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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:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
None.
Analytical monitoring:
yes
Details on sampling:
All treatments were analytically monitored at the beginning and the end of the test.
Vehicle:
no
Details on test solutions:
Tests solutions were prepared from dilutions of a stock solution. A known volume of test item (25.0 mg) was poured into a flask, the volume was then made up to 500 mL with test medium. The solution was kept under high speed stirring at ambient temperature during approximately 24 hours with a magnetic stir bar. No filtration was necessary before dilution.
Test organisms (species):
Daphnia magna
Details on test organisms:
The test organisms used for this study was Daphnia magna Straus (Cladocera, Crustacea), clone 5, bred within the laboratory by acyclical parthenogenesis in a synthetic medium. D. magna cultures were fed with a mixture of the microalgae Chlorella vulgaris and Pseudokirchneriella subcapitata. The neonates used were less than 24h old at test initiation (selected by filtration) and were not first brood progeny. Test animals were not fed during the test.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Remarks on exposure duration:
None.
Post exposure observation period:
None.
Hardness:
Not measured.
Test temperature:
18.3 - 20.1°C (min-max)
pH:
7.6 - 8.0 (min-max)
Dissolved oxygen:
8.6 - 9.0 mg/L (min-max)
Salinity:
Not measured.
Conductivity:
Not measured.
Nominal and measured concentrations:
Nominal test item concentrations: 0 ; 0.9 ; 1.9 ; 4.1 ; 9.1 ; 20.0 mg/L.
Measured concentrations at 0h: 0 ; 0.9 ; 1.9 ; 4.2 ; 9.9 ; 20.4 mg/L
Measured concentrations at 48h: 0 ; 0.9 ; 2.0 ; 4.3 ; 10.0 ; 21.3 mg/L
Details on test conditions:
Culture and test vessels containing Daphnia magna (20 daphnids per tested concentration, 4 replicates per concentration) were incubated with a photoperiod of 8 hours of darkness per 24h. Test vessels were made of clear glass tubes (30 mL capacity) and covered to minimise evaporation and avoid the entry of dust into the solutions. At least 5 mL of exposure solution was provided for each neonate. The control treatment was maintained under the same conditions as the treated groups, except it did not contain any test item.
Reference substance (positive control):
yes
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
3.8 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
mobility
Details on results:
See Table 1.
Results with reference substance (positive control):
Potassium dichromate : 24h-EC50 daphnia = 0.73 mg/L
Reported statistics and error estimates:
Statistical analysis was performed using the software ToxRat® 2.10 and following the default template included in the software package.

Table1: Cumulative immobilisation of daphnia during the test.

Test solution

(mg/L)

Replicate

Total daphnids

at T0

Immobile daphnids

Mobility inhibition at 48h(%)

24h

48h

Control

a

5

0

0

0

b

5

0

0

c

5

0

0

d

5

0

0

0.85

a

5

0

0

0

b

5

0

0

c

5

0

0

d

5

0

0

1.88

a

5

0

0

5

b

5

0

0

c

5

0

0

d

5

0

1

4.13

a

5

0

2

55

b

5

0

3

c

5

0

3

d

5

0

3

9.10

a

5

0

5

100

b

5

0

5

c

5

0

5

d

5

0

5

20.00

a

5

4

5

100

b

5

4

5

c

5

3

5

d

5

4

5

 

Validity criteria fulfilled:
yes
Conclusions:
This study was designed to determine the effects of 1,3 -dibutylthiourea to Daphnia magna over a 48h period under static conditions, according to the OECD 202 Guideline. EC50 was 3.8 mg/L.
Executive summary:

This study was designed to determine the effects of the test item to Daphnia magna over a 48h period with static conditions, according to the OECD 202 Guideline. Daphnids were exposed to serial dilutions of a stock solution of the test item. Chemical analysis of the test item throughout the test period have shown stability of the substance that's why nominal concentrations were used to determine 48h-EC50 (3.8 mg/L):

The definitive test succeeded to meet the validity criterion detailed as follows:

 - The immobilisation in the control did not exceed 10% at the end of the test (0% in the definitive test),

 - The dissolved oxygen concentrations remained above 3 mg/L over the test period (above 8.4 mg/L in the definitive test).

Description of key information

One OECD 202 study is available for acute toxicity of 1,3 -dibutylthiourea to Daphnia magna. EC50 was 3.8 mg/L

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
3.8 mg/L

Additional information