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Ecotoxicological information

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:
1994-01-17 to 1994-02-04
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Guideline study but with no GLP.
Qualifier:
according to
Guideline:
EU Method C.1 (Acute Toxicity for Fish)
Version / remarks:
Cited as Directive 92/69/EEC, C.1
GLP compliance:
no
Analytical monitoring:
yes
Details on sampling:
The concentrations of the stock solutions used to prepare the other treatments were measured daily.
Vehicle:
no
Details on test solutions:
An initial solution was prepared in drinking water (Gelsenwasser AG), stirred for about 18 hours, and filtered.  The resulting solution served as a stock solution.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
TEST ORGANISM

- Common name: Common Carp

- Source: Charles River, Someren, Netherlands

- Weight at study initiation (mean and range, SD): approximately 1.1 g


ACCLIMATION

- Acclimation period: 14 days

- Acclimation conditions (same as test or not): same as test

- Type and amount of food: Alma feed, 2% body weight

- Feeding frequency: Daily

- Health during acclimation (any mortality observed): <5% mortality
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
approx. 11 deg dH
Test temperature:
19-20ºC
pH:
7.7 - 8.4
Dissolved oxygen:
75-110% saturation
Salinity:
Not applicable
Nominal and measured concentrations:
Measured concentrations of the stock solutions:  1st batch (0 hr): 1110 mg substance/l 2nd batch (24 hr): 1287 mg substance/l 3rd batch (48 hr): 1069 mg substance/l 4th batch (72 hr): 1012 mg substance/l.

Nominal concentrations: 0 (Control), 1, 3, 10, 30 and 100 mg/L
Details on test conditions:
TEST SYSTEM

- Groups of 10 fish/tank were exposed to the test material at concentrations of 0, 1, 3, 10, 30 and 100 mg/l.  

- Fresh test solutions were prepared daily.

- Aeration: continuous

- Light/dark: 16/8 hr

- Feeding: none
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
LC0
Effect conc.:
30 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
55 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Remarks on result:
other: 30-100
Duration:
96 h
Dose descriptor:
LC100
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:
The LC50 values were determined by graphical interpolation.

24 hr LC50 = 58 mg/l (30-100)
48 hr LC50 = 55 mg/l (30-100)
72 hr LC50 = 55 mg/l (30-100)
96 hr LC50 = 55 mg/l (30-100)

Validity criteria fulfilled:
yes
Conclusions:
A 96-hour LC50 values of 55 mg/L has been determined for the effects of the test substance on mortality of Cyprinus carpio. It is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to fish: 96-hour LC50 55 mg/l (nominal) (OECD 203). The LC50 is equivalent to 45 mg/l when expressed in terms of [3-(2,3-epoxypropoxy)propyl]silanetriol.

Key value for chemical safety assessment

LC50 for freshwater fish:
45 mg/L

Additional information

A 96 hour LC50 value of 55 mg/l (nominal) has been determined for the effects of the registration substance on the mortality of the freshwater fish Cyprinus carpio (Infracor Degussa Group, 1996). In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance.

 

DOC analysis of filtered stock solution confirmed very high recoveries, although the concentration of substance was sufficiently high that silanol hydrolysis products could have begun to oligomerise and theoretically, precipitate. The concentration-response relationship in this study was very steep with 0% and 100% mortality observed at successive concentration levels. No sublethal effects were reported. 90% mortality was observed by the 24 h time point in the upper concentration level with 100% mortality by 48 h. It is therefore considered that the effects are predominantly due to the toxicity of the substance (and its soluble hydrolysis products) rather than physical effects associated with undissolved materials. Therefore the effects seen in the test are attributed to a mixture of the parent substance, the [3-(2,3-epoxypropoxy)propyl]silanetriol hydrolysis product, and soluble oligomers.

 

The results may be expressed in terms of concentration of the hydrolysis product, [3-(2,3-epoxypropoxy)propyl]silanetriol, by applying a molecular weight correction: (MW of silanol = 194.26 / MW of parent = 236.34) * 55 mg/l = 45 mg/l.

 

This study is selected as Key as it is the lowest value among the reliable studies.

 

Several supporting studies on the short-term toxicity of the substance to fish are available:

A 96 hour LC50 value of 237 mg/l (nominal concentration) has been determined for the effects of the test substance on mortality of Oncorhynchus mykiss (Dow Corning, 1978).

A 96 hour LC50 value of 276 mg/l (nominal concentration) has been determined for the effects of the test substance on mortality of Lepomis macrochirus (Dow Corning, 1978).

A 96 hour LC50 value of 349 mg/l (nominal concentration) has been determined for the effects of the test substance on mortality of Pimephales promelas (Evonik, 1988).

Ecotoxicity testing for this substance is complicated by the hydrolysis and condensation reactions of the substance. 3-(2,3-Epoxypropoxy)propyltrimethoxysilane is susceptible to hydrolysis of both the trimethoxy and epoxide groups. The silanetriol formed by hydrolysis of the methoxy groups will undergo condensation reactions to form siloxane dimers, oligomers and polymers, which may precipitate and cause physical effects on the test organisms. 

 

One study reported an LC50 value of 4.9 mg/l (Evonik, 1994). However, this study has been disregarded due to major methodological deficiencies. A very high stock loading rate was used (10.2 g/l). Oligomers would have formed and it is therefore unclear as to whether the effects were physical or toxicological. The study is therefore not considered for the assessment.

[3-(2,3-Epoxypropoxy)propyl]silanetriol is susceptible to further hydrolysis reactions and the ultimate hydrolysis product 3-[3-(trihydroxysilyl)propoxy]propane-1,2-diol is considered unlikely to exhibit significant ecotoxic effects based on QSAR estimated E(L)C50s >>100 mg/l (ECOSAR).