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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:
2020-04-30 to 2020-10-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
adopted 28th July, 2011
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material:provided by sponsor/91112Y
- Expiration date of the lot/batch:12 March 2021

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material:Controlled room temperature (15-25oC, ≤70% relative humidity), protected from light and humidity (tight closed container)

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Because the test item is a reaction mass and has a very poor solubility in test media, test item stock solution was prepared using a saturated solution method (water accommodated fraction, WAF) according to the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, OECD No. 23 (2000).
Analytical monitoring:
yes
Details on sampling:
- Concentrations:
- Sampling method:
Control -start 4mL/tubes, 3 tubes
100mg/L WAF-Start 4mL/tubes, 3 tubes
Control -End 4mL/tubes, 3 tubes
100mg/L WAF-End 4mL/tubes, 3 tubes
- Sample storage conditions before analysis: Kept below -15℃
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
Because the test item is a reaction mass and has a very poor solubility in test media, test item stock solution was prepared using a saturated solution method (water accommodated fraction, WAF) according to the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, OECD No. 23 (2000). Saturated test item solution (nominal loading rate of 100.0 mg/L) was prepared by dispersing/dissolving the amount of test item into the test medium (OECD Medium) two days before the start of the experiment. This solution was shaken for about 24 hours at approximately 30°C and then equilibrated for about 24 hours at approximately 20°C. The non-dissolved test material was removed by filtration through a fine (0.22 µm) filter to give the appropriate WAF solution. The maximum amount of test material in the medium was exposed applying this procedure.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: Pseudokirchneriella subcapitata
- Source (laboratory, culture collection): The algae were supplied by the SAG: Collection of Algal Cultures, Inst. Plant Physiology, and University of Göttingen, GERMANY. Cultured under standardised conditions (see OECD 201) in the Ecotoxicological Laboratory of Charles River Laboratories Hungary Kft.


Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
Culture temperature was checked at the beginning of the experiment and each day thereafter in a flask filled with water, in the climatic chamber. In addition, water temperature was continuously measured (with a min/max thermometer) within the climate chamber. The temperature was in the range of 22.6 – 22.8 °C measured in the flask and between 21.3 and 23.2 °C measured within the climate chamber.
pH:
The pH was checked at the beginning and at the end of the test in each test vessels. The pH of the control medium was not increased by more than 1.5 units during the test. The range of the pH was 7.57 – 9.11 during the experiment.
Nominal and measured concentrations:
nominal loading rate of 100.0 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:250 mL sterile Erlenmeyer flasks
- Type (delete if not applicable):closed
- Initial cells density: 10000 algal cells per mL test medium
- Control end cells density: 705000 algal cells per mL test medium
- No. of vessels per concentration (replicates):6
- No. of vessels per control (replicates):6

GROWTH MEDIUM
- Standard medium used: yes


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH:The pH was checked at the beginning and at the end of the test in each test vessels. The pH of the control medium was not increased by more than 1.5 units during the test. The range of the pH was 7.57 – 9.11 during the experiment.
- Light intensity and quality:
The algal culture flasks were continuously illuminated. The light intensity at the position occupied by algal culture flasks during the test was about 7754 lux (equivalent to ~105 μE/m2/s), which was ensured with fluorescent lamps (with a spectral range of 400-700 nm). The differences in light intensity between the test vessels did not exceed ± 15 % and therefore provided equal conditions for each test vessel.

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


TEST CONCENTRATIONS
- Range finding study:0.1,1 ,10, 100 mg/L nominal loading rate WAF
- Test concentrations: 100 mg/L nominal loading rate WAF
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
NOELR
Remarks:
(No Observed Effect Loading Rate) the highest loading rate at which no significant inhibition of growth is observed relative to the control
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Basis for effect:
other: biomass, growth rates and yield
Duration:
72 h
Dose descriptor:
LOELR
Remarks:
(Lowest Observed Effect Loading Rate) the lowest loading rate at which a significant inhibition of growth is observed relative to the control
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Basis for effect:
other: biomass, growth rates and yield
Key result
Duration:
72 h
Dose descriptor:
EL50
Remarks:
the calculated loading rate of test item which results in a 50 % reduction of growth rate (μ) relative to the control
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL50
Remarks:
the calculated loading rate of test item which results in a 50 % reduction of biomass (b) relative to the control
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EL50
Remarks:
the calculated loading rate of test item which results in a 50 % reduction of yield (y) relative to the control
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Basis for effect:
other: yield (migrated information)
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): none
Results with reference substance (positive control):
- Results with reference substance valid? YES
- EC50:
The 72h ErC 50: 0.88 mg/L, (95 % confidence limits: 0.81 – 0.96 mg/L)
The 72h EbC 50: 0.60 mg/L, (95% confidence limits: 0.55 – 0.65 mg/L)
The 72h EyC 50: 0.53 mg/L, (95 % confidence limits: 0.48 – 0.57 mg/L)
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the test, the test item gave an EL50 of growth rate of >100mg/L at 72 h based on nominal concentrations.
Executive summary:

In a 72 -hour acute toxicity study, the cultures of algae (Pseudokirchneriella subcapitata

 , 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662))were exposed to the test item at nominal concentrations of 100 mg/L under static conditions in accordance with the OECD201.  The NOEC and EL50 values based on growth rate/biomass/yield were 100 and >100 mg/L, respectively. 

 

There were no compound related abnormalities effects.

 

The test item is not classified based on the guideline requirements for algae toxicity study.

 

Results Synopsis

 

Test Organism: algae; Pseudokirchneriella subcapitata

Test Type: static

 

72hr ErL50:  >100 mg/L       

72hr EyL50:  >100 mg/L        

72hr EbL50:  >100 mg/L  

72hr NOELR:  100 mg/L                  

Description of key information

72hr ErL50:  >100 mg/L; 72hr EyL50:  >100 mg/L; 72hr EbL50:  >100 mg/L; 72hr NOELR:  100 mg/L (Algae; Pseudokirchneriella subcapitata,OECD201,GLP)

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information