Silicic acid, sodium salt

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms

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 27, German National guidelines. The method conforms with OECD 209.

Deviations:

no

Principles of method if other than guideline:

Bacterial oxygen consumption test

GLP compliance:

yes

Remarks:

Henkel KGaA Forschung Biologie, Oekologie.

Analytical monitoring:

not specified

Vehicle:

not specified

Test organisms (species):

Pseudomonas putida

Nominal and measured concentrations:

10000 mg product/L (nominal)

Duration:

30 min

Dose descriptor:

EC0

Effect conc.:

3 454 mg/L

RESULTS: EXPOSED
- Effect data (Immobilisation): EC0 10000 mg product/l (3454
mg active matter/L) (pH 11.1, at start 8.0), oxygen
consumption was reduced by 8.13% i.e. < 10%
- Concentration / response curve: not reported
- Cumulative immobilisation: not reported
- Effect concentration vs. test substance solubility: not
reported
- Other effects: not reported
RESULTS CONTROL: not reported
RESULTS: TEST WITH REFERENCE SUBSTANCE
- Concentrations: not reported
- Results: not reported

Reference 2

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

other: growth inhibition test; Umweltbundesamt, Berlin: Bewertung wassergefaehrdender Stoffe. Erarbeitet von der ad-hoc-Arbeitsgruppe 1 "Bewertung wassergefaehrdender Stoffe"

Deviations:

yes

Remarks:

The OD of the inoculum used in the tests was slightly higher than given in the protocol. 200 ml Erlenmeyer flasks were used instead of 250 ml flasks. Disposable plastic cuvettes were used for OD determinations instead of glass cuvettes.

Principles of method if other than guideline:

growth inhibition test

GLP compliance:

yes

Remarks:

TNO Division of Technology for Society, Delft, The Netherlands.

Analytical monitoring:

no

Vehicle:

not specified

Test organisms (species):

Pseudomonas putida

Total exposure duration:

18 h

Details on test conditions:

Type: aquatic

Duration:

18 h

Dose descriptor:

EC0

Effect conc.:

> 3 480 mg/L

Basis for effect:

growth inhibition

Remarks on result:

other: for neutralised concentrations (pH 7.6-7.8)

Duration:

18 h

Dose descriptor:

EC0

Effect conc.:

> 348 mg/L

Basis for effect:

growth inhibition

Remarks on result:

other: for unneutralised concentrations (pH>9)

RESULTS EXPOSED:
- Nominal/measured concentrations: Not reported
- EC0 (toxicity threshold): > 10000 mg/l for neutralised
concentrations (pH 7.6-7.8). Equivalent to >3480 mg active
matter/l. 
- EC0 (toxicity threshold): > 1000 mg/l for unneutralised
concentrations (pH > 9). Equivalent to > 348 mg active
matter/l.
RESULTS CONTROL: No effects
RESULTS TEST WITH REFERENCE SUBSTANCE: No reference
substance was tested

Reference 3

Endpoint:

toxicity to microorganisms

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well-documented study designed to evaluate the influence of silicate on functioning of model sewage treatment plant rather than the toxicity towards microorganisms.

Principles of method if other than guideline:

Method: other: OECD Confirmatory test

GLP compliance:

yes

Remarks:

Henkel KGaA Forschung|Biologie, Oekologie.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 25 mg/L

RS-Freetext:
RESULTS: EXPOSED
- Biodegradation: >90% of added sodium silicate was detected in the  effluent. No significant elimination was observed. The test substance had  no adverse effects on the model sewage plant.
RESULTS CONTROL: There were no significant differences in DOC, pH or dry  mass of sludge between the control and silicate-dosed biodegradation unit.
STATISTICAL RESULTS: Not reported.

Description of key information

EC0 (18h, growth inhibition) > 10000 mg/L for neutralized concentrations (pH 7.6-7.8). Equivalent to > 3480 mg active matter/L (Pseudomonas putida)
EC0 (18h, growth inhibition) > 1000 mg/L for unneutralised concentrations (pH > 9). Equivalent to > 348 mg active matter/L (Pseudomonas putida)
EC0 (30min, oxygen consumption inhibition) 3454 mg/L

Additional information

The toxicity of a sodium silicate solution (MR 3.46, 34.8 wt%) has been determined with a growth inhibition test in compliance with German standards and GLP using the bacterium Pseudomonas putida (Hanstveit 1989). The 18 h toxicity threshold (EC10, 10 % inhibition) of a neutralised silicate solution of pH 7.6 - 7.8 was > 3480 mg active matter/L, the highest concentration tested, while for the unneutralised solution (pH 7.9 - 10.4) effects were found at concentrations above 348 mg active matter/L. In a further GLP guideline study complying with German standards corresponding to OECD 209, the toxicity to Pseudomonas putida was tested in an oxygen consumption inhibition test. Concentrations of a sodium silicate solution (MR 3.0, 34.54 wt%) of up to 3454 mg active matter/L at pH 8.0 - 11.1 did not cause toxic effects (Kirch 1993).