Chlorodimethyloctadecylsilane

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:

2002-05-10 to 2002-08-14

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 10 mg/l nominal loading rate test medium was prepared by dilution of the filtered stock dispersion. This is not in agreement with OECD guidance. As a result, there is uncertainty over the properties of this test medium and the results can only be interpreted with reference to the highest treatment. An equivalent 48-h EC50 value has been determined by the reviewer based on a consideration of the measured dissolved organic carbon concentrations in the test media.

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 -20ºC 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 hours. 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 hours

- 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+/-1ºC

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.

Measured concentrations were <5% of the theoretical values at the start and end of the test.

The results are expressed in the test report relative to nominal concentrations (loading rates). The results have been further interpreted by the reviewer been based on a consideration of the measured dissolved organic carbon concentrations in the test media.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- 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 hours light, 8 hours dark

- Light intensity: approximately 500 lux

EFFECT PARAMETERS MEASURED: mobility after 24 and 48 hours

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:

EL50

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

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

< 100 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: exposure is expected to be predominantly to the hydrolysis products

Details on results:

- Immobilisation 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 EL50 value of >100 mg/L and a NOELR 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.

Description of key information

EC50 (48 h) > 100 mg/L (nominal, OECD 202, Daphnia magna)

Additional information

One study is available testing the short term toxicity of chloro(dimethyl)octadecylsilane (CAS 18643-08-8) to aquatic invertebrates according to OECD 202 and GLP (2003). Daphnia 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.