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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
effects on growth of green algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 24 March to 20 August 2021
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Batch/Lot number: 465884
Description: White to off-white to slightly yellow solid
Purity: 100%
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 100 mg/L
- Sampling method: samples were taken and analyzed at the beginning and at the end of the experiment.
- Sample storage conditions before analysis:
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution with a concentration of 100.0 mg/L (nominal) was prepared with direct addition of the test item, mixed into the algal growth medium (OECD Medium), then distributed into the appropriate test flasks. As a Limit test was carried out, further dilution of stock solution was not performed.
The test solution was prepared just before introduction of the algae (start of the experiment).
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: 61.81 SAG
- Source (laboratory, culture collection): The algae were supplied by the SAG: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, GERMANY.
- Age of inoculum (at test initiation):
- Method of cultivation: Stock cultures are small algal colonies that are inoculated onto agar regularly. These are transferred to fresh agar medium at least once every two months and are maintained under standardised conditions according to the test guidelines.

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions (same as test or not): same
- Any deformed or abnormal cells observed: yes
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22 - 23°C
pH:
7.52–8.92
Nominal and measured concentrations:
Nominal 100 mg/L; Measured concentration (
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Type (delete if not applicable): The flasks were covered with air-permeable stoppers.
- Material, size, headspace, fill volume: 100 mL
- Initial cells density: 1E+04 algal cells per mL test medium
- Control end cells density:
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuously illuminated
- Light intensity and quality: 7931 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:The cell concentrations were determined at 24, 48 and 72 hours after starting the test by microscopic method.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0.1, 1, 10, 100 mg/L
- Results used to determine the conditions for the definitive study: Because no toxic effect was observed during the preliminary concentration range-finding test, only one test concentration of the test item in the test medium (100 mg/L nominal loading rate) and one control group were tested in a Limit Test.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
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:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
yield
Details on results:
Morphological deviations of the algal cells:
There were no observed morphological deviations during the experiment.

Average specific growth rates:
The results of the statistical evaluation (based on 2 Sample t-Test; α=0.05) show that the 0-72 h average specific growth rate was not statistically significantly different from the untreated control value.

Areas under the growth curves:
The results of the statistical evaluation (based on 2 Sample t-Test; α=0.05) show that the 0-72 h areas were not statistically significantly different from the untreated control value.

Yield:
The results of the statistical evaluation (based on 2 Sample t-Test; α=0.05) show that the 0-72 h yield was not statistically significantly different from the untreated control value.
Results with reference substance (positive control):
72h EC50 for growth rate is 0.89 mg/L, for biomass is 0.61 mg/L, for yield is 0.53 mg/L.
These results are within the acceptable range (ErC50-value: 0.60 mg/L to 1.03 mg/L, EbC50-value: 0.20 mg/L to 0.75 mg/L according to the ISO Guideline No. 8692) hence this reference study shows that the acute immobilisation test on Raphidocelis subcapitata is valid in this laboratory.
Validity criteria fulfilled:
yes
Conclusions:
The 72h-EC50 of test item to Green Algae is determined as > 100 mg/L, NOEC = 100 mg/L.
Executive summary:

The effect of test item was assessed on algal growth using the unicellular green alga Raphidocelis subcapitata, over an exposure period of 72 hours.
Because a toxic response was not observed during the preliminary concentration range-finding test, a Limit Test was carried out using only one test concentration of 100.0 mg/L (nominal) and one control group.


Under the conditions of this algal growth inhibition test the calculated endpoints for the effect of test item were the following: 72h ErC50, EbC50, EyC50 > 100 mg/L, NOEC = 100 mg/L.

Description of key information

The 72h-EC50 of test item to Green Algae is determined as > 100 mg/L, NOEC = 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information