Trimethoxyphenylsilane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-09-29 to 2009-10-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A dosing stock solution was prepared by mixing 1.52 mL of Trichloro(phenyl)silane (density 1.32 g/cm3) with 2.0 mL of tetrahydrofuran (THF) using Hamilton syringes. The 100 mg test item/L test solution was prepared prior to test initiation by adding 1.76 mL of the dosing stock solution to 10 L dilution water using a Hamilton syringe. Prior to addition of the dosing stock solution, the container containing the dilution water was placed on a magnetic stirrer. The spiked solution was stirred continuously over night. The pH of the solution was then adjusted to 7.0 with 1 N sodium hydroxide (NaOH).

A control vessel containing only dilution water and a solvent control vessel containing dilution water and 0.10 mL/L THF were established and maintained under the same conditions as the treatment solutions.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Source: The trout were originally obtained from Forellenzucht P. Hohler-Gasser, a commercial supplier located in Zeiningen, Switzerland.

- Length at study initiation (length definition, mean, range and SD): mean total length of 34 mm (range 29 to 39 mm).

- Weight at study initiation (mean and range, SD): mean wet weight of 0.42 g (range 0.20 to 0.63 g)

- Feeding during test: none


ACCLIMATION

- Acclimation conditions (same as test or not): Prior to testing, the fish were maintained in a holding tank (under renewal conditions) under a photoperiod of 16 hours light and 8 hours darkness with a 30 minute transition period.

- Culture water: The culture water was modified well water from the municipality of Horn, deionized with a Culligan Reverse Osmosis system. The deionized well water was reconstituted according to the formulation given in the Official Journal of the European Communities

- Type and amount of food: The fish were fed Hokovit 502, a dry, commercially available food, generally once daily. Fish were not fed during the 24-hour period prior to test initiation and during the exposure period.

- Health during acclimation (any mortality observed): No mortality was observed among the test fish population during the 12-day period prior to testing.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

160 mg/L as CaCO3

Test temperature:

14.9 - 15.5ºC

pH:

7.2 - 7.5

Dissolved oxygen:

8.9 - 10.7 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Control, solvent control and 100 mg/l (nominal)

Details on test conditions:

TEST SYSTEM

- Test vessel: The test vessels were 12.5 l vessels constructed of stainless steel, each containing 10 l of test solution. The test vessels were loosely covered with a glass plate during the 96-hour exposure.

- Replication: One test vessel for the 100 mg test item/L treatment and for the controls was prepared.

- Number of test organisms per treatment: The test was initiated when seven trout were impartially selected and distributed to each test vessel.

- Biomass loading: The mean organism loading was 0.3 g of biomass per liter of test solution.

- Temperature: The test vessels were placed in a water bath in order to maintain exposure solution temperatures at 15 ± 2°C.

- Aeration: Test solutions were gently aerated (with oil-free air) throughout the duration of the exposure period.

- Lighting: The test was illuminated to a light intensity of 200 to 500 lux using fluorescent bulbs. A 16-hour light, 8-hour dark photoperiod was maintained with an automatic timer.

- Observations: All test vessels were examined at 0, 24, 48, 72 and 96 hours of exposure for mortality. In addition observations of the physical characteristics of the test solutions (e.g., clear solution, precipitate, film on the surface of the test solution) were made and recorded at each 24-hour interval. Biological observations, including adverse effects on the exposed trout, were performed and recorded at each 24-hour interval. Effects for this study were based on mortality, defined as the lack of movement by the exposed organisms (i.e., absence of gill movement and reaction to gentle prodding).

- Water quality and lighting: The pH, dissolved oxygen (DO) concentration and temperature were measured at 0, 24, 48, 72 and 96 hours in each test solution. Continuous temperature monitoring was performed in the control solution throughout the exposure period. The pH was measured with a WTW 323 pH meter, dissolved oxygen and daily temperature were measured using a WTW Oxi 325 dissolved oxygen meter. Light intensity was measured with a Pancontrol LX 1308 lux meter.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: 0

Reported statistics and error estimates:

Since no 50% mortality was observed during the 96 hours of exposure, no 24-, 48-, 72- and 96-hour median lethal concentrations (LC50) were calculated.

Sublethal observations / clinical signs:

There were no effects on mortality in the control or treated media.

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 value of >100 mg/l and a 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 primarily exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification for grouping of substances provided in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Salinity:

Not applicable

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Reference 3

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2008-05-29 to 2008-06-02

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Low test item concentrations were used.

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0 (Control), 0 (Solvent control) and 0.20 mg/L

- Sampling: Prior to the start of the definitive exposure, water samples were removed from the treatment level and the controls and analyzed for trimethoxyphenylsilane concentration. Results of these pretest analyses were used to judge whether sufficient quantities of trimethoxyphenylsilane were being delivered to the test aquaria and whether the appropriate test concentrations were being maintained in order to initiate the definitive exposure.

During the in-life phase of the definitive study, two water samples from the treatment level and the controls were collected and analyzed for trimethoxyphenylsilane at 0 hour (test initiation) and 96 hours (test termination). The replicates used for sampling were alternated between intervals. Samples were collected from the approximate midpoint of the test vessel by pipette. In addition, a sample of the stock solution was analyzed for trimethoxyphenylsilane at 0-hour.

Three quality control (QC) samples each were prepared at each sampling interval and remained with the appropriate set of exposure solution samples throughout the analytical process. These QC samples were prepared in dilution water at nominal concentrations similar to the exposure concentration range. Results of the analyses of the QC samples were used to judge the precision and quality control maintained during the analysis of exposure solution samples.

Vehicle:

yes

Details on test solutions:

- Stock solution preparation: A 2.0 mg a.i./mL stock solution was prepared by placing 0.2012 g of test substance (0.1988 g as active ingredient) in a 100 mL volumetric flask and bringing it to volume with DMF. The resulting stock solution was observed to be clear and colorless.

A 1.0 μL/mL solvent stock solution was prepared by bringing 100 mL of DMF to a final volume of 100 mL with deionized water. The resulting stock solution was observed to be clear and colorless.

- Test solutions: Prior to test initiation, a 50-mL Glenco® gas-tight syringe in conjunction with a Harvard Apparatus Pump was calibrated to deliver 0.0400 mL/cycle of the 2.0 mg a.i./mL trimethoxyphenylsilane stock solution into the diluter system's chemical mixing chamber which also received 0.400 L of dilution water per cycle. The mixing chamber was positioned over a magnetic stir plate and Teflon®-coated stir bar, which continuously mixed the contents of the mixing chamber. The constant mixing aided in the solubilization of the test substance in the dilution water. The concentration of trimethoxyphenylsilane in the solution contained within the mixing chamber was equivalent to that of the nominal test concentration (0.20 mg a.i./L).

The solvent control solution was prepared utilizing a similar system, calibrated to deliver 0.0400 mL/cycle of the solvent control stock solution (1.0 μL/mL) to 0.400 L of dilution water per cycle which was subsequently delivered to the solvent control vessels. The concentration of DMF in the solvent control vessels was equivalent to the concentration of solvent present in the treatment level solution (0.10 mL/L).

- Diluter calibration and operation: The diluter system was calibrated prior to test initiation and at test termination by measuring delivery volumes of test substance and dilution water. The function of the diluter system (e.g., flow rates, stock solution consumption) was monitored daily and a visual check was performed twice each day. Flow-splitting cells were employed to equally distribute the solutions to the replicate vessels at a rate of 100 mL of test solution per vessel per cycle. Flow splitting accuracy of the diluter cells was within 10% of the nominal value. The exposure system was in operation for six days prior to initiation of the definitive exposure to allow equilibration of the test substance in the diluter apparatus and exposure vessels.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Source: The rainbow trout used during this study (SSL Lot No. 08A60) were obtained from TroutLodge, Inc., a commercial supplier located in Sumner, Washington.

- Holding and acclimation prior to test: Prior to testing, these fish were held in a 500-L fiberglass tank under a photoperiod of 16 hours light and 8 hours darkness. The well water which flowed into this holding tank was characterized as having a total hardness and total alkalinity range as calcium carbonate (CaCO3) of 42 and 20 to 24 mg/L, respectively, pH range of 7.2 to 7.3, a dissolved oxygen percent saturation range of 98 to 100%. The temperature ranged from 13 to 14°C and specific conductance ranged from 200 to 210 micromhos per centimeter (μmhos/cm). The fish used during the definitive exposure were maintained under these conditions for at least two weeks prior to testing.

- feeding: The fish were fed live brine shrimp, ad libitum, daily. Fish were not fed during the 24-hour period prior to test initiation or during the exposure period.

- Health prior to test: No mortality was observed among the test fish population during the 48 hours period prior to testing.

- Size of fish: A representative sample (N = 30) of the fish from the test population had a mean wet weight of 1.1 g (range 0.74 to 1.4 g) and a mean total length of 47 mm (range 41 to 53 mm).

Test type:

flow-through

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

42 mg/L as CaCO3

Test temperature:

14-16 °C

pH:

6.6-7.5

Dissolved oxygen:

6.7-10 mg/L (>60% ASV)

Salinity:

Not applicable

Nominal and measured concentrations:

0 (Control), 0 (Solvent control) and 0.20 mg/L (nominal)

The mean measured concentration was defined as 0.074 mg a.i./L (37% of nominal concentration). These recoveries are considered to be the maximum achievable recoveries under testing conditions due to the rapid hydrolysis of this compound combined with the limited aqueous solubility of the test substance.

The results are interpreted with reference to nominal and mean measured exposure concentrations.

Details on test conditions:

- Exposure system: The toxicity test was conducted using an exposure system consisting of an intermittent-flow proportional diluter (Mount and Brungs, 1967) and a set of 12 exposure vessels. The exposure system was designed to provide one concentration of the test substance, a solvent
(dimethylformamide (DMF, CAS No. 68-12-2)) control and a dilution water control.

The diluter system was calibrated prior to test initiation and at test termination by measuring delivery volumes of test substance and dilution water. The function of the diluter system (e.g., flow rates, stock solution consumption) was monitored daily and a visual check was performed twice each day. Flow-splitting cells were employed to equally distribute the solutions to the replicate vessels at a rate of 100 mL of test solution per vessel per cycle. Flow splitting accuracy of the diluter cells was within 10% of the nominal value. The exposure system was in operation for six days prior to initiation of the definitive exposure to allow equilibration of the test substance in the diluter apparatus and exposure vessels.

Each glass exposure aquarium measured 30 x 15 x 20 centimeters (cm). Water depth was maintained at a constant level by an overflow drain 15 cm from the bottom of each aquarium. The total test solution volume was therefore maintained at 6.8 L. The flow of exposure solution provided approximately 6 solution volume replacements and provided a 90% test solution replacement rate of approximately 9 hours. Exposure aquaria were labeled to identify the nominal test substance concentration and designated replicate.Test vessels were impartially placed in a water bath containing circulating chilled water designed to maintain the test solution at a temperature of 14 ± 1°C. A chiller was used to maintain a constant temperature in the exposure system.

- Dilution water: The dilution water (well water) used during this study was from the same source as the water used to culture rainbow trout and was characterized as having a total hardness and total alkalinity range (as CaCO3) of 42 mg/L and 20 to 23 mg/L, respectively, a pH range of 7.0 to 7.1 and a specific conductance of 200 μmhos/cm. The TOC concentration of the dilution water source was 0.44 and 0.45 mg/L, respectively, for May and June 2008.

- Replication: Four replicate vessels were established for the treatment level and the controls. The definitive study was initiated when rainbow trout were selected impartially from the holding tank and placed two at a time in each replicate test aquarium. This procedure was repeated until each aquarium contained ten fish for each treatment level and the control (40 fish per treatment and the controls).

- Test organism loading: The test organism loading concentration was 0.25 grams of biomass per liter of solution per day.

- Lighting: A 16-hour light, 8-hour dark photoperiod was maintained at a light intensity of 15 to 40 footcandles (160 to 430 lux). Sudden transitions from light to dark and vice versa were avoided.

- Observations: All aquaria were examined after 0, 24, 48, 72 and 96 hours of exposure as follows: mortalities were recorded and dead fish removed, biological observations, including adverse effects (e.g., lethargy, loss of equilibrium) of the exposed rainbow trout, and observations of the physical characteristics of the test solutions (e.g., presence of precipitate, film on the solution's surface) were made and recorded. Effects for this study were based on death, defined as the lack of movement by the exposed organisms (i.e., absence of gill movement and reaction to gentle prodding).

- Monitoring of test conditions: Dissolved oxygen concentration, temperature and pH were measured at each 24-hour interval in each treatment level aquaria and the controls. Continuous temperature recording was also performed in replicate B of the control.

- Range-finding test: A preliminary range finding exposure was conducted under flow-through conditions at nominal concentrations of 0.013, 0.025, 0.050, 0.10 and 0.20 mg a.i./L, a control and a solvent (DMF) control. Five rainbow trout were exposed to each treatment level and control. Following 96 hours of exposure, no mortality or adverse effects were observed among fish exposed to any of the treatment levels tested or the controls. Based on these results and consultation with the Study Sponsor, a single nominal trimethoxyphenylsilane concentration of 0.20 mg a.i./L, which was slightly above the functional solubility of the test substance in well water, was selected for the definitive test.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 0.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 0.074 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.074 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

Following 96 hours of exposure, no mortality or adverse effects were observed among fish exposed to the treatment level tested or the controls.

Reported statistics and error estimates:

The test was conducted as a limit test (one concentration) and the concentration tested did not produce ≥ 50% mortality, the LC50 was therefore empirically estimated to be greater than the nominal concentration for the single treatment level tested.

The No-Observed-Effect Concentration (NOEC) during the 96-hour exposure period was also determined. The NOEC is defined as the highest concentration tested at and below which there was no toxicant-related mortality or physical and behavioral abnormalities (e.g., lethargy), with respect to the control organisms.

Sublethal observations / clinical signs:

Table 1. Results of analysis of test media

 

Nominal concentration (mg/L)	Mean measured concentration (mg/L)	Mean measured concentration as percentage of nominal
0 (Control)	<0.0046*	-
0 (Solvent control)	<0.0046*	-
0.20	0.074	37

*The limit of quantification (LOQ) of the analytical method was 0.0046 mg/L

 

Table 2. Test results

 

Nominal concentration (mg/L)	Mean percentage mortality after 96 hours
0 (Control)	0
0 (Solvent control)	0
0.20	0

 

Validity criteria fulfilled:

yes

Conclusions:

A 96 hour LC50 value of >0.20 mg/L and NOEC of ≥0.20 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss. The results are expressed relative to nominal test substance concentration. The corresponding mean measured concentration of the substance in the treated test medium over the course of the test was 0.074 mg/L. However the substance is subject to rapid hydrolysis and it is therefore likely that the test organisms were primarily exposed to hydrolysis products retained in the test media.

Description of key information

LC50 (96 h) > 100 mg/L (nominal, O. mykiss, OECD 203)

It is likely that the test organisms were predominantly exposed to the hydrolysis products of the test substance.

Additional information

One experimental study for the short-term toxicity of trimethoxyphenylsilane to fish is available, in which an LC50 (96 h) value of > 0.20 mg/L and a NOEC (96 h) of ≥0.20 mg/L were determined for the mortality of Oncorhynchus mykiss (OECD Guideline 203 Fish Acute Toxicity Test, Springborn Smithers 2008).

The results are expressed relative to the nominal test substance concentration. The corresponding mean measured concentration of the substance in the treated test medium over the course of the test was 0.074 mg/l.

The maximum, nominal concentration tested (0.2 mg/l) was slightly above the functional solubility of the test substance trimethoxyphenylsilane (parent form) in the fish test medium (well water), which had been determined in a preliminary solubility trial and ranged from 0.043 - 0.13 mg/L. However, the highest tested concentration is also well below the predicted solubility of the substance (1700 mg/L). Therefore, it was considered appropriate to read across from the structurally analogous substance, trichlorophenylsilane (98-13-5), as both substances hydrolyse rapidly to phenylsilanetriol.

In the read-across source study, a limit test was conducted at a test concentration of 100 mg/l (OECD Guideline 203 Fish Acute Toxicity Test, Springborn Smithers 2009). No effects were observed at this concentration to Oncorhynchus mykiss. As the substance is subject to rapid hydrolysis, it is therefore likely that the test organisms were primarily exposed to hydrolysis products retained in the test media.