Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008-04-11 - 2008-04-21
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The test had been conducted according to relevant guidelines with only a minor deviation (three treatment replicates instead of six for a limit test). It was performed compliant to GLP and all the validity criteria of the guideline are fulfilled. The results are plausible and well documented.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
OECD-Guideline 201 demands 6 treatment replicates for a limit test. Deviating from this, only 3 treatment replicates had been tested as demanded for standard testing of different test substance concentrations.
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss Ordinance on Good Laboratory Practice, adopted on 18th May 2005 [OGLP, SR 813.112.1) based on OECD-GLP 1997 (C(97)186/Final)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable

Sampling and analysis

Analytical monitoring:
no
Details on sampling:
not applicable

Test solutions

Vehicle:
no
Details on test solutions:
Due to the limited water solubility of the test substance, in a concentration of 100 mg/L was moderately stirred in algal medium for 96 h at room temperature. After this incubation time, the undissolved material was first removed by a glass fiber filter (MILLIPORE AP15) and subsequently by membrane filtration (0.1 µm, Supore-100) to obtain a water accommodated fraction for the algal growth test. The pH of the OECD medium was not adjusted before the test. Blanks of test medium without test substance served as controls. Three replicates of the test substance and five replicates for the blank control were prepared. An exponentially growing preculture of algae was used to inoculate sterile test flasks. Test flasks were placed on an orbital shaker at a nominal shaking speed of 160 revolutions per min.

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Axenic slope culture of Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) 86.81 SAG (Collection of Algal Cultures, Institute of Freshwater Ecology, University of Göttingen, D-37073 Göttingen, Germany.
Culture: 100 mL flask containing 50 mL of sterile OECD medium inoculated with cell material from axenic slope culture.
Continuous illumination (6000-10000 lux), from high pressure sodium lamp Eye Sunlux Ace (Eye, Tokio, Japan).
Temperature: 22 ± 2 °C, thermo-controlled room.
Sensitivity control: Periodically conducted reference test with potassium dichromate.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
not applicable

Test conditions

Hardness:
according to OECD standard medium
Test temperature:
22°C +/- 2°C
pH:
8 +/- 0.2
Dissolved oxygen:
not applicable
Salinity:
not applicable
Nominal and measured concentrations:
Due to the poor water solubility of the test item, a ilmit test had been performed at 100 mg/L nominal concentration.
Details on test conditions:
According to OECD-guideline 201.
Reference substance (positive control):
no
Remarks:
Potassium dichromate as reference substance in periodically performed sensitivity tests - however, no data presented in the report.

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Limit test at 100 mg/L nominal concentration due to poor solubility of test item in water
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: Limit test at 100 mg/L nominal concentration due to poor solubility of test item in water
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Limit test at 100 mg/L nominal concentration due to poor solubility of test item in water
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: Limit test at 100 mg/L nominal concentration due to poor solubility of test item in water
Details on results:
Based an the results of the study it can be concluded that the EC50 (growth rate, 0-72 h) and the EC50 (yield, 0-72 h) of the test item to Desmodesmus subspicatus is >100 mg/L.
The STUDENT-t test for homogeneous variances revealed that the test item caused a significant growth stimulation (hormesis) in Desmodesmus subspicatus. Nevertheless, since no inhibition was observed, the no-observed-effect concentration (NOEC) for growth rates and yield with respect to the loading rate was equal to or larger as 100 mg/L.
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
The no observed effect concentration (NOEC) is the highest concentration for which the observed effect is not significantly different from the controls. The statistical significance of differences between effects observed for control and test substance treatments was determined by STUDENT-t test for homogeneous variances using the ToxRat Standard Version 2.09 (ToxRat Solutions GmbH, Alsdorf, Germany).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
In a fresh water algal growth inhibition test with Desmodesmus subspicatus the toxicity of the submission substance to aquatic plants had been tested (reliability category 2, compliant to GLP). A static limit test had been performed at a nominal concentration of 100 mg/L due to the poor solubility of the test item. The submission substance prooved to be non-toxic to Desmodesmus subspicatus under the applied test conditions:
NOEC (growth rate / yield, 72h) equal to or larger as 100 mg/L;
EC50 (growth rate / yield, 72h) > 100 mg/L;
Executive summary:

The median growth inhibiting concentrations (EC50) based an the average specific growth rate and the yield (algal biomass production) within 3 days, of the test item to the green alga Desmodesmus subspicatus were investigated over a period of 72 h. The only applied nominal test concentration was 100 mg/L. Due to the limited water solubility of the test substance, only the water accommodated fraction of the test item was tested. This water accommodated fraction was prepared by moderately stirring the respective concentration per liter of algal medium for 96h. After this incubation time, the undissolved material was first removed by a glass fiber filter and subsequently by membrane filtration to obtain a water accommodated fraction for the algal growth test. 3 parallel test vessels were used for the tested concentration of the test substance. No chemical analysis of the test media was conducted.

At the loading rate of 100 mg/L no growth inhibition (<10%) with respect to algal growth rates and algal yield (biomas production) compared to the untreated controls were observed.

The no-observed-effect concentration (NOEC) for growth rates and yield with respect to the loading rate was ¿ 100 mg/L nominal concentration.

Based on the results of the study it can be concluded that the EC50 (growth rate / yield, 0 -72 h) of the test item to Desmodesmus subspicatus are >100 mg/L nominal concentration.