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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2007-02-02 to 2007-02-06
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
Analytical monitoring:
yes
Details on sampling:
- Sampling: Samples were removed from each treatment level and the control at each sampling interval (i.e., 0 and 96 hours). Samples were collected from the approximate midpoint of the test vessel by volumetric pipet. Three quality control (QC) samples were prepared at each sampling interval and remained with the set of exposure solution samples through the analytical process. 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. The QC samples and the samples from each treatment level were analysed for 3-(triethoxysilyl)propiononitrile concentration.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The toxicity test was conducted using an exposure system consisting of an intermittent-flow proportional diluter (Mount and Brungs, 1967), a temperature-controlled water bath and a set of six exposure vessels. The exposure system, constructed entirely of glass and silicone sealant, was designed to provide five concentrations of the test substance and a dilution water control. 
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
TEST ORGANISM

- Common name: Rainbow trout

- Source: Springborn Smithers culture facility.  

- Holding conditions: Prior to testing, juvenile rainbow trout were held in 500-L fiberglass tanks.  Water which flowed into this holding tank was characterized as having total hardness and total alkalinity ranges as calcium carbonate (CaCO3) of 44 to 48 mg/L and 21 to 23 mg/L, respectively, and a specific conductance range of 190 to 220 micromhos per centimeter (µmhos/cm). Other parameters monitored in the holding tank were pH with a range of 7.1 to 7.4, dissolved oxygen concentration range of 87 to 94% of saturation.  

- Acclimation period: The fish used during the definitive exposure were maintained under these conditions for two weeks prior to testing. The temperature in the holding tank ranged from 10 to 14 ºC during the 14-day period prior to test initiation.  

- Feeding during holding period: The fish were fed a dry commercial flaked fish food (Trout Chow), ad libitum, daily. Fish were not fed during the 24-hour period prior to test initiation or during the exposure period. Representative samples of the food source were analyzed periodically for the presence of pesticides, PCBs and toxic metals by GeoLabs, Inc., Braintree, Massachusetts. None of these compounds have been detected at concentrations that are considered toxic in any of the samples analyzed. Based on these analyses, food sources were considered to be of acceptable quality since all analyte concentrations were below levels of concern.

- Mortalities prior to the test: No mortality was observed among the test fish population during the 7-day period prior to testing.  

- Size of test fish: A representative sample (N = 30) of the fish from the test population had a mean wet weight of 0.50 g (range 0.40 to 0.67 g) and a mean total length of 39 mm (range 37 to 42 mm).

- Test organism loading: 0.12 grams of biomass per liter of solution per day.

- Allocation to test vessels: Rainbow trout were selected impartially from the holding tank and placed two at a time in each test aquarium. This procedure was repeated until each aquarium contained ten fish for each treatment level and the control.  
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
The dilution water had total hardness and alkalinity (as CaCO3) ranges of 52 to 56 mg/L and 20 to 40 mg/L
Test temperature:
11 to 14ºC
pH:
6.8-7.2
Dissolved oxygen:
6.4-10 mg/L
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: 0 (Control), 7.5, 15, 30, 60 and 120 mg/L

Mean measured concentrations: 0 (Control), 5.9, 11, 23, 54 and 110 mg/L

The results are presented and interpreted with reference to mean measured concentrations.
Details on test conditions:
Test conditions:

- Exposure system: The toxicity test was conducted using an exposure system consisting of an intermittent-flow proportional diluter (Mount and Brungs, 1967), a temperature-controlled water bath and a set of six exposure vessels. The exposure system, constructed entirely of glass and silicone sealant, was designed to provide five concentrations of the test substance and a dilution water control.  

- Temperature control: Test vessels were impartially positioned in a water bath containing circulating chilled water to maintain the test solution temperatures at 12 ± 1ºC.  

- Lighting: Exposure vessels were maintained throughout the 96 hour test in an area illuminated by Sylvania Oktron® fluorescent bulbs at an intensity of 32 to 40 footcandles at the surface of the test solutions. The photoperiod was 16 hours light and 8 hours of darkness. Sudden transitions from light to dark and vice versa were avoided.  Light intensity was measured with a VWR traceable light meter.  

- Exposure system (e.g., flow rates, stock solution consumption): 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 per day in order to provide a 90% test solution replacement rate of approximately 9.0 hours (Sprague, 1969). Exposure aquaria were labeled to identify the replicate designation and the nominal test substance concentration.

- Dilution water source: Well water.

- Dilution water chemistry (hardness, alkalinity, pH, TOC): The dilution water had total hardness and alkalinity (as CaCO3) ranges of 44 to 46 mg/L and 20 to 23 mg/L, respectively, a pH of 6.9 to 7.1 and a specific conductivity range of 190 to 200 µmhos/cm. The TOC concentration of the dilution water was 0.58 mg/L for the month of February 2007.  

- Element (unit) basis (i.e., mortality):  Mortality
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
>= 110 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 110 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:
No test concentration resulted in >50% mortality. The LC50 values were therefore empirically estimated to be greater than the highest test concentration. The NOEC was determined by visual examination of the raw data.

No mortality or adverse effects were observed among the fish exposed to any of the treatment levels tested or the control.

Validity criteria fulfilled:
yes
Conclusions:
A 96-hour LC50 value of >110 mg/L and a NOEC of =110 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 exposed to a solution that was predominantly of the test substance but also contained its hydrolysis products.

Description of key information

96 h LC50 >110 mg/L, O. mykiss, read-across from CAS 919-31-3, measured based on parent substance.

Key value for chemical safety assessment

Additional information

There is no reliable short-term toxicity to fish data available for 3-(trimethoxysilyl)propiononitrile (CAS 2526-62-7), therefore, good quality data for an appropriate structural analogue, 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), have been read across. Both substances share the same silanol hydrolysis product, 3-(trihydroxysilyl)propiononitrile. The other hydrolysis products are methanol and ethanol, respectively. In the test with 3-(triethoxysilyl)propiononitrile (CAS 919-31-3), the observations are attributed to the exposure of test organisms to 3-(triethoxysilyl)propiononitrile in the test system.

 

A 96-hour LC50 value of >110 mg/L and a NOEC of =110 mg/L have been determined for the effects of the read-across substance 3-(triethoxysilyl)propiononitrile (CAS 919-31-3) on mortality of Oncorhynchus mykiss (highest concentration tested, measured concentration), in accordance with test guidance OECD 203 (Springborn Smithers, 2007). The measured concentrations are expressed in terms of parent substance. However, due to the rapid hydrolysis rate of the tested substance and the test system being flow-through, it is likely that the test organisms were exposed to both the test substance and its hydrolysis products. This is confirmed by the fact that the measured concentration of parent substance is lower than the nominal concentrations (but within 20%). Results expressed relative to nominal concentrations are EC50 >120 mg/l.

During the test with the read-across substance, the test organisms are likely to have been predominantly exposed to the parent substance. The read-across is therefore supported by a fish 96 h LC50 QSAR prediction for the silanol hydrolysis product, 3-(trihydroxysilyl)propiononitrile, using ECOSAR v2.0 for the prediction of the aquatic toxicity of neutral organics. A predicted value of 2 800 000 mg/l was determined.