Silicic acid, sodium salt

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

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:

other: Guideline study, but no information on purity of test substance.

Qualifier:

according to guideline

Guideline:

other: DIN 38412, Teil 9 (Algal growth inhibition test), German National Guideline; the method conforms with OECD 201

GLP compliance:

yes

Remarks:

Henkel KGaA Forschung Biologie, Oekologie.

Analytical monitoring:

not specified

Vehicle:

not specified

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 8681
- Source (laboratory, culture collection): Institute of Plant Physiology, University of Göttingen
- Method of cultivation: not reported
ACCLIMATION
- Pretreatment: 3-4 days incubation in the test medium without test substance

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.5-24.0

pH:

7.8-7.9 after 24 hrs, 8.2-10 after 72 hrs

Nominal and measured concentrations:

nominal: 1, 10, 100, 1000 mg product/L

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC0

Effect conc.:

35 mg/L

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

207 mg/L

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 345.4 mg/L

Conc. based on:

act. ingr.

Basis for effect:

growth rate

RESULTS: EXPOSED - Effect data/Element values: EC0 (0-72 hrs, algal biomass): 100 mg product/L. Equivalent with 34.54 mg active matter/L. EC50 (0-72 hrs, algal biomass): 600 mg product/L. Equivalent with 207 active matter/L. EC0 (0-72 hrs, growth rate): > 1000 mg product/L. Equivalent with 345.4 mg active matter/L. The test substance is slightly toxic to Scenedesmus subspicatus. - Cell density data: Reduced cell density at 1000 mg product/L. - Growth curves: Reduced growth rate at 1000 mg product/L. RESULTS CONTROL: No growth inhibition was registered. RESULTS TEST WITH REFERENCE SUBSTANCE: No tests were conducted with a reference substance. STATISTICAL RESULTS: Not reported.

Description of key information

EC50 (72 h, biomass): 207 mg/L (Scenedesmus subspicatus)
EC50 (72 h, growth rate): > 345.4 mg/L (Scenedesmus subspicatus)
However, for the purpose of risk assessment and as explained in the section on the calculation of Predicted No Effect Concentrations, the PNEC is derived from the ubiquitous SiO2 background concentration in freshwater in Europe, which is 7.5 mg/L.

Additional information

Sodium silicate (MR 3.0, 34.54 wt%) was tested on the algae Scenedesmus subspicatus, in a GLP guideline study according to German standard method DIN 38412, part 9, which corresponds to OECD guideline 201 (Rieche 1995). The 72 h EC50 based on biomass was 207 mg active matter/L at pH 8.2 - 9.5. The EC50 for growth rate was determined as > 345.4 mg active matter/L, the highest concentration tested.