1,3,4-thiadiazole-2,5-dithiol

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:

2017-01.10 - 2017-04-04 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

as of 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0, 100 mg/L (limit test)
- Sampling method: One litre of all treatments was removed for supporting chemical analysis just after freshly prepared.
- Sample storage conditions before analysis: The supporting analyses could not be performed on the same day of collection of the specimens. Therefore, these specimens from freshly prepared test solutions were stored deep-frozen and analysed later-on after thawing.

Vehicle:

no

Details on test solutions:

REPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was tested at concentrations 10 mg/L (screening test) and 100 mg/L (screening test and main test, performed as a limit test) prepared in drinking water from the municipal drinking water supply entering the institute. The drinking water used for the test refers to the OECD Guideline 203 and is controlled regularly (monthly). The test item was introduced into the water by direct weighing into the different treatments to give the final nominal concentrations. pH of the test solutions was not adjusted. The maximum nominal concentration used for the test was 100 mg/L. As the test item may be biodegraded partially the test was conducted semi-statically. For this purpose, the test solutions were prepared daily.
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): not stated

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: zebra fish
- Source: Aquahandel.de (Holtenser Weg 6a, 37186 Moringen)
- Length at study initiation (length definition, mean, range and SD): length ≈ 2.0 ±1.0 cm

ACCLIMATION
- Feeding frequency during acclimation: The fish were not fed 24 hr prior to testing.

FEEDING DURING TEST
The fish were not fed 24 hr prior to testing and during the whole test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Post exposure observation period:

none

Hardness:

The hardness of the diluting water at the period of the fish test was calculated to be equivalent to 263 mg/L CaCO3.

Test temperature:

21.3 to 24.2 °C (screening test)
21.3 to 23.2 °C (main test)

pH:

The pH of the test solutions was not adjusted.
7.81 to 8.66 °C (screening test)
7.22 to 8.37 (main test)

Dissolved oxygen:

8.0 to 8.7 mg O2/L (screening test)
7.8 to 8.7 mg O2/L (main test)

Nominal and measured concentrations:

Nominal: 0, 100 mg/L (limit test)
Measured (after correction): 0, 104.4 - 105.1 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass aquaria with a volume of about 5 L
- Aeration: The test solutions were aerated during the incubation period (96 hr) in order to verify an oxygen content of >60% of the saturation value during the study
- Renewal rate of test solution (frequency/flow rate): daily
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
- Culture medium different from test medium: no
- Intervals of water quality measurement: monthly

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : behaviour, mortality (daily)

TEST CONCENTRATIONS
- Test concentrations: 0, 100 mg/L (limit test)

Reference substance (positive control):

not required

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- Behavioural abnormalities: None, animals without symptoms
- Mortality of control: none
- Other adverse effects control: none stated
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

Results with reference substance (positive control):

n/a

Validity criteria fulfilled:

yes

Conclusions:

The study was performed according to OECD TG 203 with no relevant deviations, the results were so obtained via a scientifically reasonable method. Hence, there is no doubt that the obtained results are not reliable: Under the conditions used for the test, no significant toxic effects of the test item towards fish were observed at 100 mg/L (main test, performed as a limit test). As a conclusion of the analytical part of this study, it can be stated that the concentrations of the test item remained sufficiently stable during incubation. Based on this, the reported effect concentrations should refer to the nominal concentrations tested. The following LC-values (effective concentrations) were determined accordingly:
Mortality
LC50 > 100 mg/L
LOEC > 100 mg/L
NOEC >= 100 mg/L
Based on these results, the test item does not need to be classified as acute or chronic toxic to the aquatic environment.

Executive summary:

2,5-Dimercapto-1,3,4-thiadiazole (“DMTD”) was tested for acute toxicity towards fish according to OECD Guideline No.203 (1992) under GLP using zebra fish. In order to investigate the influence of the test item towards the fish, the animals were exposed to up to 100 mg of the test item per litre of test solution. Under the conditions used for the test, no significant toxic effects of the test item towards fish were observed at 100 mg/L (main test, performed as a limit test). As a conclusion of the analytical part of this study, it can be stated that the concentrations of 2,5-Dimercapto-1,3,4-thiadiazole (“DMTD”) remained sufficiently stable during incubation. Based on this, the reported effect concentrations should refer to the nominal concentrations tested. The following LC-values (effective concentrations) were determined accordingly:

On the Basis of the Nominal Concentrations [mg/L]

LC10       >100          95%-CL                lower          n.d.                                         upper          n.d.                                                                 LC20       >100          95%-CL                lower          n.d.                                         upper          n.d.                                                                                                            LC50       >100          95%-CL                lower          n.d.                                         upper          n.d.                                                                             Mortality               LOEC       >100                                       NOEC       ≥ 100

The criteria of validity of results given by the OECD Guideline 203 were kept within this study. In the control no dead animals were observed. In the test solutions the oxygen concentration did not drop below a value of 60% of the saturation value (»5 mg O₂/L).

Description of key information

Short-term toxicity to fish: LC50 (96h) > 100 mg/L, LC0 (96h) ≥ 100 mg/L, NOEC (96h) ≥ 100 mg/L for rainbow trout (Oncorhynchus mykiss) (OECD 203, static)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L

Additional information

There is a Klimisch 1 OECD 203 (rainbow trout over 96h) study available, indicating that the test item does not need to be classified as hazardous to the aquatic environment, neither acute nor chronic, according to Regulation (EC) No 1272/2008 and amendments. In this study, the results were LC50 (96h) > 100 mg/L, LC0 (96h) ≥ 100 mg/L, and NOEC (96h) ≥ 100 mg/L. There is no indication given that this data is not relevant for the assessment of ecotoxicological properties of DMTD. Hence, no data gap was identified, and the key value of LC50 = 100 mg/L, can be chosen for further risk assessment, although it must be noted that the actual LC50 is expected to be higher and the value was only stated as such due to limitations in the IUCLID entry field.