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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:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
Aug 28- 31, 2006
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
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: all
- Sampling method: -
- Sample storage conditions before analysis: direct analysis
Vehicle:
no
Details on test solutions:
Reconstituted water

Macro nutrients:
NaHCO3 50 mg/L
CaCl2 x 2 H2O 18 mg/L
NH4Cl 15 mg/L
MgSO4 x 7 H2O 15 mg/L
MgCI2 x 6 H2O 12 mg/L
KH2PO4 1.6 mg/L



Trace elements:

Na2EDTA x 2 H2O 100.00 µg/L
FeC13 x 6 H2O 80.00 µg/L
MnC12 x 4 H2O 415.00 µg/L
H3BO3 185.00 µg/L
Na2MoO4 x 2 H2O 7.00 µg/L
ZnC12 3.00 µg/L
CoCl2x 6 H2O 1.50 µg/L
CuC12 x 2 H2O 0.01 µg/L

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus
- Strain: No. SAG 86.81
- Source (laboratory, culture collection): Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universitat Göttingen, Germany
- Age of inoculum (at test initiation): freshly prepared
- Method of cultivation: under standardised lab conditions

ACCLIMATION
- Acclimation period: Prior to start the study, the algae were grown in reconstituted water as preculture and the growth rate was determined.
- Culturing media and conditions (same as test or not): same
- Any deformed or abnormal cells observed: no
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
250 mg/L
Test temperature:
22 -23 °C
pH:
7.6 - 10.5
Nominal and measured concentrations:
nominal: 1, 1.78, 3.16, 5.62, 10.0 mg/L
measured: 0.04, 0.07, 0.15, 0.31, 0.66 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 mL
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: headspace
- Aeration: no
- Initial cells density: 10000
- No. of organisms per vessel: 10000
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.25 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 0.22-0.28
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.4 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 0.36-0.45
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.07 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Details on results:
- Pretest

In the preculture, the factor of cell growth was approx. 74.5. The algae increased from 10000 cells/ml at the start to 744661 cells/ml after 72 hours.

- Main study

The nominal test material concentrations and the growth inhibition data (mean) after 72 hours exposure are given below:

---------------------------------------------------------------------------------------------------
Nominal
conc. (mg/L) Cell density per mL Growth
inhibition
(0-72 hours)
nominal analytical 0 hour 24 hours 48 hours 72 hours IA lµt
---------------------------------------------------------------------------------------------------
Control 10000 82620 294570 784431
1.00 0.04 10000 79449 284631 782379 1.9 0.1
1.78 0.07 10000 75672 278517 697302 8.9 2.7
3.18 0.15 10000 64272 226973 618030 22.7 5.5
5.62 0.31 10000 62160 151761 295834 54.8 22.3
10.00 0.66 10000 28221 21828 17550 95.5 87.1
---------------------------------------------------------------------------------------------------

IA = inhibition of cell growth in percent
Iµt= inhibition of growth rate in percent


Validity criteria fulfilled:
yes
Conclusions:
The test material, prepared in reconstituted  water, was tested in the Algae growth  inhibition test using a closed static test system. The solubility in water was very poor. Nevertheless high toxicity was observed as the 72 hours EC50-values to Desmodesmus subspicatus were calculated to be 0.40 mg/L based on growth rate. The 72-h NOEC was determined to be 0.07 mg/L.
Executive summary:

Study design

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested.
Due to the volatility of the test material 100 ml Erlenmeyer flasks were filled with 120 ml test medium and sealed with ground stoppers to form a closed system reducing the loss of the test material concentrations within the exposure period.
The algae were exposed to different concentrations of test material and the growth was calculated after 24, 48, or 72 hours of exposure in the test media.
Based on the results of a pretest, the main study was performed with nominal concentrations of 1.00, 1.78, 3.16, 5.62, and 10.00 mg test material/L reconstituted water. The study design included three replicates per test material concentration, each containing about 120 ml test medium and 10000 cells/ml at the start of the experimental phase and a control without algae. Analyses of the test material concentrations were performed with all doses at the start and after 24, 48, or 72 hours.
This study was performed according to GLP and the methods applied are fully compliant with OECD TG 201.

Results

The limit of quantification of the analytical method was about 0.02 mg/L. At the start, the analytically determined concentrations were about 4 to 5 % and at the end about 3 to 7 % of the nominal concentrations. The analytical test concentrations were calculated the geometric mean individual values. The EC50 values were calculated with these geometric mean exposure concentrations.

The following results were obtained after exposure of Desmodesmus subspicatus to different concentrations of the test material:

Concentration in [mg/ml]
Mean Cell Density per ml
Growth Inhibition (0-72h)
nominal
analytical
0 h
24 h
48 h
72 h
Biomass
Growth rate
0
0
10000
82620
294570
784431
-
-
1.00
0.04
10000
79449 284631 782379
1.9
0.1
1.78 0.07 10000 75672 278517
697302 8.9 2.7
3.18 0.15 10000 64272 226973 618030 22.7 5.5
5.62 0.31 10000 62160 15176 295834 54.8 22.3
10.00 0.66 10000 28221 21828 17550 95.5 87.1


The median effective concentration (EC50), which would result in a 50 % growth inhibition and  the 95% confidence interval compared to tbe control, was calculated from the analytically determined concentrations. The analytical EC50s and the NOEC are given below:

Biomass: 72 h EC50 = 0.25 (0.22-0.28) mg/L
Growth Rate. 72 h EC50 = 0.40 (0.36-0.45) mg/L
NOEC = 0.07 mg/L
 

Conclusion

The test material, prepared in reconstituted  water, was tested in the Algae growth  inhibition test using a closed static test system. The solubility in water was very poor. Nevertheless high toxicity was observed as the 72 hours EC50-values to Desmodesmus subspicatus were calculated to be 0.40 mg/L based on growth rate. The 72-h NOEC was determined to be 0.07 mg/L.

Description of key information

The test material, prepared in reconstituted  water, was tested in the Algae growth  inhibition test using a closed static test system. The solubility in water was very poor. Nevertheless high toxicity was observed as the 72 hours EC50-values to Desmodesmus subspicatus were calculated to be 0.40 mg/L based on growth rate. The 72-h NOEC was determined to be 0.07 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.4 mg/L
EC10 or NOEC for freshwater algae:
0.07 mg/L

Additional information