3-trimethoxysilylpropane-1-thiol

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:

1995-07-31 to 1995-08-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 100, 180, 350, 550 and 1000 mg/L and the fresh stock solutions used to prepare the test media.

- Sampling method: Concentrations of test substance hydrolysis products determined in fresh media at all concentrations after preparation and again before renewal after 24 hours. The concentrations of the fresh stock solutions used to prepare the test media was also determined.

- Sample storage conditions before analysis: not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by dilution of a 1000 mg/L stock solution. Stock solutions were prepared by stirring for 18 h followed by filtration. TOC concentration of stock solution determined and used as the basis for determining the nominal test concentrations.

- Differential loading: Five nominal test concentrations 100, 180, 350, 550 and 1000 mg/L

- Controls: Dilution water

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM

- Common name: Zebrafish

- Source: West aquarium, Bad Lauterberg, Germany

- Length at study initiation (length definition, mean, range and SD): 3.0 cm +/-0.5 cm

- Feeding during test: none

ACCLIMATION

- Acclimation period: at least 14 days

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

- Type and amount of food: TetraMin® at 1% of body weight

- Feeding frequency: Daily

- Health during acclimation (any mortality observed): The fish exhibit normal behaviour and are free from visible signs of disease at the start of the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

≈ 12ºdH

Test temperature:

20 - 22ºC

pH:

8.0 - 8.4

Dissolved oxygen:

84 - 111%

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 100, 180, 350, 550 and 1000 mg/L.

Initial measured concentrations: 100, 157, 334, 502 and 1005 mg/L.

Concentrations in media prior to replacement after 24 hours: 109, 156, 327, 514 and 929 mg/L.

Geometric mean measured concentrations (0-24h): 104, 156, 330, 508 and 968 mg/L.

The test results are presented and interpreted with reference to nominal concentrations.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type (delete if not applicable): open aquarium

- Material, size, headspace, fill volume: 20 L

- Aeration: Continuous

- Renewal rate of test solution (frequency/flow rate): Daily

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 1

- No. of vessels per control (replicates): 1

- Biomass loading rate: 0.49 g/L


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Potable water from Gelsenwasser AG


OTHER TEST CONDITIONS

- Adjustment of pH: None

- Photoperiod: 16 h light/8 h dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Mortality after 24, 48, 72 and 96 h


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.8

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

350 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

439 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Remarks on result:

other: Concentrations bounding LC50: 350 - 550 mg/l

Key result

Duration:

72 h

Dose descriptor:

LC50

Effect conc.:

451 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

486 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Key result

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

742 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: Zero

Reported statistics and error estimates:

LC50 determined by graphical interpolation

Sublethal observations / clinical signs:

Table 1. Test results

Nominal test substance concentration (mg/L)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	0	0
100	0	0	0	0
180	0	0	0	0
350	0	0	0	0
550	0	70	90	100
1000	100	100	100	100

Validity criteria fulfilled:

yes

Conclusions:

A 96-h LC50 value of 439 mg/L and NOEC of 350 mg/L have been determined for the effects of the test substance on mortality of Brachydanio rerio based on nominal concentrations of the substance. The test substance hydrolyses in water and it is therefore likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to fish: 96-hour LC₅₀ 439 mg/l (nominal) (EG Guideline 92/69 EWG Part C1), mortality of Brachydanio rerio. The LC₅₀ is equivalent to 345 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

345 mg/L

Additional information

A 96-hour LC₅₀ value of 439 mg/l (nominal) has been determined for the effects of the registration substance on mortality of Brachydanio rerio (new name: Danio rerio), conducted in accordance with EU Method C.1 (Acute Toxicity for Fish) and in complaince with GLP (Hüls 1995).

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. At the loading concentration used in preparation of stock, it is expected that oligomers and/or cross-linked aggregates may have been present to some extent, though no specific evidence of precipitation or physical effects on test animals is described. While this is an uncertainty, it is considered that the study results are suitable to be used (with caution), with effects attributed in principle to intrinsic ecotoxicity of silanol (and oligomers).

The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, by applying a molecular weight correction: (MW of silanol = 154.26 / MW of parent = 196.34) * 439 = 345 mg/l.

The reliability of three other LC₅₀ values in the range 2.4 to 253 mg/l, that were obtained from the open literature, could not be determined.

To support the proposed long-term read-across data, short-term aquatic toxicity data with 3-(triethoxysilyl)propanethiol (CAS 14814-09-6,EC No. 238-883-1) are included, for comparison of aquatic effects between the registered and read-across substances.

A 96-hour LC₅₀ value of >2.55 mg/l has been determined for the effects of 3-(triethoxysilyl)propanethiol (CAS 14814-09-6) on mortality of Danio rerio in a threshold toxicity test, conducted in accordance with OECD TG 203 and in compliance with GLP (Noack 2021). This value is equivalent to >1.65 mg/l when expressed in terms of the silanol hydrolysis product, 3-(trihydroxysilyl)propanethiol).

During the test with 3-(triethoxysilyl)propanethiol (CAS 14814-09-6), it is likely that the fish were exposed predominantly to the parent substance, especially at the beginning of the tests, with increasing amounts of hydrolysis products towards the end of the test media renewal period.

 

Refer to IUCLID Section 6, CSR Section 7.0, for further discussion of the approach to chemical safety assessment for this registration substance.