3-(trimethoxysilyl)propyl isocyanate

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:

2002-08-26 to 2002-12-19

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)

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: A single nominal test concentration of 100 mg/l was prepared by adding 50 mg of test substance to 500 ml of dilution water and stirring intensely for 24 hours.

- Controls: Dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Strain: Clone 5

- Source: Laboratory culture derived from animals originally obtained in 1997 from the Umweltbundesamt, Institut für Wasser-Boden- und Lufthygie
ne, Berlin, Germany.

- Age at study initiation (mean and range, SD): 7.5-24 hours

- Feeding during test: none

ACCLIMATION

- Acclimation conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

250 mg/l as CaCO3

Test temperature:

21ºC

pH:

7.8-7.9

Dissolved oxygen:

=8.0 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

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

Measured concentrations were between 94 and 95% of nominal at the start of the test and between 87 and 88% at the end of the test. The mean measured concentration was 91 mg/l.

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

Details on test conditions:

TEST SYSTEM

- Test vessel: beaker

- Type: open

- Material, size, headspace, fill volume: glass, 250 ml containing 150 ml of test medium

- Aeration: none

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 2

- No. of vessels per control (replicates): 2

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: start and end of test

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 h light, 8 h dark

- Light intensity: 460 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mobility after 24 and 48 hours

TEST CONCENTRATIONS

- Range finding study; yes

- Test concentrations: 100 mg/l

- Results used to determine the conditions for the definitive study: no effects

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

mobility

Key result

Duration:

48 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:

mobility

Details on results:

- Behavioural abnormalities: none

- Mortality of control: 0

Results with reference substance (positive control):

no data

Reported statistics and error estimates:

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

No toxic effects were observed following 48 hours exposure to a nominal concentration of 100 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of >100 mg/L and NOEC of =100 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal concentrations. 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 invertebrates: 48 hr EC₅₀ >100 mg/L (nominal) (limit test) (OECD 202), or >67 mg/L when expressed in terms of concentration of the silanol hydrolysis product 3-aminopropylsilanetriol.

Additional information

A 48-hour LC₅₀ value of >100 mg/L (highest concentration tested) has been determined for the effects of the registration substance on mobility of Daphnia magna based on nominal concentrations of the substance (IBACON, 2003b).

 

The isocyanate group is very rapidly hydrolysed to the corresponding amine (half-life of <5 minutes), 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 silanol hydrolysis product as the registration substance, 3-aminopropylsilanetriol (half-life of 8.5 hours at pH 7 and 25°C).

 

A 48-hour EC₅₀ value of 331 mg/L has been determined for the effects of 3-aminopropyl(triethoxy)silane (CAS 919-30-2) on mobility of the freshwater invertebrate Daphnia magna (Hüls, 1993).

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. 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.

 

A 48-hour LC₅₀ of 580 mg/l have also been determined for the effects of the same read-across substance on mortality of the marine invertebrate Acartia tonsa (Test Institute, 2005). The test substance is susceptible to hydrolysis and it is therefore likely that the test organisms were exposed to the hydrolysis products of the substance. The LC₅₀  is equivalent to 360 mg/L expressed in terms of concentration of the hydrolysis product.

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 in the key studies (PFA, 2016am).

 

In addition, short-term toxicity to invertebrates data have been read-across from 3-(trimethoxysilyl)propylamine (CAS 13822-56-5). This substance is the same substance as the amine which is formed very rapidly when the registered substance comes into contact with water/moisture. Both the 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 EC₅₀ value of 302 mg/L was reported (Chandra, 1997).

 

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.