Dilithium glutarate

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 May 2017 - 26 June 2017

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

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

29 July 2016

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Pentanedioic acid, lithium salt (1:2)

EC Number:

608-319-2

Cas Number:

29126-51-0

Molecular formula:

C5H8O4.2Li

IUPAC Name:

Pentanedioic acid, lithium salt (1:2)

Test material form:

solid: particulate/powder

Details on test material:

White powder

Specific details on test material used for the study:

White powder
Source: ExxonMobil Research and Engineering (Paulsboro, NJ)
Lot#16-41779
Expiration date: 19 May 2018

In vitro test system

Test system:

human skin model

Remarks:

MatTEK EpiDerm SCT

Source species:

human

Cell type:

non-transformed keratinocytes

Justification for test system used:

The 3-Dimensional Human Dermal Epithelial Model (EpiDerm™, MatTek, Ashland, MA) is made up of normal human keratinocytes in serum free medium. The cells form an epithelial tissue that consists of organized basal, spinous, granular, and cornified layers analogous to those found in vivo. The EpiDerm™ model also contains epidermis-specific differentiation markers such as pro-filaggrin, the K1/K10 cytokeratin pair, involucrin, and type I epidermal transglutaminase, as well as keratohyalin granules, tonofilament bundles, desmosomes, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns characteristic of in vivo epidermis. Each lot of tissues was Quality Assured by MatTek, Inc. according to specific QC standards including: histology (cell layers), tissue viability (MTT mean optical density) and reproducibility (SD).

Vehicle:

unchanged (no vehicle)

Details on test system:

The normal human-derived keratinocytes were cultured at the air-liquid interface in a chemically defined medium on a permeable polycarbonate insert (surface 0.5 cm2). They were cultured in chemically defined serum free medium to form a multi-layered epithelium similar to that found in native epidermis. Each lot of tissues was Quality Assured by MatTek according to specific QC standards including: histology, tissue viability (MTT mean optical density), reproducibility (SD) and tissue thickness.

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: MatTEK EpiDerm 200-SCT
- Tissue batch number(s): 26404
- Delivery date: 23 May 2017
- Date of initiation of testing: 23 May 2017

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 3 minute exposure at room temperature and 60 minute exposure at ~37°C and ~5% CO2

REMOVAL OF TEST MATERIAL AND CONTROLS
-Volume and number of washing steps: Tissues were rinsed approximately 20 times with 1 mL DPBS, and gently blotted with cotton swab.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1.0 mg/mL
- Incubation time: 3 hours
- Spectrophotometer: Synergy H4 Spectrophotometer
- Wavelength: 570 nM

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: MTT QC assay result OD =1.839 ± 0.079
- Barrier function: ET-50 Asaay Result = 8.04 hrs
- Morphology: Viability and barrier function are within acceptable ranges and indicate appropriate formation of the epidermal barrier, the presence of a functional startum corneum, a viable basal cell layer and intermediate spinous and granular layers.
- Contamination: Biological contaminants not detected

NUMBER OF REPLICATE TISSUES: 3

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 negative control

yes, concurrent positive control

Amount/concentration applied:

~25 mg of the test substance (24.7 mg for 3 minute tissue 1, 25.2 mg for 3 minute tissue 2, 25.3 mg for 3 minute tissue 3, 24.7 mg for 60 minute tissue 1, 24.6 mg for 60 minute tissue 2 and 24.6 mg for 60 minute tissue 3)

Duration of treatment / exposure:

Tissues were exposed to controls and test substance for approximately 3 minutes at room temperature and approximately 60 minutes in a humidified incubator at ~37°C and ~5% CO2.

Number of replicates:

n=3

Results and discussion

In vitro

Results

Results 1

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

3 minutes

Value:

87.8

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Results 2

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

60 minutes

Value:

79.9

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

In the in-vitro EpiDerm SCT Skin Model, the relative mean tissue viability obtained after 3-minute and 1-hour treatments with Dilithium glutarate compared to the negative control tissues was 87.8% and 79.9%, respectively. These findings do not warrant classification of Dilithium Glutarate as a Category 1 Skin Corrosive under the Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).

Executive summary:

The MatTek EpiDerm™ SCT skin model was used to assess the potential dermal corrosivity of dilithium glutarate by determining the viability of the tissues following exposure to the test substance via MTT. The objective of this study was to assess the dermal corrosivity of neat (undiluted) Dilithium glutarate. Tissues were exposed to test substance and controls for three minutes and one hour.

Pre-testing for coloration and MTT auto-reduction were negative, therefore no data corrections were necessary. The MTT data show the positive control, 8N potassium hydroxide (KOH), reduced tissue viability to 29.0% of negative control after 3 minutes exposure and to 9.6% of negative control after 1 hour exposure. The MTT data show that the test substance, dilithium glutarate reduced tissue viability to 87.8% of negative control after 3 minutes exposure and to 79.9% of negative control after 1 hour exposure. These findings do not warrant classification of Dilithium Glutarate as a Category 1 Skin Corrosive under the Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).