Trimethoxysilane

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:

2004-05-06 to 2004-05-08

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 202 (Daphnia sp. Acute Immobilisation Test)

Principles of method if other than guideline:

OECD. 2000. Guideline for Testing of Chemicals. Daphnia sp., Acute Immobilization Test. Revised Proposal tor Updating Guideline #202. October 2000.
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

- Method: A 100 mg a.i./L stock solution was prepared by adding 0.215 mL of trimethoxysilane to 2.0 L of dilution water (based on a purity of 97.1% and a density of 0.957 g/mL). The solution was mixed overnight with a magnetic stir plate and Teflon®-coated stir bar.  Each test concentration was prepared by adding the appropriate amount of the 100 mg a.i./L stock solution to an intermediate vessel and bringing it to a final volume of 1.0 L with dilution water.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: Springborn Smithers culture facility. 

- Method of culture: Daphnids were cultured in 1.0-L glass vessels containing 0.80 L of water. Water used to culture the daphnids was prepared in the same manner and has the same characteristics as the dilution water. Daphnids were fed a unicellular green algae, Ankistrodesmus falcatus (4 x 10E7cells/mL) and YCT (yeast, cereal leaves and flaked fish food) suspension daily, at a rate of 2.0 mL algae and 0.5 mL YCT solution per vessel per day. Daphnids were obtained by removing all immature daphnids from the culture vessel, thus isolating mature gravid daphnids <24 hours prior to initiating the test. Young produced by these organisms were subsequently pipetted into the test beakers.

- Age at study initiation: < 24 hours

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

Total hardness and alkalinity: 180 mg/L and 110 mg/L as CaCO3

Test temperature:

20 to 22ºC

pH:

7.7-8.0

Dissolved oxygen:

7.6-9.0 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 13, 22, 36, 60 and 100 mg a.i./L. (nominal)

Details on test conditions:

TEST SYSTEM

- Test vessel: The toxicity test was conducted in 250-mL glass beakers, each containing 200 mL of test solution.  

- Aeration: No aeration was provided to the test vessels.


TEST DESIGN

- Replication: Four replicate test vessels were established for each treatment lever and a dilution water control.

- Number of daphnids per treatment: Twenty daphnids were impartially selected and distributed to each concentration and the control (five daphnids per replicate vessel). 

- Control group: Dilution water control


TEST MEDIUM / WATER PARAMETERS

- Dilution water source: Fortified well water based on the formula for hard water (U.S. EPA, 1975).

- Dilution water chemistry (hardness, alkalinity. pH, TOC): The dilution water had a total hardness and alkalinity as CaCO3 of 180 mg/L and 110 mg/L, respectively, a pH range of 7.9 to 8.0 and a specific conductivity of 500 umhos/cm. The TOC concentration of the dilution water source was 0.40 mg/L for the month of May 2004.


OTHER TEST CONDITIONS

- Light intensity: The test area was illuminated with fluorescent bulbs at an intensity range of 65 to 83 footcandles at the solutions' surface. 

- Photoperiod: 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 (with observation intervals if applicable): Immobilization . 

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

- Range finding study

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

- Results used to determine the conditions for the definitive study: No immobilisation in any treatment

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Details on results:

- Was control response satisfactory: Yes. No immobilization or adverse effects were observed among daphnids exposed to the control.

Reported statistics and error estimates:

No treatment level resulted in any immobilisation. The EC50 and NOEC values were therefore empirically estimated to be =the highest test concentration.

The highest concentration producing 0% immobilization was 100 mg a.i./L.   The lowest concentration producing 100% immobilization was > 100 mg a.i./L. Biological observations: - Number immobilized as compared to the number exposed: Number immobilized: 0, Number exposed: 120 (includes control) - Was control response satisfactory (yes/no/unknown): Yes. No immobilization or adverse effects were observed among daphnids exposed to the control.

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 of >100 mg/L and NOEC of =100 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

48-hour EC₅₀: >100 mg/L, mobility of Daphnia magna.

Additional information

A 48-hour EC₅₀ value of >100 mg/L (nominal concentration) (highest concentration tested) has been determined for the effects of trimethoxysilane (CAS 2487-90-3) on mobility of the freshwater invertebrate Daphnia magna, in accordance with Test Guideline OECD 202 and in compliance with GLP (Springborn Smithers, 2004b).

 

The test substance is susceptible to rapid 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.