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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:
26 Oct. 1998 - 30 Oct. 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
version 07 June 1984
Deviations:
yes
Remarks:
The initial cell concentration was a about 8x higher than recommended.
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stirring the suspensions for 24 h in 0.5 l ultrapure water, followed by  filtration through paper filter.
- Eluate: Water extracts from 6250, 630, and 60 mg silicate/0.5 L, diluted to the target concentration
by additions of stock solutions needed for testing.
- Differential loading: yes
- Controls: without or with respective filtrates, but without algae
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): none
- Evidence of undissolved material (e.g. precipitate, surface film, etc): not specified


Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: green alga
- Strain: CHODAT
- Source (laboratory, culture collection): Pflanzenphysiol. Inst. University of Göttingen/Germany
- Age of inoculum (at test initiation): see below
- Method of cultivation: preculture 3 days prepared before test from a stock culture

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Post exposure observation period:
none
Hardness:
not specified
Test temperature:
24.9 +-0.3°C
pH:
Initial pH: 8.00 (control); between 8.12 and 8.58 (tests)
final pH: 10.74 - 10.76
Dissolved oxygen:
--
Salinity:
not applicable
Nominal and measured concentrations:
96, 1008, and 10,000 mg/L nominal
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type: open
- Material, size, headspace, fill volume: 50 ml glass cylinders
- Aeration:
- Renewal rate of test solution (frequency/flow rate): none
- Initial cells density: approx. 8 x10^4/ml
- Control end cells density: 2.83 x10^6/ml
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 7 (algal growth control), 3 (TS controls without algae)


GROWTH MEDIUM
- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic medium from ultrapure water
- Total organic carbon: no data
- Alkalinity: not specified
- Ca/Mg ratio: not specified
- Conductivity: not specified



OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: approx. 8000 lux [>= 120 µE/(m2*sec)]


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer at 578 nm after 24, 48, and 72 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: biomass and growth rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: biomass and growth rate
Details on results:
- Exponential growth in the control (for algal test): yes,
After 72 h, an increase in biomass (cell numbers) at a factor of >30 was achieved at any concentration.

- Observation of abnormalities (for algal test): no particular findings specified

- Any stimulation of growth found in any treatment: slight stimulation rather than inhibition observed
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
not applicable
Validity criteria fulfilled:
yes
Conclusions:
Under the test conditions, the test substance exhibited no acute and chronic toxic effect towards the test system (Scenedesmus subspicatus CHODAT).

Description of key information

No acute and chronic aquatic toxicity identified: EL50 > 10,000 mg/L,
NOELR = 10,000 mg/L.

Key value for chemical safety assessment

Additional information

No toxicity towards algae - including the marine environment - is expected from exposure to synthetic amorphous Silicic acid, aluminum sodium salt (CAS 1344-00-9, NAS).