Dimethoxydimethylsilane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

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 analogue approach justification provided in Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 126 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.:

>= 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Conclusions:

An LC50 (96 h) of >126 mg/L and a NOEC (96 h) of ≥126 mg/L have been determined for the effects of the source substance on mortality of the fish species Oncorhynchus mykiss in a study according to OECD guideline 203 and GLP. The source substance is the hydrolysis product of the target substance. Since the hydrolysis half life is < 1 h, the results derived for the source substance describe additionally the effects of the the target substance.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-06-30 to 2008-07-25

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:

yes

Details on sampling:

- Concentrations: The test article concentration was measured in each test chamber at test initiation (before the addition of the fish) and at test termination.
- Sampling method: Water samples (10 mL) were collected from mid-depth of the test chambers using a glass pipette.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The nominal test concentration was 120 mg/L. Appropriate aliquots (3.6 g) of the test article were added directly to 30-L of aerated dilution water in the test chambers. The mixtures were stirred using a glass pipette for approximately 1 minute. The negative control was dilution water only. All test solutions appeared clear and colorless.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Thomas Fish Company, Anderson, California on June 27, 2008. The identity of the species was verified by the supplier.
- Length at study initiation (length definition, mean, range): 49 mm (46-52 mm)
- Holding conditions: The fish were held at a temperature of 11.6 to 11.7 °C.
- Type and amount of food: During holding, rainbow trout were fed finfish starter #2 obtained from Zeigler Brothers, Gardners, PA. The trout chow is analyzed annually for selected contaminants. No contaminants had been shown to be present in the trout chow at concentrations that might affect the outcome of this study. Feeding was discontinued at least 48 hours prior to test initiation and the fish were not fed during the test.
- Health during acclimation (any mortality observed): no mortality

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

111 mg/L as CaCO3

Test temperature:

12 ± 1 °C

pH:

7.6-8.4

Dissolved oxygen:

≥8.7 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control) and 120 mg/L

Measured concentrations at test initiation: 120-126 mg/L

Measured concentrations at test termination: 128-131 mg/L

Mean measured test concentration: 126 mg/L (105% of nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: Test chambers were 38-L glass aquaria containing approximately 30 L of test solution. Test chambers were impartially placed in a temperature-controlled environmental chamber set to maintain a temperature of 12±1 °C. Each test chamber was loosely covered with a piece of plexiglass. Test chambers were labeled with the study number, test article concentration and replicate.
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- Biomass loading rate: 0.28 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The dilution water was municipal water obtained from Bay City, Michigan. The water was dechlorinated using a carbon filter and aerated prior to use.
- Culture medium different from test medium: No
- Intervals of water quality measurement: The laboratory water is monitored weekly for hardness, alkalinity, conductivity, total residual chlorine and pH. The water is monitored once a year for selected inorganics, total suspended solids (TSS), total organic carbon (TOC) and selected organic compounds. No contaminants have been shown to be present in the water at concentrations that might affect the outcome of this study.

OTHER TEST CONDITIONS
- Light intensity: Lighting used to illuminate the test vessels was provided by cool white fluorescent bulbs with a photoperiod of 16 hours light and 8 hours dark. Light intensity at test initiation was 34 foot-candles.

EFFECT PARAMETERS MEASURED: Mortality after 24, 48, 72 and 96 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Limit test

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 126 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.:

>= 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: 0%

Reported statistics and error estimates:

The 24, 48, 72 and 96-hour LC50 values were estimated by visual inspection of the mortality data. Confidence limits could not be calculated because only one concentration was tested.

Sublethal observations / clinical signs:

No mortality or other effects were observed in the control or treated test media.

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 of >126 mg/L and a NOEC of ≥126 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss.

Description of key information

LC50 (96 h) > 126 mg/L (meas. arithm. mean, OECD 203, O. mykiss; read across from silanol hydrolysis product DMSD)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Remarks:

for silanol hydrolysis product (relevant assessment entity)

Effect concentration:

> 126 mg/L

Additional information

Experimental data for dimethoxy(dimethyl)silane (CAS No. 1112-39-6) are not available. However, since dimethoxy(dimethyl)silane hydrolyses rapidly to dimethylsilanediol (DMSD) and methanol (DT50 < 0.6 h) the hydrolysis products rather than the parent substance should be considered for the assessment and read-across data for the hydrolysis product, dimethylsilanediol, are considered appropriate for the environmental assessment. The other hydrolysis product, methanol, is well described in the public domain literature. It has a low environmental hazard profile and is therefore not considered contributory to the overall aquatic toxicity of the registered substance (OECD SIDS, 2004). Thus, the ecotoxicity assessment was based on the silanol hydrolysis product dimethylsilanediol (DMSD, CAS No. 1066-42-8).

The available study with the freshwater fish Oncorhynchus mykiss was performed according to OECD 203 (GLP). Fish were exposed to dimethylsilanediol under static conditions to a nominal limit concentration of 120 mg/L for 96 h (Dow Corning Corporation, 2009a). The concentrations in test solution were verified by HPLC/RID analysis and confirmed that the substance is stable. Since no effects on mortality were recorded the LC50 (96 h) was derived to be > 126 mg/L (measured arithmetic mean).

Reference
OECD SIDS, 2004. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.