[3-(2,3-epoxypropoxy)propyl]trimethoxysilane

Short-term toxicity to fish

Link to relevant study record(s)

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

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 (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

55 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

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 (fish)

Details on results:

- Mortality of control: 0

Reported statistics and error estimates:

The LC50 values were determined by graphical interpolation.

Sublethal observations / clinical signs:

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

Fresh water fish

Fresh water fish

Effect concentration:

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)propyl]trimethoxysilane 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).