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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:
Study plan 2012-01-09, Performance of study 2012-01-31, Draft report 2012-02-23, Final report 2012-03-22
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Strain: CHODAT
Family: Chlorophyceae
Order: Chlorococcales
The culture of Desmodesmus subspicatus was obtained in Oct. 2011 by MBM Science-bridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae were kept as stock culture on solid agar at 8 °C. From an aliquot of this stock culture the pre-culture was prepared.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
26 °C
pH:
Control at beginning: 7.1; after 72 h: 10.4;
Treatment at beginning: 7.0; after 72 h: 9.9;
Reference substance (positive control):
yes
Remarks:
K2Cr2O7
Duration:
72 h
Dose descriptor:
NOEC
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:
EC50
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:
biomass
Remarks:
Biomass Integral, area under the curve (AUC)
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield

Results on cell numbers:

The cell numbers were determined by photometric measurement of optical density. The number of cells was slightly higher in the treatment group after 72 hours compared to the control (1,187,567 +/-78,259 cells/mL, 1,122,324 +/-139,063 cells/mL, respectively). The appearance of the alga at the end of the test was analysed microscopically and for the treatment and control group normal growth was observed.

Results on measured concentrations:

The measured concentration of the test substance diethyl carbonate at the beginning of the experiment was 106.78 mg/L and 92.89 mg/L after 72 h. As the analytical determinations of the test substance showed good correlation between nominal and measured concentrations, the determination of the biological results was based on the nominal concentrations.

Results on growth rate, AUC, and yield:

 Nominal concentration [mg/L]  growth rate [1/day]  AUC [Cell concentration/(mL*day)]  Yield [Cell concentration/mL]
 0  1.84 +/-0.04  877,494 +/-90,090  1,117,799 +/-139,063
 100  1.86 +/-0.02  901,140 +/-55,811  1,183,041 +/-78,259

Results on the positive control:

At concentrations from 0.04 to 0.25 mg/L of K2Cr2O7 the algal growth was normal compared to the control (0 mg/L K2Cr2O7). At 0.4 and 0.63 mg/L the cells were smaller and at the highest concentrations (1.0, 1.6 mg/L) the cells did not grow anymore (inhibition of growth rate by 48.62 and 54.02 %, respectively).

Validity criteria fulfilled:
yes
Conclusions:
The toxic potential of the test substance diethyl carbonate was determined in an algal growth inhibition test. The test was performed as limit test at a concentration of 100 mg/L of diethyl carbonate. At this concentration no inhibition was observed. Therefore, the concentration 100 mg/L was stated as NOEC, and all EC50s (growth rate, biomass, yield) were considered to lie above 100 mg/L.

Description of key information

Determined NOEC in short-term-toxicity study to algae was ≥ 100 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

The author of the short-term-toxicity study (72 h) of the test substance diethyl carbonate to algae (Desmodesmus subspicatus) evaluated a NOEC ≥ 100 mg/L.