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Short-term toxicity to fish

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Endpoint:
short-term toxicity to fish
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result was obtained by an appropriate predictive method
Principles of method if other than guideline:
The ECOSAR ‘neutral organics’ QSARs for acute data have been applied and the effect concentrations calculated using log Kow and molar mass as input variables. An additional factor of *0.2 has been applied to the results.

The USEPA model ECOSAR was used as the basis for the estimation. This method is well-validated for ‘neutral organics’, i.e. those which act by a general narcotic mechanism, the potency of which is usually related to log Kow. Its scope is acute and long-term effects for the three standard trophic levels.
The method was validated for use with organosilicon compounds with a high weight percent of Si and limited or no additional functionality. Many of the reliable data for the category are limit values, therefore, the data were considered in terms of the range of theE(L)C50, in accordance with normal classification bands:    
E(L)C50 < 1 mg/l;
E(L)C50 in the range > 1 mg/l to 10 mg/l;
E(L)C50 in the range > 10 mg/l to 100 mg/l;
E(L)C50 > 100 mg/l.

In broad terms ECOSAR predicted correctly for most substances for each trophic level. However, performance was improved significantly by application of a factor of 0.2 to each predicted value (expressed in mg/l). This is equivalent to saying that the organosilicon substances are slightly more toxic than the general ECOSAR ‘neutral organics’ regression lines, although still well within the range of each model. The factor of 0.2 is applicable to fish,Daphniaand algae, across the whole range of log Kowvalues.
It is concluded that the acute effects of the substances in the sub-category can therefore be predicted from ECOSAR, with a minor modification.
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
1 400 mg/L
Conclusions:
A 96 h LC50 value of 1400 mg/l was obtained for the hydrolysis product of the submission substance using an appropriate calculation method. The results are considered to be reliable.
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:
OECD Guideline 203 (Fish, Acute Toxicity Test)
GLP compliance:
yes (incl. certificate)
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:
Nominal concentrations: Control, solvent control and 100 mg/l
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
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
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.

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.
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
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality

Description of key information

QSAR (96-h) LC50 of 1400 mg/L derived for the hydrolysis product, phenylsilanetriol.

Key value for chemical safety assessment

Additional information

No measured data was available for triethoxy(phenyl)silane (CAS 780-69-8). Therefore it was considered appropriate to read across from the structurally analogous substance, trichloro(phenyl)silane (CAS 98-13-5) as both substances hydrolyse rapidly to phenylsilanetriol. A limit test was conducted according to the OECD guideline 203 (2009). A test concentration of 100 mg/L was used for the test. No effects were observed at this concentration to the test organism Oncorhynchus mykiss. As the substance is subject to rapid hydrolysis, it is very likely that the test organisms were primarily exposed to hydrolysis products retained in the test media. An LC50 of 1400 mg/L was calculated for the hydrolysis product using an appropriate calculation method (Fisk P, 2010a).