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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:
05 January 2010-08 January 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study has been performed according to OECD and/or EC guidelines and according to GLP principles
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Deviations:
no
Qualifier:
according to
Guideline:
other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000.
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations:all test concentrations and the control. In addition, the filter used for preparation of the test solutions was retained for possible analysis of the undissolved residue
- Sampling method:
Frequency at t=0h, t=24h and t=72h
Volume 4.8 ml
Storage Samples were stored in a freezer until analysis.

At the end of the exposure period, the replicates with algae were pooled at each concentration before sampling.
Vehicle:
no
Details on test solutions:
Preparation started with a loading rate of 100 mg/l applying one day of magnetic stirring to reach maximum solubility of the test substance in the test medium. The obtained aqueous mixture was filtered through a 0.45 µm membrane filter (Whatman, rc 55) and the clear and colourless filtrate was used as the highest test concentration. The lower test concentrations were prepared by subsequent dilutions of the filtrate in test medium.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture
- Age of inoculum (at test initiation): 4 days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 1 x 10E4 cells/ml.
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24°C.


Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
0.24mmol/l (24 mg CaCO3/l)
Test temperature:
between 21.6 and 23.9°C
pH:
Between 7.8 - 8.1
Dissolved oxygen:
not applicable
Salinity:
not applicable
Nominal and measured concentrations:
The measured concentration of Barium in the samples taken from the undiluted filtrate at the start of the test was 0.79 mg/l. This concentration remained stable throughout the test period (97-98% of initial). The concentration of Lead was below or just above the linear range of the calibration curve. The analysis of the filter used for the preparation of the highest test concentration showed a relatively high content of lead.
Details on test conditions:
TEST SYSTEM
- Type: open
- Material, size, headspace, fill volume: 100 ml, normal headspace, 50 ml
- Aeration: no
- Initial cells density: 10000 cells/ml
- Control end cells density: 1178000 cells/ml
- No. of vessels per concentration (replicates): 6 for the highest concentration, 3 for the lowertest concentrations
- No. of vessels per control (replicates): 1 6

GROWTH MEDIUM
- Standard medium used: yes


OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: TLD-lamps of the type ‘Cool-white’ of 30 Watt, with a light intensity within the range of 68 to 77 µE/m2/s



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
72 h NOErC, 72 h NOEbC, 72 h ErC50, 72 h EbC50


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Test concentrations: 0, 0.10, 1.0, 10 and 100% of a filtered solution prepared at a loading rate of 100 mg/l
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 other: mg/l (loading rate)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 100% of the filtered solution prepared at a loading rate of 100 mg/l
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: mg/l (loading rate)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 100% of 0.45 µm filtered solution prepared at a loading rate of 100 mg/l
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 other: mg/l (loading rate)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 100% of 0.45 µm filtered solution prepared at a loading rate of 100 mg/l
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: mg/l (loading rate)
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Remarks on result:
other: 100% of 0.45 µm filtered solution prepared at a loading rate of 100 mg/l
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.79 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
element
Remarks:
dissolved barium in filtrate
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.79 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
element
Remarks:
dissolved barium in filtrate
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.79 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
element
Remarks:
dissolved barium in filtrate
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.79 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
element
Remarks:
dissolved barium in filtrate
Basis for effect:
other: yield
Details on results:
- Exponential growth in the control (for algal test): yes
- Effect concentrations exceeding solubility of substance in test medium: yes
No significant differences were recorded between the values for growth rate or yield at any of the test concentrations when compared to the control group.
Microscopic observations at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.
Results with reference substance (positive control):
- Results with reference substance valid: yes
- EC50:
The EC50 for growth rate reduction (ERC50: 0-72h) was 1.2 mg/l with a 95% confidence interval ranging from 0.65 to 2.3 mg/l.
The EC50 for yield inhibition (EYC50: 0-72h) was 0.65 mg/l with a 95% confidence interval ranging from 0.31 to 1.3 mg/l.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the present study Silicic acid(H2Si2O5), barium salt(1:1), lead-doped did not reduce growth rate or inhibit yield of Pseudokirchneriella subcapitata exposed to a filtered solution prepared at a loading rate of 100 mg/l. The actual concentration of dissolved Barium in this filtrate was 0.79 mg/l.

The 72h-EC50 for both growth rate reduction and yield inhibition was beyond the range tested and therefore exceeded the solubility limit of Silicic acid(H2Si2O5), barium salt(1:1), lead-doped in test medium.

Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information