3-(trimethoxysilyl)propyl isocyanate

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:

2002-08-26 to 2003-01-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0(Control) and 100 mg/l

- Sampling method: Duplicate samples of test media were taken at the start and end of the test.

- Sample storage conditions before analysis: samples were analysed immediately after collection.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Three, four litre volumes of test media with a nominal concentration of 100 mg/l were prepared by intense stirring for 24 hours. The three volumes were then aggregated to produce the final test medium.

- Controls: Dilution water

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trout

- Source: Forellenzuchtbetrieb Tautenhahn, 98646 Trostadt, Germany

- Length at study initiation (length definition, mean, range and SD): 5.13 +/-0.39 cm

- Weight at study initiation (mean and range, SD): 1.26 +/-0.23 g

ACCLIMATION

- Acclimation period: 4 weeks

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

- Type and amount of food: commercial fish food

- Health during acclimation (any mortality observed): no mortalities observed

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

250 mg/l as CaCO3

Test temperature:

15-17ºC

pH:

7.7-7.9

Dissolved oxygen:

=8.7 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control) and 100 mg/l

Measured concentrations were 88% of nominal at the start of the test and 76% at the end of the test. The mean measured concentration was therefore 82 mg/L.

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

Details on test conditions:

TEST SYSTEM

- Test vessel: aquaria

- Type (delete if not applicable): open

- Material, size, headspace, fill volume: glass, 20 litre capacity with 12 litre of test medium

- Aeration: yes

- Renewal rate of test solution (frequency/flow rate): none

- No. of organisms per vessel: 7

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

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

- Biomass loading rate: 0.74 g/l

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted freshwater prepared by adding analytical grade salts to deionised water.

- Alkalinity: 0.8 mmol/l

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 h light, 8 h dark

- Light intensity: 320-420 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mortality after 2, 24, 48, 72 and 96 hours

TEST CONCENTRATIONS

- Spacing factor for test concentrations: not applicable

- Range finding study

- Test concentrations: not reported

- Results used to determine the conditions for the definitive study: not reported

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.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 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:

- Behavioural abnormalities: none

- Mortality of control: 0

Reported statistics and error estimates:

There were no toxic effects observed in the test and therefore no statistical tests were required.

Sublethal observations / clinical signs:

No toxic effects were observed following 96-hour exposure to a nominal concentration of 100 mg/l.

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 value of >100 mg/L and NOEC of =100 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss based on nominal concentration of the substance. The test substance is susceptible to hydrolysis and it is 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 hr LC₅₀ >100 mg/L (nominal) (limit test) (OECD 203), or >67 mg/L when expressed in terms of concentration of the silanol hydrolysis product 3-aminopropylsilanetriol.

Additional information

A 96-hour LC₅₀ value of >100 mg/L (highest concentration tested) has been determined for the effects of the registration substance on mortality of Oncorhynchus mykiss based on nominal concentrations of the substance (IBACON, 2003a).

The isocyanate group is very rapidly hydrolysed to the corresponding amine (half-life of <5 minutes or less), and further hydrolysis of the alkoxy groups proceeds at a slower rate (half-life of 2.6 h at pH 7 and 20-25°C, estimated) to 3-aminopropylsilanetriol and methanol, therefore, it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance during the static test.

The results may be expressed in terms of concentration of the hydrolysis product, 3-aminopropylsilanetriol, by applying a molecular weight correction: (MW of silanol = 137.21 / MW of parent = 205.29) * >100 mg/L = >67 mg/L as 3-aminopropylsilanetriol.

 

Reliable supporting data are read across from an appropriate structural analogue, 3-aminopropyl(triethoxy)silane (CAS 919-30-2), which is a close structural analogue of 3-(trimethoxysilyl)propylamine (CAS 13822-56-5), the amine which is formed very rapidly when the registered substance comes into contact with water/moisture.  3-Aminopropyl(triethoxy)silane (CAS 919-30-2) also reacts in water to the same final hydrolysis product as the registration substance, 3-aminopropylsilanetriol (half-life of 8.5 hours at pH 7 and 25 °C).

A 96-hour LC₅₀ of >934 mg/L (measured DOC concentration) (highest concentration tested) has been determined for the effects of 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on mortality of Brachydanio rerio  (tested as Danio rerio), in accordance with OECD Test Guideline 203 (Hüls, 1994).

The test substance is susceptible to hydrolysis and it is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

The results may be expressed in terms of concentration of the hydrolysis product, 3-aminopropylsilanetriol, by applying a molecular weight correction: (MW of silanol = 137.21 / MW of parent = 221.37) * >934 mg/L = >579 mg/L. This value is read across to 3-(trimethoxysilyl)propyl isocyanate (CAS 15396-00-6) without further correction.

 

In addition, short-term toxicity to fish data have been read-across from 3-(trimethoxysilyl)propylamine (CAS 13822-56-5). This substance is the same as the amine which is formed very rapidly when the registered substance comes into contact with water/moisture. Both substances then hydrolyse at the same rate to form the hydrolysis products 3-aminopropylsilanetriol and methanol (half-life of 2.6 h at pH 7 and 20-25°C, estimated). However, the result is of non-assignable reliability, taken from a secondary data source. An LC₅₀  value of 1264 mg/L was reported (Chandra, 1997).

 

Condensation reactions leading to insoluble oligomers/polymers can be a problem for ecotoxicity testing with substances generating silanols. This has been considered for this substance and is not considered to have been an issue at the test media stock concentration up 1000 mg/L in the key studies (PFA, 2016am).

 

Refer to the IUCLID Section 6 endpoint summary (Section 7.0 of the CSR) for further discussion of the approach to chemical safety assessment for this registration substance, and for justification for read-across used.