Cesium tungsten oxide

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 Nov-21 Nov 2016

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

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted 28 July 2015

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Commission Regulation (EC) No. 761/2009, adopted 23 July 2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

The Department of Health of the Government of the United Kingdom, London, England

Test material

Test material information

Constituent 1

Test material form:

solid: nanoform, no surface treatment

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

The reconstructed human epidermis model showed evidence of being a reliable and relevant stand-alone test for predicting rabbit skin irritation being used as a replacement for the Draize Skin irritation test. Test items are applied topically as the dermal route is the most likely exposure route and the results of the study are believed to be of value in predicting the likely skin irritancy potential to man.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: The EpiSkin™ model
- Tissue batch number(s): 16-EKIN-046
- Delivery date: 15 Nov 2016
- Date of initiation of testing: 15 Nov 2016

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment/exposure: 37 °C
- Temperature of post-treatment incubation: 37 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: All tissues were rinsed repeatedly with DPBS with Ca++ and Mg++ for approximately 40 seconds after the exposure period.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL
- Incubation time: 3 h
- Spectrophotometer: Anthos 2001 microplate reader
- Wavelength: 562 nm
- Filter: no reference filter was used
- Linear OD range of spectrophotometer: no data

NUMBER OF REPLICATE TISSUES: 3
CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
- Fresh tissues/killed tissues: killed tissues
- Procedure used to prepare the killed tissues: incubating in distilled water at 37 °C for 48 h
- N. of replicates: 3
- Method of calculation used: direct comparison of treated to untreated water-killed tissues

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

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be non-corrosive to skin if the viability after 15 minutes exposure period to the test substance followed by 42 hours post-exposure incubation is greater than or equal to 50%.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied: 10 mg

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): DPBS, 10 µL

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

Duration of treatment / exposure:

15 min

Duration of post-treatment incubation (if applicable):

42 h

Number of replicates:

3

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

15-min exposure followed by 42-hour post-exposure incubation period

Value:

113.5

Vehicle controls validity:

not examined

Negative controls validity:

valid

Remarks:

100%

Positive controls validity:

valid

Remarks:

11.1%

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Direct-MTT reduction: An assessment found the test item was able to directly reduce MTT. The results of the procedure showed that no interference due to direct reduction of MTT occurred. It was therefore considered unnecessary to use the results of the water-killed tissues for quantitative correction of results or for reporting purposes.
- Colour interference with MTT: An assessment found the test item had the potential to cause colour interference with the MTT endpoint. The results of the procedure showed that no colour interference occurred. It was therefore considered unnecessary to use the results of the colour correction tissues for quantitative correction of results or for reporting purposes.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: The mean OD562 for the negative control treated tissues was 0.844 and the standard deviation value of the viability was 14.2%. The negative control acceptance criteria was therefore satisfied.
- Acceptance criteria met for positive control: The relative mean tissue viability for the positive control treated tissues was 11.1% relative to the negative control treated tissues and the standard deviation value of the viability was 1.5%. The positive control acceptance criteria was therefore satisfied.
- Acceptance criteria met for variability between replicate measurements: The relative mean tissue viability for the test item treated tissues was 113.5% after a 15-minute exposure period and 42-hour post-exposure incubation period. The standard deviation calculated from individual tissue viabilities of the three identically test item treated tissues was 13.6%. The test item acceptance criteria was therefore satisfied.

Any other information on results incl. tables

 Mean OD562 Values and Viabilities for the Negative Control, Positive Control, and Test Items

Item	OD562 of tissues	Mean OD562 of triplicate tissues	± SD of OD562	Relative individual tissue viability (%)	Relative mean viability (%)	± SD of Relative mean viability (%)
Negative control item	0.839	0.844	0.120	99.4	100*	14.2
	0.966			114.5
	0.727			86.1
Positive control item	0.090	0.094	0.013	10.7	11.1	1.5
	0.109			12.9
	0.084			10.0
Test item	0.906	0.958	0.115	107.3	113.5	13.6
	1.090			129.1
	0.879			104.1

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

OD = Optical density

SD = Standard deviation

Applicant's summary and conclusion

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulation (EC) No 1272/2008

Conclusions:

EU CLP: Not classified for Irritation
UN GHS: Not classified for Irritation (Category 3: cannot be determined)

Executive summary:

The skin irritation potential of the undissolved test item was assessed in accordance with OECD Guidance 439.  Triplicate tissues were exposed to the test item for ≥ 15 minutes. At the end of the exposure period the test item was rinsed and the tissues incubated for a further 42 h in the presence of maintenance solution. Each tissue was then loaded with MTT for 3 h and any resultant colour extracted. After incubation and extraction, the solutions were aliquoted for absorbance measurements. Absorbency at 562 nm for each well was measured using a spectrophotometer. The test item did not cause interference in interpretation of the MTT colourmetric assy. Mean viability of tissues exposed to the test substance after 60 minutes were > 100 %. The quality criteria required for acceptance of the results were met.  Under the conditions of this study the test substance is considered not to be irritant to the skin in accordance with EU CLP regulation.