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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 29/06/03 to 09/02/05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Dept. of Health, UK
Test material information:
Composition 1
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not relevant
Analytical monitoring:
yes
Details on sampling:
The test samples were analysed following filtration through glass wool to remove algal cells.
Vehicle:
no
Details on test solutions:
For the purpose of the definitive test, the test material was dissolved directly in culture medium.
An amount of test material (195.5 mg) was dissolved in culture medium and the volume adjusted to 0,5 L to give a 200 mg ai/L stock solution from which serial delutions were made to give 100, 50, 25, 12.5 mg ai/L stock solutions. An aliquot (250 mL) of each stock solution was mixed with algal suspension (250 mL) to give the required test concentrations of 6.25, 12,5, 25, 50 and 100 mg ai/L.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Strain: CCAP 276/20
- Source: Culture Collection of Algae and Protozoa (CCAP), Institute of Freshwater Ecology, Cumbria.
- The culture was maintained in the laboratory at a temperature of 21°C (+ or - 1°C), under continuous illumination (intensity approximately 7000 lux) and constant aeration.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
no data
Test temperature:
21 °C (+ or - 1°C)
pH:
From pH 7.3 at 0 hours to pH 8.3 at 72 hours
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
Nominal concentration: 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 ml glass conical flasks.
- Flasks plugged with polyurethane foam bungs
- 3 flasks each containing 100 ml of test preparation were used for the control and each treatment group.
- Initial nominal cell density: 10^4 cells per mL

OTHER TEST CONDITIONS
- Illumination: continuous (intensity approximately 7000 lux)
- Shaking: constant, at 150 rpm for 72 hours.

TEST CONCENTRATIONS
- Range finding study:
- Test concentrations: nominal test concentrations of 0.10, 1.0, 10 and 100 mg ai/l.
- Results used to determine the conditions for the definitive study: After 72 hours no effect on algal growth was observed.
Reference substance (positive control):
not specified
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
39 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
biomass
Remarks on result:
other: 95% confidence limits: 34 - 45 mg ai/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
65 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Remarks on result:
other: 95% confidence limits 58 - 74 mg ai/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Remarks on result:
other: There were no statistically significant differences between the control, the 6.25 and the 12.5 mg ai/L test concentrations (P≥0.05).
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
biomass
Remarks on result:
other: 95% confidence limits 2.4 – 2.8 mg ai/L
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
3.2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Remarks on result:
other: 95% confidence limits 3.0 – 3.5 mg ai/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
1.45 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Details on results:
The test material was unstable in the test medium for the duration of the test.
Results with reference substance (positive control):
no data
Validity criteria fulfilled:
yes
Remarks:
The cell concentration of the control cultures increased by a factor of 49 after 72 hours. This increase was in line with the OECD Guideline that states the enhancement must be at least by a factor of 16 after 72 hours.
Conclusions:
Given this decline in measured test concentrations it was considered justifiable to base the results on the nominal test concentrations (ai: active ingredient) of the test item itself. The 72h-EC50 (biomass) based on the nominal test concentrations was 39 mg ai/L and the 72h- EC50 (growth rate) was 65 mg ai/L. The 72h No Observed Effect Concentration (NOEC) was 1.45 mg ai/L.

Description of key information

The EC50 (72 h) for freshwater algae (Desmodesmus subspicatus): 39 mg/L  (biomass; OECD TG 201; static).
NOEC (72h): 12.5 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
39 mg/L
EC10, LC10 or NOEC for freshwater algae:
12.5 mg/L

Additional information

It was considered justifiable to base the results on the nominal test concentrations of MeaTG, despite the fact that the test material was slightly unstable in the test medium for the duration of the test.