2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06-13-16 to 09-20-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Aliquots were removed from each prepared concentration every day on fresh and old solutions for the definitive test.
Analytical analysis was performed immediately after sampling.

Vehicle:

no

Details on test solutions:

Test solutions were prepared from dilutions of a stock solution.
439 µL of test item was poured into a 5L volumetric flask, the volume was then made up to 5000 mL with test medium.
The solution was kept under high speed stirring at ambient temperature during approximately 10 minutes with a magnetic stir bar.

No undissolved particles were observed, this solution was thus not filtered before dilution.
The pH of the test solutions were not adjusted.
Test solutions were renewed everyday throughout the 96h test period (semi-static test).

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

The test organisms were Danio rerio (Teleostei, Cyprinidae), obtained on the 28 July 2016 from a recognised supplier: La Grande Rivière France (69490 Saint-Forgeux).
All fish were in good health and free from any apparent malformation.
Mortality of the batch was less than 5% in the week preceding the start of the study.
No disease treatments were administered throughout holding and testing.

Holding was maintained within the laboratory at a temperature of 21-25°C in glass tanks.
A light cycle of 12 h light and 12 h dark was applied, illumination being provided by fluorescent tubes (intensity between 400 and 800 lux at the surface of the tanks).
Tanks were aerated to ensure that the dissolved oxygen concentration is at least 60% of air saturation value in holding tanks and in test tanks.
During holding, fish were fed twice per day with ground flake food TetraMin®.

The fish were not fed for a period of 24h prior to test commencement and throughout the duration of the test

Fish were added to the test tanks within 30 min of the completion of preparation of the test solutions.
All test fish were weighed prior to the test and a representative number of test fish batch (10 at random) was measured after the test to assess compliance with guideline criteria.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

22.7 °C

pH:

7.5 - 8.0

Dissolved oxygen:

79.0 - 102.3 % saturation

Salinity:

Freshwater.

Conductivity:

Not measured.

Nominal and measured concentrations:

Nominal concentrations:
0 ; 0.9 ; 2.1 ; 4.5 ; 10 ; 22 mg/L

Geometric mean concentrations:
0 ; 0.09 ; 0.16 ; 0.23 ; 5.7 ; 16.1 mg/L

Details on test conditions:

- Test tanks (filled with 2.5 L of test solution) containing fish were incubated with a photo period of 9 hours of darkness per 24 h
- All test tanks were made of clear glass and covered by plates with ventilation holes to minimise evaporation and avoid the entry of dust into the solutions.
- Test solutions were prepared using the synthetic medium.
- Chemical reagents used for the preparation of the dilution water was were of “analytical grade”.
- The control treatment was maintained under the same conditions, with no test item.

Reference substance (positive control):

yes

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

5.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

mortality (fish)

Details on results:

Mortalities are presented in table 1.
No mortality were observed in the control.
No abnormal behaviour was observed.
Calculated 96h-LC50 is 6.2 mg/L.

Results with reference substance (positive control):

The sensitivity of the test system and the methodology are evaluated with every batch of fish by performing an acute toxicity test on potassium dichromate. The values of 24h-LC50 obtained with the batch used was as follows: Batch 16/Br/01/2: 24h-LC50 = 173.6 mg/L (obtained on 11 August 2016). This result is consistent with the laboratory control quality chart.

Reported statistics and error estimates:

Raw data were treated according to the recommendations of the guideline. All statistical analysis were conducted using the Software ToxRatPro Version 3.1.0.

As there was evidence that the concentration of the substance being tested were not satisfactorily maintained within ± 20% of the nominal or measured initial concentration throughout the test, analysis of the results was based on geometric mean concentration during exposure.

Sublethal observations / clinical signs:

Table 1:

Test solution (mg/L)	Cumulative dead fish					Mortality at the end of the period
	T0	T24h	T48h	T72h	T96h
Control	0	0	0	0	0	0.0%
0.9	0	0	0	0	0	0.0%
2.1	0	0	0	1	1	14.3%
4.5	0	0	0	0	0	0.0%
10.0	0	0	0	1	1	14.3%
22.0	0	2	6	7	7	100.0%

Validity criteria fulfilled:

yes

Conclusions:

The acute toxicity of the test item to Danio rerio exposed for 96h was assessed according to the OECD 203 Guideline. Validity criteria were fulfilled.
An important loss of the test item was observed. As a consequence the exposure concentrations were based on the geometric mean of measured concentrations. On this basis, 96h-LC50 was 5.7 mg/L

Executive summary:

This study was designed to determine the effects of the test item to Danio rerio over a 96h period with static conditions (Range–finding test) then semi-static test (Definitive test), according to the OECD 203 Guideline. The test solutions (including control) were prepared from dilutions of a stock solution and renewed daily throughout the test (semi-static test).

Chemical analysis of the test item throughout the test period have shown unstability of the substance. That's why geometric means of measured concentrations were used to determine 96h-LC50 = 5.7 mg/L

Description of key information

This study was designed to determine the effects of the test item toDanio rerioover a 96h period with static conditions (Range–finding test) then semi-static test (Definitive test), according to the OECD 203 Guideline. The test solutions (including control) were prepared from dilutions of a stock solution and renewed daily throughout the test (semi-static test).

Chemical analysis of the test item throughout the test period have shown unstability of the substance. That's why geometric means of measured concentrations were used to determine 96h-LC50 = 5.7 mg/L

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

5.7 mg/L

Marine water fish

Marine water fish

Effect concentration:

0.5 mg/L