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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:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
sampling schedule:
control: at 72h
test concentration: 100 mg/L at 0 and 72h

Routinely, the samples were analysed immediately. Only in exceptional cases, they were stored overnight deep frozen and protected from light.
Vehicle:
no
Details on test solutions:
To produce the only test item concentration 100.3 mg of the test item were added to 1 litre of dilution water, treated for 60 seconds at 8000 rpm with an ultra turrax and stirred for 24 h on a magnetic stirrer.
Undissolved particles of the test item were removed by filtration using a folded filter with a pore size of 7-12 μm and an aseptic filter Sartobran sterile capsules with a pore size of 0.45 μm + 0.2 μm. The pH was measured to be 7.8.
100 mL of the solution were taken and 0.485 mL of the algal inoculum was added to each replicate resulting in a final cell density of 5000 cells/mL. For each test item concentration and the control 6 replicates were prepared. All flasks were sealed with cotton stoppers.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
- Name : Desmodesmus subspicatus (formerly Scenedesmus subspicatus) Strain No. 86.81 SAG
- Source : Strain of the test species obtained from 'The Collection of Algal Cultures' of the Institute of Plant Physiology at the University of Göttingen (Germany).
- Maintenance and Acclimatisation : Exponentially growing stock cultures were maintained in the test facility under constant temperature conditions (21-24 °C with a maximum fluctuation of +/- 2 °C) at a light intensity in th e range 60 to 120 E x m-2 x s-1 (measured in the range 400 to 700 nm using a spherical quantum flux meter). The growth medium (according to BRINGMANN & KÜHN (1977) was renewed once a week. Cell density measurements were made using a microcell counter, Sysmex F300, Digitana.
- Preparation of pre cultures : Pre cultures were set up three days before the start of a test. They were grown under identical exposure conditions as the stock cultures, except from the use of a different growth medium.
- Test cultures : The algal inocula for the test were taken from an exponentially growing pre culture and were mixed with the growth medium to make up to a final cell density of about 5000 cells per millilitre in the test medium.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
1.3°dH (corresp. to 22.5 mg/L CaCO3)
Test temperature:
21-24°C
pH:
Control: 7.9 at 0 h and 9.9 at 72 h
100 mg/L: 7.9 at 0 h amd 10.3 at 72h
The pH value in the control after 72 hours increased by more than 1.5 pH units. This increase is not regarded to be relevant to the results as all validity criteria were met.
Nominal and measured concentrations:
Nominal: 100 mg/L
No toxic effects against algae were observed at a limit test concentration of 100 mg/L, corresponding to a measured concentration of < 0.0334 mg/L, which reflects the maximum water solubility under exposure conditions.
Details on test conditions:
- Test vessels : 300 mL Erlenmeyer flasks with cotton stoppers test volume: 100 mL
- Culturing apparatus : Shaking incubator in which a temperature in the range 21 °C to 24 °C was maintaine d at +/- 2 °C, and continuous uniform illumination was provided in the spectral range 400 to 700 nm. Temperature was measured and recorded daily.
- Light intensity : A light intensity ranging from 60 to 120 E x m-2 x s-1, or an equivalent range of 4000 to 8000 lux, was measured. The light intensity was checked before the start of the study.
- Cell density measurements : Cell densities were measured in a microcell counter (Sysmex F300, Digitana) by taking small aliquots from each test flask, which were not replaced.
- Experimental design : 1 test concentration plus 1 control, 6 replicates per concentration, 6 replicates per control, initial cell density in the test cultures approximately 5000 cells per millilitre. Additionally highest test concentration without algae.
- Method of administration: direct weighing
- Criteria of effects : The criteria of adverse effects used in this study were the item-induced inhibition of yield [y] and growth rate [r] of the algal population.
- Calculation: All calculations were carried out using the statistics programme ToxRatPro Version 2.10 (released 2010-02-20). For the calculations all algae counts were divided by a factor of 10000.
- In order to avoid an impairment of the test system, an additional replicate was used for analysis and pH measurement at the beginning of the test. Chemical analysis and pH measurement at the end of the test were performed using replicate I of the test concentrations and the control vessels.
- In order to check whether or not significant amounts of the test item were incorporated into the algal biomass during the test period, a test flask at the limit test concentration without algae was run in parallel to the test concentration.
Reference substance (positive control):
no
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:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
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.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
No toxic effects against algae were observed at a limit test concentration of 100 mg/L, corresponding to a measured concentration of < 0.0334 mg/L, which reflects the maximum water solubility under exposure conditions.
Validity criteria fulfilled:
yes
Remarks:
Cell density in control cultures increased by a factor >16 within 72 h, mean coefficient of variation for section-by-section specific growth rates in the control <35 %, the variation of average specific growth rates (control) during test <7%.
Conclusions:
No toxic effects against algae were observed at a limit test concentration of 100 mg/L. The 72h-NOEC was reported as >= 100mg/L, and the 72h-EC50 was given as > 100 mg/L.
Executive summary:

In order to test acute toxicity to algae of the substance, Desmodesmus subspicatus was exposed to the test solution of 1 nominal concentration of the test substance (100 mg/L) and blank control solution for a period of 72 h under static conditions. The applied guideline was OECD Guideline 201 (Alga, Growth Inhibition Test). The cell densities were measured at 24 hour intervals. Inhibition of the algal population was measured as reduction in growth rate (index r), relative to control cultures grown under identical conditions. No toxic effects against algae were observed at a limit test concentration of 100 mg/L, corresponding to a measured concentration of < 0.0334 mg/L, which reflects the maximum water solubility under exposure conditions.

Description of key information

No toxic effects against algae were observed at a limit test concentration of 100 mg/L. The 72h-NOEC was reported as >= 100mg/L, and the 72h-EC50 was given as > 100 mg/L.
No toxic effects against algae were observed at a limit test concentration of 100 mg/L, corresponding to a measured concentration of < 0.0334 mg/L, which reflects the maximum water solubility under exposure conditions.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

"should read: NOEC >= 100 mg/L"