Silicon tetrachloride

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-10-11 to 1993-10-15

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: NOEC and EC50 are based on a single measurement of the stock solution before dilution and addition to test vessels.

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

Cited as Directive 84/449/EEC, C.2 (Acute toxicity for Daphnia)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The measured Dissolved Organic Carbon Concentration was determined in the fresh stock solution that was used to prepare the test media..

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The hard-to-dissolve test substance was added to the synthetic fresh water to provide a concentration of 1 g/l, and was stirred for 18 hours.  Then the solution was filtered and the carbon content was determined.  This solution served as the initial solution and contained a DOC value of 433 mg/l, which corresponds to a substance content of 938 mg/l.  Test concentrations selected for the main test were 235, 328, 469, 657, and 844 mg/l. 

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: Daphnia magna were produced through internal self-production.  The mother specimens were maintained in M4 medium per Elendt in 1-liter beakers for breeding.  The daily amount of nutrient, consisting of Scenedesmus subspicatus, was so measured that the amount added was totally consumed by the specimens.  At regular intervals of about four weeks, the young were isolated from the tanks.  They were the basis for further breeding.  Juveniles (less than 24 hours old) were isolated and used for testing in synthetic fresh water (294 mg/l CaCl2 x 2 H2O; 123 mg/l MgSO4 x 7 H2O; 63 mg/l NaHCO3; 5.5 mg/l KCl; the sum of the Ca2+ and Mg2+ was 4:1, and the ratio of Na+ to K+ was 10:1).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

-

Test temperature:

20+/-1ºC

pH:

7.0-7.1

Dissolved oxygen:

7.8-8.5 at test termination

Salinity:

Not applicable

Nominal and measured concentrations:

Test concentrations selected for the main test were 0(Control), 235, 328, 469, 657, and 844 mg/l based on the measured concentration in the stock solution. 

Details on test conditions:

Static exposure tests were conducted at 20 + 1oC.  The tests were conducted in the dark.  The test vessels were glass cylinders graduated to 10 ml.  Four vessels, each containing five neonates, were used for each test concentration and for the control (total of 20 neonates/test concentration).  The test organisms were not fed during the test and no aeration was applied.  Test organisms were observed for mortality (immobilization) at 24 and 48 hours after test initiation.  Dissolved oxygen and pH were measured at test termination for each test concentration and control. 

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 844 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis products

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 844 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Remarks:

measured concentration of stock solution.

Basis for effect:

mobility

Remarks on result:

other: Exposure is to the hydrolysis products

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

> 844 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis products

Basis for effect:

mobility

Details on results:

- Immobilisation of control: 0

Results with reference substance (positive control):

The previous test conducted with the positive control, potassium dichromate, showed 20% immobilization at 24-hours with 0.9 mg/l, and 100% immobilization at 24-hours with 1.9 mg/l.

Reported statistics and error estimates:

There were no significant effects in the test and therefore statistical analysis of the results was not required

There was no immobilisation at any test concentration or in the control group.  

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of >844 mg/L and a NOEC of ≥844 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to invertebrates: 48-hour EC₅₀ >844 mg/l (based on DOC analysis of initial stock solution) (highest concentration tested) (OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)), read-across from an analogous/structurally related substance, tetraethyl orthosilicate (CAS 78-10-4). The EC₅₀ is equivalent to >389 mg/l when expressed in terms of the silanol hydrolysis product.

Additional information

There are no reliable short-term data available for silicon tetrachloride (CAS 10026-04-7) therefore good quality data from an appropriate structural analogue, tetraethyl orthosilicate (CAS 78-10-4), have been read across. The substances share the same silanol hydrolysis product, monosilicic acid. The other hydrolysis products are hydrogen chloride for silicon tetrachloride and ethanol for tetraethyl orthosilicate.

A 48-hour EC₅₀ value of >844 mg/l (based on DOC analysis of initial stock solution) (highest concentration tested) has been determined for the effects of tetraethyl orthosilicate (CAS 78-10-4) on mobility of Daphnia magna (Hüls, 1989) in accordance with test guideline EU method C.2 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) * >844 = >389 mg/l.

Refer to IUCLID Section 6, CSR Section 7.0, and the ecotoxicity RAAF report attached in Section 13 of IUCLID or Annex 4 of the CSR, for further discussion of the approach to chemical safety assessment and justification for read across.