Silicic acid, sodium salt

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable procedure and publication

Principles of method if other than guideline:

Method: other: no method cited

GLP compliance:

no

Analytical monitoring:

not specified

Vehicle:

not specified

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
Age/size/weight/loading: 4-7 cm body length, 0.7-4.0 g body weight, 4-5 months old

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Test temperature:

14-17°C

pH:

6.8 - 8.0

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

260 - 310 mg/L

Sublethal observations / clinical signs:

Results: exposed - Nominal/measured concentrations: not reported - Effect data (Mortality): LC50 (24 h): 352 mg/L (average of 4 replicates; range: 314-390 mg/L); LC50 (48 h): 302 mg/L (range: 266-340 mg/L); LC50(96h): 281 mg/L (range: 260-310 mg/L) - Concentration / response curve: not reported - Effect concentration vs. test substance solubility: Samples which have higher concentration than 300 mg/L decreased to 160 mg/L through polymerization at pH 7.2 - 7.8. At higher S. SiO₂concentration as 350 mg/L, the negative charge of colloidal silica increased with aging time at neutral zone. - Other effects: The death of rainbow trout were considered to be caused by necrosis of the gill filaments with the colloidal silica. Results: Control - Number/percentage of animals showing adverse effects: not reported - Nature of adverse effects: not reported. Results: Test with reference substance - Concentrations: not reported - Results: not reported.

Conclusions:

The authors state that the allowable S. SiO2 concentration
of a treated waste water containing water glass would be 150
mg/L in order to avoid sol formation. Thence, 100 mg/L of S.
SiO2 concentration could practically be set as an allowable
concentration of the treated effluent.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

yes

Remarks:

in the final test a range of concentrations with 5600 mg/L as the highest concentration was tested instead of 1000 mg/L

GLP compliance:

yes

Remarks:

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

Analytical monitoring:

no

Details on sampling:

pH and oxygen concentration (daily)

Vehicle:

yes

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: Zebra fish
- Source: M.B. Ruysbroek B.V. (Noordvliet 159, Maassluis)
- Age/size/weight/loading: size 2.5±0.2 cm long, weight 0.14±0.03 g
- Feeding during test: no

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

96 h

Hardness:

210 mg/l CaCO3

Test temperature:

25±1°C

pH:

8.0-8.2 after aeration

Dissolved oxygen:

> 6.0 mg/l

Salinity:

trace elements << 1 mg/L

Nominal and measured concentrations:

100, 180, 320, 560, 1000, 1800, 3200 and 5600 mg silicate solution/L corresponding to 35, 63, 111, 195, 348, 626, 1114 and 1949 mg active matter/L

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

348 mg/L

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

1 108 mg/L

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

1 949 mg/L

Sublethal observations / clinical signs:

RESULTS: EXPOSED - Nominal/measured concentrations: 24h, 48h, 72h and 96h LC50: 3710, 3360, 3269 and 3185 mg/L respectively. 96h LC100: 5600 mg/L, 96 h NOEC (mortality): 1000 mg/L and 96 h NOEC (swimming behaviour): 3200 mg/L - Effect data (Mortality): at 96 hours all fish had died at 5600 mg/L (1949 mg active matter/L) It is suggested that mortality at concentration >= 1800 mg/L may have been caused by the high pH value.  - Concentration / response curve: the slope was 0.24 (95% confidence interval 0.14-0.33) - Effect concentration vs. test substance solubility: not reported - Other effects: the fish did not show any abnormal behavior. RESULTS: CONTROL - Number/percentage of animals showing adverse effects: surviving fish did not show abnormal swimming behaviour - Nature of adverse effects: not applicable.

Reference 3

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Only toxicological values available, no further test conditions have been described in the review document

Principles of method if other than guideline:

Method: no data

GLP compliance:

not specified

Analytical monitoring:

not specified

Test organisms (species):

Lepomis macrochirus

Test type:

not specified

Water media type:

not specified

Total exposure duration:

96 h

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

301 - 478 mg/L

Sublethal observations / clinical signs:

RS-Freetext:
No further test results have been provided.

Description of key information

LC50 (96 h): 1108 mg/L (Brachydanio rerio)
LC50 (96 h): 260 - 310 mg/L (Onchorhynchus mykiss)
NOEC (96 h, Mortality): 348 mg/L (Brachydanio rerio)
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

A semi-static study with Brachydanio rerio by Adema (1988), following OECD guideline 203, was performed under GLP for a sodium silicate solution (MR 3.46, 34.8 wt %). The 96 h LC50 was determined to be 1108 mg active matter/L. The NOEC values for mortality and swimming behaviour were 348 and 1114 mg active matter/L, respectively. The pH varied depending on the test substance concentration from 7.9 to 10.3.

In another non-GLP study, Maruyama et al. (1989) examined the toxicity of a neutralised sodium silicate solution (MR 3.1, concentration not indicated) to rainbow trout (Oncorhynchus mykiss). In four replicates the 96 h LC50 varied from 260 mg/L (pH 6.8 - 7.5,) to 310 mg/L (pH 7.2 - 8.0). Necrosis of gill filaments as a result of the formation of colloidal silica was observed. However, this is considered a physical rather than toxic effect.