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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study with analytical monitoring
according to guideline
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
Details on test solutions:
- Since the test item is poorly soluble in water, a modification of the standard method for the preparation of aqueous media was performed with help of water accomodated fractions (WAF).
- Using this approach, aqueous media were prepared by shaking the test item with dilution water at 20 rpm for 24 hours at room temperature to ensure equilibration between the test item and the water phase.
- For each loading level, an appropriate amount of the test item was weighed out and transferred into a brown glass flask with an appropriate amount of dilution water.
- After the completion of shaking and following a 1-h settlement period, the test item phase was separated by siphon and the test organisms exposed to the clear aqueous phase, the WAF.
- Exposures are expressed in terms of the original concentrations of the test item in water at the start of the mixing period (loading levels) irrespective of the actual concentrations of the test item in the WAFs.
- All solutions were clear and colourless
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Strain: Desmodesmus subspicatus CHODAT SAG 86.81
- Origin: Sammlung von Algenkulturen (SAG), Pflanzenphysiolgisches Institut der Universität Göttingen, 37073 Göttingen, Germany
- Cultivation at test facility: fresh stocks are prepared every month on Z-Agar. Light intensity amounts to 35-70 µE * m-2 * s-1 for 24 h per day
- Culture medium: nutrient medium Z according to Lüttge et al. (1994)
- Preculture: a four day old preculture, prepared in dilution water, was used as inoculum. For the start of the test, the preculture was direclty pipetted into each test concentration and control.
Test type:
Water media type:
Limit test:
Total exposure duration:
72 h
Test temperature:
21.5 - 23.5°C
7.76 - 8.34
Nominal and measured concentrations:
- Nominal loadings of the test item: 0.10, 0.316, 1.0, 3.16, 10.0 and 31.6 mg/L plus control
- The measured concentrations of the test item in the fresh media (0 h) were in the range of 110 to 119 % of the nominal values. The recoveries of the test item in the old media (72 h) were in the range of 110 to 118 % of the nominal values.
Details on test conditions:
- Test vessel: sterile Erlenmeyer flasks (250 ml volume) with cotton wool plugs
- Test volume: 100 ml
- No. replicates / loading level: 3
- No. replicates / control: 6
- Agitation: test vessels were placed on a rotary shaker and oscillated at approx. 70 rpm
- Initial cell density: nominal: approx. 2 - 5E+3 cells/ml
actual: 4.33E+3 cells/ml

- Light intensity: 60 - 120 µE * m-2 * s-1
- Light regime: 24 hours/day light
- Light source: fluorescent tubes, OSRAM L 36 W/11-865, cool daylight
- Light homogeneity: within +- 15 % over incubation area
Reference substance (positive control):
Potassium dichromate
72 h
Dose descriptor:
Effect conc.:
1.8 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL 1.56 - 2.04
72 h
Dose descriptor:
Effect conc.:
9.51 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL 8.09 - 31.6
Details on results:
- Biological observations: microscopic evaluation of the cells at the start and the end of the incubation period revealed no morphological abnormalities.
Results with reference substance (positive control):
ErC50 (72 h) = 0.631 mg/L (nominal)
Validity criteria fulfilled:

Description of key information

Acutely toxic to aquatic algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
9.51 mg/L
EC10 or NOEC for freshwater algae:
1.8 mg/L

Additional information

The acute toxicity to algae was investigated in a GLP test according to OECD guideline 201 using Desmodesmus subspicatus as test organism [Dr. U. Noack-Laboratorien, 2013]. Because of the low solubility of the test substance a water accomodated fraction (WAF) with 6 different loadings was prepared. The experiment was conducted under static conditions over a test period of 72 h and the test loadings were monitored analytically. At test termination, an ErL50 of 9.51 mg/L (nominal) and an ErL10 of 1.8 mg/L (nominal) was determined.