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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:
from 2017-06-15 to 2017-06-28
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)
Version / remarks:
2006
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
01 March 2016
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)
Version / remarks:
1996
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
TOXI-COOP Toxicological Research Center Zrt.
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test item is poorly water soluble material. In order to achieve the maximum solubility level, the test solution was prepared as follows: a supersaturated solution (100 mg/L nominal loading) was prepared by dispersing/dissolving an amount of 0.08 g test item in 800 mL test medium (OECD medium). This solution was agitated by orbital shaker (~350 rpm) for approx. one day and then the non-dissolved test material was separated by filtration through a membrane filter (0.2 μm) in order to obtain the saturated test solution (corresponding to 100 mg/L nominal concentration).
- Controls: Yes. The dilution water (OECD medium) without addition of the test item was used as a control solution.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Species: Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapita and Selenastrum capricornutum) (Printz-Starr).
- Strain number : 61.81 SAG (identical strains: CCAP 278/4; UTEX 1648; ATCC 22662)
- Source: The algae were supplied by the SAG: Collection of Algal Cultures, Inst. Plant Physiology, University of Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany
- Age of inoculum (at test initiation):
- Method of cultivation: The stock cultures are small algal cultures that are planted on agar regularly. These are transferred to fresh medium at least once every two months under standardised conditions according to the test guidelines. The pre-culture is intended to give an amount of algae suitable for the inoculation of test cultures. The 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. (The pre-culture was incubated for four days at this test.)

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22.1 - 22.9 °C (measured in the flask)
21.0 - 23.0 °C (measured within the climate chamber)
pH:
7.70 - 9.20
Nominal and measured concentrations:
Nominal concentration: 100 mg/L
No measured concentrations.
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flaks of ~250 mL volume with 100 mL test medium.
- Type: closed. The flasks were covered with air-permeable stoppers.
- Initial cells density: 10^4 cells/mL
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: Continuously illumination
- Light intensity and quality: The average light intensity during the test was 7900 lux, 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 %.

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: counting chamber

PRELIMINARY TEST
- Test concentrations: A non-GLP preliminary experiment was carried out at saturation concentration (100 mg/L nominal loading) to determine the approximate toxicity of the test item.
- Results used to determine the conditions for the definitive study: Significant toxic effects were not observed during the preliminary test therefore only one test concentration at saturation (equivalent to 100 mg/L nominal concentration) was tested in a limit test. A concurrent control group ran parallel.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: growth rate and yield
Details on results:
- Growth Inhibition: The growth inhibition calculated for the 72 hours exposure in treatment group compared to the control was -1.2 % for the average specific growth rate and -6.7 % for the yield.
The results of the statistical evaluation showed that the 0-72 h average specific growth rate and yield at the treatment group (saturated solution; equivalent to 100 mg/L nominal concentration) was not statistically significantly different from the untreated control (T-test; 2-tailed; α = 0.05).
- Microscopic Examination: Abnormal appearance of the algal cells was not observed during the experiment.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- 72h ErC50: 0.99 mg/L, (95 % confidence limits: 0.68 – 1.49 mg/L)
- 72h EyC50: 0.59 mg/L, (95 % confidence limits: 0.47 – 0.75 mg/L)
Validity criteria fulfilled:
yes
Conclusions:
In this 72-h algal growth inhibition test with Raphidocelis subcapitata, the obtained results showed that the test item had no toxic effect on the algae at aquatic saturation (equivalent to 100 mg/L nominal concentration). Accordingly, the 72-h EC10, EC20, EC50 and the LOEC values based on growth rate and yield were determined to be >100 mg/L. The 72-h NOEC was determined to be 100 mg/L. The results are based on nominal test item concentrations.
Executive summary:

A 72-h algal growth inhibition test with Raphidocelis subcapitata according to OECD guideline 201 was perfromed. The test item is a poorly water soluble material and therfore a saturated solution (100 mg/L nominal loading) was prepared and the alga (initial cell denisty: 10^4 cells/mL) were exposed to the test media containing the test item plus a control group for 72 hours. In this 72-h algal growth inhibition test with Raphidocelis subcapitata, the obtained results showed that the test item had no toxic effect on the algae at aquatic saturation (equivalent to 100 mg/L nominal concentration). Accordingly, the 72-h EC10, EC20, EC50 and the LOEC values based on growth rate and yield were determined to be >100 mg/L. The 72-h NOEC was determined to be 100 mg/L. The results are based on nominal test item concentrations.

Description of key information

In a 72-h algal growth inhibition test with Raphidocelis subcapitata an EC10, EC20, EC50 and a LOEC values based on growth rate and yield were determined to be >100 mg/L. The 72-h NOEC was determined to be 100 mg/L. The results are based on nominal test item concentrations.

Key value for chemical safety assessment

Additional information

A 72-h algal growth inhibition test with Raphidocelis subcapitata according to OECD guideline 201 was perfromed. The test item is a poorly water soluble material and therfore a saturated solution (100 mg/L nominal loading) was prepared and the alga (initial cell denisty: 10^4 cells/mL) were exposed to the test media containing the test item plus a control group for 72 hours. In this 72-h algal growth inhibition test with Raphidocelis subcapitata, the obtained results showed that the test item had no toxic effect on the algae at aquatic saturation (equivalent to 100 mg/L nominal concentration). Accordingly, the 72-h EC10, EC20, EC50 and the LOEC values based on growth rate and yield were determined to be >100 mg/L. The 72-h NOEC was determined to be 100 mg/L. The results are based on nominal test item concentrations.

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