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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:
31.07.2017 - 2.08.2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experiment test result performed using standard test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
Short term toxicity of test chemical to aquatic algae was performed according to the 201 OECD guideline in a static system.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
yes
Remarks:
Acetone
Details on test solutions:
The stock solution 10 mg/l was prepared by dissolving dark liquid in acetone. Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. It was not possibile to test higher concentrations of sample because of low solubilities.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name:
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Institute of botany of the ASCR
- Initial biomass concentration: 5x10(3) cells /ml
- Method of cultivation: No data available

ACCLIMATION - No data available
- Acclimation period:
- Culturing media and conditions (same as test or not):
- Any deformed or abnormal cells observed:
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
±1 hour
Test temperature:
23±2°C
pH:
Test at highest concentration: 7.9 (changes to 7.5 during tests)
Control: 8.1 (changed to 7.6 during test)
Control + acetone: 8.0 changes to 7.5
Nominal and measured concentrations:
0, 0, 2.3, 3.4, 5, 7.4, 10.8 mg/l nominal concentration.
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 ml Glass vessel
- Type (delete if not applicable): closed (with air permeable stopper)
- Sample volume: 15 ml
- Initial cells density: 5x10(3) cells/ml
- No. of vessels per concentration (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: Continuous
- Light intensity and quality: 6000-8000 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microscope with counting chamber Cyrus I or electronic particle counter.
- Other: ErC50 was calculated using non-linear regression by the software Prism 4.0
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (K2Cr2O7)
Key result
Duration:
72 h
Dose descriptor:
other: ErC50
Effect conc.:
15.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 11.9 - 20.6 mg/l
Results with reference substance (positive control):
Results with reference substance valid
- EC50: 0.75 mg/L
Reported statistics and error estimates:
ErC50 is calculated from the inhibition of growth rate by non-linear regression using software Prism 4.0, GraphPad.
Validity criteria fulfilled:
not specified
Conclusions:
The median effective concentration (ErC50) for the test substance, in Desmodesmus subspicatus was determined to be 15.7 mg/L on the basis of effects on growth rate in a 72 hour study.
Executive summary:

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance according to OECD Guideline 201. The stock solution 10 mg/l was prepared by dissolving dark liquid in acetone.

Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. It was not possibile to test higher concentrations of sample because of low solubilities thus chemical dissolved in the acetone. Test conducted on 0, 0, 2.3, 3.4, 5, 7.4, 10.8 mg/l nominal concentration in static system. Potassium dichromate used as a positive control. ErC50 is calculated from the inhibition of growth rate by non-linear regression using software Prism 4.0, GraphPad. Effects on the growth rate of the organism were studied after the exposure period of 72 hrs.

The median effective concentration (ErC50) for the test substance, in Desmodesmus subspicatus was determined to be 15.7 mg/L on the basis of effects on growth rate in a 72 hour study. This value indicates that the substance is likely to be hazardous to aquatic algae and can be classified as aquatic chronic 3 category as per the CLP criteria.

The test chemical is as such insoluble in water and hence for the experiment performed the test chemical was dissolved in acetone as the solvent. It is likely that acetone can interfere with the toxicity observed. In natural conditions, the test chemical will be exposed to the test organism in water and as it is insoluble in water, it is less likely to affect the growth of algae and cyanobacteria. Based on the above criteria it can be concluded that the chemical was not toxic and cannot be classified as per the CLP classification criteria.

Description of key information

The median effective concentration (ErC50) for the test substance, in Desmodesmus subspicatus was determined to be 15.7 mg/L on the basis of effects on growth rate in a 72 hour study.

Key value for chemical safety assessment

EC50 for freshwater algae:
15.7 mg/L

Additional information

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance according to OECD Guideline 201. The stock solution 10 mg/l was prepared by dissolving dark liquid in acetone. Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. It was not possibile to test higher concentrations of sample because of low solubilities thus chemical dissolved in the acetone. Test conducted on 0, 0, 2.3, 3.4, 5, 7.4, 10.8 mg/l nominal concentration in static system. Potassium dichromate used as a positive control. ErC50 is calculated from the inhibition of growth rate by non-linear regression using software Prism 4.0, GraphPad. Effects on the growth rate of the organism were studied after the exposure period of 72 hrs. The median effective concentration (ErC50) for the test substance, in Desmodesmus subspicatus was determined to be 15.7 mg/L on the basis of effects on growth rate in a 72 hour study. This value indicates that the substance is likely to be hazardous to aquatic algae and can be classified as aquatic chronic 3 category as per the CLP criteria. The test chemical is as such insoluble in water and hence for the experiment performed the test chemical was dissolved in acetone as the solvent. It is likely that acetone can interfere with the toxicity observed. In natural conditions, the test chemical will be exposed to the test organism in water and as it is insoluble in water, it is less likely to affect the growth of algae and cyanobacteria. Based on the above criteria it can be concluded that the chemical was not toxic and cannot be classified as per the CLP classification criteria.