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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
STOCK SOLUTION:
To produce the stock solution the test substance was weighted into water and treated in an ultrasonic bath for 1 h.
Test organisms (species):
Scenedesmus sp.
Details on test organisms:
TEST ORGANISM:
-Species: Scenedesmus subspicatus CHODAT
-Origin: Institute of Plant Physiology, University Göttingen
-Cultivation: in a light chamber at 23 ± 2 °C and with a quantum flux which equals 120 µE/m2*s.
-Water for dilution: deionized water
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
n.a.
Test temperature:
23 °C
pH:
8.1-10.3
Dissolved oxygen:
n.a.
Salinity:
n.a.
Conductivity:
n.a.
Nominal and measured concentrations:
nominal concentrations: 0.32, 1, 3.16, 10, 31.6 mg/L
Details on test conditions:
TEST CONDITIONS:
-Test procedure:
-Erlenmeyer flasks (300 mL) with stoppers
-100 mL of test medium
-light chamber an d shaker (PVP)
-Determination of the effects on the growth of Scenedesmus subspicatus within a 72 h exposure period
-Counting: Microcellcounter Sysmex F-300 Digitana
-Method of administration: Stock solution (39.5 mg/L)
-Test concentrations: 0.32, 1, 3.16, 10, 31.6 mg/L
-Solubilizer or other auxiliaries: ultrasonic bath
-Inoculum: Algal suspension taken from an exponentially growing preculture which was used to adjust an initial cell density of 10,000 cells per milliliter
-Control: Inoculum in nutrient medium and water for dilution
-Water for dilution: deionized water
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
10 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
1.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
4.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: confidence limit: 3.0-6.1 mg/L
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.97 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: confidence limit: 0.41-1.6 mg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: Dunnett test
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: Dunnett test
Validity criteria fulfilled:
not applicable
Remarks:
The biomass increased exponentially by a factor of at least 16 within the 72-hour test period; the coefficient of variation cannot be calculated as just the mean values of the specific growth rates are reported and not the single treatment replicates
Conclusions:
The acute toxicity of the test item to the aquatic algae Scenedesmus subspicatus was determined after 72 h of exposure and showed an ErC10 of 1.6 mg/L and an ErC50 of 10.0 mg/L. Measured cell density was used to calculate a NOEC of 0.32 mg/L.
Executive summary:

The study was performed according to EU Method C.3 'Algal Inhibition Test', which is equivalent to OECD Guideline for Testing of Chemicals No. 201 'Alga Growth Inhibition Test'. Exponentially growing algae cells of Scenedesmus subspicatus were exposed to the test item under static conditions for 72 h to a range of concentration, nominally 0.32, 1.0, 3.16, 10.0, 31.6 mg/L. Auxiliary used to prepare the test media was an ultrasonic bath. The cell densities were measured at 24 hour intervals. Growth rate and inhibition of growth rate after 72 h were measured relative to control culture grown under identical conditions. The results are expressed in terms of nominal concentrations and a 72h-ErC10 = 1.6 mg/L and a 72h-ErC50 = 10.0 mg/L were determined. Additionally, the cell density was used to calculate a No Observed Effect Concentration (NOEC) and a Lowest Observed Effect Concentration (LOEC) according to Dunnett test. The NOEC was calculated to be 0.32 mg/L and the LOEC was calculated to be 1.0 mg/L. This toxicity study is classified as acceptable and can be used for assessment.

Description of key information

The acute toxicity of the test item to the aquatic algae Scenedesmus subspicatus was determined after 72 h of exposure and showed an ErC10 of 1.6 mg/L and an ErC50 of 10.0 mg/L. Measured cell density was used to calculate a NOEC of 0.32 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
10 mg/L
EC10 or NOEC for freshwater algae:
0.32 mg/L

Additional information

The study was performed according to EU Method C.3 'Algal Inhibition Test', which is equivalent to OECD Guideline for Testing of Chemicals No. 201 'Alga Growth Inhibition Test'. Exponentially growing algae cells of Scenedesmus subspicatuswere exposed to the test item under static conditions for 72 h to a range of concentration, nominally 0.32, 1.0, 3.16, 10.0, 31.6 mg/L. Auxiliary used to prepare the test media was an ultrasonic bath. The cell densities were measured at 24 hour intervals. Growth rate and inhibition of growth rate after 72 h were measured relative to control culture grown under identical conditions. The results are expressed in terms of nominal concentrations and a 72h-ErC10 = 1.6 mg/L and a 72h-ErC50 = 10.0 mg/L were determined. Additionally, the cell density was used to calculate a No Observed Effect Concentration (NOEC) and a Lowest Observed Effect Concentration (LOEC) according to Dunnett test. The NOEC was calculated to be 0.32 mg/L and the LOEC was calculated to be 1.0 mg/L. This toxicity study is classified as acceptable and can be used for assessment.