Dimethoxymethyloctadecylsilane

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:

2002-05-13 to 2002-07-19

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with acceptable 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. As a consequence it has been necessary to reinterpret the results with reference to measured concentrations.

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)

Remarks:

Freie und Hansestadt Hamburg, Behörde für Arbeit, Gesundheit und Soziales, Hamburg, Germany

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 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: yes, 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 ± 1°C

pH:

7.33-8.38

Dissolved oxygen:

≥80% ASV

Salinity:

not applicable

Nominal and measured concentrations:

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

The measured concentrations at the start and end of the test were <5% of the theoretical values. The discrepancy is attributed by the report author to the low solubility of the test substance.

The test results are expressed in the test report relative to nominal concentrations (loading rates). The results have been reinterpreted by the reviewer with reference to the measured DOC concentrations and corresponding test substance concentrations.

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

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: measured DOC concentration; exposure is likely to be to hydrolysis products

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 1 - < 1.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: measured DOC concentration; exposure is likely to be to hydrolysis products

Basis for effect:

mobility

Details on results:

- Immobilisation of control: 0%
- Any observations 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 low solubility of the substance and its hydrolysis product.

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. The test results have also been reinterpreted by the reviewer in terms of measured DOC concentrations back-calculated to a corresponding concentration of the test substance and in terms of the expected water solubility of the hydrolysis product.

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	0
10	0	0
100	0	10

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	7.0	<1.0	<1.0
100	70.3	1.3	1.1

Description of key information

EL50 (48 h) > 100 mg/L (nominal, OECD 202, Daphnia magna)

Additional information

One reliable study is available for dimethoxymethyloctadecylsilane (CAS 70851-50-2). The test was performed according to OECD 202 and GLP (2003). Daphnia magna was exposed to 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. The test item concentrations were monitored by DOC measurements during the test. However, measured values ranged between 1.3 mg/L and below the detection limit. Due to rapid hydrolysis of the substance in aqueous environments (2.6 h at 20 °C), it is very likely that the test organisms were exposed to the hydrolysis products of the test substance. The study resulted in an EL50 (48 h) of > 100 mg/L (nominal). Based on these results dimethoxymethyloctadecylsilane is not assumed to cause harmful short-term effects to aquatic invertebrates.