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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
October 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to guideline
Guideline:
other: The Guideline for the Testing of Chemicals 201, Growth Inhibition Test for Alga. MEP, China, 2004
GLP compliance:
yes
Remarks:
HJ/T 155-2004 the Guideline of Good Laboratory Practices on Chemical Testing, MEP, China
Specific details on test material used for the study:
- Analytical purity: 99.9 %
- Lot/batch No.: 301601
Analytical monitoring:
yes
Details on sampling:
The test substance concentration in the test solution was measured at the start and the end of the exposure. At the start, About 50 mL solution sampled from the container for preparation in exposure group was used for the measurement. At the end of the exposure, about 50 mL test solution from one test vessel of the exposure group was used for the measurement. About 2 mL supernatant liquid was analysed for concentration after centrifugation (1100 g, 10 min).
Vehicle:
no
Details on test solutions:
The test substance solution was prepared by dissolving 0.1003 g test substance in the medium and making up to 500 mL.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
- Species: Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum)
- Source: Freshwater Algae Culture Collection of the Institute of Hydrobiology
- Culture conditions: temperature: 21 ℃ - 24 ℃ ± 2 ℃; light: 4400-8800 lux
- Initial cell density: 1×104 cells/mL
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
not applicable
Hardness:
no data
Test temperature:
22.9-23.1 °C
pH:
Control group (0 mg/L)
- value at the start: 8.07
- value at the end: 7.90

Treatment group (100 mg/L):
- value at the start: 6.90
- value at the end: 7.91
Dissolved oxygen:
no data
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentration: 100 mg/L
Measured concentration at the start: 100.2 mg/L
Measured concentration at the end: 100.2 mg/L
Details on test conditions:
Lighting: 6.43 - 7.52 Klux
Photoperiod: 12 h light : 12 h dark
Shaking speed: 100 rpm
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Details on results:
No abnormality was observed during and at the end of the exposure.
Results with reference substance (positive control):
According to the sensitivity test, which is performed twice a year the ErC50 (72h) was 2.848 mg/L which can fit the sensitivity requirement (ErC50 (72h) =3.38±1.30 mg/L).
Validity criteria fulfilled:
yes
Conclusions:
The EC50 (72h) of test substance 1,1-Dimethylurea on Pseudokirchneriella subcapitata was greater than 100 mg/L which was calculated as nominal concentration under the test conditions of this study.
Executive summary:

To evalute the effects of 1,1 -Dimethylurea on growth and reproduction of an unicellular freshwater algae species a study according to OECDGuideline 201 ("Alga, Growth Inhibition Test") was performed.

Only one limit concentration with 100 mg/L and one control group were designed for the definitve test according to the result of the preliminary test. Each group had 6 replicates and the duration of the test was 72 hours. The cell densities of each group were counted at 24, 48 and 72 hours after the start of the exposure and the inhibition values were calculated at 72 h. Furthermore, the cell conditions for one vessel in exposure group and control group were observed under microscope at the ens of the exposure.

The measured concentrations were both 100.2 mg/L at the beginning and at the end of the test. The growth inhibition rates (%Ir) of 1,1 -Dimethylurea on Pseudokirchneriella subcapitata were -4.79 - 3.50 %, the average value was -1.57 %. The percent inhibiton in yield (%Iy) was -16.86 - 10.93 %, the average value was -5 .55 %. So the EC50(72 h) was greater than 100 mg/L which was calculated as nominal concentration.

Description of key information

The EC50 (72h) of test substance 1,1-Dimethylurea on Pseudokirchneriella subcapitata was greater than 100 mg/L which

was calculated as nominal concentration under the test conditions of this study.

Key value for chemical safety assessment

Additional information

To evalute the effects of 1,1 -Dimethylurea on growth and reproduction of an unicellular freshwater algae species a study according to OECDGuideline 201 ("Alga, Growth Inhibition Test") was performed.

Only one limit concentration with 100 mg/L and one control group were designed for the definitve test according to the result of the preliminary test. Each group had 6 replicates and the duration of the test was 72 hours. The cell densities of each group were counted at 24, 48 and 72 hours after the start of the exposure and the inhibition values were calculated at 72 h. Furthermore, the cell conditions for one vessel in exposure group and control group were observed under microscope at the ens of the exposure.

The measured concentrations were both 100.2 mg/L at the beginning and at the end of the test. The growth inhibition rates (%Ir) of 1,1 -Dimethylurea on Pseudokirchneriella subcapitata were -4.79 - 3.50 %, the average value was -1.57 %. The percent inhibiton in yield (%Iy) was -16.86 - 10.93 %, the average value was -5 .55 %. So the EC50(72 h) was greater than 100 mg/L which was calculated as nominal concentration.