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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:
Oct - Dec 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
The water-accommodated fractions (WAFs) were prepared for the test. This was done by weighing the nominal load of 10 / 32 / 100 / 320 / 1000 mg/L, resp. resp. 9.3 / 29.9 / 93.5 / 299 / 935 µL/L test item (based on a density of 1.07 g/mL), adding the corresponding amount of algal medium and stirring at 130 rpm for 7 days. After a settling phase of 24 hours the lower phase of the resulting solution was taken and used for the test.
Algal medium used for the test as negative control was also stirred at 130 rpm for 7 days and let to stand for 24 hours, since it has been shown in a non-GLP pre-test that Silicon (Si) content increases also in dilution water with the time of stirring.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Genus: Desmodesmus
Species: subspicatus
SAG Strain Number: 86.81
Taxonomic position: Chlorophyta - Chlorophyceae

Source: MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen
The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
pH:
at 0h: 7.7 in all concentrations and blank
at 72h: 7.6 in all concentrations and blank
Details on test conditions:
Treatments tested: 1000 / 320 / 100 / 32 / 10 mg/L nominal concentration (The concentrations to be tested are based on non GLP pre-tests)
Number of replicates: 6 replicates for the blank control
3 replicates for each treatment
Vessels: glass flasks total volume 65 mL
Duration: 72 hours
Lighting: 5000 lux
Temperature: 20.4 – 22.5 °C
Replicates (Blank control): 45 ±1 mL algal medium and algae
Replicates (Treatments): 45 ±1 mL test solution and algae
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1.5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
LOELR
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
LOELR
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Results with reference substance (positive control):
Parameter Value 95% confidence interval
72h ErC50 0.79 mg/L 0.79 mg/L – 0.79 mg/L
72h EyC50 0.39 mg/L 0.35 mg/L – 0.45 mg/L
Validity criteria fulfilled:
yes
Conclusions:
Results of the test item based on nominal concentration
Endpoint NOELR LOELR EL10 EL50
Growth Rate ≥1000 mg/L > 1000 mg/L > 1000 mg/L > 1000 mg/L
Yield ≥1000 mg/L > 1000 mg/L *208.85 mg/L > 1000 mg/L

Results of the test item based on measured concentration
Endpoint NOEC LOEC EC10 EC50
Growth Rate ≥ 1.5 mg/L > 1.5 mg/L > 1.5 mg/L > 1.5 mg/L
Yield ≥ 1.5 mg/L > 1.5 mg/L *0.75 mg/L L > 1.5 mg/L
Executive summary:

The toxicity of the test item against Desmodesmus subspicatus was determined according to OECD 201 resp. EU C.3

The water-accommodated fractions and the control were prepared directly in algal medium and calibration was per-formed in the same batch of algal test medium. The measured concentrations in the experiment were evaluable.

The study was performed using 5 concentrations ranging from 10 to 1000 mg/L (nominal).

Statistically significant inhibition of algal growth was not observed at any concentration.

At the start and at the end of the study, the content of the test item in the test solution was determined based on Si measurement as component of the test item (17.1 %). The Si content was determined via ICP-OES measurement. The Si content was measurable in the test solution and in the control, but in very low concentration.

The measured concentrations at the beginning were in agreement to the different loading rates and showed clearly the presence of dissolved test substance in the test solutions

During the study, the Si content in all solutions was increased. This was caused by Si dissolving out of the glass vessels. Therefore, the determination of the result was based on the measured concentration at the beginning. Additionally, the results were presented based on the nominal concentration.

All validity criteria were met.

No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.

Description of key information

The toxicity of the test item against Desmodesmus subspicatus was determined according to OECD 201 resp. EU C.3

The tests is based on the water-accommodated fractions of the test item.

The study was performed using 5 concentrations ranging from 10 to 1000 mg/L (nominal).

Statistically significant inhibition of algal growth was not observed at any concentration.

Results of the test item based on nominal concentration

Endpoint             NOELR                     LOELR                  EL50

Growth Rate       ≥1000 mg/L      > 1000 mg/L         > 1000 mg/L

Yield                   ≥1000 mg/L      > 1000 mg/L         > 1000 mg/L

Key value for chemical safety assessment

Additional information

At the start and at the end of the study, the content of the test item in the test solution was determined based on Si measurement as component of the test item (17.1 %). The Si content was determined via ICP-OES measurement. The Si content was measurable in the test solution and in the control, but in very low concentration.

The measured concentrations at the beginning were in agreement to the different loading rates and showed clearly the presence of dissolved test substance in the test solutions

During the study, the Si content in all solutions was increased. This was caused by Si dissolving out of the glass vessels. Therefore, the determination of the result was based on the measured concentration at the beginning.