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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-01-10 - 2017-03-09 (experimental phase)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
Version dated 13-Apr-2004
Deviations:
yes
Remarks:
Instead of storage at freezing conditions, t0 specimens were stored at 2-8°C until analysis – this represents a deviation of the study plan which is not considered to have an influence on the integrity of the results and of the test
GLP compliance:
yes (incl. certificate)
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, 1.0, 2.0, 4.0, 8.0, 10 mg/L
- Sampling method: Specimens were drawn from freshly prepared treatments and those incubated for 48 hr.
- Sample storage conditions before analysis: The supporting analysis of the specimens could not be performed on the same day of collection of the specimens. Therefore, the specimens were stored at 2-8°C and then analysed.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was weighed in ELENDT M4 dilution water followed by stirring on a magnetic stirrer for 10 min (screening test) / 5 min (main test) being necessary to dissolve the test item sufficiently in the test medium. pH of the treatments was not adjusted.
- Controls: ELENDT M4 dilution water without any test item
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): none stated
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water flea
- Strain/clone: Daphnia magna STRAUS (clone 5)
- Source: obtained from Dr. M. Bergtold, BASF, D-67117 Limburgerhof; the strain originally derived from the Institut National de Recherche Chimique Appliquee, France in 1978
- Feeding during test: During the test the daphnia were not fed.


ACCLIMATION
- Acclimation period: The cultivation of the daphnia is performed in a way that the animals are transferred in new test medium at an interval of 1 to 3 days followed by feeding.
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: Desmodesmus subspicatus- and/or Chlorella-cells
- Feeding frequency: following each transfer in new test medium
- Health during acclimation (any mortality observed): no mortality stated

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES:
Daphnias used for the test are not older than 24 hr. Therefore, in every case, daphnia are transferred into fresh medium one day before starting of the daphnia test in order to get daphnia for the test younger than 24 hr.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
none
Hardness:
250 mg/L CaCO3
Test temperature:
19.3 - 20.6 °C during the definitive main test (20.0 - 20.3 °C during the screening test)
pH:
8.24 - 9.28 during the definitive main test (5.75 - 8.30 during the screening test)
Dissolved oxygen:
8.3 - 8.9 mg O2/L during the definitive main test (8.2 - 8.7 during the screening test)
Nominal and measured concentrations:
Nominal: 0, 1.0, 2.0, 4.0, 8.0, 10 mg/L (definitive main test)
Found (t0): 0.0, 1.05, 2.11, 4.22, 8.37, 10.69 mg/L
Found (t48h): 0.0, 0.99, 1.97, 4.04, 8.16, 10.43 mg/L
Mean (t0 - t48h): 0.0, 1.02, 2.04, 4.13, 8.27, 10.56 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: carboys
- Material, size, headspace, fill volume: glass, 100mL volume
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4 (definitive main test), 2 (screening test)
- No. of vessels per control (replicates): 4 (definitive main test), 2 (screening test)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Elendt M4 (test medium according to OECD 202); the stock solutions with the macronutrients were individually prepared in ultrapure water (for each salt a separate solution). From these individual stock solutions, the medium was prepared.
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Photoperiod: 16 hr of light and 8 hr of darkness

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

VEHICLE CONTROL PERFORMED: yes, medium only

RANGE-FINDING STUDY
- Test concentrations: 1, 10, 100 mg/L
Reference substance (positive control):
yes
Remarks:
To verify the sensitivity of the test system towards toxic items the effect of potassium dichromate towards different animals of this breed was tested prior to beginning of the test.
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
5.95 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
other: EC20
Effect conc.:
4.46 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
3.83 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LOEC
Effect conc.:
4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Mortality of control: no immobilisation noted
- Other adverse effects control: none stated
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none stated
- Effect concentrations exceeding solubility of substance in test medium: no
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Limit test: no
- Dose-response test: yes
- ECx: EC50 (24 hr) = 0.95 mg/L
- Other: In order to verify the sensitivity of the test system towards toxic items the effect of potassium dichromate towards different animals of this breed was tested prior to beginning of the test. The value of the EC50 (24 hr) in this period of time was at 0.95 mg/L potassium dichromate. This value is in accordance with the recommendations of 0.6 to 2.1 mg/L K2Cr2O7 given in OECD Guideline 202 (Daphnia sp., Acute Immobilisation Test).
Reported statistics and error estimates:
Statistical evaluation was done using the commercial computer program ToxRat Professional Version 3.2.1.
Validity criteria fulfilled:
yes
Conclusions:
The study was performed according to OECD TG 202 without deviations which may have impact on the validity of the study. Thus, 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, there was a significant immobilisation of the daphnias at concentrations >2.0 mg/L (definitive main 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 EC-values were determined accordingly after 48 hours:
Mobility:
LOEC = 4.0 mg/L
NOEC = 2.0 mg/L
EC50 = 5.95 mg/L
Based on these results, the test item does not need to be classified as acute toxic to the aquatic environment. With regard to chronic toxicity, taking into account the facts that the test item is soluble in water, i.e. above the determined EC50 value, and not readily biodegradable, the test item should be classified as aquatic chronic Cat. 2.
Executive summary:

2,5-Dimercapto-1,3,4-thiadiazole (“DMTD”) was tested for acute toxicity towards daphnia according to OECD-Test Guideline 202 (version dated 13-Apr-2004) in compliance with GLP. In order to investigate the influence of the test item towards the daphnia, the swimming behaviour of the animals was recorded. Under the conditions used for the test, there was an immobilisation of the daphnia at concentrations >2 mg/L. As a conclusion of the analytical part of this study, it can be stated that the concentrations 2,5-Dimercapto-1,3,4-thiadiazole (“DMTD”) remained sufficiently stable during incubation of 48hr. As a result of the supporting analysis it can be stated that the results of the biological part should be based on the nominal concentrations applied because the recoveries of the nominal concentrations were all >80%.

The following EC-values (effective concentrations) were determined accordingly:

Basis: Nominal Concentrations [mg/L]

t24hr

t48hr

NOEC

≥ 10.00

2.00

LOEC

>10.00

4.00

                      EC10

7.57

3.83

                      EC20

11.71

4.46

                      EC50

n.d. (>10.00)

5.95

n.d. = not determined for mathematical reasons.

The test is considered valid as all conditions for validity were met.

Description of key information

Short-term toxicity to aquatic invertebrates: NOEC (24h) ≥ 10 mg/L and NOEC (48h) = 2.00 mg/L, EC50( 24h) > 10 mg/L and EC50 (48h) = 5.95 mg/L for Daphnia magna (OECD 202, static)

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
5.95 mg/L

Additional information

There is a Klimisch 1 OECD 202 (Daphnia magna over 48h) study available, indicating that the test item does not need to be classified as acute toxic to the aquatic environment. With regard to chronic toxicity, the test item should be classified as aquatic chronic Cat. 2 according to Regulation (EC) No 1272/2008 and amendments, taking into account the facts that the test item is soluble in water, i.e. above the determined EC50 value, and not readily biodegradable.

In this study, the results were NOEC (48h) = 2.00 mg/L and EC50 (48h) = 5.95 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 EC50 = 5.95 mg/L, can be chosen for further risk assessment.