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Ecotoxicological information

Short-term toxicity to fish

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short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1993-10-11 to 1993-10-15
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
EU Method C.1 (Acute Toxicity for Fish)
Version / remarks:
Cited as Directive 92/69/EEC, C.1
GLP compliance:
Analytical monitoring:
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.
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:

- Common name: Zebrafish

- Source: West Aquarium, Bad Lauterburg, Germany

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

- Feeding during test: none


- 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:
Water media type:
Limit test:
Total exposure duration:
96 h
10.7 ºdH
Test temperature:
Dissolved oxygen:
4.3-8.9 mg/L (the low value of 4.3 mg/L did not affect the outcome of the test)
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 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


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


- Adjustment of pH: No

- Photoperiod: 16 hours light, 8 hours dark



- Spacing factor for test concentrations: Limit test
Reference substance (positive control):
96 h
Dose descriptor:
Effect conc.:
>= 245 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
96 h
Dose descriptor:
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:
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.

Key value for chemical safety assessment

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.