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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
Study period:
2008-12-06 to 2009-01-15
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
Date of inspection 2005-09-14 to 2005-09-16 and 2005-10-26 to 2005-10-28; Date of signature 2006-01-11
Analytical monitoring:
Details on sampling:
- Zero and 72 h (test system)
- Zero and 72 h (control)
Details on test solutions:
- The only test concentration was prepared by adding 125.0 mg of test material to 1 L of dilution water.
- The pH was determined to be 2.9 and was adjusted to 8.1 with 1 M sodium hydroxide solution.
- 80 mL of the stock solution was taken and diluted with 10 mL nutrient medium and 10 mL algal inoculum with a cell density of 5000 cell/mL to give a final concentration of 100 mg/L.
- Six replicates were prepared for the test item and controls.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- The test species was obtained from "The Collection of Algal Cultures" of the Institute of Plant Physiology at Göttingen University, Germany.
- Exponentially growing stock cultures were maintained at 23 ± 2 °C and light intensity 60-120 μE m-2 s-1 (measured in the range 400-700 nm using a spherical quantum flux meter).
- The nutrient medium was renewed once a week.
- Cell density measurements were made using a microcell counter.
- Pre-cultures were set up 4 d before the start of the test and, with the exception of the nutrient medium, were grown under identical exposure conditions to the stock cultures.
- Algal inocula for a test were taken from an exponentially growing pre-culture and were mixed with the nutrient medium (see Annex 1, attached) to give a final cell density of approximately 5,000 cell/mL in the test medium.

Test type:
Water media type:
Limit test:
Total exposure duration:
72 h
Post exposure observation period:
Not applicable
Not reported
Test temperature:
21 ± 2 °C to 25 ± 2 °C
- Test system pH 7.9 (zero hours)
- Test system pH 8.7 (72 h)
- Control pH 7.8 (zero hours)
- Control pH 8.6 (72 h)
Dissolved oxygen:
Not reported
Not applicable
Nominal and measured concentrations:
100 mg/L (nominal)
Details on test conditions:
- Test vessels: Erlenmeyer flasks (300 mL) with cotton stoppers
- Culturing apparatus: Light chamber in which temperature range was maintained and continuous uniform illumination was provided in the spectral range 400 to 700 nm
- Light intensity: 60-120 μE m-2 s-1 or an equivalent range of 4000 to 8000 lx
Reference substance (positive control):
not specified
72 h
Dose descriptor:
Effect conc.:
> 100 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
growth rate
72 h
Dose descriptor:
Effect conc.:
> 100 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
Details on results:
- Results were expressed in terms of nominal concentrations.
- Recovery rates were corrected for sulphate content of the controls.
- Recovery rates ranged from 99.1 % to 99.3 % of nominal values at zero h.
- Recovery rates ranged from 99.6 % to 101.6 % of nominal values at 72 h.
- Recovery rates relate to the concentration of 48.0 % H2SO4 in the test material.
Reported statistics and error estimates:
Not reported


See comparison of overall physico-chemical and toxicity profiles for target and source chemicals in the data matrix (attached).

Validity criteria fulfilled:
No toxic effects on algae were observed at a limit test concentration of 100 mg/L, the ErC50 (0-72 h) was reported as > 100 mg/L, and the No Observed Effect Concentration (NOEC) was reported as ≥ 100 mg/L.

Description of key information

ErC50 > 100 mg/L (OECD 201)
NOEC ≥ 100 mg/L (OECD 201)

Key value for chemical safety assessment

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

Additional information

No toxic effects on algae were observed at a limit test concentration of 100 mg/L sulphuric acid.