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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Exp. part: March 03 - Oct 25, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
The samples were taken from the biological phase of the study. Collecting, storage and handing over of the samples were the Study Director’s responsibility. The information concerning the samples was provided by the Study Director.
Duplicate samples from the freshly prepared test media (containing algae) of all test concentrations and from the control were taken at the start of the test.
For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, duplicate samples from the test media of all test concentrations and the control (containing algae) were taken at the end of the test (after the 72 hours test period) by pouring together the contents of the test beakers of each treatment. In addition, samples were taken after 24 and 48 hours test duration by taking aliquots of each replicate per concentration which were merged.
The samples were diluted by a factor of two with acetonitrile.
Additional samples of the control and of the dilution solvent were taken at each sampling without any sample treatment.
Vehicle:
no
Details on test solutions:
Due to the low limit of water solubility of the test item, a filtrate of nominal 100 mg/L and dilutions of 1:3, 1:9, 1:27 and 1:81 of this filtrate were tested corresponding to following nominal concentrations of the test item: 100, 33.3, 11.1, 3.7 and 1.23 mg test item/L, and a control. The amounts of test item could only be indicated at test start at the test concentration of nominal 100 mg test item/L (i.e. the filtrate of 100 mg test item/L), which is assumed to be about 26 µg test item/L at test start decreasing over the course of the test.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Selenastrum capricornutum
- Strain: 61.81 SAG
- Source (laboratory, culture collection): "Sammlung von Algenkulturen, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen", 37073 Göttingen, Germany.
- Method of cultivation: The algae were cultivated in the laboratories of ibacon under standardised conditions according to the test guidelines.

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
24 mg/L
Test temperature:
22.3 to 22.6 °C
pH:
8 - 9.6
Nominal and measured concentrations:
In the test samples no quantifiable amounts of test item were detected. The concentration of the filtrate of the test concentration of nominal 100 mg test item/L is assumed to be about 26 µg test item/L at test start decreasing over the course of the 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:
EC10
Effect conc.:
91.9 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 49.1 - > 100 mg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
33.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): none
- Unusual cell shape: no
- Colour differences: no
- Flocculation: no
- Adherence to test vessels: no
- Aggregation of algal cells: no
- Other: -
- Any stimulation of growth found in any treatment:
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values:
- Effect concentrations exceeding solubility of substance in test medium:
Results with reference substance (positive control):
Parameter (0-72 h)
EC50 (yield) = 0.442 mg/L
EC50 (growth rate) = 1.11 mg/L
EC50 (biomass) = 0.487 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The influence of the test material on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static concentration-response test. The 72-hour EyC50 was calculated to be > 100 mg test item/L and the 72-hour ErC50 value was estimated to be >100 mg test item/L. The 72-h ECr10 value was determined to be 91.9 mg/L and the 72-hour NOErC is 33.3 mg/L.
The initial concentrations and the maintenance of the exposure concentrations during the test were determined in the analytical part but didn’t result in quantitative results. All reported results refer to nominal values since the concentrations of the test samples could not be quantified.
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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 201. A detailed read across justification is provided in chapter 13 of this dossier.
Reason / purpose:
read-across source
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.:
91.9 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 49.1 - > 100 mg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
33.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Conclusions:
For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 201. The read across yields EC50 values exceeding 100 mg/L nominal exposure. A detailed read across justification is provided in chapter 13 of this dossier.

Description of key information

No data for toxicity to aquatic algae and cyanobacteria are available for the test item, however, a Guideline study under GLP conditions was conducted with a structural analogue substance to cover the endpoint adequately.

The 72 -h EC50 value was determined to greater than 100 mg/L (nominal) and the 72 -h EC10 value was determined to be 91.9 mg/L (estimated) based on growth rate in a study according to OECD Guideline 201.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
91.9 mg/L

Additional information