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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: read-across from a guideline study
Justification for type of information:
Toxicity of Orivone to algae is based on read-across from p-tert-butylcyclohexanon. The documentation is presented in the Endpoint summary of Aquatic toxicity.
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
60 mg/L
Nominal / measured:
meas. (TWA)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
26 mg/L
Nominal / measured:
meas. (TWA)
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Remarks:
The information is based on read across and presented with adequate and reliable documentation.
Conclusions:
The EC50 and EC10 are 60 and 26 mg/l, respectively based on read across from p-tert-butyl cyclohexanone which is tested acciording to OECD TG 201.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
25 Jun 2002 to 28 Jun 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
This information is used for read across to Orivone.
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
1992
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Test material information:
Composition 1
Analytical monitoring:
yes
Details on sampling:
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 72 hours. Analysis was also performed on the stock solution at 0 hours.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
A stock solution was prepared to give the desired series of test concentrations. To achieve this, 125.2 mg of the test substance were added to 1 litre of dilution water and treated for 1 h in an ultrasonic bath and afterwards stirred for 24 h on a magnetic stirrer. Finally undissolved particles of the test substance were removed by filtration using a folded filter of pore size 7-12 µm.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Strain: non-axenic strain
- Source: 'The Collection of Algal Cultures' of the Institute of Plant Physiology at the University of Göttingen (Germany)
- Maintenance of stock cultures: Exponentially-growing stock cultures are maintained in the test facility under constant temperature conditions (23 ± 2 °C) at a light intensity in the range 60 - 120 µE·m-2·s-1 (measured in the range 400 to 700 nm using a spherical quantum flux meter). The nutrient medium (according to BRINGMANN & KUHN (1977) is renewed once a week. Cell density measurements are made using a microcell counter.
- Preparation of pre-cultures: Pre-cultures are set up three days before the start of a test. They are grown under identical exposure conditions as the stock cultures, except from the use of a different nutrient medium
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21 - 25 °C
pH:
- Test start (0h): 7.8 - 7.9
- Test termination (72h): 10.2 - 10.3
Nominal and measured concentrations:
- Nominal concentrations: 0 (control), 3.2, 6.3, 13, 25, 50 and 100 mg/L
- Measured concentrations at t=0: - Measured concentrations at t=72:
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks with stoppers
- Fill volume: 300 mL
- Initial cells density: approximately 1.0E+04 cells per mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- Culturing apparatus: light chamber that control temperature and provide continuous illumination

TEST MEDIUM / WATER PARAMETERS
- Composition: see 'Any other information on materials and methods incl. tables'
- Other: Solid NaHCO3 is added to the nutrient media to make up a final concentration of 50 mg/L in the solutions of the pre-cultures and test cultures.

OTHER TEST CONDITIONS
- Light intensity: in the range of 60 to 120 µE·m-2·s-1 (equivalent to 4000 to 8000 lux)

EFFECT PARAMETERS MEASURED:
- Algal cell densities: The cell densities were measured at 24 hour intervals. Cell density measurements were made using a microcell counter.
- Inhihibition: Inhibition of the algal population was measured as reduction in growth and growth rate, relative to control cultures grown under identical conditions.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
60 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
26 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
45 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% C.L.: 40 - 50 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
25 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% C.L.: 20 - 30 mg/L
Details on results:
Inhibition of growth rate was observed from approximately 25 mg/L (3%) and increased in a dose-dependent manner up to 58.6% inhibition at 100 mg/L. See 'Any other information on results'.
Results with reference substance (positive control):
No positive control was used.
Reported statistics and error estimates:
Probit analysis and Dunnett's test.

Table: Mean cell density during the test

Nominal concentration [mg/L]

Cell density [cells/mL]

(initial cell density of 10E+04 cells/mL)

24 h

48 h

72 h

Control

38889

174444

345000

3.2

37778

185556

342222

6.3

40000

176667

345444

13

40000

185556

341111

25

34444

181111

301111

50

34444

128889

183333

100

3333

42222

43333

Table: Mean growth rate (r)

Nominal concentration [mg/L]

Growth rate

[1/d]

Inhibition (+) / Increase (-)

[%]

Control

1.18

0.0

3.2

1.18

0.2

6.3

1.19

-0.8

13

1.18

0.3

25

1.13

3.8

50

0.97

17.9

100

0.49

58.6

Table: Mean growth (b) [integral of biomass]

Nominal concentration [mg/L]

Area under growth curve

Inhibition (+) / Increase (-)

[%]

Control

360833

0.0

3.2

369444

-2.4

6.3

368889

-2.2

13

371111

-2.8

25

341111

5.5

50

230000

36.3

100

72222

80.0

ADDITIONAL TEST RESULTS

Growth rate:

- NOErC: 12.1 mg/L

- ErC05: 21 mg/L

- ErC90: 136 mg/L

- ErC95: 171 mg/L

Biomass:

- NOEbC: 21.1 mg/L

- EbC05: 22 mg/L

- EbC90: 78 mg/L

- EbC95: 92 mg/L

Validity criteria fulfilled:
yes
Conclusions:
The 72-h ErC50 and ErC10 values are 60 and 26 mg/L, respectively, in freshwater algae (D. subspicatus).
Executive summary:

The toxicity towards freshwater algae was determined in a study according to OECD TG 201 and in compliance with GLP criteria. In this study, exponentially growing freshwater algae (Desmodesmus subspicatus) were exposed to nominal test substance concentrations of 0 (control), 3.2, 6.3, 13, 25, 50 and 100 mg/L for 72 hours under static conditions. Analytical confirmation showed that measured concentrations ranged from 68 - 108% of nominal values at 0 hours, and from 58 - 85% of nominal values at 72 hours, respectively. Therefore, all results are expressed in terms of mean measured concentrations. The cell densities were measured at 24 h intervals. Inhibition of the algal population was measured as growth rate (index r) and reduction in growth (index b), relative to control cultures under identical conditions. Inhibition of growth rate was observed from approximately 25 mg/L (3%) and increased in a dose-dependent manner up to 58.6% inhibition at 100 mg/L. Biomass was also inhibited from approximately 25 mg/L (5.5%), and increased in a dose-dependent manner up to 80% at 100 mg/L. Based on these results, the 72-h ErC50 and 72-h EbC50 were determined at 60 and 45.0 mg/L. The 72-h ErC10 and 72 -h EbC10 were 26 and 25 mg/L, respectively.

Description of key information

No data is available for Orivone. Therefore read-across is performed to the close structural analogue p-tert-butylcyclohexanone (CAS 98-53-3). Its toxicity towards freshwater algae was determined in a study according to OECD TG 201 and in compliance with GLP criteria. In this study, exponentially growing freshwater algae (Desmodesmus subspicatus) were exposed to nominal test substance concentrations of 0 (control), 3.2, 6.3, 13, 25, 50 and 100 mg/L for 72 hours under static conditions.Analytical confirmation showed that measured concentrations ranged from 68 - 108% of nominal values at 0 hours, and from 58 - 85% of nominal values at 72 hours, respectively. Therefore, all results are expressed in terms of mean measured concentrations. The cell densities were measured at 24 h intervals. Inhibition of the algal population was measured as growth rate (index r) and reduction in growth (index b), relative to control cultures under identical conditions. Inhibition of growth rate was observed from approximately 25 mg/L (3%) and increased in a dose-dependent manner up to 58.6% inhibition at 100 mg/L. Biomass was also inhibited from approximately 25 mg/L (5.5%), and increased in a dose-dependent manner up to 80% at 100 mg/L. Based on these results, The 72-h ErC50and 72-h EbC50 were determined at 60 and 45.0 mg/L. The 72-h ErC10 and 72 -h EbC10 were 26 and 25 mg/L, respectively. There is no need to convert the toxicity of the source chemical data towards Orivone, because of the comparable properties of the substances.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
60 mg/L
EC10, LC10 or NOEC for freshwater algae:
26 mg/L

Additional information