Dicyclopentyldimethoxysilane

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

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:

range finding test not conducted; tudy conducted in the dark

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A stock solution of 1 g/L was prepared by and stirred for 18 h, then it was filtered. DOC in the stock solution was measured (11.1 mg/l) and it was determined to be equivalent to 17.6 mg/L of test substance.

- Controls: dilution water

- Evidence of undissolved material (e.g. precipitate, surface film, etc): none reported

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Strain: 5

- Source: grown in lab

- Age at study initiation (mean and range, SD): <24 h

- Method of breeding: every 2 to 3 days theyoung are siphoned out.

- Feeding during test: no


ACCLIMATION

- Acclimation period: animals were bred in lab

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

- Type and amount of food: Scenedesmus subspicatus

- Feeding frequency: daily

- Health during acclimation (any mortality observed): animals appeared healthy

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

pH:

7.8-7.9

Dissolved oxygen:

8.4-8.7

Nominal and measured concentrations:

Nominal concentrations: 0, 1.6, 2.6, 4.9, 8.8, 16 mg/L

Details on test conditions:

TEST SYSTEM

- Test vessel: round vessel

- Material, size, headspace, fill volume: filled with 10 ml

- Aeration: not reported

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 2

- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: artificial test medium was prepared with deionised water

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: 24 h


OTHER TEST CONDITIONS

- Adjustment of pH: none reported

- Photoperiod: none

- Light intensity: darkness

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mobility every 24 h


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.8

- Justification for using less concentrations than requested by guideline: not applicable

- Range finding study: no

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

12 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

also exposed to hydrolysis product

Basis for effect:

mobility

Remarks on result:

other: Estimated concentration based on DOC measured concentration of the stock solution

Details on results:

- Mortality of control: 0%

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none reported

- Effect concentrations exceeding solubility of substance in test medium: yes for the parent compound. However the test substance woud have hydrolysed. the water solubility for the hydrolysis product is >100 mg/l.

Results with reference substance (positive control):

- Results with reference substance valid? yes

- Mortality: 100% after 24 h at 2 mg/L

Table 2. Cumulative and precentage mortality.

Nominal concentration (mg/l)	24 h		48 h
	mobile (#)	immobility (%)	mobile (#)	immobility (%)
control	20	0	20	0
1.6	20	0	20	0
2.6	20	0	20	0
4.9	20	0	20	0
8.8	20	0	18	10
16	1	95	0	100

Validity criteria fulfilled:

yes

Conclusions:

A 48 h EC50 of 12 mg/L has been reported for the effects of the test substance on the immobility of the freshwater invertebrate Daphnia magna. The test organisms would have been exposed to a mixture of the parent compound and the hydrolysis product.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997-04-01 to 1997-04-04

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:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Start of test - 0(Control), filtered 100 mg/l stock dispersion and 1:10 dilution of the filtered stock dispersion. End of test - 0(Control), 100 mg/l stock dispersion filtrate incubated under test conditions but without daphnia present.

- Sampling method: Duplicate samples were taken at the start and end of the test.

- Sample storage conditions before analysis: Samples were analysed immediately after collection and transport to the analytical laboratory.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A supersaturated stock suspension of the test substance was prepared at a nominal concentration of 100 mg/l by stirring 49 mg of the test substance in 500 ml of dilution water for 6 hours in the dark. At the end of this time it was anticipated that the substance would have converted to its hydrolysis product dicyclopentylsilanediol. The suspension was passed through a folded filter paper and after discarding the first 50 ml was diluted 1:10 and 1:32 as the two highest treatments. The 1:10 dilution was then further diluted to produce 1:100 and 1:320 dilutions. The 1:100 dilution was again diluted to produce 1:1000 and 1:3200 dilutions. Finally the 1:1000 dilution was used to prepare a 1:10000 dilution.

- Controls: Dilution water

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Strain: Clone 5

- Source: University of Sheffield, Sheffield, U.K.

- Age at study initiation: 6-24 hours

- Feeding during test: none

ACCLIMATION

- Acclimation period: no data

- Acclimation conditions: same as test conditions

- Type and amount of food: no data

- Feeding frequency: no data

- Health during acclimation: no data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/l as CaCO3

Test temperature:

20ºC

pH:

7.7-8.1

Dissolved oxygen:

≥8.3 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

Nominal treatment levels: 0(control) and 1:10, 1:32, 1:100, 1:320, 1:1000, 1:3200 and 1:10000 dilutions of a filtered dispersion prepared at a anominal concentration of 100 mg/l.

The test substance is likely to have been present as its hydrolysis product dicyclopentylsilanediol.

The measured concentration of the hydrolysis product of the test substance in the undiluted filtered stock dispersion was initially 74-75 mg/l. After 48 hours incubation under the test conditions but without daphnia present it was 73-75 mg/l i.e. unchanged. The mean measured concentrations in the 1:10 dilution of the filtered stock dispersion was 7 mg/l.

Details on test conditions:

TEST SYSTEM

- Test vessel: Beaker

- Type: open

- Material, size, fill volume: Glass, 100 ml with 50 ml of test medium

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 2

- No. of vessels per control (replicates): 2

- Biomass loading rate: 1 daphnid/5 ml of test medium

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted fresh water prepared by adding analytical grade salts to double-distilled 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

- Photoperiod: 16 h light, 8 h dark

- Light intensity: <1200 lux

EFFECT PARAMETERS MEASURED: mobility after 24 and 48 hours

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3.2

- Range finding study: yes

- Test concentrations: not reported

- Results used to determine the conditions for the definitive study: not reported

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 7 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: concentration of hydrolysis product in 1:10 dilution of 100 mg/l filtered dispersion of the test substance

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.9 mg/L

Nominal / measured:

estimated

Conc. based on:

other: mean concentration of hydrolysis product in diluted 100 mg/l dispersion of the test substance

Basis for effect:

mobility

Remarks on result:

other: 2.2-3.9

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.7 mg/L

Nominal / measured:

estimated

Conc. based on:

other: mean concentration of hydrolysis product in diluted 100 mg/l dispersion of the test substance

Basis for effect:

mobility

Details on results:

- Mortality of control: 0

- Other adverse effects control: none

Reported statistics and error estimates:

The 48-h EC50 value and its 95% confidence interval was calculated by moving-average interpolation. The NOEC was determined directly from the raw data.

Table 1. Test results

Treatment	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
Undiluted filtrate of 100 mg/l dispersion	0	0
1:10 dilution	0	100
1:32 dilution	0	25
1:100 dilution	0	0
1:320 dilution	0	0
1:1000 dilution	0	0
1:3200 dilution	0	0
1:10000 dilution	0	0

Table 2. Measured and estimated mean concentrations of the hydrolysis product of the test substance (dicyclopentylsilanediol) over 48 hours.

Treatment	Mean measured# and estimated* concentration of dicyclopentylsilanediol in test media over 48 hours (mg/l)
Undiluted filtrate of 100 mg/l dispersion	74#
1:10 dilution	7#
1:32 dilution	2.2*
1:100 dilution	0.7*
1:320 dilution	0.22*
1:1000 dilution	0.07*
1:3200 dilution	0.022*
1:10000 dilution	0.007*

Validity criteria fulfilled:

yes

Conclusions:

A 48-h EC50 value of 2.9 mg/l has been determined for the effects of the test substance on mobility of Daphnia magna. A NOEC of 0.7 mg/l has been determined in the same test. The test organisms were exposed to the pre-hydrolysed form of the dichlorocyclopentylsilane, ie. the silanol hydrolysis product diyclopentylsilanediol.

Description of key information

48 h EC₅₀ 12 mg/l, Daphnia magna, reliability 1, (parent substance) (Hüls, 1995e)

48 h EC₅₀ 2.9 mg/l, Daphnia magna, reliability 1, (hydrolysis product, read-across from dichloro(dicyclopentyl)silane (CAS 139147-73-2)) (RCC, 1998)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

2.9 mg/L

Additional information

A 48-hour EC₅₀ nominal value of 12 mg/l (estimated, based on stock solution DOC measurement) has been reported for the effects of dicyclopentyl(dimethoxy)silane (CAS 126990-35-0) on the immobility of the freshwater invertebrate Daphnia magna (Hüls, 1995e). The test organisms would have been exposed to a mixture of the parent compound and the hydrolysis product.

A 48-h EC₅₀ value of 2.9 mg/l (measured) has been determined for the effects of the read-across test substance, dichloro(dicyclopentyl)silane (CAS 139147-73-2),

on mobility of Daphnia magna (RCC, 1998). A NOEC of 0.7 mg/l has been determined in the same test. The test organisms were exposed to the pre-hydrolysed form of dichloro(dicyclopentyl)silane, i.e. the silanol hydrolysis product diyclopentylsilanediol. The read-across from dichloro(dicyclopentyl)silane to dicyclopentyl(dimethoxy)silane is considered to be reliable because both dicyclopentyl(dimethoxy)silane and dichloro(dicyclopentyl)silane hydrolyse in contact with water to produce dicyclopentylsilanediol. The other hydorolysis products are methanol and hydrochloric acid respectively; the properties of these substances are well characterised

Methanol is non-hazardous to the aquatic environment at the concentrations relevant to this assessment and it is considered unlikely that its presence would significantly affect the outcome of tests performed with dicyclopentyl(dimethoxy)silane.

Effects of hydrochloric acid on aquatic organisms are limited to those that result from changes to pH in unbuffered media (see IUCLID Section 6, Ecotoxicological Information discussion, and Section 7.0 of the CSR for further details).

Both the studies conducted with dicyclopentyl(dimethoxy)silane (Hüls, 1995e) and the hydrolysis product dicyclopentylsilanediol (RCC, 1998) have been used as key studies for the assessment of short-term toxicity to invertebrates.

Other studies report EC₅₀ values in the range 0.66 to 15 mg/l; however the studies are all reliability 4. In the La Noyearie (1989) and Corning Hazelton (1996b) studies it was not possible to correlate nominal and actual concentration because the test medium were prepared by diluting a single stock solution that had partially hydrolysed. Additionally, the test substance concentrations could not or were not determined analytically in solution, and the test media were prepared in excess of the limit of solubility. However, while the Corning Hazelton (1996b) has been assigned reliability 4 due to the potential for nominal and exposure concentrations to be poorly correlated, the study does provide evidence that the registered substance is toxic to freshwater invertebrates. One other available result is from a summary report to which reliability could not be assigned due to lack of information; the report presents the same result reported in La Noyearie (1989).