Tetraethyl orthosilicate

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-10-11 to 1993-10-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Version / remarks:

Cited as Directive 92/69/EEC, C.1

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples of freshly prepared test media were taken at the start of each successive 24 hour exposure period (0, 24, 48 and 72 hours). Samples of old test medium were taken at the end of the first 24-hour exposure period in order to assess the stability of the exposure concentrations.

Vehicle:

no

Details on test solutions:

A stock solution was prepared by adding the test substance to potable water at the rate of 1 g/L. After mixing the medium was filtered and the aqueous phase used as the test medium. The average measured Dissolved Organic Carbon Concentration determined in the fresh test medium over the course of the test (245 mg/L) was used as the basis for expressing the test results.

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM

- Common name: Zebrafish

- Source: West Aquarium, Bad Lauterburg, Germany

- Length at study initiation: 3.0+/-0.5 cm

- Feeding during test: none


ACCLIMATION

- Acclimation period: 14-days

- Acclimation conditions: same as test

- Type and amount of food: Tetramin® at 1% of body weight

- Feeding frequency: Daily

- Health and pre-treatment: The specimens were pre-conditioned (treatment: 3x per week with malachite green) and subjected to a 14-day quarantine.  They were used in testing only after this treatment.  Only specimens displaying normal behaviour at the beginning of the test and free of obvious disease were used in the study.  Fish were not fed during the test.       

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

10.7 ºdH

Test temperature:

20+/-1ºC

pH:

7.5-8.4

Dissolved oxygen:

4.3-8.9 mg/L (the low value of 4.3 mg/L did not affect the outcome of the test)

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal loading used to prepare test medium: 1000 mg/L

Mean measured DOC concentration in the test medium: 245 mg/L

The mean measured DOC concentration has been used as the basis for expressing the test results.

Details on test conditions:

TEST SYSTEM

- Test vessel: 20 litre aquarium

- Type (delete if not applicable): open

- Aeration: Yes, continuous

- Renewal rate of test solution: daily

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 1

- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Potable water from Gelsenwasser AG


OTHER TEST CONDITIONS

- Adjustment of pH: No

- Photoperiod: 16 hours light, 8 hours dark


EFFECT PARAMETERS MEASURED: Daily mortalities


TEST CONCENTRATIONS

- Spacing factor for test concentrations: Limit test

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 245 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 245 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: 0

Reported statistics and error estimates:

There were no mortalities observed in the test and therefore statistical analysis of the results was not required.

Sublethal observations / clinical signs:

Table 1. Results of analysis of test media

Nominal loading of test substance (mg/L)	Measured DOC concentration in fresh medium at start of test (mg/L)	Measured DOC concentration in old medium after 24 hours (mg/L)	Measured DOC concentration in fresh medium after 24 hours (mg/L)	Measured DOC concentration in fresh medium after 48 hours (mg/L)	Measured DOC concentration in fresh medium after 72 hours (mg/L)	Mean measured DOC concentration (mg/L)
1000	316	247	227	281	156	245

Table 2. Test results

Mean measured DOC concentration (mg/L)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	0	0
245	0	0	0	0

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 of >245mg/L and a NOEC of ≥245 mg/L have been determined for the effects of the test substance on mortality of Brachydanio rerio. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to fish: 96-hour LC₅₀ >245 mg/l (mean measured): (highest concentration tested) (test guideline EU method C.1 (Acute Toxicity for Fish)). The LC₅₀ is equivalent to >113 mg/l when expressed in terms of the silanol hydrolysis product, monosilicic acid.

Additional information

A 96-hour LC₅₀ value of >245 mg/l (mean measured DOC) (highest concentration tested) has been determined for the effects of tetraethyl orthosilicate (CAS 78-10-4) on mortality of Danio rerio (Hüls, 1993) in accordance with test guideline EU method C.1 (Acute Toxicity for Fish) and in compliance with GLP. In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, monosilicic acid, by applying a molecular weight correction: (MW of silanol = 96.1 / MW of parent = 208.33) * >245 = >113 mg/l.

Refer to IUCLID Section 6, CSR Section 7.0, for further discussion of the approach to chemical safety assessment.