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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:
2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Chemical name Phosphinic acid, phenyl(2,4,6-trimethylbenzoyl)-,ethyl ester
BMG sample no. M1302-00840-01
CAS no. 84434-11-7
Empirical formula C18H21O3P
Physical form Liquid, viscous
Water solubility Insoluble at 20°C: 35 mg/l
Purity (1H-NMR) 95.7 g/100 g
Purity (GC) 97.0 area-% (DB-1) – 97.8 area-% (DB-1701)
Test substance storage At room temperature, protected from light
Analytical monitoring:
yes
Details on sampling:
HPLC analyses of the test substance concentrations were conducted in the definitive test at the beginning, after 24, 48 and 72 h of exposure.
Vehicle:
no
Details on test solutions:
The loadings of the test material were prepared by adding the respective amounts of an acetonic stock solution to empty glass vessels. After complete evaporation of the solvent, the algal medium (Table 1) was added, moderately stirred for a minimum of 24 h, followed by filtration (0.45 µm cellulose acetate membrane sterile syringe filter, VWR International). The resulting saturated solutions were used in the test.
The pH of the OECD medium was adjusted before filtration (pH 8.0 ± 0.2). Blanks of the test medium without test substance served as controls. An exponentially growing preculture of algae was used to inoculate sterile test flasks.
For each test series, the following test flasks were set up:
• Test suspension (Tn); containing test medium, test substance and algae (three replicate samples)
• Blank control (Bn); containing test medium and algae (six replicate samples)
Test flasks were placed on an orbital shaker at a nominal shaking speed of about 130 revolutions per min.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Test organism: Axenic slope culture of Desmodesmus subspicatus 86.81 SAG (Collection of Algal Cultures, Institute of Freshwater Ecology, University of Göttingen, D-37073 Göttingen, Germany)
Culture: 250 ml flask containing 100 ml of sterile OECD medium (Table 1) inoculated with cell material from axenic slope cultures
Illumination: Continuous (2000–3000 lux) from Osram Fluora L18W77 and Osram Daywhite L18W840 (Osram AG, Winterthur, Switzerland)
Temperature: 22 ± 2 °C, thermo-controlled room
Control of sensitivity: The culture is yearly re-purchased. Potassium dichromate is used to control the sensitivity of the culture twice a year.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
22 ± 2°C, thermo-controlled room
pH:
control: 8.0 - 8.1
exposure groups: 7.7 - 7.9
Nominal and measured concentrations:
The loading rates were 0.625, 1.25, 2.50, 5.00, 10.0 and 20.0 mg/l. Three parallel test vessels were used for each loading rate of the test substance.
Details on test conditions:
Test vessel: 250 ml flasks, all-glass, with 100 ml of test medium, shaken (about 130 rpm)
Test medium: Recommended OECD medium
Preculture: Exponentially growing liquid culture of Desmodesmus subspicatus
Illumination Source: continuous from Osram Fluora L 18W77 and Osram Daywhite L 18W840 (Osram AG, Winterthur, Switzerland)
Light intensity (target): the light intensity amounts to about 3000 lux which corresponds to about 40 μE•m- 2•s-2 according to the OECD TG no. 2011
Homogeneity (target): the light intensity is maintained within ±15% from the average light intensity over the incubation area
Temperature (target): 22 ± 2°C, thermo-controlled room
pH: The pH of the control medium should not increase by more than 1.5 units during the test
Test type: Static exposure conditions over a period of 72 h
Starting cell density: 0.50–0.85 μg/ml with respect to dry weight corresponding to about 2–5•103 cells/ml (i.e. OD680 of about 0.005 units)

Observations and measurements
pH Determined in the medium which is used for the control and in the water saturated solutions Observations Cell concentrations were determined every 24 h using a spectrophotometer (680 nm wavelength). Aliquots of 5 ml were removed from each test flask under sterile conditions. Cell concentrations at time 0 h were only determined in the control vessels.




Duration:
72 h
Dose descriptor:
EC10
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
not determinable
Duration:
72 h
Dose descriptor:
EC20
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
not determinable
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.01 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
not determinable
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
0.033 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.239 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
HPLC analysis of Lucirin TPO-L was performed at the beginning of the exposure, and after 24, 48 and 72 h of exposure. The measured concentrations at the beginning of the exposure were <0.1, 0.152, 0.298, 0.710, 1.93 and 4.80 mg/l. The analysis revealed that the test concentrations could not be satisfactorily maintained: the mean measured concentration after 72 h for the highest loading rate of 20.0 mg/l was 0.512 mg/l. The measured concentrations for the lower loading rates were below the limit of quantification (LOQ) of the analytical method of 0.1 mg/l.
Therefore, the evaluation of the results was based on the geometric mean concentrations (GM0-72h) of <0.1, 0.066, 0.226, 0.356, 0.731 and 1.47 mg/l.
Validity criteria fulfilled:
yes
Conclusions:
The 72 hour ErC50 of the test material to Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was determined to be 1.01 mg/l under the conditions of the test.

Description of key information

The study was conducted to recognised testing guidelines, and with GLP certification.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.01 mg/L

Additional information