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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
adopted in 1979
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0, 1.56, 25 and 100 mg/L treatments
- Sampling method: Samples were taken at the beginning and at the end of the test.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A stock solution was prepared by adding 125 mg test substance to 1L of demineralized water and stirring for about 10 minutes at 22 °C. The stock solution was subsequently diluted with demineralized water to prepare the test concentrations.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
-Test species and strain: Desmodesmus subspicatus CHODAT (SAG 86.81)
- Source (laboratory, culture collection): obtained at regular intervals from SAG and kept in liquid culture in the in-house lab
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23 ± 2 °C
pH:
7.8 - 9.3
Nominal and measured concentrations:
Nominal: 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mg/L
Measured concentrations: The concentration control analysis were performed with test solutions of the following nominal concentrations of the test substance: 0 (control), 1.56, 25, 100 and 125 mg/L. The measured concentrations were determined to be: < 1, 1.6, 26.3, 106.8 and 116.6 mg/L (mean values)
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks plugged with gas permeable siliconesponge caps containing 100 mL test solution
- Initial cells density: 10000 cells/mL
- Control end cells density: 57-fold
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: demineralized water
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH values were measured at the beginning and at the end of the test.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: permanent illumination
- Light intensity and quality: 120 µE/m2*s (400-700 nm)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: after 72h in a counting chamber (Neubauer improved)
- Chlorophyll measurement: In vivo Chlorophyll-a fluorescence (pulsed excitation with light flashes having a wavelength of 435 nm) was measured using an EOS Filterfluorometer after 0, 24, 48 and 72h exposure time.
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 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.:
14 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
23.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.77 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no
- Any stimulation of growth found in any treatment: no

Since the analytically determined concentrations of the test substance in the test solutions were within +20% of the nominal concentrations, the effect concentration can be expressed relative to the nominal concentration.

Validity criteria fulfilled:
yes
Conclusions:
The test substance did not show to be acutely harmful (72h-EC50 > 100 mg/L) but harmful at chronic exposure to freshwater algae (72h-EC10 = 14 mg/L) in a GLP guideline study using Desmodesmus subspicatus as test organism.

Description of key information

EC50 (72h) > 100 mg/L, EC10 (72h) = 14 mg/L (nominal, analytically verified) for Desmodesmus subspuicatus (EU method C.3)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
14 mg/L

Additional information

One study investigating a toxicity of 3-(amidinothio)propionic acid (CAS 5398-29-8) to freshwater algae is available. The study was performed according to GLP and EU method C.3 using Desmodesmus subspicatus as test organism (BASF 1997). Test concentrations between 0.39 and 100 mg/L were tested. Nominal concentrations were verified analytically. The 72h-EC50 value is determined to be > 100 mg/L and the 72h-EC10 value is determined to be 14 mg/L based on nominal concentrations.