Trimethoxysilane

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:

2004-05-06 to 2004-05-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with GLP but no analysis of exposure concentrations

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Principles of method if other than guideline:

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.

OECD. 1992. Guideline for Testing of Chemicals. Fish Acute Toxicity Test. Guideline #203. Adopted 17 July 1992.

U.S. EPA. 1975. Methods for Acute Toxicity Tests with Fish, Macroinvertebrates and Amphibians. Ecological Research Series (EPA-660/3-75-009). 61 pp.

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 colourless 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 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 trouts 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 16 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

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

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

Sublethal observations / clinical signs:

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 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-hour LC₅₀: >100 mg/L, mortality of Oncorhynchus mykiss.

Additional information

A 96-hour LC₅₀ of >100 mg/L (nominal concentration) (highest concentration tested) has been determined for the effects of trimethoxysilane (CAS 2487-90-3) on mortality of Oncorhynchus mykiss, in accordance with OECD Test Guideline 203 and in compliance with GLP (Springborn Smithers, 2004a).

The test substance is susceptible to hydrolysis and, due to the test media preparation (stirring overnight) and exposure regime (static), it is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance, monosilicic acid and methanol. Methanol is non-toxic to the environment and it is considered unlikely that its presence significantly affected the results of the test performed with trimethoxysilane.