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Short-term toxicity to fish

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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 below and the overall justification for grouping of substances attached in IUCLID Section 13.
Reason / purpose:
read-across source
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
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
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:
OECD Guideline 203 (Fish, Acute Toxicity Test)
GLP compliance:
yes (incl. certificate)
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 11.7ºC.

- 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+/-1ºC. 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 hours


TEST CONCENTRATIONS

- Spacing factor for test concentrations: Limit test

- Results used to determine the conditions for the definitive study:
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
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
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.

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 (mean measured concentration, OECD 203)

Key value for chemical safety assessment

Additional information

There are no data available on short-term toxicity to fish for Diethoxy(dimethyl)silane (CAS 78-62-6). In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read-across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read-across from the analogue substance dimethylsilanediol (CAS 1066-42-8) has been applied to support the environmental hazard assessment of diethoxy(dimethyl)silane (CAS 78-62-6). Details on the read across justification can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13. The study with the analogue substance dimethylsilanediol (CAS 1066-42-8) was performed according to OECD 203 (GLP). Oncorhynchus mykiss was exposed to the substance in a limit test to a test item concentration of 120 mg/L (nominal) and a control under static conditions. The test concentration remained stable for the duration of the study resulting in a mean measured test concentration of 126 mg/L (105% of nominal). No mortality was recorded after 96 h resulting in a LC50 (96 h) > 126 mg/L

Based on these results of the analogue substance, Diethoxy(dimethyl)silane (CAS 78-62-6) is not assumed to cause harmful effects towards fish.