Sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18. Jan. 2016 - 21. Jan. 2016 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well-documented GLP OECD 492 guideline study on the registered substance itself without deviations

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Version / remarks:

OECD Guidelines for the Testing of Chemicals, Part 405, adopted 02. Oct. 2012 “Acute Eye Irritation / Corrosion”

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: OECD Guideline for the Testing of Chemicals, Part 492, adopted 28. Jul. 2015, “Re-constructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage”

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Kaiser-Friedrich-Straße 7, 55116 Mainz, Germany

Test material

Test material information

Constituent 1

Reference substance name:

Sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate

EC Number:

242-644-7

EC Name:

Sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate

Cas Number:

18880-36-9

Molecular formula:

C6H13NO3S3.Na

IUPAC Name:

sodium 3-[(dimethylcarbamothioyl)sulfanyl]propane-1-sulfonate

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate, DPS
- Substance type: pure substance
- Storage condition of test material: Room Temperature (20 ± 5°C)
- Other: Homogeneity: homogeneous

Test animals / tissue source

Species:

human

Strain:

other: three-dimensional human cornea model tissue model

Details on test animals or tissues and environmental conditions:

Test System

Specification
Commercially available EpiOcularTM kit.
The EpiOcularTM tissue consists of normal, human-derived keratinocytes which have been cultured to form a stratified squamous epithelium similar to that found in the human cornea. It consists of highly organized basal cells. These cells are not transformed or transfected with genes to induce an extended life span. The EpiOcularTM tissues are cultured in specially prepared cell culture inserts with a porous membrane through which nutrients can pass to the cells. The tissue surface is 0.6 cm².

Origin
EpiOcularTM tissues were procured from MatTek In Vitro Life Science Laboratories, Mylnské Nivy 73, 82105 Bratislava, Slovakia.
Designation of the kit: OCL-212-EIT
Day of delivery: 19. Jan. 2016
Batch no.: 21590

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 54.2 mg and 54.8 mg
- Concentration (if solution): The tissues were pre-wetted with 20 µL DPBS buffer.

VEHICLE
“Dulbecco`s Phosphate Buffered Saline” (DPBS)

Duration of treatment / exposure:

6h

Observation period (in vivo):

18h post-treatment incubation

Number of animals or in vitro replicates:

each 2 tissues for the test item, positive and negative controls

Details on study design:

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The inserts were thoroughly rinsed with DPBS.
- Time after start of exposure: 6h

SCORING SYSTEM: relative absorbances, MTT Assay

Results and discussion

In vitro

Results

Results 1

Irritation parameter:

other: viability, relative to negative control

Run / experiment:

mean

Value:

7.3

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: test item, time point: 6h

Results 2

Irritation parameter:

other: viability, relative to negative control

Run / experiment:

mean

Value:

38.5

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: positive control, time point: 6h

In vivo

Irritant / corrosive response data:

Under the conditions of the test system, sodium 3-[[(dimethylamino)thioxomethyl]thio] propanesulphonate, DPS is considered as eye irritant in the EpiOcularTM Eye Irritation Test, but no conclusion regarding its labelling as either GHS category 1 or 2 for serious eye damage resp. eye irritation potential can be drawn.

Any other information on results incl. tables

Findings and Results

 

Measured Values

As blank, the optical density of isopropanol was measured in eight wells of the 96-well-plate. The measured values and their mean are given in the following table:

 

Table Absorbance Values Blank Isopropanol (OD at 570 nm)

Replicate	1	2	3	4	5	6	7	8	Mean
Absorbance	0.035	0.038	0.035	0.038	0.036	0.038	0.037	0.039	0.037

 

The absorbance values of negative control, test item and positive control are given in the following table:

 

Table Absorbance Values Negative Control, Positive Control and Test Item (OD at 570 nm)

Desig-nation	Measure-ment	Negative Control	Positive Control	sodium 3-[[(dimethylamino)thioxomethyl] thio]propanesulphonate, DPS
Tissue 1	1	1.938	0.769	0.156
	2	1.882	0.759	0.152
Tissue 2	1	1.710	0.675	0.178
	2	1.678	0.664	0.174

 

From the measured absorbances, the mean of each tissue was calculated, subtracting the mean absorbance of isopropanol as given in the table below (= corrected values).

 

Table Mean Absorbance Negative Control, Positive Control and Test Item

Designation	Negative Control	Positive Control	sodium 3-[[(dimethylamino)thioxomethyl]thio] propanesulphonate, DPS
Mean – blank (Tissue 1)	1.873	0.727	0.117
Mean – blank (Tissue 2)	1.657	0.633	0.139

 

Comparison of Formazan Production

For the test item and the positive control, the following percentage values of formazan production were calculated in comparison to the negative control:

 

Table % Viability Positive Control and Test Item

Designation	Positive Control	sodium 3-[[(dimethylamino)thioxomethyl]thio] propanesulphonate, DPS
% Viability (Tissue 1)	41.2%	6.6%
% Viability (Tissue 2)	35.8%	7.9%
% Viability Mean	38.5%	7.3%

 

Assessment

Eye irritation is assessed using the criteria given in the following table (source: MatTek Corporation):

 

Table Assessment of Eye Irritation

% Viability	Assessment	GHS classification
> 60 %	Non eye irritant	No GHS category for eye irritation
≤ 60 %	Eye irritant	GHS category 1 or 2

 

Validity

Validity criteria and results are stated in the following table:

 

Table Validity

Criterion	Demanded	Found
OD of negative control	≥ 0.8 and ≤ 2.5	1.8
% Formazan production of positive control	< 50% of negative control	38.5%
Variation within replicates	< 20%	12.2% (negative control) 5.4% (positive control) 1.2% (test item)

 

Values for negative control and for positive control were within the range of historical data of the test facility.

Therefore, the experiment is considered valid.

Applicant's summary and conclusion

Interpretation of results:

study cannot be used for classification

Conclusions:

Testing was performed via a GLP OECD 492 guideline study on the registered substance itself. The present in vitro method is recommended in a tiered testing approach and the validity criteria are met, making the results sufficiently reliable to assess the corrosivity / eye irritating potential of sodium 3-[[(dimethylamino)thioxomethyl]thio] propanesulphonate to the eye. The present in vitro method allows the identification of chemical substances and mixtures to be classified as GHS category 1 or 2 or of substances which do not require classification. A limitation of this Test Guideline is that it does not allow discrimination between eye irritation/reversible effects on the eye (Category 2) and serious eye damage/irreversible effects on the eye (Category 1), nor between eye irritants (optional Category 2A) and mild eye irritants (optional Category 2B), as defined by UN GHS.
According to OECD Guideline no. 492, the test chemical is identified as potentially requiring classification and labelling according to UN GHS (Category 2 or Category 1) if the mean percent tissue viability after exposure and postexposure incubation is less than or equal (≤) to 60%.
After treatment with the test item, the relative absorbance values were reduced to 7.3 %.
This value is well below the threshold for eye irritation potential (≤ 60%).
Hence, no conclusion can be drawn whether the substance needs to be classified as as GHS category 1 or 2, for a clear distinction an in vivo study would be required based on the current state of the art. However, based on the tonnage band of the substance, in vivo testing is not required, and with regard to animal welfare no further testing will be performed and the result of the present study will be considered inconclusive.

Executive summary:

The eye irritating potential of sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate was assessed in a OECD 492 GLP guideline study.

One valid experiment was performed.

The test item sodium 3-[[(dimethylamino)thioxomethyl]thio]propanesulphonate, DPS was applied to a three-dimensional human cornea model tissue model in duplicate for an exposure time of 6 h.

The solid test item was applied to each tissue.

After treatment, the respective substance was rinsed from the tissue; then, cell viability of the tissues was evaluated by addition of MTT, which can be reduced to formazan. The formazan production was evaluated by measuring the optical density (OD) of the resulting solution.

Demineralised water was used as negative control, Methyl acetate was used as positive control.

The controls showed the following results: After treatment with the negative control, the absorbance values were within the required acceptability criterion of 0.8 ≤ mean OD ≤ 2.5, OD was 1.8. The positive control showed clear eye irritating effects, the relative absorbance value was reduced to 38.5 % (< 50%).

Variation within tissue replicates was acceptable (< 20%).

After treatment with the test item, the relative absorbance values were reduced to 7.3 %.

This value is well below the threshold for eye irritation potential (≤ 60%).

Under the conditions of the test system, sodium 3-[[(dimethylamino)thioxomethyl] thio]propanesulphonate, DPS is considered as eye irritant in the EpiOcularTM Eye Irritation Test, but no conclusion regarding its labelling as either GHS category 1 or 2 for serious eye damage resp. eye irritation potential can be drawn.