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Ecotoxicological information

Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2004-05-06 to 2004-05-10
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to an appropriate OECD test guideline, with acceptable restrictions as no exposure concentrations were analysed
Qualifier:
according to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Qualifier:
according to
Guideline:
other: ASTM. 2002. Standard practice for conducting acute toxicity tests with fishes, macroinvertebrates and amphibians. Standard E729-96. American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: A 100 mg a.i./L stock. solution was prepared by adding 4.3 mL of trimethoxysilane to 40 L of dilution water (based on a purity of 97.1% and a density of 0.957 g/mL). The solution was mixed overnight and was observed to be clear and colorless with no undissolved test substance visible following mixing. Each test concentration was prepared by adding the appropriate amount of the 100 mg a.i./L stock solution to the test vessel and bringing it to a final volume of 15 L with dilution water.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM

- Common name: Rainbow trout

- Source: Test organisms were obtained from Trout Lodge, Sumner, Washington. 

- Length at study initiation (length definition, mean, range): 40 mm (range 38 to 42 mm)

- Weight at study initiation (mean and range): 0.62 g (range 0.47 to 0.74 g)

- Holding conditions: During the 14-day period prior to testing, rainbow trout were held in a 500-L fiberglass tank under a photoperiod of 16 hours light and 8 hours dark. The temperature in the holding tank ranged from 13 to 15 °C during this 14-day period. The water which flowed into the fish holding tank and was characterized as having a total hardness and alkalinity as CaCO3 of 36 mg/L and 24 mg/L, respectively, a pH of 7.5, and a specific conductivity of 130 umhos/cm. The fish were fed a dry commercial flaked fish food and brine shrimp, ad libitum,daily. Fish were not fed during the 48-hour period prior to test initiation or during the exposure period.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
Total hardness and alkalinity: 44 mg/L and 28 mg/L as CaCO3
Test temperature:
13 to 15 ºC
pH:
6.1-7.0
Dissolved oxygen:
5.1-9.8 mg/L
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 0 (Control), 13, 22, 36, 60 and 100 mg a.i./L
Details on test conditions:
TEST SYSTEM

- Test vessel: The toxicity test was conducted in 20.8-L aquaria constructed entirely of glass and silicone sealant impartially placed in a temperature-controlled water bath designed to maintain exposure solution temperatures at 14 +/- 1 deg C. A single aquarium was established for each treatment level and the control with the aquaria containing 15 L of test solution. Gentle, oil-free aeration was initiated at the 48-hour observation interval to raise and maintain dissolved oxygen levels at or above 60% of saturation.

- Test design (number of replicates, individuals per replicate, concentrations): Ten rainbow trout were impartially selected and distributed to each exposure vessel. Fish were added two at a time to each test vessel until each test vessel contained ten fish. A total of 10 organisms were exposed to each treatment level and the control.


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Laboratory well water.

- Dilution water chemistry (hardness, alkalinity, pH, TOC): The dilution water had a total hardness and alkalinity as CaCO3 of 44 mg/L and 28 mg/L, respectively, a pH of 7.6 and a specific conductivity of 130 umhos/cm. The TOC concentration of the dilution water source was 0.40 mg/L for the month of May 2004.

- Water chemistry in test (D.O., pH), in the control, and at least one concentration where effects were observed: The dilution water control vessel had a measured DO concentration of 9.7 mg/L at test initiation and 9.4 mg/L at test termination. The pH measured in the dilution water control was 6.8 at test initiation and test termination.


OTHER TEST CONDITIONS

- Lighting (quality, intensity, and periodicity): The test area was illuminated with fluorescent bulbs at an intensity range of 32 to 57 footcandles at the solutions' surface. The test area received a regulated photoperiod of l6 hours of light and 8 hours of darkness. Sudden transitions from light to dark and vice versa were avoided. Light intensity was measured once during the test.


EFFECT PARAMETERS MEASURED: Mortality

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.6

- Range finding study

- Test concentrations: 1, 10 and 100 mg/L

- Results used to determine the conditions for the definitive study: 20% mortality in 100 mg/L after 24 hours. No effects in other treatments or Control
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: hydrolysis product tested
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: hydrolysis product tested
Details on results:
- Mortality of control: 0
Reported statistics and error estimates:
No effects were observed in the test. The results were therefore not subject to statistical analysis

24-, 48-, 72-, and 96-hour LC50: > 100 mg a.i./L.


NOEC through 96 hours 100 mg a.i./L.


The highest concentration producing 0% mortality was 100 mg a.i./L.  The lowest concentration producing 100% mortality was > 100 mg a.i./L.

Biological observations:

- Number of mortalities as compared to the number exposed: Number of mortalities: 0, Number exposed: 60 (includes
control)

- Concentration response with 95% confidence limits: > 100 mg a.i./ L (empirically estimated), corresponding 95% confidence intervals could not be calculated.

- Cumulative mortality: 0% mortality was observed among fish exposed to all treatment levels tested.

- Was control response satisfactory (yes/no/unknown): Yes.
No mortality or adverse effects were observed among fish exposed to the control.

Validity criteria fulfilled:
yes
Conclusions:
A 96-hour LC50 of >100 mg/L and NOEC of ≥100 mg/L have been determined for the effects of the test substance and its hydrolysis product on mortality of Oncorhynchus mykiss. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

(96 h) LC50: >100 mg/L mortality Oncorhynchus mykiss. Reliability 2.

Key value for chemical safety assessment

Additional information

No measured data are available for fish for triethoxysilane (CAS 998-30-1). However, studies are available for the structurally analogous substance, trimethoxysilane (CAS 2487-90-3). It is considered appropriate to read across for acute fish results for trimethoxysilane (CAS 2487-90-3) to triethoxysilane (CAS 998-30-1) as both substances hydrolyse in the presence of water to yield silanetriol. Silanetriol will break down further into inorganic, naturally occurring substances such as silica and silica acid. The hydrolysis half-life of triethoxysilane (CAS 998-30-1) and trimethoxysilane (CAS 2487-90-3) indicate that under conditions relevant to ecotoxicity assessment, both will hydrolyse to silanetriol.

A 96 hour LC50of >100 mg/l and NOEC of ≥100 mg/l (OECD Guideline 203 Fish, Acute Toxicity Test, Springborne Smithers 2004) have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss. It is likely that the test organisms were exposed to the hydrolysis products of the substance.Therefore, the environmental hazard assessment, including sediment and soil compartments due to water and moisture being present, is based on the properties of the hydrolysis product, ethanol.