Registration Dossier

Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2012-03-28 to 2012-04-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
During the MTT assay isopropanol / 2 N HCl 49:1 (v/v) should have been used as extractant solution. Due to inattention isopropanol without HCl was used as extractant solution. Due to Harlan CCR’s experimental experience concerning formazan salt extraction with and without acidifying of isopropanol, and due to the long extraction period of nearly three days, the risk of inadequate extraction is minimized. Therefore, the described deviation did not have a detrimental impact on the outcome of the study.
Justification for type of information:
Zircon, cadmium yellow is a zircon-type oxide/pigment with the main structural element ZrSiO4 (Zr in an dodecahedral O environment) which forms a strong and inert matrix. Zr and Si are the main components with percentages of ~46% w/w and 15% w/w respectively. The amount of Cd as component is about 2% w/w.

The read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated is a zircon-type pigment as well with an identical crystallographic structure and a very similar composition. Zr content is ~46% w/w and the Si content is ca. 14% w/w. Cd is present in about 4.7% w/w. Minor amounts of Se and S (1.53 and 1.04% w/w, respectively) are present as well.

Besides the obvious structural analogy the solubility of both pigments in aqueous and physilogical media are as follows (determination of Zr and Cd):

Solubility of Cd from the pigment Zircon, cadmium yellow in physiological media was in a range of 0.180 µg/L (PBS) and 0.398 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from 0.140 µg/L (GMB) - 0.722 µg/L (GST) was measured.

Solubility of Zr from the pigment Zircon, cadmium yellow in physiological media was in a range of below LOD and 0.812 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from below LOD (ASW) - 1.44 µg/L (ALF) was measured.

The read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated afforded after 2 hours a solubility for the element Cd in range of 0.07 µg/L (GMB) 2.58 µg/L (GST) and after 24 hours a solubility of 0.07 µg/L (GMB) to 6.13 µg/L (GST).

Solubility of Zr from the pigment Silicic acid, zirconium salt, cadmium pigment encapsulated in physiological media was in a range of below LOD and 0.52 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from below LOD - 1.25 µg/L (ALF) was measured.

T/D testing of the pigment Zircon, cadmium yellow afforded the following solubility at 1mg loading after 28 days:
Cadmium: below LOD (<0.0048) and 0.2077 ± 0.0993μg/L at pH 8 and pH 6, respectively
Zirconium:
T/D testing of the read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated afforded the following solubility at 1mg loading after 28 days:
Cadmium: 0.34 ± 0.09 μg/L and 0.86 ± 0.39 μg/L at pH 8 and pH 6, respectively
Zirconium:
In sum, the two zircon type pigments are structurally identical with very similar composition and both show a very low solubility in different artificial and aqueous media. In fact, the read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated shows slightly higher dissolution and bioaccessibility without showing any signs of systemic or local toxicity in various studies (acute inhalation, skin/eye irritation, sensitisation). No toxicity on algae, fish and invertebrates could be observed in respective studies.
Hence, read-across to Silicic acid, zirconium salt, cadmium pigment encapsulated is fully justified.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Version / remarks:
2010-07-22
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)
Version / remarks:
2009
Deviations:
no
Qualifier:
according to
Guideline:
other: ECVAM international validation study on in vitro tests for acute skin irritation (Altern Lab Anim. 2007 Dec; 35 (6):559-601)
GLP compliance:
yes (incl. certificate)
Remarks:
signed 2009-03-30

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Details on test material:
- Name of test material (as cited in study report): Silicic acid, zirconium salt, cadmium pigment encapsulated
- Physical state: solid, bright red powder, odourless
- Stability in solvent: not relevant

Specific details on test material used for the study:
STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at room temperature, kept dry in closed container

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
other: normal, human-derived epidermal keratinocytes
Cell source:
other: not specified
Source strain:
not specified
Details on animal used as source of test system:
not applicable
Justification for test system used:
In an international validation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiSkin™ and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.
Vehicle:
water
Details on test system:
RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiSkin™ tissues (purchased from SkinEthic Laboratories)
- Tissue batch number: 12-EKIN-013
- Experiation date: 2012-04-02
- Delivery date: 2012-03-28
- Date of initiation of testing:2012-03-28

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1.5 °C
- Temperature of post-treatment incubation: 37 ± 1.5 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
After the end of the treatment interval the inserts were removed from the plate and the tissues were rinsed with PBS to remove any residual test material. Then the inserts were placed in the plates with maintenance medium. The tissues were incubated for about 42 hours at 37 ± 1.5 °C, 5 ± 0.5% CO2.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 0.3 mg/mL
- Incubation time with MTT: 3 hours
- Extraction of formazan: after the incubation period, MTT solution was aspirated from the wells and the wells were rinsed with PBS. Tissue samples were cut out of the inserts with a biopsy punch and transferred into plastic vials. The tissue samples were immersed into extractant solution by pipetting 0.5 mL extractant solution (isopropanol) into each vial. The tissue samples were completely covered by isopropanol. The vials were sealed to inhibit isopropanol evaporation. The formazan salt was extracted for about 69 hours in the refrigerator.
Per each tissue sample 2 x 200 μL aliquots of the formazan blue solution were transferred into a 96-well flat bottom microtiter plate. Optical density (OD) was read with a spectrophotometer. Mean values were calculated from the 2 wells per tissue sample.
- Spectrophotometer: microplate reader (Versamax® Molecular Devices)
- Wavelength: 570 nm
- Filter: 1 nm

TEST FOR DIRECT MTT REDUCTION
To test for the ability of the test item to directly reduce MTT approx. 10 mg of the test item were added to 1 mL of MTT solution and the mixture was incubated in the dark at room temperature for 60 minutes. Untreated MTT medium was used as control. If the MTT solution colour turned blue/purple, the test item was persumed to have reduced the MTT.

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Barrier function: tissues passed analysis for tissue functionality
- Morphology: well-differentiated epidermis consisting of a basal layer, several spinous and granular layers and a thick stratum corneum.
- Contamination: absence of bacteria, fungus and mycoplasma as well as absence of HIV 1 and 2 antibodies, hepatitis C antibodies and absence of hepatitis B antigen
Please also refer to the field "Attached background material" below.

PREDICTION MODEL / DECISION CRITERIA
The mean optical density of the three negative control tissues was calculated. This value corresponds to 100% tissue viability in the current test. For each individual tissue treated with the test item or the positive control the individual relative tissue viability was calculated according to the following formula: relative viability(%) = (OD test item/ OD negative control) x 100
For the test item and the positive control the mean relative viability ± standard deviation of the three individual tissues was calculated and used for classification according to the following prediction model: if the mean relative tissue viability of three individual tissues is less than or equal to 50% of the negative control, the test item needs to be classified and labeled for its skin irritation potential: Category 2 – irritant, H315 according to Regulation (EC) No 1272/2008.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): approx. 10 mg

VEHICLE
- Amount(s) applied (volume or weight with unit): 20 µL of deionised water

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

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 µL
Duration of treatment / exposure:
15 ± 1 minutes
Duration of post-treatment incubation (if applicable):
about 42 hours
Number of replicates:
Test item: triplicates
Negative control: triplicates
Positive control: triplicates

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Remarks:
(mean)
Value:
92.3
Vehicle controls validity:
not examined
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Other effects / acceptance of results:
- OTHER EFFECTS:
- Direct-MTT reduction: optical evaluation of the MTT-reducing capacity of the test item after 1 hour incubation with MTT-reagent did not show blue colour.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: after treatment with the negative control, the absorbance values (1.233, 1.178, and 1.129, respectively) were well within the required acceptability criterion of mean OD ≥ 0.6 till ≤ 1.5 for the 15 minutes treatment interval.
- Acceptance criteria met for positive control: treatment with the positive control induced a decrease in the relative absorbance as compared to the negative control to 21.4 % (acceptability criterion: positive control is ≤ 40 %).
- Acceptance criteria met for variability between replicate measurements: the standard between the % variabilities of the test item, positive and negative controls were below 5 % (threshold of the "OECD Guideline for the Testing of Chemicals 439: In vitro Skin Irritation: Reconstructed Human Epidermis Test Method”: 18%).
Please refer to the field "Any other information on results incl. tables" below

Any other information on results incl. tables

HISTORICAL DATA

Positive Control

Negative Control

Number of Studies

163

Number of Studies

163

Period

July 2007 – March 2012

Period

July 2007 – March 2012

Mean Viability

19.7%

Mean OD

1.012

Standard Deviation

10.0%

Standard Deviation

0.215

Range of Viabilities

0.7% - 39.7%

Range of ODs

0.590 – 1.680

Table 1: Results after treatment with silicic acid, zirconium salt, cadmium pigment encapsulated and controls

Dose group

Treatment Interval

Absor-bance
570 nm
Tissue 1*

Absor-bance
570 nm Tissue 2*

Absor-bance
570 nm Tissue 3*

Mean Absor-bance
of 3 Tissues

Rel. Absor-bance

[% of Negative Control]**

Negative Control

15 min

1.233

1.178

1.129

1.180

100.0

Positive Control

15 min

0.254

0.254

0.250

0.253

21.4

Test item

15 min

1.057

1.089

1.124

1.090

92.3

* Mean of two replicate wells after blank correction

** relative absorbance per treatment group [rounded values]: 100 x (meanabsorbancetestitem)/(mean absorbancenegative control)

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test item is not irritating to the skin.
According to the Regulation (EC) No 1272/2008 and subsequent regulations, the test item is not irritating to the skin.