Triethoxy(3-isocyanatopropyl)silane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-06-22 to 1993-06-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Principles of method if other than guideline:

DIN 38412 Part 1; EG Guideline 92/69/EWG

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The DOC concentration of the filtered stock solution used to prepare the test media was determined.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method:The test substance was added to dilution water to provide a nominal concentration of 1 g/l and stirred for 18 hours. The solution was filtered and the DOC content determined to be 534 mg/L, which is equivalent to 1093 mg/L of the test substance. This solution served as the primary stock solution of the test substance for preparation of the other test concentrations. The test began immediately after preparation of the test solution.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Common name: Daphnia magna

- Strain: Clone 5

- Source: Stock culture

- Age at study initiation (mean and range, SD): <24 h

- Method of breeding: Parthenogenetic reproduction

- Feeding during test: None

ACCLIMATION

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

- Type and amount of food: Scenedesmussubspicatus, sufficient to be consumed each day leaving no residue

- Feeding frequency: daily

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

Water hardness was reported  as 2.5mmol/L and alkalinity was reported as 0.8 mmol/L.

Test temperature:

20ºC

pH:

The control pH was 7.5 units and the test vessel pH ranged from 7.5 to 8.7 units. 

Dissolved oxygen:

The control DO was 8.4 mg/L and the test vessel DO ranged from 7.8 to 8.7 mg/L.

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations (based on measured concentrations in stock solution):  0, 8.7, 16.4, 28.4, 54.7, 94.0, 174.9, 306.0, 546.5, and 983.7 mg/L.

Details on test conditions:

TEST SYSTEM

The test vessels were glass cylinders graduated to 10 ml. Each concentration had 4 replicate vessels and each vessel contained 5 test organisms.  The age of the test organisms was <24 hours and they were not fed during the test.  Vessels were kept in the dark at 20ºC and not aerated during the  test.

The dilution water was synthetic fresh water with a hardness of approximately 294 mg/L as CaCO3

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

94 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(but exposure is to hydrolysis products)

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

331 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(but exposure is to hydrolysis products)

Basis for effect:

mobility

Remarks on result:

other: 249-441

Details on results:

- Mortality of control: 0

Results with reference substance (positive control):

24 h EC50 lies between 0.9 and 1.9 mg/L

Reported statistics and error estimates:

EC50 values were calculated by Probit analysis. The NOEC was determined by visual examination of the raw data

Table 1. Test results

Nominal test concentration (mg/L)	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	0
8.7	0	0
16.4	5	5
28.4	0	0
54.7	0	0
94.0	5	10
174.9	19	19
306.0	45	50
546.5	40	60
983.7	62	100

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of 331 mg/L and NOEC of 94 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

48 hour EC₅₀: Freshwater: 331 mg/l, mobility of Daphnia magna; equivalent to 205 mg/l as 3-aminopropylsilanetriol, read across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2).

48 hour LC₅₀: Marine water: 580 mg/l, mortality of Arcatia tonsa; equivalent to 359 mg/l as 3-aminopropylsilanetriol, read across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

205 mg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

359 mg/L

Additional information

No data are available for the registered substance.

The isocyanate group is very rapidly hydrolysed to the corresponding amine (half-life <5 minutes at pH 7), and further hydrolysis of the alkoxy groups proceeds at a slower rate (half-life of 8.5 hours at pH 7 and 25°C).

Data are read across from 3-aminopropyl(triethoxy)silane (CAS 919-30-2), the amine which is formed very rapidly when the registered substance comes into contact with water / moisture:

A 48 hour EC₅₀ value of 331 mg/l (nominal concentration) has been determined for the effects of 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on mobility of the freshwater invertebrate Daphnia magna, in accordance with Test Guideline OECD 202 and in compliance with GLP (Hüls, 1993).

 

The test substance is susceptible to hydrolysis and, due to the test media preparation (stirring for 18 hours) and exposure regime (static), 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) * 331 mg/l = 205 mg/l.

 

Both the registration substance and the substance used as surrogate for read-across are susceptible to hydrolysis reaction of the alkoxysilane groups (to silanols) and to potential condensation reactions (described in Section 4.8). During the tests with the read-across substance, pre-hydrolysis and filtration were used as part of media preparation. Analytical recoveries by DOC were high (within 20% of nominal). Models would suggest that the irreversible condensation is unlikely for these silanol hydrolysis products at the concentrations relevant to the studies (PFA, 2016am).

 

In a separate test, a 48 hour LC₅₀ value of 580 mg/l (nominal concentration) has also been determined for the effects of 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on mortality of the marine copepod Acartia tonsa, in accordance with test guideline ISO 14669 - 1999: water quality – Determination of acute lethal toxicity to marine copepods (Copepoda, Crustaceae) (Test Institute, 2005). It is likely that the test organisms were 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) * LC₅₀ 580 mg/l = 359 mg/l.

 

These findings are supported by a 48 hour EC₅₀ in Daphnia magna >100 mg/l, determined for 3-(trimethoxysilyl)propyl isocyanate (CAS 15396-00-6) (IBACON, 2003). For this substance the isocyanate group is very rapidly hydrolysed to the corresponding amine (half-life <5 minutes at pH 7), and further hydrolysis of the alkoxy groups proceeds at a slower rate (half-life of 2.6 hours at pH 7 and 20-25°C, estimated) to 3-aminopropylsilanetriol and methanol.