Trichloro(octadecyl)silane

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:

2002-05-10 to 2002-08-14

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:

yes

Remarks:

The 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: 0 (control), 10.0 and 100 mg/L.
- Sampling method: one aliquot from the freshly prepared test media of all test concentrations was taken at the start of the test before filling the test vessels. A combined aliquot was collected from the test media of all 4 replicate test vessels at each concentration at the end of the test.
- Sample storage conditions before analysis: samples were stored at -20 °C prior to analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: a stock suspension of the test substance was prepared at a nominal loading rate of 100 mg/L by shaking for 48 h. The suspension was then filtered through a 0.45 μm cellulose acetate filter. Further treatments were prepared by dilution of the resulting stock solution.
- Controls: dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: IRChA, France
- Age at study initiation: 6 - 24 h
- Method of breeding: laboratory stock culture
- Feeding during test: none

ACCLIMATION
- Acclimation period: at least 1 week
- Acclimation conditions: same as test
- Type and amount of food: log-phase Scenedesmus subspicatus and a small amount of aerated sewage sludge
- Feeding frequency: not reported
- Health during acclimation (any mortality observed): not reported

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

20 ± 1 °C

pH:

7.10 - 8.05

Dissolved oxygen:

≥ 80% ASV

Salinity:

not applicable

Nominal and measured concentrations:

Nominal treatments: 0 (control), 10 and 100 mg/L.

Details on test conditions:

TEST SYSTEM
- Type: open
- Material, size, fill volume: glass, 50 mL with 50 mL of test medium
- Aeration: none
- Renewal rate of test solution: static test
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 1 daphnid/10 mL

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted fresh water
- Alkalinity: 0.8 mmol/L
- Ca/mg ratio: 4:1
- 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: approximately 500 lux

EFFECT PARAMETERS MEASURED: mobility after 24 and 48 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Range finding study
- Results used to determine the conditions for the definitive study: no data

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: exposure is expected to be predominantly to the hydrolysis products

Details on results:

- Immobilization of control: 5%
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: It is speculated in the test report that the lack of agreement between nominal and measured exposure concentrations may be a consequence of the hydrolysis of the test substance and low solubility of the substance and its hydrolysis products.
- Effect concentrations exceeding solubility of substance in test medium: it is possible that the solubility of the test substance and/or its hydrolysis products was exceeded in the test.

Reported statistics and error estimates:

There were insufficient levels of immobilisation to determine a definitive EL50 value. The NOELR has been reassessed by the reviewer in light of the lack of agreement between nominal and measured exposure concentrations. An equivalent 48 h EC50 has been determined by the reviewer based on a consideration of measured DOC concentrations in the test media back-calculated to equivalent test substance concentrations.

Table 1. Test results.

Nominal test substance concentration/loading rate (mg/L)	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	5
10	0	10
100	10	20

Table 2. Results of analysis of test media

Nominal test substance concentration/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	6.9	<1.0	<1.0
100	69.2	1.4	<1.0

Validity criteria fulfilled:

yes

Conclusions:

A 48 h EC50 value of >100 mg/L and a NOEC of <100 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal loading rate. It is likely that the test organisms were exposed to the hydrolysis product of the test substance. An equivalent 48 h EC50 of >0.000005 mg/l and NOEC of <0.000005 mg/l have therefore been determined by the reviewer based on a consideration of the solubility of the hydrolysis product. It is possible that the hydrolysis product has surface active properties.

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:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: exposure is expected to be predominantly to the hydrolysis products

Details on results:

- Immobilization of control: 5%
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: It is speculated in the test report that the lack of agreement between nominal and measured exposure concentrations may be a consequence of the hydrolysis of the test substance and low solubility of the substance and its hydrolysis products.
- Effect concentrations exceeding solubility of substance in test medium: it is possible that the solubility of the test substance and/or its hydrolysis products was exceeded in the test.

Description of key information

EC50 (48 h) > 100 mg/L (nominal, OECD 202, Daphnia magna) based on read across from CAS 18643-08-8

Additional information

No data on the toxicity of trichloro(octadecyl)silane (CAS 112-04-9) towards aquatic 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 octadecyldimethylchlorosilane (CAS 18643-08-8) 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 analogue substance octadecyldimethylchlorosilane (CAS 18643-08-8) was performed according to OECD 202 under GLP conditions with Daphnia magna as the test organism (2003). D. magna was exposed to the nominal concentrations of 0 (control), 10 mg/L and 100 mg/L 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 EC50 (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, trichloro(octadecyl)silane (CAS 112-04-9) is not assumed to cause harmful effects towards aquatic invertebrates.