Disodium disilicate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Only two standard parameters were studied: body weight and survival. Background concentration in the diet varied between 0.1 and 1.0% of SiO2 (w/w). Nitrogen and phosphorous retention/excretion was measured only in the males at the end of the exposure period. For justification of read across see endpoint summary.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Effects of soluble silica on growth, nutrient balance and reproductive performance of albino rats.

Author:

Smith, G. S. et al.

Year:

1973

Bibliographic source:

J. Animal Sc. 36|(2), 271-278.

Reference 2

Reference Type:

secondary source

Title:

Unnamed

Year:

2004

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Oral exposure of weanling rats via drinking water for 180 days.
The study was conducted to assess the influence of silica in the diet on growth and nutrient balance.

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, sodium salt

EC Number:

215-687-4

EC Name:

Silicic acid, sodium salt

Cas Number:

1344-09-8

IUPAC Name:

sodium hydroxy(oxo)silanolate

Details on test material:

SOURCE: Diamond Alkali Company, Cleveland, Ohio, USA
PURITY: Not indicated
IMPURITY/ADDITIVE/ETC.: Not indicated
ANY OTHER INFORMATION: Molar ratio 3.2. Background concentration in the diet varied between 0.1 and 1.0% of SiO2 (w/w). Test substance Sodium Silicate was used.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ORGANISMS
- Age: Weanling

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

180 d (m-f) + 17 days (m)

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
789.5 and 1587 mg sodium  silicate/L
Basis:
nominal in water

Doses / concentrations 2

Remarks:

Doses / Concentrations:
600 and 1200 mg SiO2/l
Basis:

No. of animals per sex per dose:

6

Control animals:

yes

Details on study design:

Post-exposure period: no

Examinations

Observations and examinations performed and frequency:

CLINICAL OBSERVATIONS AND FREQUENCY: 
- Mortality: registered with unknown frequency
- Body weight: registered every week
- Urinalysis: nitrogen and phosphorous registered daily from day 181-197 in males. 

Other examinations:

Analysis of faeces: nitrogen and phosphorous registered daily from day 181-197 in males.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Details on results:

TOXIC RESPONSE/EFFECTS BY DOSE LEVEL: 
- Mortality and time to death: None
- Clinical signs: no effects
- Body weight gain: Some statistically significant differences in body weight between experimental groups and controls were registered, but these were small (6% or less), not consistent and not dose related.
- Urinalysis: significant, but not dose-related effects on nitrogen and  phosphorus retention (p<0.05)
- Other: In the male low dose group nitrogen retention was 50% lower that in the control group, while in the high dose group no such difference was observed. In a repeat experiment no clear and significant differences in nitrogen retention were found. In both experiments phosphorous retention seemed somewhat increased in the male high dose groups (approximately 12%), while in the low dose groups no effect of treatment was seen.

Effect levels

Dose descriptor:

NOAEL

Effect level:

> 159 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects observed

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOAEL in rats after repeated oral administration of sodium silicate over 180 days was dertemined to be > 159 mg/kg bw/day.

Executive summary:

In a subchronic toxicity study sodium silicate was administered to 6 Sprague-Dawley rats /sex/dose in drinking water at dose levels of 79 and 159 mg/kg bw/day.

TOXIC RESPONSE/EFFECTS BY DOSE LEVEL:

- Mortality and time to death: None

- Clinical signs: no effects

- Body weight gain: Some statistically significant differences in body weight between experimental groups and controls were registered, but these were small (6% or less), not consistent and not dose related.

- Urinalysis: significant, but not dose-related effects on nitrogen and phosphorus retention (p<0.05)

- Other: In the male low dose group nitrogen retention was 50% lower that in the control group, while in the high dose group no such difference was observed. In a repeat experiment no clear and significant differences in nitrogen retention were found. In both experiments phosphorous retention seemed somewhat increased in the male high dose groups (approximately 12%), while in the low dose groups no effect of treatment was seen.

The NOAEL is > 159 mg/kg bw/day.