Tributyl-2-thiourea

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 November 2016

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 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Version / remarks:

26 July 2013

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Tributyl-2-thiourea

EC Number:

219-350-2

EC Name:

Tributyl-2-thiourea

Cas Number:

2422-88-0

Molecular formula:

C13H28N2S

IUPAC Name:

1,1,3-tributylthiourea

Test material form:

liquid

Details on test material:

- Name of test material (as cited in study report): Tri butyl thiourea
- Appearance: Clear pale to medium brown liquid
- Storage conditions: At room temperature

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent vehicle

yes, concurrent positive control

Amount / concentration applied:

TEST MATERIAL
- Amount applied: 750 μl per cornea

NEGATIVE CONTROL
- Amount applied: 750 µl of physiological saline per cornea

POSITIVE CONTROL
Amount applied: 750 µl 99.9% ethanol per cornea

Duration of treatment / exposure:

10 minutes

Number of animals or in vitro replicates:

Test item: 3
Negative control: 3
Positive control: 3

Details on study design:

TEST SITE
- Isolated bovine cornea

REMOVAL OF TEST SUBSTANCE
- Washing: yes, with cMEM (Eagle’s Minimum Essential Medium, Life Technologies)
- Time after start of exposure: 10 minutes

SCORING SYSTEM:
- After exposure the cornea is thoroughly rinsed to remove the test substance followed by incubation for 120 ± 10 minutes in cMEM. Then, corneas were incubated in sodium-fluorescein solution for 90 ± 5 minutes (both incubations at 32 ± 1°C).

- The mean opacity and mean permeability values (OD490) were used for each treatment group to calculate an in vitro score:

In vitro irritancy score (IVIS) = mean opacity value + (15 x mean OD490 value).

TOOL USED TO ASSESS SCORE:
- opacitymeter and microplate reader

DATA EVALUATION:
A test substance that induces an IVIS ≤ 3 is not classified for eye irritancy (UN GHS: no category);
A test substance that induces an IVIS > 55 is defined as a corrosive or severe irritan (UN GHS: catgegory 1);
For a test substance that induces an IVIS >3 and ≥ 55, no prediction on irritant potency can be made.

Results and discussion

In vitro

Results

Irritation parameter:

in vitro irritation score

Run / experiment:

Mean of 3 replicates

Value:

0.8

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

(-0.2)

Positive controls validity:

valid

Remarks:

(50.2)

Other effects / acceptance of results:

- The result was based on the mean value of the individual scores (-0.7, 0.6 and 2.4)
- One of the negative control eyes was excluded from the analysis since the IVIS was >3 due to an opacity value of 3.1 which was just outside the historical control data range of -2.9-3.0. However, since the other 2 eyes completely met the acceptance criteria and the test item results were not influenced by this result, the deviation does not affect the study outcome.
- The acceptability criteria were met, therefore the study is considered valid.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Based on the outcome of a Bovine Corneal Opacity and Permeability test (BCOP) performed according to OECD gudieline and GLP principles, it is concluded that Tri butyl thiourea is not irritant or corrosive for the eye.

Executive summary:

A Bovine Corneal Opacity and Permeability test (BCOP) was performed with Tri butyl thiourea according to OECD guideline 437 and GLP principles. Tri butyl thiourea was applied undiluted (750 µL/ cornea, n=3). The mean in vitro irritancy score of the positive control (ethanol) was 50, and the mean in vitro irritancy score of the negative control (physiological saline) was 0.9. It was therefore concluded that the test conditions were adequate and that the test system functioned properly. Tri butyl thiourea did not induce ocular irritation through opacity or permeability, resulting in a mean in vitro irritancy score of 0.8 after 10 minutes of treatment. Since Tri butyl thiourea induced an IVIS ≤ 3, no classification is required for eye irritation or serious eye damage.