Silicic acid, calcium salt

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 Aug. 2010 - 17 Aug. 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

performed under GLP

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:

other: Commission Regulation (EC) No. 761/2009, Method B.46: “In Vitro Skin Irritation: Reconstructed human epidermis model test” adopted 23. July 2009

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: OECD Guideline for the Testing of Chemicals, Draft Proposal for a New Guideline, In Vitro Skin Irritation: Reconstructed Human Epidermis (RhE) Test Method, Version 7.6, 9 September 2009

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: ECVAM international validation study on in vitro tests for acute skin irritation: Report on the validity of the EPISKIN and EpiDerm assays and on the Skin Integrity Function Test (Altern Lab Anim. 2007 Dec; 35 (6): 559-601)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: Protocol for IN VITRO EpiDermTM SKIN IRRITATION TEST (EPI-200-SIT), Rev. 3/23/2009, MatTek Corporation, Ashland, MA 01721, USA

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

crystalline calcium silicate hydrate (xonotlite - tobermorite)

IUPAC Name:

crystalline calcium silicate hydrate (xonotlite - tobermorite)

Constituent 2

Reference substance name:

calcium oxosilanebis(olate)

EC Number:

935-756-9

Cas Number:

1344-95-2

Molecular formula:

Xonotlite Ca6Si6O17(OH)2 Tobermorite Ca5(Si6O16)(OH)2.4H2O

IUPAC Name:

calcium oxosilanebis(olate)

Constituent 3

Reference substance name:

Amorphous silicic acid, calcium salt

Molecular formula:

CaSiO3.nH2O

IUPAC Name:

Amorphous silicic acid, calcium salt

Details on test material:

- Name of test material (as cited in study report): crystalline calcium silicate hydrate (xonotlite - tobermorite)
- Physical state: White solid
- Analytical purity: Confidential
- Lot/batch No.: Confidential
- Stability under test conditions: H2O: 96h; EtOH; acetone; CH3CN; DMSO: unknown
- Storage condition of test material: Room Temperature: (20 ± 5°C)

In vitro test system

Test system:

human skin model

Remarks:

Human skin model: EpiDermTM tissue (Epi-200-Kit)

Source species:

human

Cell type:

other: human reconstructed epidermis model followed by a cell viability test

Cell source:

other: Human skin model: EpiDermTM tissue (Epi-200-Kit)

Source strain:

other: not relevant

Justification for test system used:

The test consists of a topical exposure of the neat test item to a human reconstructed epidermis model followed by a cell viability test. Cell viability is measured by dehydrogenase conversion of MTT [(3-4,5-dimethyl thiazole 2-yl) 2,5-diphenyl-tetrazoliumbromide], in cell mitochondria, into a blue formazan salt that is quantitatively measured after extraction from tissues. The percent reduction of cell viability in comparison of untreated negative controls is used to predict skin irritation potential and is used for the purpose of classification as irritating or non-irritating according to chemicals law (EU CLP, UN GHS).

Vehicle:

unchanged (no vehicle)

Details on test system:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): DPBS-Buffer
- Time after start of exposure: 60 minutes

After further incubation for about 42 hours the tissues were treated with the MTT [(3-4,5-dimethyl thiazole 2-yl) 2,5-diphenyl-tetrazoliumbromide] solution for 3 hours ± 5 min, following extraction of the colorant from the cells. The amount of extracted colorant was determined photometrically at 570 nm.

SCORING SYSTEM: The photometric absorption of the negative controls is considered as 100%. For the mean of the 3 replicates of test item and positive control, formazan production is calculated as % photometric absorption compared with the negative control. Skin irritation potential of the test item is assessed as follows: % Formazan production < 50% of negative control = Irritant; % Formazan production > 50% of negative control = Non-irritant.

Control samples:

other: Negative control: Dulbecco’s Phosphate Buffered Saline (DPBS buffer without CaCl2 and without MgCl2). Positive control: Sodium dodecylsulphate (SDS), CAS No. 151-21-3, solution in deionised H2O containing 5% SDS.

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 24.3, 24.5 and 25.5 mg of the test item were applied to each of triplicate tissues.
- Concentration (if solution): 100 %, wetted with 25 µL Dulbecco’s Phosphate Buffered Saline (DPBS)

Positive and negative controls: 30 µL were dosed per tissue

Duration of treatment / exposure:

60 minutes

Number of replicates:

Three tissues of the human skin model EpiDerm™ were treated with the test item, the negative or the positive control.

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

other: % Formazan production

Remarks:

mean % of Negative Control

Run / experiment:

Tissue 1 , 2 and 3 with test substane

Value:

119.5

Vehicle controls validity:

not applicable

Remarks on result:

other:

Remarks:

Reversibility: Not applicable.

Results 2

Irritation / corrosion parameter:

other: % Formazan production

Remarks:

Mean % of Negative Control

Run / experiment:

Tissue 1, 2 and 3 with positive control

Value:

10.9

Vehicle controls validity:

not applicable

Positive controls validity:

valid

Remarks on result:

other:

Remarks:

Reversibility: Not applicable.

In vivo

Irritant / corrosive response data:

The relative absorbance values were increased to 119.5% after the treatment. This value is above the threshold for irritation (50%). Therefore, the test item is considered as not irritant. Note: optical density values of more than 100% of the negative control are not unusual.

Any other information on results incl. tables

The optical density of the negative control was well within the required acceptability criterion of 1.0 < mean OD < 2.5. The positive control induced a decrease in the relative absorbance as compared to the negative control to 10.9 % (required: ≤ 20%) ensuring the validity of the test system. Variation within replicates was within the accepted range for negative control, positive control and test item. For these reasons, the result of the test is considered valid.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

After the treatment with the test item, the relative absorbance values were increased to 119.5 %. This value is well above the threshold for irritation potential (50%). Therefore, Crystalline calcium silicate hydrates (xonotlite - tobermorite) is considered as not irritant in the Human Skin Model Test.

Executive summary:

The Skin Irritation Potential of crystalline calcium silicate hydrates (xonotlite - tobermorite) was deterrmined in the Human Skin Model Test following EU-Method B.46 and OECD Guideline, Draft Proposal for a New Guideline, In Vitro Skin Irritation: Reconstructed Human Epidermis (RhE) Test Method, Version 7.6, 9 September 2009. Three tissues of the human skin model EpiDerm^TM were treated with crystalline calcium silicate hydrates (xonotlite - tobermorite) for 60 minutes. 25 mg of the solid test item (wetted with 25 µL DPBS-buffer) were applied to each tissue and spread to match the tissue size. DPBS-buffer (Dulbecco’s Phosphate Buffered Saline) was used as negative control, 5% Sodium dodecylsulphate (SDS) solution was used as positive control. The photometric absorption of the negative controls is considered as 100%. For the mean of the 3 replicates of test item and positive control, formazan production is calculated as % photometric absorption compared with the negative control. Skin irritation potential of the test item is assessed as follows: % Formazan production < 50% of negative control = Irritant; % Formazan production > 50% of negative control =Non-irritant. After treatment with the negative control, the absorbance values were within the required acceptability criterion of 1.0 < mean OD < 2.5. The positive control showed clear irritating effects. Variation within tissues was acceptable (< 18%). After the treatment with the test item, the relative absorbance values were increased to 119.5 %. This value is well above the threshold for irritation potential (50%). Therefore, crystalline calcium silicate hydrates (xonotlite - tobermorite) is considered as not irritant in the Human Skin Model Test.