Trichlorosilane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

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:

other: 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

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

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.

Table 1. Test results

Nominal concentration (mg/L)	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	0
13	0	0
22	0	0
36	0	0
60	0	0
100	0	0

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) o 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.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2006-09-06 to 2006-09-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Prior to the start of the definitive exposure, one water sample was removed from the high, middle and low treatment levels and the control solution and analyzed for ethyl silicate concentration. Results of these pretest analyses were used to judge whether sufficient quantities of ethyl silicate were being delivered to the test vessels and whether the appropriate test concentrations w ere being maintained in order to initiate the definitive exposure.

During the in-life phase of the definitive study, one water sample (alternating between replicates A and B) from each treatment level and the control solution was collected, extracted and analyzed for ethyl silicate at 0 hour (test initiation) and 48 hours (test termination). Samples were collected from the approximate midpoint of the test vessel by pipet.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: During the definitive study, ethyl silicate (density 0.93 g/mL, 930 mg a.i./mL) was delivered directly into the diluter's mixing chamber via syringe. The resulting solution was observed to be clear and colorless with an oily film of undissolved substance on the solution's surface. A Glenco® 50 -mL gas-tight syringe in conjunction with a Harvard Syringe Pump was calibrated to deliver 0.2118 mL/cycle of the 930 mg a.i./mL ethyl silicate solution into the diluter system's chemical mixing chamber which also received 0.390 L of dilution water per cycle. The mixing chamber was positioned over a water-driven magnetic stirrer and was partially submerged within an ultrasonic water bath which continuously mixed the contents of the mixing chamber. The concentration of ethyl silicate in the solution contained within the mixing chamber was equivalent to that of the highest nominal test concentration (500 mg a.i./L) and was proportionally diluted (50%) to produce the remaining nominal test concentrations (250, 125, 63, 3l and 0 (control) mg a.i./L).

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: From laboratory stock cultures

- Age at study initiation (mean and range, SD): <24 hours

- Method of breeding: Juvenile daphnids (< 24 hours old) were obtained from the laboratory cultures by removing all immature daphnids from the culture vessels 24 hours prior to test initiation, thereby isolating all mature gravid adult daphnids in the culture. Daphnids produced by these adult organisms were removed from the cultures and used as test organisms. The adult daphnids used to produce offspring for this test (l) did not contain ephippia, (2) produced offspring prior to being l2 days old, (3) were not used in any portion of a previous test and (4) mortality 48 hours prior to test initiation was < 20%.

CULTURE CONDITIONS

- Culture medium: The culture water was prepared by fortifying well water based on the formula for hard water and filtering it through an Amberlite XAD-7 resin column to remove any potential organic contaminants. This water had a total hardness range and total alkalinity as calcium carbonate (CaCO3) of 160 to 170 mg/L and 110 mg/L, respectively, a pH range o f 7.9 to 8.2, a dissolved oxygen concenration range of 7.5 to 9.7 mg/L, a temperature range of 20 to 22ºC and a specific conductance range of 500 to 600 micromhos per centimeter. All water quality ranges presented here were measured during thc two weeks prior to testing.

- Lighting: The daphnid culture area received a regulated photoperiod of 16 hours of light and 8 hours of darkness. Light intensity of 68 to 99 footcandles (730 to 1100 lux) at the surface of the culture solutions was provided by fluorescent bulbs.

- Feeding of stock cultures: Daphnids were fed a unicellular green algae (Ankistrodesmus falcatus, 4 x l0E7 cells/ml) at a rate of 0.5 to 1.5mL per vessel daily depending on the age of the adult organisms in the culture vessel and 0.5 mL of a combination of yeast, cereal leaves and flaked fish food (YCT) daily. Daphnids were not fed during the exposure.

- Feeding during test: None

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

160-170 mg/L as CaCO3

Test temperature:

2l to 23ºC

pH:

8.0 to 8.1

Dissolved oxygen:

7.2 to 8.8 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 31, 63, 125, 250 and 500 mg a.i./L

Mean measured concentrations ranged from l5 to 37% of nominal levels and were defined as < LoQ (Control), 11, 14, 34, 70 and 75 mg a.i./L.

Analytical variability in the two highest test concentrations was likely due to solubility of the test substance under the test conditions maintained.

Details on test conditions:

TEST SYSTEM

- Exposure vessel type (e.g., size, headspace, sealed, aeration, # per treatment):  Each test vessel (1600-mL square glass battery jars) had two 2-cm holes drilled in the sides, 15 cm  from the bottom, which were covered with Nitex® 40 mesh screen for  drainage.  The total test solution volume was maintained at 1400 mL.  Two  replicate test vessels were established for each treatment level and a  dilution water control.  No aeration was provided to the test vessels. 

- 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 range and alkalinity as CaCO3 of 160 to 170 mg/L and 110 mg/L, respectively, a pH range of 8.1 to 8.2 and a specific conductivity range of 500 to 600 µmhos/cm.  The TOC concentration of the dilution water was 0.38 mg/L for the month of September 2006.  

-Lighting (quality, intensity, and periodicity):  The test area was illuminated with fluorescent bulbs.  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.

- Water chemistry in test (D.O., pH), in the control, and at least one concentration where effects were observed:  The dilution water control vessels had a measured DO concentration of 8.8 mg/L at test initiation and test termination.  The pH measured in the dilution water control vessel replicates was 8.1 at test initiation and ranged from 8.0 to 8.1 at test termination.  

- Element (unit) basis (i.e., immobilization):  Immobilization

- Test design (number of replicates, individuals per replicate, concentrations):  Twenty daphnids were impartially selected and distributed to each concentration and the control (two replicates, ten daphnids per replicate vessel).  

- Method of calculating mean measured concentrations (i.e., arithmetic mean, geometric mean, etc.):  Arithmetic mean.  

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 75 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 75 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobilisation of control: 0

Reported statistics and error estimates:

There were no significant effects on mobility at any of the test concentrations and therefore statistical analysis of the results was not required.

Table 1. Results of analysis of test media

Nominal concentration (mg/L)	Measured concentration at start of test (mg/L)	Measured concentration at end of test (mg/L)	Mean measured concentration (mg/L)	Mean measured concentration as % of nominal
0 (Control)	<0.44	<0.46	Not applicable	Not applicable
31	12	10	11	37
63	14	13	14	22
125	37	30	34	27
250	79	61	70	28
500	59	91	75	15

Table 2. Test results

Mean measured concentration (mg/L)	Percentage immobilisation after 24 hours	Percentage immobilisation after 48 hours
0 (Control)	0	0
11	0	0
14	0	0
24	0	0
70	0	0
75	0	5

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of >75 mg/L and NOEC of ≥75 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. Under the flow-through exposure conditions used in the test it is likely that the test organism will have been primarily exposed to the test substance.

Description of key information

Short-term toxicity to invertebrates: 48-hour EC₅₀: >100 mg/l, mobility of Daphnia magna; equivalent to >79 mg/l as monosilicic acid, read across from trimethoxysilane (CAS 2487-90-3).

Additional information

There are no reliable short-term data available for trichlorosilane (CAS 10025-78-2) therefore good quality data from an appropriate structural analogue, trimethoxysilane (CAS 2487-90-3), have been read across. The substances share the same silanol hydrolysis product, monosilicic acid. The other hydrolysis products are hydrogen chloride for trichlorosilane (CAS 10025-78-2) and methanol for trimethoxysilane (CAS 2487-90-3).

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.

The results may be expressed in terms of concentration of the hydrolysis product, monosilicic acid, by applying a molecular weight correction: (MW of silanol = 96.10 / MW of parent = 122.20) * >100 mg/l = >79 mg/l.  

 

Supporting data have also been read across from tetraethyl orthosilicate (CAS 78-10-4), which hydrolyses rapidly to monosilicic acid and ethanol:

A 48-hour EC₅₀ value of >75 mg/l (measured concentration) (highest concentration tested) has been determined for the effects of tetraethyl orthosilicate (CAS 78-10-4) on mobility of Daphnia magna (Springborn Smithers Laboratories, 2006) in accordance with Test Guideline OECD 202 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) * >75 = >35 mg/l.

 

Refer to IUCLID Section 6, CSR Section 7, and the ecotoxicity RAAF report attached in IUCLID Section 13 or as an Annex in the CSR, for further discussion of the approach to chemical safety assessment and justification for read across.