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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:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Analytical evaluation of the test concentrations of the test item and the control was carried out via LC-MS/MS from freshly prepared media after 0 hours and old test media after 72 hours. Samples for the test item analysis at the beginning of the exposure were taken from an additionally prepared replicate with algae. For the test item analysis after 72 hours, samples were taken out of the test replicates.
Vehicle:
no
Details on test solutions:
Stock solution, preparation of the test media: 200 mg/L were freshly prepared with dilution water and agitated gently until the solution was visually clear.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Test organism: Pseudokirchneriella subcapitata HINDAK, SAG 61.81
Reason for the selection of the test organism: Pseudokirchneriella subcapitata is a suitable green alga species according to the guideline.
Origin: Sammlung van Algenkulturen (SAG), Pflanzenphysiologisches lnstitut der Universitat Gottingen, Nikolausberger Weg 18, D-37073 Gottingen
Cultivation at test facility: Fresh stocks are prepared every month on Z-Agar. Light intensity amounted to 35 - 70 μE · m-2 · s-1 for 24 hours per day.
Culture medium: Nutrient medium Z according to LOTTGE et al. ( 1994)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
22.3 CaCO3 mg/L
Test temperature:
21.5 - 22.5 deg C
pH:
7.88 - 9.53
Nominal and measured concentrations:
nominal: 12.5 - 25.0 - 50.0 - 100 - 200 mg/L
The measured concentrations of the test item at the start of exposure were in the range of 107 - 119 % of the nominal test item concentration. At the end of exposure, the measured concentrations were in the range of 109 - 117 % of the nominal value.
Details on test conditions:
Stock solution, preparation of the test media: 200 mg/L were freshly prepared with dilution water and agitated gently until the solution was visually clear.
Test concentrations: 5 concentrations were tested in a geometrical series with a dilution factor of 2: 12.5 - 25.0 - 50.0 - 100 - 200 mg/L.
Control: Six replicates (without test item) were exposed under the same conditions as the test concentrations.
Reference Item: Potassium dichromate was tested as reference item
Test Method: Static procedure
Duration of the test: 72 hours
Replicates: 3 replicates per concentration level and 6 for the control were tested.
Test container: Sterile Erlenmeyer flasks (vol. 250 ml) with cotton wool plugs
Test volume: 100 ml
Dilution water: According to the guidelines
Preculture: A three days old preculture, prepared in dilution water, was used as inoculum.
Initial cell density: Nominal: approximately 5000 - 50000 cells/ml; Actual: 6153 cells/ml
Application: Application was carried out by adding appropriate volumes of the stock solution to the replicate test vessels.
Incubation: The flasks were positioned randomly and repositioned daily.
Temperature (target): 21 - 24°C, controlled at ± 2°C
Agitation: Test containers were placed on a rotary shaker and oscillated at approximately 70 rpm.
Light intensity (target): Approximately 60 - 120 μE · m-2 · s-1
Light regime: 24 hours/day light
Light source: Fluorescent tubes, OSRAM L 36 W/11-865, cool daylight
Light homogeneity (target): Within ± 15 % over incubation area

Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
45.2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
80.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
179 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Each test concentration of the test item and the control were analytically verified by LC-MS/MS at the start and the end of exposure. The measured concentrations of the test item at the start of exposure were in the range of 107 - 119 % of the nominal test item concentration. At the end of exposure, the measured concentrations were in the range of 109 - 117 % of the nominal value.
Validity criteria fulfilled:
yes
Conclusions:
The ErC50 of the test item was 179 mg/L (95% confidence interval: 168 - 188 mg/L) and the ErC10 was 45.2 mg/L (95% confidence interval 36.9-54.0 mg/L), based on analytically confirmed nominal concentrations.
Executive summary:

In a 72 h toxicity study conducted according to OECD guideline 201, EC Method C.3 and GLP principles, freshwater algae (Pseudokirchneriella subcapitata) were exposed to the test substance at nominal concentrations of 12.5, 25.0, 50.0, 100 and 200 mg/L (3 replicates per concentration) and an untreated control (6 replicates), under static conditions. Measured concentrations in the test solution were at 107 - 119% relative to nominal at the start of the test and 109 - 117% at the end of the exposure. Therefore, effect parameters were based on nominal concentrations. The EC50 for growth rate inhibition (72h-ErC50) was 179 mg/L , the 72h-ErC10 was 45.2 mg/L. The study met all validity criteria, and is considered reliable without restriction.

Description of key information

ErC50: 179 mg/L

ErC10: 45.2 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
179 mg/L
EC10 or NOEC for freshwater algae:
45.2 mg/L

Additional information

In a 72 h toxicity study conducted according to OECD guideline 201, EC Method C.3 and GLP principles, freshwater algae (Pseudokirchneriella subcapitata) were exposed to the test substance at nominal concentrations of 12.5, 25.0, 50.0, 100 and 200 mg/L (3 replicates per concentration) and an untreated control (6 replicates), under static conditions. Measured concentrations in the test solution were at 107 - 119% relative to nominal at the start of the test and 109 - 117% at the end of the exposure. Therefore, effect parameters were based on nominal concentrations. The EC50 for growth rate inhibition (72h-ErC50) was 179 mg/L , the 72h-ErC10 was 45.2 mg/L. The study met all validity criteria, and is considered reliable without restriction.