Triethoxyhexadecylsilane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-04-15 to 2002-07-25

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Guideline study with restrictions. The study was conducted according to an appropriate OECD test guideline, with acceptable restrictions. The restrictions were that the analytical results showed that measured DOC concentrations were <5% of nominal. The results have been reinterpreted with reference to the measured concentrations of dissolved organic carbon in the test media

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Test media were not prepared in accordance with OECD guidance for testing difficult substances

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Nominal treatments: 100 mg/L and 10 mg/L (10% concentration of 100 mg/L water-soluble fraction)

- Sampling method: A sample of test media were taken from all treatments at the start (before introducing the test organisms) and at the end of the test.

- Sample storage conditions before analysis: Not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A water-soluble fraction of the test substance was prepared by mixing 100 mg/l of the test substance with dilution water for 48 hours and then filtering (0.45 μm) to remove undissolved test substance. The water-soluble fraction was tested undiluted and at one-tenth of its original concentration.

- Controls: Dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Strain: IRCHA

- Source: LPT Laboratory Culture

- Age at study initiation (mean and range, SD): 6-24 hours

ACCLIMATION

- Acclimation period: at least one week

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

- Type and amount of food: algae (Scenedesmus subspicatus) plus a small quantity of sewage (only during the holding period) from the aerated phase of treatment

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

20+/-1ºC

pH:

7.61-8.15

Dissolved oxygen:

≥80% ASV

Nominal and measured concentrations:

Nominal loading rates: 0 (Control), 100 mg/L and 10 mg/L (10% concentration of 100 mg/L water-soluble fraction).

A loading rate of 100 mg/L is above the expected solubility of the substance in the test medium. Measured dissolved organic carbon concentrations were below 5% of the theoretical values at the start and end of the test.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type (delete if not applicable): open

- Material, size: glass, 38 mm diameter, 60 mm tall, 50 mL volume

- Aeration: none

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: aerated reconstituted 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 ot test

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 h light/8 h dark

- Light intensity: 500 Lux

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

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 10

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

< 10 other: percent concentration of the 100 mg/l water-soluble fraction

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobilization of control: 5%

- Effect concentrations exceeding solubility of substance in test medium: A loading rate of 100 mg/L is above the expected solubility of the substance in the test medium.

Reported statistics and error estimates:

There were insufficient toxic effects to determine an EL50 value. The EC50 and NOELR values were determined directly from the raw data.

Table 1. Test results

Nominal test substance loading rate (mg/L)	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	5
10 (10% concentration of 100 mg/L water-soluble fraction)	0	10
100	0	15

Table 2. Results of analysis of test media

Nominal test substance loading rate (mg/L)	Theoretical DOC concentration (mg/L)	Actual DOC concentration at start of test (mg/L)	Actual DOC concentration at end of test (mg/L)
10 (10% concentration of 100 mg/L water-soluble fraction)	6.6	<0.5	0.5
100	65.8	<0.5	0.9

Validity criteria fulfilled:

yes

Conclusions:

A 48-h EL50 value of >100 mg/L has been determined for the effects of the test substance on mobility of Daphnia magna based on nominal loading rate of the test substance. The NOELR in the test corresponded to a <10% concentration of the 100 mg/L water soluble fraction.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAF

Basis for effect:

mobility

Remarks on result:

other: Result from source substance CAS 16415-12-6 (key)

Description of key information

EL50 (48 h) > 100 mg/L (nominal, OECD 202, Daphnia magna) based on read across from CAS 16415-12-6

Additional information

No data on the toxicity of triethoxy(hexadecyl)silane (CAS 16415-13-7) towards freshwater invertebrates are available. In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read-across from the analogue substance hexadecyl(trimethoxy)silane (CAS 16415-12-6) has been applied to support the environmental hazard assessment of the substance. Details on the read-across justification can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

The study with the source substance hexadecyl(trimethoxy)silane (CAS 16415-12-6) was performed according to OECD 202 under GLP conditions with Daphnia magna as the test organism. D. magna was exposed to the nominal loading rates of 10 mg/L, 100 mg/L (10% concentration of 100 mg/L water-soluble fraction) and a control for 48 h. The test item solution was prepared by mixing 100 mg test item/L, shaking for 48 h and filtering through a 0.45 µm filter. An EL50 (48 h) of > 100 mg/L (nominal) was determined in the study. Due to rapid hydrolysis of the substance in aqueous environments, it is very likely that the test organisms were mainly exposed to the hydrolysis products of the test substance.

Based on the results of the analogue substance, triethoxy(hexadecyl)silane (CAS 16415-13-7) is not assumed to cause harmful effects towards aquatic invertebrates.