Dichloro(methyl)(phenyl)silane

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:

2002-05-06 to 2003-02-06

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, GLP, described in sufficient detail. The restrictions are that the analytical work done did not cover the test conditions upon which the final conclusions are based.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Nominal concentrations: 0(Control), 2.15, 4.64, 21.5, 46.4 and 100 mg/L

- Sampling method: An 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 taken from the test media of all four exposure vessels of all treatments at the end of the test.

- Sample storage conditions before analysis: Samples were stored at -20ºC before analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The substance hydrolyses in water. An initial stock suspension was prepared at a nominal concentration of 100 mg/L by shaking for approximately 30 minutes. The suspension was then filtered through a 0.45 μm cellulose-acetate filter. The solution was diluted to prepare additional treatment levels.

- pH adjustment: A second series of treatments was prepared with adjustment of pH. The pH was adjusted to 7.9 by addition of NaOH. No precipitation was noted during or following pH adjustment.

- Controls: Dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: IRChA, France

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

- Method of breeding: Laboratory stock culture

- Feeding during test: none

ACCLIMATION

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

- Type and amount of food: green algae (Scenedesmus subspicatus) and a small amount of aerated sewage

- Feeding frequency: 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:

First test (without pH adjustment): 6.95-8.12 (2.15-21.5 mg/L nominal treatments), <5.6 (46.4 mg/L nominal treatment) and <3.0 (100 mg/L nominal treatment)

Second test (with pH adjustment): 7.76-8.02

Dissolved oxygen:

≥80% ASV

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control), 2.15, 4.64, 10.0, 21.5, 46.4 and 100 mg/L

In the first test (without pH adjustment), the measured concentrations of dissolved organic carbon (DOC) were close (approx 75%) to the theoretical values at the start of the test. By the end of the test the values in the 100 mg/L treatment had declined to approximately 15% of the theoretical values. The concentrations in the other treatments had remained stable. The decline in concentration in the 100 mg/L treatment was interpreted by the study report authors as being attributable to the formation of insoluble condensation products at the low pH. These products will have adsorbed to glass surfaces of the test vessels.

The results are reported with reference to nominal test concentrations.

No measured concentrations are available to support the interpretation of the second test.

Details on test conditions:

Unless otherwise stated, these test conditions apply to both the first test and the second test.

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 (frequency/flow rate): 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 of test medium


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted freshwater prepared by adding salts to fully demineralised 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 (first test only)

- Photoperiod: 16 h light, 8 h dark

- Light intensity: 500 lux +/-20% provided by white fluorescent lights


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


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2

- Range finding study: no

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

38 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: Without pH adjustment

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

< 2.15 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: Without pH adjustment

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

Remarks on result:

other: With pH adjustment

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

< 2.15 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: With pH adjustment

Details on results:

- Mortality of control: 5% (First test - without pH adjustment), 0% (Second test - with pH adjustment)

Reported statistics and error estimates:

The EC50 values were calculated by Probit Analysis using Probit Program Version 1.5, US Environmental protection Agency, 1992. The NOECs were obtained directly from the raw data.

Table 1. Test results - first test (without pH adjustment)

Nominal concentration (mg/l)	Mean % immobile Daphnia after 24 hours	Mean % immobile Daphnia after 48 hours
0 (Control)	0	5
2.15	0	5
4.64	5	25
10.0	0	0
21.5	10	30
46.4	10	55
100	100	100

Table 2. Results of analysis of test media - first test (without pH adjustment)

Nominal concentration of test substance (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)
2.15	0.944	1.5	1.2
4.64	2.04	2.5	2.3
10.0	4.40	4.5	5.3
21.5	9.44	9.0	9.8
46.4	20.4	20.5	23
100	44.0	30.7	6.5

Note: theoretical DOC concentrations recalculated by the current reviewer.

Table 3. Test results - second test (with pH adjustment)

Nominal concentration (mg/l)	Mean % immobile Daphnia after 24 hours	Mean % immobile Daphnia after 48 hours
0 (Control)	0	0
2.15	0	5
4.64	0	10
10.0	5	10
21.5	5	15
46.4	10	20
100	20	25

Validity criteria fulfilled:

yes

Conclusions:

A 48-h EC50 value of 38 mg/L and a NOEC of <2.15 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal test concentrations and under conditions with no pH adjustment. Under conditions where pH was adjusted, the corresponding values were >100 mg/L and <2.15 mg/L. Due to the very rapid hydrolysis of the registered substance, it is very likely that the test organisms were exposed to the hydrolysis products of the substance rather than the parent substance. Under the corresponding pH conditions these are expected to have been predominantly methylphenylsilanediol (CAS No. 3959-13-5) and chloride.

Description of key information

Short-term toxicity to invertebrates: 48-hour EC₅₀ >100 mg/l (nominal) (highest concentration tested) (OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system. The result may be expressed in terms of concentration of the hydrolysis product: 48-hour EC₅₀ >81 mg/l as methylphenylsilanediol.

 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

81 mg/L

Additional information

A 48-hour EC₅₀ value of 38 mg/l has been determined for the effects of the test substance on mobility of Daphnia magna based on nominal test concentrations and under conditions of no pH adjustment. However, pH was reported to be <5.6 in the 46.4 mg/L nominal treatment and <3.0 in the 100 mg/L nominal treatment, therefore the result is not reliable and is disregarded. Under conditions where pH was adjusted the corresponding value was >100 mg/l. Due to the very rapid hydrolysis it is very likely that the test organisms were exposed to the hydrolysis products of the substance rather than the parent substance. The results may be expressed in terms of concentration of the hydrolysis product, methylphenylsilanediol, by applying a molecular weight correction: (MW of silanol = 154.24 / MW of parent = 191.13) * [CONCENTRATION OF PARENT = >100] = >81 mg/l.

 

The following data are used to support the read-across in the fish and algal trophic levels:

A 48-hour EC₅₀ value of >100 mg/l has been determined for the effects of the supporting analogue substance, trichloro(phenyl)silane (CAS 98-13-5), on mobility of Daphnia magna. It is likely that the test organisms were predominantly exposed to the hydrolysis products of the test substance, phenylsilanetriol and hydrochloric acid.