Pyridinium dichromate

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August - November 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

13 April 2004

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.40 (In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test (TER))

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Pyridinium dichromate

EC Number:

243-478-8

EC Name:

Pyridinium dichromate

Cas Number:

20039-37-6

Molecular formula:

C5H5N.1/2Cr2H2O7

IUPAC Name:

pyridinium dichromate

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: MatTek´s EpiDerm System consists of normal, human-derived epidermal keratinocytes which have been cultured 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) are cultured on specially prepared cell culture inserts (MILLICELLs, 10 mm ) and shipped as kits, containing 24 tissues on shipping agarose.

REMOVAL OF TEST MATERIAL AND CONTROLS
- washing with PBS

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
After incubation with the test substance and washing with PBS, the tissues were incubated with MTT medium at 37 °C and 5 % CO2. After 3 hours, the MTT medium was aspirated from all wells and the tissues were gently rinsed with PBS (2 times). For extraction, the tissues were incubated with extractant solution (isopropanol) for 2 hours with shaking. After the extraction period, the tissues were pierced with an injection needle and the extract (now a blue formazan solution) was allowed to run into the well from which the tissue was taken. The 24-well plates were placed on a shaker for 15 minutes until the solutions were homogeneous in colour. For the Epiderm Skin Corrosivity Test per each tissue 3 × 200 μL aliquots of the blue formazan solution were transferred into a 96-well flat bottom microtiter plate and the OD was measured using the extractant solution as blank in a plate spectrophotometer at 570 nm, without reference filter.
- Incubation time: 3 h at at 37 °C and 5 % CO2
- Wavelength: 570 nm

Cell viability
Cell viability was calculated for each tissue as percent of the mean of the negative control tissues. The skin corrosivity/irritation potential of the test substance was classified according to remaining cell viability obtained after test substance treatment with either of the two exposure times.

NUMBER OF REPLICATE TISSUES:
Two tissue replicates were used for each treatment (exposure time), including distilled water as negative and 8N KOH as positive control.

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

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:
The application spoon was filled with 25 mg finely grounded test substance. The "spoonful" was levelled by gently scratching the excess material away, avoiding compression. 25 µL H2O were added for wetting of the test substance.

NEGATIVE CONTROL
- Amount(s) applied: 50 µL

POSITIVE CONTROL
- Amount(s) applied: 50 µL

Duration of treatment / exposure:

3 minutes and 1 hour

Number of replicates:

2

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1st (3 min exposure)

Value:

75.5

Negative controls validity:

valid

Remarks:

100%

Positive controls validity:

valid

Remarks:

15.1%

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1st (1 hour expoure)

Value:

1

Negative controls validity:

valid

Remarks:

100%

Positive controls validity:

valid

Remarks:

10.7%

Applicant's summary and conclusion

Interpretation of results:

Category 1 (corrosive) based on GHS criteria

Conclusions:

According to the results of this study, the test substance is considered to be corrosive to skin.

Executive summary:

The EpiDerm Skin Corrosivity/Irritation Test (Model EPI-200) was performed to reveal possible irreversible tissue damages of the skin following the application of the test substance.

The test substance (50 µL) was topically applied for 3 minutes and 1 hour to the epidermal surfaces of three-dimensional human epidermis models, followed by immediate determination of the cytotoxic effect. Two tissue replicates were used for each treatment (exposure time), including deionised water as negative and 8N KOH as positive control. Investigations performed were in conformance with the Regulation (EC) 440/2008: B.40.BIS. "In vitro skin corrosion: human skin model" and the OECD-Guideline 431 "In Vitro Skin Corrosion: Human Skin Model Test ".

Results:

The mean percentage viability of the test item-treated skin discs after 3 minutes of exposure was 75.5 % which is above the threshold of 50 % for classification. The mean percentage viability of the test–item treated skin discs after 1 hour of exposure was 1.0 % which is below the threshold of 15 % for classification.

Conclucion:                            

According to the results of this study, the test substance is considered to be corrosive to skin.