
- Incubation time: Treatment: 3 minutes, 1 hour.
- MTT incubation time: 3h
- Spectrophotometer: Microtiter plate photometer
- Wavelength: 570 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
The values for negative control and for positive control were within the range of historical data of the test facility.

NUMBER OF REPLICATE TISSUES: 2

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE : No interference was detected.

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

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- 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 vehicle

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit):
Tissue 1: 25.1 mg (3 min); 27.1 mg (1h)
Tissue 2: 25.7 mg (3 min); 27.2 mg (1h)
- Concentration (if solution): 25 μL demineralised water.

VEHICLE
- Amount(s) applied (volume or weight with unit): 50 μL
- Lot/batch no. (if required): Batch no: 20180221

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 50 μL
- Concentration (if solution): Solution in demineralised water (8 M)

Duration of treatment / exposure:

3 minutes and 1 hour.

Duration of post-treatment incubation (if applicable):

3 hours

Number of replicates:

2

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 min

Value:

102.2

Vehicle controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: mean value of 2 tissues

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1 hour

Value:

98.2

Vehicle controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: mean value of 2 tissues

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: No.
- Direct-MTT reduction: No.
- Colour interference with MTT: No.

DEMONSTRATION OF TECHNICAL PROFICIENCY: Yes.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: Yes. The criterion for optical density of the negative control (≥ 0.8 and ≤ 2.8) was fulfilled: optical density was 1.7 (3 minutes) and 1.6 (1 hour).
- Acceptance criteria met for positive control: Yes . The positive control showed clear corrosive effects. The mean value of relative tissue viability was 6.7% (1 h).
- Acceptance criteria met for variability between replicate measurements: Yes. The RSD were 0.9% (3 min treatment) and 0.0% (1h treatment), being <30%.
- Range of historical values:
Optical density negative control - 3 min: 1.197 - 3.077
Optical density negative control - 1 h: 1.377 - 2.571
% Tissue variability positive control 3 min: 9.6 - 57.3%
% Tissue variability positive control 1h: 4.1 - 24.2%

Any other information on results incl. tables

Absorbance values (OD 570 nm):

Incubation	Negative Control		Test Item		Positive Control
	Tissue 1	Tissue 2	Tissue 1	Tissue 2	Tissue 1	Tissue 2
3 min	1.694	1.691	1.726	1.707	0.427	0.407
	1.686	1.695	1.741	1.720	0.430	0.409
	1.688	1.678	1.740	1.713	0.433	0.411
1 h	1.723	1.643	1.652	1.647	0.141	0.154
	1.707	1.661	1.658	1.665	0.141	0.156
	1.744	1.644	1.660	1.661	0.145	0.155

Mean absorbance values - 3 minutes:

Designation	Negative Control	Test Item	Positive Control
Mean – blank (tissue 1)	1.651	1.697	0.391
Mean – blank (tissue 2)	1.649	1.675	0.370
Mean	1.650	1.686	0.381
RSD	0.1%	0.9%	3.9%

Mean absorbance values - 1 hour:

Designation	Negative Control	Test Item	Positive Control
Mean – blank (tissue 1)	1.686	1.618	0.104
Mean – blank (tissue 2)	1.611	1.619	0.116
Mean	1.648	1.619	0.110
RSD	3.2%	0.0%	8.1%

Tissue viability:

Test Item	Positive Control	Incubation
102.2%	23.1%	3 min
98.2%	6.7%	1 h

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

After 3 minutes and 1 hour treatment, the mean values of relative tissue viability of the test item were increased to 102.2% and 98.2%, respectively. These values value are well above the threshold for corrosivity (50%) and therefore, the test item is considered as non-corrosive to skin.

Executive summary:

An in-vitro skin corrosion test was performed according to the OECD Guideline 431 (GLP study). Two tissues of the human skin model EpiDermTM were treated with the test item for 3 minutes and 1 hour, respectively. The test item was applied to each tissue and spread to match the tissue size. Demineralised water was used as negative control and 8 M KOH was used as positive control. After treatment, the respective substance was rinsed from the tissues. Then, cell viability of the tissues was evaluated by addition of MTT, which can be reduced to a blue formazan. Formazan production was evaluated by measuring the optical density (OD) of the resulting solution. The criterion for optical density of the negative control (≥ 0.8 and ≤ 2.8) was fulfilled: optical density was 1.7 (3 minutes) and 1.6 (1 hour). The positive control showed clear corrosive effects. The criterion for the viability of the 1 hour experiment, expressed as % of the negative control (< 15%), was fulfilled, too. The mean value of relative tissue viability was 6.7%. The values for negative control and for positive control were within the range of historical data of the test facility. The mean value of relative tissue viability of the test item was increased to 102.2% after 3 minutes treatment. This value is above the threshold for corrosivity (50%). After 1 hour treat-ment, the mean value of relative tissue viability of the test item was reduced to 98.2%, lying above the threshold for corrosivity (15%). Therefore, the test item is considered as non-corrosive to skin.