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Ecotoxicological information

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:
From 07.01.1997 to 10.01.1997
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
This study was performed according to EU Method C.3 with GLP statement. All validity criteria were fulfilled but pH of the control medium was increased by more than 1.5 units during the test.
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
pH of the control medium was increased by more than 1.5 units during the test.
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
A series of concentrations in deionised water (stock solution at 30.3 mg/L, test concentrations at 2.8, 5.7, 8.5, 14.2, 24.1 and 28.4 mg/L) was prepared. The analytical monitoring was carried out at 0, 24, 48 and 72 hours.
Vehicle:
no
Details on test solutions:
No data
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Scenedesmus subspicatus (CHODAT (86.81 SAG))
- Source (laboratory, culture collection): Institute of water, soil and air hygiene, Berlin
- Age of inoculum (at test initiation): no data
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
none
Post exposure observation period:
None
Hardness:
No data
Test temperature:
23.3-23.8°C
pH:
7.5-9.3
Dissolved oxygen:
No data
Salinity:
Not applicable
Nominal and measured concentrations:
- Nominal concentrations: 0.76, 1.5, 3.3, 6.8, 13.6 and 27.3 mg/L.
Details on test conditions:
TEST SYSTEM
- Test vessel: no data
- Aeration: yes
- Type of flow-through (e.g. peristaltic or proportional diluter): not applicable
- Renewal rate of test solution (frequency/flow rate): not applicable
- Initial cells density: 20 000 cells/mL
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 8
- No. of vessels per vehicle control (replicates): not applicable

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
According to EU Method C.3

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Light intensity and quality: ca. 8000 Lux
- Salinity (for marine algae): not applicable

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer (adsorption measured at 685 nm).

TEST CONCENTRATIONS
- Spacing factor for test concentrations: ca. 2
- Range finding study: no
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
22 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
11 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Analytical monitoring: See table 6.1.5/1 in "Any other information on results incl. tables". The measured values after 72 hours were not greater by more than 20% of the fresh concentrations. Based on this information, the results were based on nominal concentration only.
- Cell density: See table 6.1.5/2 in "Any other information on results incl. tables".
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
None

Table 6.1.5/1: Analytical monitoring

Stability control (mg/L)

Actual concentration at 0h (mg/L)

Measured concentration at 24h (mg/L)

Measured concentration at 48h (mg/L)

Measured concentration at 72h (mg/L)

2.8

5.7

8.5

14.2

24.1

28.4

2.4

5.3

8.1

14.4

23.5

28.4

3.0

4.9

7.4

12.5

21.9

25.1

3.0

5.4

8.3

14.1

22.0

28.6

3.1

5.3

7.7

13.8

21.9

31.9

Stock solution test

30.3

-

-

-

Table 6.1.5/2: Cell densities during the test (cell x 10^4 /mL)

 

Repl.

Control

Test concentrations (mg/L)

0.76

1.5

3.3

6.8

13.6

27.3

Initial

1

2

2

2

2

2

2

2

After 24 hours

1

2

3

4

5

6

7

8

6

6

6

6

5

6

5

5

6

6

5

5

6

 

6

6

5

6

4

7

6

7

6

6

6

6

6

5

5

 

5

5

5

5

5

5

5

5

5

5

Mean

SD

6

0.5

6

0.5

5

0.8

6

0.5

6

0.5

5

0

5

0

After 48 hours

1

2

3

4

5

6

7

8

30

27

26

28

28

28

27

27

38

38

37

30

31

38

36

36

38

36

37

40

35

37

41

38

37

36

37

40

20

21

25

25

26

6

7

6

7

6

Mean

SD

28

1.1

35

3.5

37

1

38

2.2

38

1.4

23

2.4

6

0.5

After 72 hours

1

2

3

4

5

6

7

8

90

85

94

94

95

99

103

108

100

102

106

117

121

104

99

106

108

114

100

98

103

116

137

102

102

106

108

119

56

57

48

49

57

6

8

5

8

6

Mean

SD

96

6.8

109

8.3

106

4.9

111

14.5

107

6.2

53

4

7

1.2

Validity criteria fulfilled:
yes
Conclusions:
On the basis of the growth rate, the 72h-ErC50 and 72h-ErC10 were determined to be 22 mg/L and 11 mg/L, respectively, based on nominal concentrations. The NOEC value was 6.8 mg/L based on cell growth.
Executive summary:

This study was performed according to EU Method C.3 with GLP statement, to assess the algae growth inhibition of the test substance to Scenedesmus subspicatus under static condition during 72 hours.

A stability test was performed to measure the concentrations of the test substance in aqueous solution during 72 hours. Results show that the test substance is stable during the test duration.

On the basis of the growth rate, the 72h-ErC50 and 72h-ErC10 were determined to be 22 mg/L and 11 mg/L, respectively, based on nominal concentrations. The NOEC value was 6.8 mg/L based on cell growth.

All validity criteria were fulfilled but pH of the control medium was increased by more than 1.5 units during the test.

Description of key information

EU Method C.3, GLP, key study, validity 2:

72h-ErC50 = 22 mg/L, based on nominal concentration;

72h-ErC10 = 11 mg/L, based on nominal concentration;

72h-NOEC biomass = 6.8 mg/L, based on nominal concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:
22 mg/L
EC10 or NOEC for freshwater algae:
6.8 mg/L

Additional information

To assess the toxicity of the registered substance to aquatic algae, one key study is available. This study was performed according to EU Method C.3 (similar to OECD Guideline 201) with GLP statement

Scenedesmus subspicatus were exposed to a series of six test substance concentrations with one control, under static conditions during 72 hours.

A stability test was performed beside the study, to measure the concentrations of the substance in aqueous solution during 72 hours. Results show that the substance was stable over the study period in the abiotic flasks, therefore concentrations were based on nominal values.

On the basis of the growth rate, the 72h-ErC50 and 72h-ErC10 were determined to be 22 mg/L and 11 mg/L. The NOEC value was 6.8 mg/L based on cell growth.

All validity criteria were fulfilled but pH of the control medium was increased by more than 1.5 units during the test.