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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:
2018-09-21 to 2018-10-09
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)
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Principles of method if other than guideline:
not applicable
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: control, 10, 18, 32, 56 and 100 mg/L
- Sampling method: Samples were taken from the control and each test group from the bulk test preparation at 0 hours and from the pooled replicates at 72 hours for quantitative analysis. set of duplicate samples was taken at 0 and 72 hours and stored frozen for further analysis if necessary.
- Sample storage conditions before analysis: All samples were stored frozen prior to analysi
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: A nominal amount of test item (200 mg) was dissolved in culture medium and the volume adjusted to 2 liters to give a 100 mg/L stock solution from which a series of dilutions was made to give further stock solutions of 56, 32, 18 and 10 mg/L. The stock solutions and each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity. The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 72 hours

- Controls: negative control

- All other template details: Not reported
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland
- Age of inoculum (at test initiation): not reported
- Method of cultivation: not reported

- All other template details: Not reported
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
Not reported
Hardness:
Not reported
Test temperature:
24 ±1 ºC
pH:
7.9 to 8.9 (control cultures)
A concentration dependent increase in pH was observed in the test preparations at 0 hours in the range of pH 8.8 at 10 mg/L through to pH 9.8 at 100 mg/L which was considered to be due to an intrinsic property of the test item
Dissolved oxygen:
Not reported
Salinity:
Not reported
Conductivity:
Not reported
Nominal and measured concentrations:
Nominal test concentrations (mg/L): 10, 18, 32, 56 and 100.


Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to range from 84% to 109% of nominal and so the results are based on nominal test concentrations only
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL glass conical flasks
- Material, size, headspace, fill volume: 250 mL glass conical flasks each containing 100 mL of test preparation and plugged with polyurethane foam bungs to reduce evaporation
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: 5.0E+3 cells/mL for control
- Control end cells density: 1.82E+06 cells/mL for control.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): not applicable

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no
- Intervals of water quality measurement: pH was measured at the start and after 72 hours
- All other template details: Not reported

OTHER TEST CONDITIONS
- Sterile test conditions: not reported
- Adjustment of pH: no.
- Photoperiod: continuous
- Light intensity and quality: approximately 7000 lux
- Salinity (for marine algae): not applicable

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: coulter counter after 25, 48, 72 hours
- Chlorophyll measurement: not reported

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: range finding test: 0.10, 1.0, 10 and 100 mg/L.
- Results used to determine the conditions for the definitive study: The results of the range-finding test showed no effect on growth at the test concentrations of 0.10, 1.0 and 10 mg/L. However, growth was observed to be reduced at 100 mg/L.
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
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
67 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
18 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
78 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
26 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
14 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
18 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no abnormalities after 72h
- Colour differences: At the start of the test all control and test cultures were observed to be clear colorless solutions. After the 72-Hour test period all control, 10, 18 and 32 mg/L test cultures were green dispersions whilst the 56 and 100 mg/L test cultures were light green dispersions.
- All other template details: Not reported
Results with reference substance (positive control):
ErC50 (0 to 72 hour) : 1.6 mg/L; 95% confidence limits 1.4 to 1.8 mg/L
EyC50 (0 to 72 hour) : 0.77 mg/L; 95% confidence limits 0.68 to 0.87 mg/L

NOEC growth rate: 0.25 mg/L
NOEC yield: 0.25 mg/L
LOEC growth rate: 0.50 mg/L
LOEC yield: 0.50 mg/L
Reported statistics and error estimates:
Not reported

Exposure of Pseudokirchneriella subcapitata to the test item gave the following results:

 Response variable  EC50 (mg/L) NOEC (mg/L) LOEC (mg/L) 
 Growth Rate  >100*  18  32
 Yield  78 18  32

* It was not possible to calculate an ErC50 value as no more than 15% inhibition of growth rate occurred at the maximum concentration employed

Validity criteria fulfilled:
yes
Remarks:
Cell concentration of the control cultures increased by a factor of 364 after 72 h. The mean coefficient of variation for section by section specific growth rate for the control cultures was 9%.
Conclusions:
There were no statistically significant differences (P=0.05), between the control, 10 and 18 mg/L test concentrations, however all other test concentrations were significantly different (P<0.05) and, therefore the NOEC based on growth rate was 18 mg/L. Correspondingly the LOEC based on growth rate was 32 mg/L.
There were no statistically significant differences (P=0.05), between the control, 10 and 18 mg/L test concentrations however all other test concentrations were significantly different (P<0.05) and, therefore the NOEC based on yield was 18 mg/L. Correspondingly the LOEC based on yield was 32 mg/L.
Executive summary:

An algal growth inhibition tests for the test was performed accroding to OECD 201. Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 10, 18, 32, 56 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ±1 °C. Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to range from 84% to 109% of nominal and so the results are based on nominal test concentrations only.

Description of key information

An algal growth inhibition tests for the test was performed accroding to OECD 201. Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 10, 18, 32, 56 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ±1 °C. Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to range from 84% to 109% of nominal and so the results are based on nominal test concentrations only.

Key value for chemical safety assessment

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

Additional information