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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:
01.08.2017 to 18.08.2017
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
Qualifier:
according to guideline
Guideline:
EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
For determination of the test item concentrations, three replicate samples (5 mL per replicate) were taken from each test concentration and six replicates (5 mL per replicate) from the control at the start and at the end of the test.
Vehicle:
no
Details on test solutions:
The test solutions used in the test were prepared by mechanical dispersion without using any solubilising agents. A stock solution was first prepared by dissolving an amount of 0.08 g test item in 800 mL dilution water (OECD Medium) to obtain the nominal concentration of 100 mg/L. The test solutions of subsequent lower test concentrations were prepared by appropriate diluting of this stock solution
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Raphidocelis subcapitata (Printz-Starr)
- Strain: 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662)
- Source: SAG: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany
- Method of cultivation: Small algal cultures that are regularly planted on agar are transferred to fresh medium at least once every two months under standardised conditions according to the test guidelines. Pre-culture was prepared with Algal Mineral Salts Culture Medium, incubated under the conditions of the test and used when still exponentially growing, normally after an incubation period of 2 - 4 days.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not specified
Test temperature:
21.5 – 21.9°C (test vessel), 21.4 - 22.9°C (climate chamber)
pH:
7.68 – 9.08 (control: 7.69 -9.08)
Dissolved oxygen:
not specified
Salinity:
not applicable
Conductivity:
not specified
Nominal and measured concentrations:
The following nominal concentrations were tested: 1.23, 3.70, 11.1, 33.3 and 100 mg/L.
The measured concentrations of the test item were in the range of 102 – 104 % of the nominal at the start and 89 – 99 % at the end of the test.
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flask
- Type: covered with air-permeable stoppers
- Medium volume per flask: 100 mL
- Initial cells density: 10^4 cells/mL
- Control end cells density: 97×10^4 cells/mL (mean value)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (OECD medium according to OECD 201)

OTHER TEST CONDITIONS
- Photoperiod: continuously
- Light intensity and quality: 7914 lux, fluorescent lamps

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: counting chamber
- Morphological Changes of Algal Cells: microscopy

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3
- Range finding study: yes
- Test concentrations: 0.1, 1, 10 and 100 mg/L plus a control
- Results used to determine the conditions for the definitive study: no significant growth inhibition at any test concentration
Reference substance (positive control):
yes
Remarks:
Potassium dichromate, test period: 07 – 10 March
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.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
11.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
33.3 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:
EC10
Effect conc.:
2.45 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
11.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
33.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control: Yes, cell density in the control has increased from nominal N = 1 × 10^4 cells/mL at the start of the test (0 hours) to 97 x 10^4 at the end of the test (72 hours).
- Observation of abnormalities: No morphological abnormalities were observed in the control and in any of the test concentrations.
Results with reference substance (positive control):
The 72h ErC50: 0.99 mg/L (95 % confidence limits: 0.68 – 1.49 mg/L). The 72h EyC50: 0.59 mg/L (95 % confidence limits: 0.47 – 0.75 mg/L).
Reported statistics and error estimates:
For the determination of the LOEC and NOEC, ANOVA and Dunnett’s test (α = 0.05) was used and for the determination of the ECx values Probit analysis was used.
Validity criteria fulfilled:
yes
Conclusions:
In this 72-h algal growth inhibition test the effects of the test item on the growth of Raphidocelis subcapitata was determined. The 72-h EC10, EC20, EC50 for growth were determined to be > 100 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 2.45, 37.3 and > 100 mg/L, respectively. The LOEC and NOEC values based on growth rate and yield were determined to be 33.3 and 11.1 mg/L, respectively. The results are based on nominal test item concentrations.
Executive summary:

The purpose of this study was to determine the effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata. Exponentially growing cultures of Raphidocelis subcapitata were exposed to test item concentrations of 1.23, 3.7, 11.1, 33.3 and 100 mg/L. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours. The 72-h EC10, EC20, EC50 for growth were determined to be > 100 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 2.45, 37.3 and > 100 mg/L, respectively. The LOEC and NOEC values based on growth rate and yield were determined to be 33.3 and 11.1 mg/L, respectively. The results are based on nominal test item concentrations.

Description of key information

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP (reference 6.1.5-1). The study was conducted under static conditions with an initial cell density of 1x10^4 cells/mL for a period of 72 hours. The EC50, EC10 and NOEC based on growth rate were determined to be > 100 mg/L (nominal).

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
11.1 mg/L

Additional information

The effect of the test item on the growth of a unicellular green algal species Raphidocelis subcapitata was determined according to OECD 201, Regulation (EC) No. 226/2016 Method C.3 and EPA OPPTS 850.5400 and under GLP (reference 6.1.5-1). The study was conducted under static conditions with an initial cell density of 1x10^4 cells/mL for a period of 72 hours. Five concentrations were tested in a geometrical series with a dilution factor of 3: 1.23, 3.7, 11.1, 33.3 and 100 mg/L. The 72-h EC10, EC20, EC50 for growth were determined to be > 100 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 2.45, 37.3 and > 100 mg/L, respectively. The LOEC and NOEC values based on growth rate and yield were determined to be 33.3 and 11.1 mg/L, respectively. The results are based on nominal test item concentrations.

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