2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane

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:

other: Reliable study conducted according to an international guideline (ISO/FDIS 14669 a PARCOM ring test protocol). The study was conducted in compliance to GLP and analytical monitoring was carried out.

Qualifier:

according to guideline

Guideline:

other: ISO/FDIS 14669 a PARCOM ring test protocol

Deviations:

yes

Remarks:

test media prepared as Water Accomodated Fractions (WAFs)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all

- Sampling method: samples of 100 g were taken in 250 ml glass bottles

- Sample storage conditions before analysis: samples weretransferred the same day (cooled) to the analytical laboratories.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: The WAFs were prepared by adding known amounts of the test substance directly into 3 L of seawater in Erlenmeyer flasks and stirred for 20 h using a magnetic stirrer. Following stirring the test media were left to stand for 48 h to enable phase separation. The aqueous phases were then tapped directly into the vessels (first 200 ml discarded). The pH of the WAFs was not adjusted ot the level of the dilution water.

- Controls: seawater and stirred seawater - treated similarly as the test substance loading rate - were used as controls.

- Evidence of undissolved material (e.g. precipitate, surface film, etc): at the start and at the end of the test all test media were clear and colourless (visually assessed).

Test organisms (species):

other aquatic crustacea: Acartia tonsa

Details on test organisms:

TEST ORGANISM

- Source: Water Quality Institute

- Age at study initiation: 6 days old

- Method of breeding: not reported

- Feeding during test: no


ACCLIMATION

- Acclimation period: not reported

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

- Type and amount of food: not reported

- Feeding frequency: not reported

- Health during acclimation (any mortality observed): not reported

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

range: 20 to 20.1 degrees C

pH:

range: 8.1 to 8.4

Dissolved oxygen:

min. 6.5 mg/l

Salinity:

30‰

Nominal and measured concentrations:

Nominal loading rates: control, 100, 180, 320, 560 and 1000 mg/l loading rate as WAFs
Measured concentrations (initial): <0.01, 4.4, 0.34, 0.56, 0.16, 7.3 mg/l
Measured concentrations (after 48 h): <0.01, 0.82, 0.02, 0.02, 0.02, 1.2 mg/l

Details on test conditions:

TEST SYSTEM

- Test vessel: scintillation vials

- Type (delete if not applicable): covered with perspex plate

- Material, size, fill volume: glass, 20 ml scintillation vials, filled with 10 lml of each WAF and the controls

- Aeration: no

- No. of organisms per vessel: 1

- No. of vessels per concentration (replicates): 10

- No. of vessels per control (replicates): 10


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: natural seawater originating from Eastern Scheldt. The water is obtained in large batches and checked upon arrival for contamination with mineral oil, volatile aromatics and chlorinated hydrocarbons by chemical analysis upon arrival. Before storage the water is filtered through a sand filter, and immediately before use the water is filtered over a carbon filter and a 5 um membrane filter. The salinity of the seawater was ca. 32‰; before use it was filtered over a 0.2 um membrane filter and then diluted with ultrapure water to ca. 30‰.

- Total organic carbon: 1.24 mg/l

- Culture medium different from test medium: no

- Intervals of water quality measurement: pH and DO were measured at the beginning of the test before the introduction of the test animals, and after 24 h and 48 h. Temperature was measured in one control vessel at the start and at the end of the test. The salinity of the dilution water was measured at the start of the test.


OTHER TEST CONDITIONS

- Adjustment of pH: none reported

- Photoperiod: not reported

- Light intensity: not reported


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : after 24 h and 48 h the number of living animals were counted.

TEST CONCENTRATIONS

- Spacing factor for test concentrations: ca. 2

- Range finding study

- Test concentrations: same as test

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

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

LL50

Effect conc.:

272 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

(WAFs)

Basis for effect:

mobility

Remarks on result:

other: (197-374) >LoS

Duration:

48 h

Dose descriptor:

LL50

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAFs

Basis for effect:

mobility

Remarks on result:

other: >LoS

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

WAFs

Basis for effect:

mobility

Remarks on result:

other: >LoS

Duration:

48 h

Dose descriptor:

LL100

Effect conc.:

7.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: >LoS

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

4.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: >LoS

Details on results:

- Behavioural abnormalities: 1 slow swimming organism after 48 h at the 100 mg/l loading rate concentration.

- Mortality of control: 0%

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none, the media were clear

- Effect concentrations exceeding solubility of substance in test medium: yes, however the study was conducted using WAFs.

Reported statistics and error estimates:

The LL50 was calculated by a parametric model developed by Kooijman. NOEL was determined by the concentration at which 90% of the test organisms were in good condition compared to the controls.

The results of the analytical monitoring are presented under "Nominal and measured concentrations". There appears to be no correlation between nominal loading rates and measured concentrations. In the reviewers opinion, this is most likely due to the fact that measured concentrations were all higher than the water solubility (2 μg/l). The measured concentrations decreased further during the 48 h test duration.

Table 1. Summary of living and mobile Acartia tonsa observed.

Time (h)	Loading rate (mg/l)
	0	0*	100	180	320	560	1000
0	10	10	10	10	10	10	10
24	10	10	10	9	6	5	2
48	10	10	10	7	3	2	0

* stirred control

Validity criteria fulfilled:

yes

Conclusions:

A 48-h LL50 value of 272 mg/l loading rates, conducted as WAFs, (not possible to extrapolate to measured concentrations) has been determined for the effects of the test substance on immobility of the marine copepod Acartia tonsa. The LL50 is above the water solubility limit of the substance (LoS), therefore the LL50 is >LoS.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2001-01-08 to 2001-01-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

other: ASTM (2000) Standard practice for conducting acute toxicity tests with fishes, macroinvertebrates and amphibians. Standard E729-96. American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

Qualifier:

according to guideline

Guideline:

other: U.S. EPA. (1975) Methods for Acute Toxicity Tests with Fish, Macroinvertebrates and Amphibians. Ecological Research Series (EPA-660/3-75-009)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Sampling method: At test initiation (0 hour) and test termination (48 hours), a sample was removed from replicates A and B of each exposure solution and the controls. Each sample was collected using a volumetric pipette from the midpoint of the test vessel and composited.

Three quality control (QC) samples were prepared at each sampling interval at nominal D5 concentrations which approximated the test concentration range and remained with the exposure solution samples throughout the analytical process. Analysis of the QC samples was used to judge the precision and quality control maintained during the analytical process.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A saturated 170 µg a.i./mL primary stock solution was prepared by placing 0.1701 g (0.1690 g as active ingredient) of D5 in a 1.0 L volumetric flask and diluting to volume with acetone (CAS No. 67-64-1).

Nominal test concentrations were 2.2, 3.7, 6.1, 10 and 17 µg/L.

A 0.32 mL/mL solvent stock control solution was prepared by placing 32 mL of acetone in a 100-mL volumetric flask and diluting to volume with distilled water.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: Springborn Smithers culture facility.

- Culture medium: Water used to culture the daphnids was prepared in the same manner and has the same characteristics as the dilution water.

- Feeding during culture: Daphnids were fed a unicellular green algae, Ankistrodesmus falcatus (4 x 107 cells/mL), at a rate of 2 mL algae per vessel per day.

- Age of test organisms: Daphnids were obtained by removing all immature daphnids from the culture vessel, thus isolating mature gravid daphnids 24 hours prior to initiating the test. Young produced by these organisms were subsequently pipetted into the test beakers.

- Age at study initiation: <24 hours

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

The dilution water had a total hardness and alkalinity as CaCO3 of 170 mg/L and 110 mg/L

Test temperature:

20 to 21°C

pH:

pH measured in the dilution water and solvent control vessels ranged from 7.9 to 8.0 at test initiation and were both 8.0 at test termination.

pH measured in the 17 µg a.i./L treatment level ranged from 7.8 to 7.9 at test initiation and was 7.9 at test termination.

Dissolved oxygen:

The dilution water and solvent control vessels had a measured DO concentration range of 9.0 to 9.1 mg/L at test initiation and 8.0 and 7.8 mg/L respectively, at test termination.

The 17 µg a.i./L treatment level had a measured DO concentration range of 8.2 to 8.4 mg/L at test initiation and 7.2 mg/L at test termination.

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations in µg/L: 2.2, 3.7, 6.1, 10 and 17

Mean measured concentrations in µg/L: 2.1, 1.6, 1.8, 2.5 and 2.9

Units: µg a.i./L

The test results are interpreted with reference to mean measured concentrations.

Details on test conditions:

TEST SYSTEM

- Test vessel: The toxicity test was conducted in a modified constant-flow diluter system designed to provide five test substance concentrations, a solvent control and a control to duplicate test vessels. The exposure system was designed as a closed system with virtually no opening to atmospheric air, which served to minimize volatilization of the test substance from water.

Each test vessel was a 350-mL glass vessel, equipped with a stopcock valve on each end. The top valve contained a glass tube to allow for solution overflow and the bottom valve contained an entry port for continued delivery of the test solution and also served as a sampling port for water quality measurements. Gaskets covered with 40 mesh Nitex® screen separated the stopcock valves from the central body and prevented escape of the daphnids. Each 350-mL glass test vessel was filled to capacity and had a depth of 32 cm.

- Material: Materials that came into contact with the test substance were limited to glass, silicone and Teflon®.

- No. of organisms per vessel: Ten daphnids were impartially selected and distributed to each replicate exposure vessel. Daphnids were added impartially to an intermediate beaker by adding no more than two daphnids to each beaker until all beakers contained two daphnids. This procedure was repeated until each beaker contained ten daphnids. Then one beaker of ten daphnids was added to each test vessel. A total of 20 organisms were exposed to each treatment level and control solution.


TEST MEDIUM / WATER PARAMETERS

- Dilution water source: Laboratory well water.

- Dilution water chemistry (hardness, alkalinity, pH, TOC): The dilution water had a total hardness and alkalinity as CaCO3 of 170 mg/L and 110 mg/L, respectively, a pH of 7.9 and a specific conductivity of 500 µmhos/cm. The TOC concentration of the dilution water source was 0.68 mg/L for the month of January 2001.

OTHER TEST CONDITIONS

Lighting (quality, intensity, and periodicity): The test area was illuminated with Sylvania Octron® fluorescent bulbs at an intensity range of 50 to 70 foot candles at the solutions' surface. The test area received a regulated photoperiod of 16 hours of light and 8 hours of darkness. Sudden transitions from light to dark and vice versa were avoided. Light intensity was measured once during the test.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 2.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

mobility

Remarks on result:

other: not calculable

Details on results:

- Mortality of control:  No immobilization or adverse effects were observed in daphnids exposed to the solvent control. Immobilization of 10% was observed in the control.  Although immobilization of 10% was observed in the control, this is considered to be within the expected range of naturally occurring variability for acute tests (ASTM, 2000).   .

Reported statistics and error estimates:

No significant treatment related effects were observed in the test. Statistical analysis of the test results was therefore not required.

- Number immobilized as compared to the number exposed: 

Number immobilized:  5, Number exposed:  140 (includes controls)

- Cumulative immobilization:  No immobilization was observed among daphnids exposed to the 1.6 and 2.9 µg a.i./L treatment levels.  Immobilization of 5% was observed in the 2.1, 1.8 and 2.5 µg a.i./L treatment levels.

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of >2.9 µg a.i./L has been determined for the effects of the test substamce on mobility of Daphnia magna. A NOEC of ≥2.9 µg a.i./L has been determined in the same test.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2007-01-16 to 2007-01-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)

Version / remarks:

(Flow-through conditions)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

On day -1, a quality control (QC) sample was prepared at the same nominal concentration as the stock solution. The QC sample and a sample from the stock solution were analysed for the substance concentration.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 16 mg/mL diluter stock solution was prepared prior to the start of the test by placing 0.3996 g of D3 in a 25-mL volumetric flask and bringing to volume with acetone. The resulting stock solution was clear and colourless with no visible undissolved substance. In addition, a 0.98 mL/mL solvent stock solution was prepared by bringing 246 mL of acetone to a final volume of 250 mL with deionised water. The resulting solution was clear and colourless.

Prior to test initiation, a 10 mL Glenco® gas-tight syringe in conjunction with a Harvard syringe pump was calibrated to deliver 0.203 mL/cycle of the 16 mg/mL stock solution into the diluter system's mixing chamber which also received 0.203 L of dilution water per cycle. The concentration of D3 in the mixing chamber was equivalent to the nominal test concentration of 1.6 mg/L.

The solvent control solution was prepared in a similar way to produce a final exposure concentration of 0.10 mL/L.

- Controls: Dilution water control and Solvent control

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source:  Springborn Smithers culture facility.  

- Culture conditions: Daphnids were cultured in 1.0-L glass vessels containing 0.80 L of water. 

- Culture medium: Water used to culture the daphnids was from the same source as the dilution water used in the test.

- Feeding: Daphnids were fed a unicellular green algae (Ankistrodesmus falcatus, 4 x 10E7 cells/mL) at a rate of 1.0  to 2.0 mL per vessel daily depending on the age of the adult organisms in  the culture vessel and 0.5 mL of a combination of yeast, cereal leaves and flaked fish food (YCT) daily.  

- Age of test organisms: Daphnids were obtained by removing all immature daphnids from the culture vessel, thus isolating mature gravid daphnids < 24 hours prior to initiating the test.  Young produced by these organisms were subsequently pipetted into the test beakers.   Age at study initiation< 24 hours

Test type:

flow-through

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

Total hardness and alkalinity (as CaCO3) of  160 mg/L and 100 mg/L respectively

Test temperature:

19-21ºC

pH:

7.8 - 8.0

Dissolved oxygen:

8.5-9.3

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 0 (Solvent control) and 1.6 mg/L

Measured concentration in stock solution used to prepare the test media: 15.2 mg/L

The test results are reported and interpreted with reference to nominal concentrations

Details on test conditions:

TEST SYSTEM

The test was conducted using an intermittent-flow proportional diluter and a set of eight exposure vessels.  The exposure system consisted of  two replicate test vessels each for the dilution water control, solvent  control and test solution.  

Test vessels consisted of 1600 mL square  glass battery jars which had two holes drilled in each side 15 cm from  the bottom.  The holes were covered with Nitex® 40-mesh screen for  drainage.  The total test solution volume was maintained at 1400 mL.  

A 16 mg/mL dilutor stock solution was prepared in acetone and analyzed to  confirm the test substance concentration in this solvent stock.  The solvent stock  solution was delivered into the diluter's mixing chamber via syringe.   The resulting solution was observed to be clear and colorless.  A Glenco®  10-mL gas-tight syringe in conjunction with a Harvard Syringe Pump was  calibrated to deliver 0.0203 mL/cycle of 16 mg/mL test substance solution into the  diluter's chemical mixing chamber which received 0.203 L of dilution  water per cycle.  The mixing chamber was continuously mixed.  The  concentration of test substance in the solution contained withing the mixing chamber  was equivalent to the nominal concentration of 1.6 mg/L.  Dilutor flow  was maintained at a rate to deliver approximately 10 solution  replacements per day.

The exposure vessels were maintained in an area illuminated with  fluorescent bulbs at an intensity of 75 to 81 footcandles (810 to 870  lux)  with a 16 hour light and eight hour dark photoperiod.  Sudden  transitions between light and dark periods were avoided.  

Dilution water  was characterized as having total hardness and alkalinity (as CaCO3) of  160 mg/L and 100 mg/L respectively, a pH of 7.8 and a specific  conductance of 500 µmhos/cm.  The total organic carbon content (TOC) was  0.30 mg/L.  

The dilution water control vessels had a dissoled oxygen  concentration range of 8.8 to 8.9mg/L at test initiation and a range of  9.2 to 9.3 mg/L during the test.  

The pH measured in the dilution water  control vessel replicates was 7.9 at test initiation and 7.8 at test  termination.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 1.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC0

Effect conc.:

>= 1.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

> 1.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Immobilisation of control:0

Reported statistics and error estimates:

There were no effects of the test substance on mobility of the test organisms and therefore statistical analysis of the results was not required.

Table 1. Test results

Treatment	Mean percentage immobilisation after 24 hours	Mean percentage immobilisation after 48 hours
0 (Control)	0	0
0 (Solvent control)	5	5
1.6 mg/L	0	0

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of >1.6 mg/L and NOEC of ≥1.6 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. A concentration of 1.6 mg/L corresponds to the approximate water solubility of the substance.

Reference 4

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1993-06-01 to 1993-06-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The concentration of hydrolysis products in stock solution determined by Total Organic Carbon analysis. The stock solution concentration (464 mg/l equivalent to a test substance concentration of 1145 mg/L) was used as the basis for determining the concentrations in the test media.

Vehicle:

no

Details on test solutions:

- Method: Test media prepared by dilution of a 1000 mg/L stock solution prepared by mixing for 18 h followed by filtration. TOC concentration of stock solution determined.

- Treatments: Control and nominal test concentrations of 57, 80, 115, 160, 229, 321 and 458 mg/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Common name: Daphnia magna

- Strain: Clone 5

- Source: Stock culture

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

- Method of breeding: Parthenogenetic reproduction

- Feeding during test: None


ACCLIMATION

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

- Type and amount of food: sufficient to be consumed each day leaving no residue

- Feeding frequency: daily

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

none

Hardness:

The sum of the Ca2+ and Mg2+ ions was 2.5 mmol

Test temperature:

20 ±1ºC

pH:

7.0 - 7.2

Dissolved oxygen:

6.5 - 8.1 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Control and nominal test concentrations of 57, 80, 115, 160, 229, 321 and 458 mg/L.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: glass cylinder containing 10 ml of test medium

- Aeration: none

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Elendt M4 medium

- Intervals of water quality measurement: end of test


OTHER TEST CONDITIONS

- Photoperiod: Dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization after 24 and 48 h exposure

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.4


STATISTICS

EC50 and confidence interval determined by Probit analysis

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

297.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 223.9 - 224.2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

168.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 126.9 - 224.2

Details on results:

- Mortality of control: 0

Results with reference substance (positive control):

- EC50: >0.9, <1.9 mg/L

Reported statistics and error estimates:

The EC50 value and its 95% confidence interval was calculated by Probit analysis.

Table 1. Test results

Nominal test substance concentration (mg/L)	Percentage immobile Daphnia after 24 hours	Percentage immobile Daphnia after 48 hours
0 (Control)	0	0
57	5	25
80	5	25
115	5	35
160	0	35
229	25	45
321	55	75
458	90	100

Validity criteria fulfilled:

yes

Conclusions:

A 48-h EC50 value of 168.7 mg/L has been determined for the effects of the test substance on mobility of Daphnia magna. A NOEC was not determined in the test. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to invertebrates: 48 hour EL₅₀ 272 mg/l loading rate (WAFs), Acartia tonsa (guideline ISO/FDIS 14669 a PARCOM ring test protocol).

Additional information

A 48 hour LL₅₀ value of 272 mg/l and NOELR of 100 mg/l loading rate (WAFs) (not possible to extrapolate to measured concentrations) have been determined for the effects of the registration substance on mobility of the marine copepod Acartia tonsa conducted in compliance with test guideline ISO/FDIS 14669 a PARCOM ring test protocol and in compliance with GLP (TNO, 2003). The LL₅₀ is above the water solubility limit of the substance (0.0073 – 0.0088 mg/l at 23°C).

For monoconstituent substances it would not normally be appropriate to test at concentrations above the solubility limit. However, the results as reported do provide strong evidence of the absence of toxicity at the solubility limit of the substance following short-term exposures.

This is the only reliable study available for this substance and it has been chosen as key.

The data above are supported by read-across evidence relevant to the impurities. The registration substance has an average purity of >70% Vi4-D4, with <20% 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane Vi5-D5 (CAS 17704-22-2; Impurity 1) and <10% 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane Vi3-D3 (CAS 3901-77-7; Impurity 2) present as impurities. After due consideration of the properties, the presence of these impurities is not expected to affect the overall hazard profile of the substance.

Read-across studies are in place as supporting studies, to consider the properties of the impurities. Data for Vi5-D5 are read-across from decamethylcyclopentasiloxane D5 (CAS 541-02-6), data for Vi3-D3 are read-across from hexamethyltrisiloxane D3 (CAS 541-05-9). These siloxanes have similar properties with regard to aquatic ecotoxicity.  Further information is given in a supporting report (PFA, 2017) attached in Section 13 of the IUCLID dossier.

A reliable short-term Daphnia study is available for the siloxane D5 (CAS 541-02-6) and is read-across to Impurity 1 (Vi5-D5) (Springborn Smithers, 2002). This study (48 hour flow through test with Daphnia magna) gave a result 48 hour EC₅₀ >2.9 µg/l. EC₅₀ was not reached within the limit of solubility in test media.

A reliable short-term Daphnia study is available for the siloxane D3 (CAS 541-05-9) and is read-across to Impurity 2 (Vi3-D3) (Springborn Smithers, 2007). This study (48 hour flow through test with Daphnia magna) gave a result 48 hour EC₅₀ >1.6 mg/l. EC₅₀ was not reached within the limit of solubility in test media.

A 48 hour EC₅₀ value of 169 mg/l has been determined for the effects of the read-across substance trimethox(vinyl)silane (CAS 2768-02-7) on mobility of Daphnia magna (Hüls, 1993). The data indicate that the vinyl side chain is unlikely to contribute significant excess ecotoxicity to the substance.