Dicyclopentyldimethoxysilane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000-02-21 to 2000-02-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0(Control), 4.6, 10, 21, 46 and 100 mg/l

- Sampling method: Duplicate samples from all test media and the control were taken at the start of the test (6.5 hours after preparation of the test media). Duplicate samples were taken again on days 2 and 4 of the test in all media containing surviving fish.

- Sample storage conditions before analysis: The samples were stored in a refrigerator prior to analysis.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Required amounts of the test substance were mixed into small amounts of test water by ultrasonic treatment for 2x15 minutes and intense stirring for approximately 15 minutes. The suspensions were then added to test aquaria and the aquaria filled with the required volume of dilution water to prepare the test concentrations. The test media were prepared 6.5 hours prior to introducing the fish to allow sufficient time for the test substance to hydrolyse.

- Controls: Dilution water

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM

- Common name: Zebra fish

- Source: City Zoo, Darmstadt, Germany.

- Length at study initiation (length definition, mean, range and SD): 3.06 +/-0.21 cm

- Weight at study initiation (mean and range, SD): 0.28 +/-0.05 g

- Feeding during test: none

ACCLIMATION

- Acclimation period: 6 weeks

- Acclimation conditions: same as test

- Type and amount of food: TETRA MIN, TETRA-Werke, Melle, Germany

- Feeding frequency: Daily up until the day prior to the test

- Health during acclimation: no mortalities and all fish were healthy

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

250 mg/l as CaCO3

Test temperature:

21ºC

pH:

6.8-8.1

Dissolved oxygen:

7.8-9.2 mg/l

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control), 4.6, 10, 21, 46 and 100 mg/l.

Measured concentrations in the 21 and 46 mg/l treatments (determined as dicyclopentylsilanediol) were in the range 86-100% of the nominal values. At the highest test concentration (100 mg/l) the measured concentrations measured at the start of the test and at 24 hours (when all fish were dead) were between 75 and 80% of the nominal value.

The test results are presented and interpreted with reference to the nominal concentrations of the test substance.

Details on test conditions:

TEST SYSTEM

- Test vessel: Aquarium

- Type: open

- Material, size, fill volume: Glass, 25 litre with 10 litres of test medium

- Aeration: yes

- Renewal rate of test solution: static test

- No. of organisms per vessel: 7

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

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

- Biomass loading rate: 0.2 g/l

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted freshwater prepared by adding analytical grade salts to deionized water.

- Alkalinity: 0.8 mmol/l

- Ca/mg ratio: 4:1

- Culture medium different from test medium: no

- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 h light/8 h dark

- Light intensity: 670-920 lux

EFFECT PARAMETERS MEASURED: mortality at 2, 24, 48, 72 and 96 hours.

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2

- Range finding study

- Test concentrations: not reported

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

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

49.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis product expressed as test substance nominal concentration

Basis for effect:

mortality (fish)

Remarks on result:

other: 32-75.9

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

21 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis product expressed as test substance nominal concentration.

Basis for effect:

mortality (fish)

Details on results:

- Behavioural abnormalities: fish showed signs of apathy and lying on their backs at a nominal concentration of 46 mg/l

- Mortality of control: 0

- Other adverse effects control: none

- Effect concentrations exceeding solubility of substance in test medium: undissolved test substance was observed on the bottom of the 100 mg/l nominal concentration test vessel.

Reported statistics and error estimates:

The LC50 value and its 95% confidence interval was calculated by moving-average interpolation. The NOEC was determined directly from the raw data.

Sublethal observations / clinical signs:

Table 1. Test results

Nominal test substance concentration (mg/l)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	0	0
4.6	0	0	0	0
10	0	0	0	0
21	0	0	0	0
46	0	0	43	43
100	100	100	100	100

Table 2. Results of analysis of test media

Nominal test substance concentration (mg/l)	Measured concentration as percentage of nominal at start of test	Measured concentration as percentage of nominal after 24 h	Measured concentration as percentage of nominal after 48 h	Measured concentration as percentage of nominal after 96 h	Range of measured concentration as percentage of nominal over test
0 (Control)	not applicable	not applicable	not applicable	not applicable	not applicable
21	86 - 93	no data	94 - 94	93 - 100	86 - 100
46	88 - 89	no data	90 - 91	90 - 90	88 - 91
100	75 - 77	79 - 80	no data	no data	75 - 80

Validity criteria fulfilled:

yes

Conclusions:

A 96-h LC50 value of 49.3 mg/l has been determined for the effects of the test substance on mortality of Brachydanio rerio. A NOEC of 21 mg/l has been determined in the same test. The test organisms were exposed to the pre-hydrolysed form of the test material, so to the silanol hydrolysis product diyclopentylsilanediol. The test result is considered to be reliable.

Reference 2

Endpoint:

short-term toxicity to fish

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 203 (Fish, Acute Toxicity Test)

Deviations:

yes

Remarks:

a range finding study was not conducted

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all

- Sampling method: direct from vessels. For the analysis of the stability of the test medium a separate tank was set up with no fish and samples taken at 0 and 24 h.

- Sample storage conditions before analysis: not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: the test solution was prepated daily. A stock solution of 1 g/L was prepared, stitrred for 18 h then filtered.

- Controls: dilution water only

- Evidence of undissolved material (e.g. precipitate, surface film, etc): not reported

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM

- Source: In house, West Aquarium, Bad Lauterberg

- Length at study initiation (mean and SD): 3 cm +/- 0.5

- Weight at study initiation (mean and range, SD):

- Method of breeding: not reported

- Feeding during test: no


ACCLIMATION

- Acclimation period: 14 d

- Acclimation conditions (same as test or not): The fish were kept in dechlorinated drinking water in 200 L glass aquarium, the temperature was 20 degC in flow-through conditions.

- Type and amount of food: Tetramin (c), 1% body weight.

- Feeding frequency: daily

- Health during acclimation (any mortality observed): mortality less than 5% in the 7 days previous to the test

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

range: 19-20°C

pH:

range: 7.8-8.5

Dissolved oxygen:

83% saturation

Nominal and measured concentrations:

Nominal concentrations: 0, 4.4, 6.1, 8.7, 12.2, 17.4 mg/L.

Details on test conditions:

TEST SYSTEM

- Test vessel: aquarium

- Type (delete if not applicable): open / closed

- Material, size, headspace, fill volume: 20 L glass tanks filed with 10 L test medium

- Aeration: continuous

- No. of organisms per vessel: 10

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

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

- Biomass loading rate: 0.54 g

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: drinkwater

- Alkalinity: 12.5 °dH

- Culture medium different from test medium: no

- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS

- Adjustment of pH: not reported

- Photoperiod: 16 h light, 8 h darkness

- Light intensity: not reported

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :

TEST CONCENTRATIONS

- Spacing factor for test concentrations: ca. 1.5

- Range finding study: not conducted

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

10.3 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

but exposure also to hydrolysis product

Basis for effect:

mortality (fish)

Remarks on result:

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

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

8.7 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

but exposure also to hydrolysis product

Basis for effect:

mortality (fish)

Remarks on result:

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

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

12.2 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

but exposure also to hydrolysis product

Basis for effect:

mortality (fish)

Remarks on result:

other: Estimated concentration based on 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: the water solubility of the parent substance is 5 mg/L, however the water solubility of the hydrolysis product is >100 mg/L. The test medium contained a mixture of parent substance and hydrolysis product. Also, no precipitation has been reported in the study therefore it is thought that the test solution did not exceed the water solubilty.

Sublethal observations / clinical signs:

Table 2. Summary of mortality over 96 h.

Nominal concentration (mg/L)	Time (h)
	24	48	72	96
Control	0	0	0	0
4.4	0	0	0	0
6.1	0	0	0	0
8.7	0	0	0	0
12.2	50	60	80	100
17.4	100	100	100	100

Validity criteria fulfilled:

yes

Conclusions:

A 96 h LC50 value of 10.3 mg/l has been determined for the effects of the test substance on the mortality of Danio rerio (tested as Brachydanio rerio). It is likely that the fish were exposed to a mixture of the parent substance and the hydrolysis product because the it was a semi-static test and because the stock solution was prepared by stirring for 18 h.

Description of key information

96-h LC₅₀ 10.3 mg/l, D. rerio, reliability 1 (parent substance) (Hüls, 1995d)

96-h LC₅₀ 49.3 mg/l, D. rerio, reliability 1 (hydrolysis product) (RCC, 2000)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

10.3 mg/L

Additional information

A 96-hour LC₅₀ nominal value of 10.3 mg/l has been determined for the effects of dicyclopentyl(dimethoxy)silane (CAS 126990-35-0) on mortality of Danio rerio (tested as Brachydanio rerio) (Hüls, 1995d). It is likely that the fish were exposed to a mixture of the parent substance and the hydrolysis products because the study was conducted under a semi-static regime and because the stock solution was prepared by stirring for 18 hours.

A 96-hour LC₅₀ value of 49.3 mg/l (measured) has been determined for the effects of dichloro(dicyclopentyl)silane (CAS 139147-73-2) on mortality of Danio rerio (tested as Brachydanio rerio) (RCC 2000). A NOEC value of 21 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 is considered to be reliable because both dicyclopentyl(dimethoxy)silane and dichloro(dicyclopentyl)silane hydrolyse in contact with water to produce dicyclopentylsilanediol. The other hydrolysis products are methanol and hydrochloric acid respectively; the properties of these substances are well characterised.

Methanol is non-hazardous to the 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.

Both the studies conducted with dicyclopentyl(dimethoxy)silane (Hüls 1995d) and the hydrolysis product dicyclopentylsilanediol (RCC 2000) are being used as key studies for the assessment of short-term toxicity to fish.

Other studies have reported LC₅₀ in the range 1.1 to >100 mg/l; however, the studies have been assigned reliability 4. In the Corning Hazelton (1996a) study it was not possible to correlate nominal and actual concentration because the test media were prepared by diluting a single stock solution. Additionally, the test substance concentrations in solution could was not determined analytically and exposure concentrations were prepared in excess of the water solubility limit of the substance. One other available result is from a summary report to which reliability could not be assigned due to lack of information.

The test media preparation method in the Hüls (1995d) study also made use of serial dilution from a single stock solution. However the test concentrations were confirmed by TOC analysis.