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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:
July 30, 2010 - December 08, 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
None
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):The water solubility (calculated: 0.00004 mg/L) was below the limit of detection. Therefore the concentration of the test material in water could not be determined and is thus given as nominal value.
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The test medium (reconstituted water and test material) was freshly prepared. The calibrated flask with test material and vehicle, reconstituted water, was treated in an ultrasound bath for 1 hour. Subsequently, the preparation was stirred with a magnetic stirrer for further 23 hours. Afterwards, the preparation was filtered through a filter funnel with a pore size of 10-16 µm. The filtrate was used for the study.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
The test system used for this study was a green unicellular algae species, Desmodesmus subspicatus, strain No. SAG 86.81, supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen". This strain is recommended by international guidelines.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
250 mg CaCO3
Test temperature:
21-22°C
pH:
start of exp.: 7.9+/-0.1end of exp.: 9.6+/-1.6
Dissolved oxygen:
saturated
Salinity:
for details see composition of reconstituted water "details on test conditions"
Nominal and measured concentrations:
Nominal concentration of 100 mg/L (limit test); due to very low water solubility and the fact that the study was a limit test, no further analysis was initiated.
Details on test conditions:
The test medium (reconstituted water and test material) was freshly prepared. The light intensity was between 4440 and 8880 Lux. The experimental part was started by inoculation of algae to the different groups so that the flasks contained about 10,000 cells/mL. The algae were taken from an exponentially growing pre-culture (growth rate 58.3) which was set up 3 days prior to the experimental part under the same conditions as in the final study. Details on composition of the reconstituted water: Macro-nutrients: 50.00 mg/L NaHCO3 18.00 mg/L CaCl2 x 2 H2O 15.00 mg/L NH4Cl 15.00 mg/L MgSO4 x 7 H2O 12.00 mg/L MgCl2 x 6 H2O 1.60 mg/L KH2PO4 Trace elements: 100.00 µg/L Na2EDTA x 2 H2O 80.00 µg/L FeCl3 x 6 H2O 415.00 µg/L MnCl2 x 4 H2O185.00 µg/L H3BO3 7.00 µg/L Na2MoO4 x 2 H2O 3.00 µg/L ZnCl2 1.50 µg/L CoCl2 x 6 H2O 0.01 µg/L CuCl2 x 2 H2O The pH of the reconstituted water after aeration is approximately 8-9.
Reference substance (positive control):
yes
Remarks:
potassium dichromate from separate study
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
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:
NOEC
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:
biomass
Key result
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:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Results with reference substance (positive control):
Regularly, a positive control test to check the test system is carried out with potassium dichromate (no results provided in the study report).
Validity criteria fulfilled:
yes
Conclusions:
An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system up to the limit of water solubility. Analytically, the 72 hours EC50 to Desmodesmus subspicatus could not be determined; it exceeded the maximum solubility of the test material in reconstituted water.
Executive summary:

Purpose

The purpose of this assay was to identify the aquatic toxicity potential the test material in algea to provide a rational basis for hazard estimation for the test item in aquatic environments.

Study design

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested. The study design included one control and one test material group with six replicates, each containing about 100 rnL reconstituted water or test medium and 10,000 cells/mL at the start of the experimental phase. The algae were exposed to a filtrate of nominal 100 mg/L and the study was performed as a limit test in an open static test system. The growth was calculated after 24, 48, and 72 hours exposure in the test medium.

Results

The calculation of the water solubility yielded a low value of 0.0004 mg/L. Due to this low water solubility esitimate, the the test material concentration in the reconstituted water could not be determined. For the test material, the following EC50 values and no effect concentration for Desmodesmus subspicatus were obtained:

72 h EC50 > 100 mg/L (nominal) based on growth rate

72 h EC10 > 100 mg/L (nominal) based on growth rate

Conclusions

An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system. The 72 hours EC50 exceeded the maximum solubility of the test material in reconstituted water.

Description of key information

An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system up to the limit of water solubility. The ErC50 and ErC10 was determined to be greater than 100 mg/L (nominal).

Key value for chemical safety assessment

Additional information