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

Sediment toxicity

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

SEDIMENT

- Sampling interval: Sediment concentrations of D5 were measured on Days 0, 7 and 28.

Vehicle:

no

Details on sediment and application:

SEDIMENT

- Formulated sediment: 10% sphagnum peat moss, 20% kaolin clay and 70% quartz sand. The final pH of the sediment was 6.6. The organic carbon content was determined to be 3.2% (without addition of feed).


PREPARATION OF SPIKED SEDIMENT

- Details of spiking: Stock solutions preparation (vehicle, solvent, concentrations) and stability: Each test concentration was prepared separately by spiking the test article into formulated sediment. Neat test article was added to a predetermined amount of conditioned and air-dried peat. The peat and the test article were mixed overnight in a Nalgene bottle on a rotary mixer. A predetermined amount of formulated sediment was added to the bottle and mixed until appearing homogenous (Approximately 30-40 minutes).

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM

- Source: Egg masses were obtained from Environmental Consulting and Testing, Superior, Wisconsin. No pretreatment

- Age of animals at beginning of exposure: Approximately 1 day after hatching

Study type:

laboratory study

Test type:

semi-static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

136-160 mg/L as CaCO3

Test temperature:

20 +/- 2 ºC

pH:

pH ranged from 8.0 to 8.4

Dissolved oxygen:

dissolved oxygen concentrations remained >= 7.4 mg/L (82% of saturation)

Salinity:

not applicable

Ammonia:

no data

Nominal and measured concentrations:

Nominal concentrations in mg/Kg: 156, 259, 432, 720, 1200 and 2000

Arithmetic mean measured concentrations in mg/Kg: 35, 70, 160, 248, 390, and 759

Details on test conditions:

TEST SYSTEM

- Test container (material, size): Test chambers were 2000-mL glass beakers containing approximately 2 cm of sediment and 8 cm of overlying water

- Aeration: yes

- Overlying water renewal: Overlying water was partially renewed on Days 7, 14 and 21 of the test

- Aeration frequency and intensity: Loose plastic covers were placed over each test chamber. Each test chamber was gently aerated.

EXPOSURE REGIME

- No. of organisms per container (treatment): Four replicates were tested in each treatment group with 20 midges in each replicate for a total of 80 midges per treatment group.

- Type and preparation of food: A 28-day ration of food (280 mg Tetramin flake food) was dry mixed into the sediment prior to the addition of the overlying water.

OVERLYING WATER CHARACTERISTCS

- Dilution water source: Well Water

- Dilution water chemistry (hardness, alkalinity, pH, TOC, TSS, salinity, Ca/Mg ration, Na/K ratio): hardness 136-160 mg/L as CaCO3 , alkalinity 176 mg/L as CaCO3 and conductivity 345 mhos/cm

OTHER TEST CONDITIONS

- Lighting (quality, intensity, and periodicity): fluorescent lighting with wavelengths similar to natural lighting, intensity was 340 lux at the surface of the water, photoperiod was 16 hours light:8 hours dark.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

70 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Development rate

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

160 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Development rate

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

257 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 213-318

Dose descriptor:

NOEC

Effect conc.:

160 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Development time and emergence ratio

Dose descriptor:

LOEC

Effect conc.:

248 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Development time and emergence ratio

Reported statistics and error estimates:

The probit method was used to calculate the 28-Day LC50 value. The NOEC was determined by hypothesis testing based on the following endpoints: 1) mortality, 2) development time, 3) emergence ratio and 4) development rate.

Table 1. Biological observations
Mean        %            Mean     Emergence     Development
Meas.     Mortality     D.T.        Ratio         Rate
Conc.                                                     (days)
(mg/kg)                                                 

0            13           16.2        0.88             0.0640
35            15           16.7        0.85             0.0629
70            16           17.5        0.88             0.0601
160          29           18.5        0.71              0.0562*
248          49           21.4*      0.53*             0.0489*
390          69           21.9*      0.31*             0.0476*
759          75           23.5*      0.26*             0.0441*

where
* indicates a significant difference from the negative control using Dunnett's test (p = 0.05).                
Was control response satisfactory:  Yes

Validity criteria fulfilled:

yes

Conclusions:

A 28-Day LC50 value of 257 mg/kg dry weight has been determined for the effects of the sediment incorporated test substance on mortality of Chironomus riparius. A NOEC of 70 mg/kg dry weight for effects on development rate and a NOEC of 160 mg/kg dry weight for effects on development time and emergence ratio have been determined in the same test.

Reference 2

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2009-05-14 to 2009-06-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 225

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Prior to dosing, a sample of each dosing stock solution was taken and analyzed for test substance concentration. In addition, each treatment level and control sediment was sampled and analyzed for test substance concentration after dosing and prior to division into the replicate test vessels. Results of the pretest analyses were used to judge whether sufficient quantities of test substance had been applied during the mixing process.

During the in-life phase of the definitive study, sediment samples were removed and analyzed for test substance concentration on test days 0 (test initiation), test day 7 and test day 28 (test termination). On test days 0, 7 and 28, samples were removed and analyzed from replicate vessels E, F and G, respectively, for each treatment level and vessels G, H and I for the controls. Overlying water samples were removed from the test vessels by decanting all of the overlying water from each vessel into a graduated cylinder. Following removal of the overlying water, the sediment was then centrifuged at approximately 10,000 g for 30 minutes. The pore water generated by centrifugation was then removed by pipet. The sediment samples were then collected from each centrifuge tube with a stainless steel spatula.

In addition, three quality control (QC) samples were prepared at each sampling interval and remained with the set of exposure samples throughout the analytical process. These QC samples were prepared in sediment (based on sediment dry weight) at concentrations of test substance similar to the treatment level range. Results of the analyses of the QC samples were used to judge the precision and quality control maintained during the analysis of exposure solution samples.

Vehicle:

yes

Details on sediment and application:

Natural freshwater sediment was the substrate used in the exposure. The natural sediment (Springborn Smithers Laboratories Batch No. 031809) was collected from a single source, Glen Charlie Pond, Wareham, Massachusetts. Prior to use and characterization, the sediment was wet pressed through a 2.0-mm sieve to remove large particles and benthic organisms and homogenized thoroughly. The natural sediment used in the study was characterized by Agvise Laboratories, Northwood, North Dakota, as having an organic carbon content of 2.2%, a pH of 6.5 and a percent moisture (at 1/3 Bar) of 18.0. The particle size distribution conducted by Agvise Laboratories resulted in average particle size distribution of 93% sand, 6% silt and 1% clay. A percent solids value of 58.46% was determined by Springborn Smithers Laboratories. A sample of the sediment pore water was generated from the sediment batch prior to testing and yielded a measured concentration of 4.5 mg/L as nitrogen (ammonia). This concentration is well below levels of concern for this organism. A representative sample of the sediment source was analyzed for the presence of pesticides, PCBs and toxic metals by GeoLabs, Inc., Braintree, Massachusetts. None of these compounds were detected at concentrations that would be considered to have an adverse impact on the results of the test.

A 20 mg a.i./mL primary stock was prepared by placing 0.5012 g (0.5000 g as active ingredient) of test substance in a 25-mL volumetric flask and bringing it to volume with acetone. The resulting stock solution was observed to be clear and colorless with no visible undissolved test substance following stirring. A 2.0 mg a.i./mL secondary stock solution was prepared by placing 2.5 mL of the 20 mg a.i./mL primary stock solution in a 25-mL volumetric flask and bringing it to volume with acetone (CAS No. 67-64-1). Dosing stock solutions were prepared from dilutions of 2.0 mg a.i./mL secondary stock solution and the 20 mg a.i./mL primary stock solution.

For each dose level, a 2.5-kg aliquot of wet sediment (1.462 kg dry weight based on a percent solids of 58.46%) along with 7.5 L of overlying water (sediment:volume ratio of 3:1) were placed in individual glass jars. Immediately prior to dosing, the contents of each jar were shaken to suspend the sediment. An 8.3-mL volume of each dosing stock solution was then added to each jar. Each jar was shaken again after dosing to distribute the test substance. After a 16-hour settling period, the water was decanted from the sediment. The sediment was transferred to a Hobart mixer and 3.66 g each of urtica powder and alpha cellulose were mixed into the sediment of each test group as a food source for the oligochaetes. This weight of urtica powder and alpha cellulose was equal to 0.25% of the dry weight for each sediment batch. Following mixing in the Hobart mixer, the treated sediments were allocated to the replicate test vessels for each exposure level.

A solvent control sample was prepared in the same manner as the treated sediment by adding 2.5 kg of wet sediment (1.462 kg dry weight based on a percent solids of 58.46%) along with 7.5 L of overlying water (sediment:volume ratio of 3:1) and 8.3 mL of acetone in a glass jar and processed in the same manner as the treated sediments. The negative control sediment group was prepared using only untreated sediment and overlying water (no test substance or solvent). The negative control and solvent control vessels were maintained under the same conditions as the treatment vessels

Test organisms (species):

Lumbriculus variegatus

Details on test organisms:

TEST ORGANISM

- Source: The oligochaetes used during this study were obtained from the main laboratory cultures maintained at Springborn Smithers. The oligochaetes from this culture were maintained in a 57-L aquarium containing approximately 40 L of culture water under flow-through conditions. The water used in the main culture is unadulterated well water from a 100-meter bedrock well and has been characterized as soft water with typical ranges as total hardness of 30 to 60 mg/L as CaCO3, alkalinity of 25 to 45 mg/L as CaCO3, pH of 6.9 to 7.7, and a specific conductance of 140 to 200 micromhos/cm. Oligochaetes were fed 15 mL of finely ground suspension (100 mg/mL) of flaked fish food weekly.

- Age of animals at beginning of exposure: Fourteen days prior to test initiation, worms from the culture were removed and artificially fragmented to synchronize the population, using a scalpel to remove the anterior ends. Synchronized oligochaetes were then acclimated to test conditions (i.e., test water and test sediment) for a period of thirteen days to regenerate new heads. The synchronization of worms is performed to avoid “uncontrolled” regeneration and reproduction that may contribute high variation in the test results.

- Feeding: Once during the acclimation period, the synchronized oligochaetes were fed 6.4 mL of a finely ground suspension (100 mg/mL) of flaked fish food.

- Holding conditions: During the holding period, dissolved oxygen ranged from 7.9 to 8.4 mg/L, pH ranged from 7.2 to 8.2 and the temperature ranged from 20 to 21 oC.

- Health prior to testing: No mortality was observed in the test population 48 hours prior to test initiation.

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

The water used during the definitive exposure was characterized as having a total hardness and total alkalinity as calcium carbonate (CaCO3) of 170 and 100 mg/L, respectively

Test temperature:

19 to 23 ºC

pH:

7.2 to 8.1

Dissolved oxygen:

7.4 to 9.2 mg/L

Salinity:

Not applicable

Ammonia:

≤0.10 - 3.7 mg/L (as N)

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 0 (Solvent control), 3.1, 6.3, 13, 25, 50 and 100 mg a.i./kg

Measured concentrations: 0 (Control), 0 (Solvent control), 1.2, 3.2, 8.8, 13, 19 and 32 mg a.i./kg

The results are interpreted with reference to measured concentrations.

Details on test conditions:

TEST SYSTEM

The test vessels used were 600-mL clear glass beakers. The sediment and overlying water were added to the test vessels two days prior to test initiation. A 75-mL (1.5-cm layer) aliquot of sediment was added to each test vessel. The wet weight of the sediment in each jar averaged 148 g (86.5 g dry weight). A turbulence reducer, consisting of a plastic disk, was used to minimize the disruption of the sediment layer during the introduction of 300 mL (6 cm) of overlying water. The total medium volume (sediment/water) was maintained at 375 mL and the ratio of sediment to water was 1:4. The turbulence reducer was composed of a modified plastic disk. The initial water level in each test vessel was marked in order to evaluate evaporation. Each test vessel was covered with a clear plastic plate to minimize evaporation and gentle aeration was provided through a glass pipette fixed approximately 2 to 3 cm above the sediment surface. Aeration was delivered at a rate of 1 to 3 bubbles per second.

Four replicate test vessels (A through D) were established for each treatment level and six vessels (A through F) were established for the control and solvent control. Four additional replicate test vessels (E through H for treatment levels and G through J for the controls) were maintained for the purpose of chemical analysis. Each replicate vessel contained ten oligochaetes, a total of 40 oligochates per concentration and 60 oligochates in the control and solvent control for the biological response replicates. The additional replicates were maintained under the same conditions and contained ten test organisms, but were not used to evaluate the biological response of the test organisms

Test vessels were positioned in a water bath containing circulating water designed to maintain the test solutions at a temperature of 20 ± 2 ºC. Test solutions were gently aerated (1 to 3 bubbles per second) two days prior to addition of the test organisms and throughout the duration of the exposure period. Test vessels were labeled to identify the nominal test concentration, study number and designated replicate. The test area was illuminated with fluorescent bulbs at an intensity range of 530 to 540 lux and a photoperiod of 16 hours light and 8 hours darkness. Light intensity was measured using a VWR Traceable light meter.

Replicate test vessels A through D for treatment levels and A through F for the control and solvent control were examined at test initiation and daily thereafter, until test termination (day 28). Daily observations of mortality and abnormal behavior (e.g., leaving sediment) were made and recorded.

On test day 28 of the exposure, the replicate vessels from each exposure level (four replicates) and controls (six replicates) were terminated to determine the number of surviving oligochaetes and the biomass of the surviving oligochaetes. Instances of dead oligochaetes were also recorded. However, dead oligochaetes often decompose in the vessels and are difficult to recover. If fewer than ten oligochaetes were observed and no dead oligochaetes were recovered, the missing individuals were assumed to have died. Surviving worms were assigned to one of three groups:

a) Large, complete worms (adults) without regenerated body regions.
b) Complete worms with regenerated, lighter-colored body regions.
c) Incomplete worms (i.e., recently fragmented worms with non-regenerated body regions.

The biomass was determined by placing the entire number of surviving oligochaetes from each replicate vessel in a tared weight tin and then drying in an oven at 100 ± 5 ºC overnight (18 to 24 hours). Following drying, the tins were cooled to room temperature in desiccators and then weighted to the nearest 0.01 mg on a calibrated analytical balance.

Water quality measurements made during the study were performed in the replicate exposure vessels (A through D or A through F). Measurements of dissolved oxygen concentration, temperature and pH were made on the day the test organisms were added (day 0) and at test termination (day 28) in each exposure vessel. In addition, dissolved oxygen concentration, temperature and pH were measured daily in one replicate vessel of each treatment level and the controls during the 28-day exposure. Daily water quality measurements were made on alternating replicates. The temperature was continuously monitored in an auxiliary vessel in the water bath throughout the study. Total hardness, alkalinity, specific conductivity, and total ammonia of the test solutions were determined at test initiation and at test termination in a composite sample from the highest treatment level (replicates A through D) and the solvent control (replicates A through F). In addition, total ammonia was determined three times per week in the solvent control and the 100 mg a.i./kg nominal treatment level.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

13 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

19 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 32 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: reproduction and biomass

Reported statistics and error estimates:

At the termination of the study, data obtained on oligochaetes reproduction (the total number of oligochaetes recovered at test termination) and biomass were statistically analyzed to identify significant treatment-related effects. The lowest test concentration that showed a statistically significant effect (Lowest-Observed-Effect Concentration, LOEC) and the highest test concentration that showed no statistically significant effect (No-Observed-Effect Concentration, NOEC) were determined.

TOXSTAT® Version 3.5 (West Inc. and Gulley, 1996) was used to perform the computations.

The EC50 is the estimated measured sediment concentration of the test substance which produces 50% reduction in reproduction or biomass in the test population of oligochaetes at test termination. During this study, no concentration tested resulted in ≥ 50% reduction in reproduction or biomass, therefore the EC50 values were empirically estimated to be greater than the highest mean measured sediment concentration.

Table 1. Results of analysis of sediment concentrations

Nominal Sediment Concentration (mg a.i./kg)	Measured Sediment Concentration (mg a.i./kg)				Mean Percent Recovery^d
	Day 0^a	Day 7^b	Day 28^c	Mean^d
Control	< 0.60^e	< 0.60	< 0.60	NA^f	NA
Solvent Control	< 0.60	< 0.60	< 0.60	NA	NA
3.1	1.1	1.6	0.92	1.2	39
6.3	3.7	3.5	2.3	3.2	50
13	13	6.9	7.0	8.8	68
25	18	14	8.3	13	54
50	24	19	15	19	39
100	39	29	29	32	32

^a      Analytical samples were removed from replicate E, with the exception of the control and solvent control which were removed from replicate G.

^b      Analytical samples were removed from replicate F, with the exception of the control and solvent control which were removed from replicate H.

^c      Analytical samples were removed from replicate G, with the exception of the control and solvent control which were removed from replicate I.

^d      Mean measured and percent recovery values were calculated using the actual analytical results and not the rounded values (two significant figures) presented in this table.

^e      Concentrations expressed as less than values were below the limit of quantitation (LOQ). The LOQ for the analysis was set at the lowest validated sample concentration.

^f      NA = Not Applicable.

Table 2. Test results

Mean MeasuredSediment Concentration (mg a.i./kg)	Mean Number Of Oligochaetes per Replicate at end of test (SD)	Mean Biomass per Replicate per Concentration in Milligrams at end of test (SD)
Control	30 (2)	46 (6)
Solvent Control	30 (3)	51 (9)
Pooled Control	30 (2)	49 (8)
1.2	31 (1)	55 (6)
3.2	31 (3)	64 (6)
8.8	28 (1)	50 (8)
13	29 (3)	47 (3)
19	26 (3)^*	44 (5)
32	22 (1)^*	44 (6)

^*      Statistically different (p ≤ 0.05) compared to the pooled control data, based on Bonferroni’s t-Test.

Validity criteria fulfilled:

yes

Conclusions:

A 28-day EC50 value of >32 mg/kg has been determined for the effects of the test substance on reproduction and biomass of Lumbriculus variegatus. A 28-day NOEC of 13 mg/kg dry weight and LOEC of 19 mg/kg dry weight have been determined in the same test based on effects on mortality.

Reference 3

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2007-09-20 to 2007-10-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Sediment concentrations of D4 were measured on  Days 0, 7 and 28.

Vehicle:

no

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT

- Details of spiking: Each test concentration was prepared separately by spiking the test article into formulated sediment. Neat test article was added to a predetermined amount of conditioned and air-dried peat. The peat and the test article were mixed overnight in a Nalgene bottle on a rotary mixer. A predetermined amount of formulated sediment was added to the bottle and mixed until appearing homogenous (Approximately 20 minutes).

- Formulated sediment:  10% sphagnum peat moss, 20% kaolin  clay and 70% quartz sand.  The final pH of the sediment was 6.9.  The  organic carbon content was determined to be  4.1% (without addition of  feed).

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM

- Source: Egg masses were  obtained from Environmental Consulting and Testing, no pretreatment.

-  Age at study initiation:  Approximately 1 day after hatching

Study type:

laboratory study

Test type:

semi-static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

Hardness: 140 - 154 mg/L as CaCO3

Alkalinity: 166 - 178 mg/L as CaCO3 

Test temperature:

20 +/-  2ºC

pH:

pH 8.2 to 8.6

Dissolved oxygen:

≥7.2 mg/L (80% of saturation)

Salinity:

Not applicable

Ammonia:

No data

Nominal and measured concentrations:

Nominal test concentrations: 0 (negative control), 31, 63,  125, 250, 500 and 1000 mg/Kg dry weight.

Arithmetic mean measured concentrations: 6.5, 7.9, 19, 44, 131 and 355 mg/Kg

Details on test conditions:

TEST SYSTEM

- Test container (material, size): Test chambers were 2000-mL glass beakers.  Loose plastic  covers were placed over each test chamber. 

- Depth of sediment and overlying water: Approximately 2 cm of sediment and 8 cm of overlying water

- Aeration: yes (Each test chamber was gently aerated)


EXPOSURE REGIME

- No. of organisms per container (treatment): Four replicates were tested in each treatment group  with 20 midges in each replicate for a total of 80 midges per treatment group. 

- Feeding regime: A 28-day ration of food (280 mg Tetramin flake food) was dry mixed into the  sediment prior to the addition of the overlying water.


RENEWAL OF OVERLYING WATER

- Details on volume additions: overlying water was partially renewed  on Days 7, 14 and 21 of the test


OVERLYING WATER CHARACTERISTCS

- Type of water: Well Water

CHARACTERIZATION OF ARTIFICIAL SEDIMENT

- Composition: 10% sphagnum peat moss, 20% kaolin clay and 70% quartz sand. The final pH of the sediment was 6.9. The organic carbon content was determined to be 4.1% (without addition of feed).


OTHER TEST CONDITIONS

- Light quality: fluorescent lighting  with wavelengths similar to natural lighting

- Photoperiod: 16 hours light:8 hours dark

- Light intensity: 355 lux at  the surface of the water


EFFECT PARAMETERS MEASURED: Survival, development time, emergence ratio and development rate


VEHICLE CONTROL PERFORMED: no


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

44 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Survival and emergence ratio

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

131 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Survival and emergence ratio

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

114 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (96 - 136 mg/Kg)

Reported statistics and error estimates:

The probit method was used to calculate the 28-Day  LC50 value.  The NOEC was determined by hypothesis testing based on the  following endpoints:  1) mortality, 2) development time, 3) emergence  ratio and 4) development rate.

Table 1. Biological observations:

Mean Meas. Conc. (mg/kg)	% Mortality	Mean D.T (days)	Emergence Ratio	Development Rate
0	8.8	18.4	0.93	0.0572
6.5	13	17.5	0.88	0.0597
7.9	11	17.9	0.89	0.0584
19	2.5	17.9	0.98	0.0586
44	19	18.7	0.85	0.0560
131	55*	18.0	0.48*	0.0579
355	88*	21.1*	0.13*	0.0496*

Where
D.T. = Development Time
* indicates a significant difference from the negative control using  

Dunnett's test (p <= 0.05).                

Was control response satisfactory:  Yes
Statistical results, as appropriate: 
28-Day LC50:  114 mg/Kg (96 - 136 mg/Kg)
NOEC:  44 mg/Kg

Validity criteria fulfilled:

yes

Conclusions:

A 28-day LC50 of 114 mg/kg sediment dry weight has been determined for the effects of the test substance on survival of Chironomus riparius. A NOEC of 44 mg/kg has been determined for effects on mortality and emergence ratio in the same test.

Reference 4

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

21 May to 21 June 2012 (includes test substance application on day -2)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the appropriate National Standard Method (OPPTS 850.1735) under GLP and analytical monitoring was carried out.

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1735 (Whole Sediment Acute Toxicity of Invertebrates, freshwater)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

SEDIMENT

- Concentrations: each treatment and control

- Sampling interval: day 0, 7 and 28

- Sample storage before analysis: not reported


PORE WATER - Pore water samples were collected by removing the entire sediment sample and centrifuging for 15 to 30 minutes at approximately 1200 g. The resulting pore water was removed from the centrifuge tube and discarded.


OVERLYING WATER - decanted and discarded
:

Vehicle:

yes

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT

- Details of spiking: a primary clear and colourless 20 mg/ml stock solution was prepared in acetone. From this 5 individual clear and colourless dosing stock solutions were prepared in dilution water (17.4, 8.68, 4.34, 2.26, 1.09 mg/ml). On day -2 the test substance was applied to the sediment. 2.0 kg (1.5 L) of sediment (0.868 kg dry weight) was added to a glass jar along 4.5 L of dilution water (water:sediment ratio 3:1). The jar contents were mixed by shaking the jar to suspend the sediment immediately prior to dosing. 5 ml of each stock solution was added to the sediment and jars were shaken again to ditribute the substance. After settling overnight, the water was decanted and the treated sediments were allocated to the replicate test vessels for each exposure level.

- Equilibration time: 24 hours + overnight settling period

- Equilibration conditions: not reported

- Controls: controls were prepared in the same way but using just overlying water

- Chemical name of vehicle: acetone

- Concentration of vehicle in test medium (stock solution and final test solution): 5.0 ml in vehicle control

- Evaporation of vehicle before use: water was decanted after overnight mixing


PREPARATION OF SPIKED WATER - not applicable

Test organisms (species):

Hyalella azteca

Details on test organisms:

TEST ORGANISM

- Source: Environmental Consulting & Testing, Superior, Wisconsin, USA

- Age of parental stock (mean and range, SD): not reported, however 5 days old when received from the supplier

- Age of animals at beginning of exposure: 10 days old


- Feeding during test

- Food type: combination of yeast, cereal leaves and flaked fish food suspension (YCT)

- Amount: 1.5 ml

- Frequency: daily


ACCLIMATION

- Acclimation period: 5 days

- Acclimation conditions (same as test or not): held under static conditions in 1-L beakers containing approximately 0.80 L of laboratory well water, dissolved oxygen ranged from 7.0 to 8.0 mg/L and temperature ranged from 25 to 26degrees C

- Type and amount of food: 2.5 mL of a combination of yeast, cereal leaves and flaked fish food suspension (YCT)

- Feeding frequency: every other day

- Health during acclimation (any mortality observed): no mortalities were observed 48 h prior to test initiation

Study type:

laboratory study

Test type:

semi-static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

no

Duration:

28 d

Exposure phase:

total exposure duration

Hardness:

Dilution water total hardness (as CaCO3): 64 to 68 mg/L

Test temperature:

range: 23 to 24 ºC

Dissolved oxygen:

range: 40 to 100%

Ammonia:

Ammonia concentrations measured in the overlying water of all treatment levels and the control during the exposure did not exceed 0.70 mg/L, and remained within the tolerance of the test organism.

Nominal and measured concentrations:

Nominal concentrations: control, solvent control, 6.3, 13, 25, 50 and 100 mg/kg dry weight
Measured concentrations (mean):

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 300 ml glass vessels, cehmically cleaned prior to testing. Each test vessel had a hole cut on the top edge of the beaker which was covered with 40-mesh Nitex® screen for drainage.

- Sediment volume: 100 mL (approximately 4-cm layer) of sediment

- Weight of wet sediment with and without pore water: 135 g wet weight per vessel with pore water

- Overlying water volume: 175 ml

- Depth of sediment and overlying water: 275 ml

- Aeration: no


EXPOSURE REGIME
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 8 + 2 for analytical monitoring
- No. of replicates per control / vehicle control: 8 + 2 for analytical monitoring

- Feeding regime: see above
- Type and preparation of food: see above
- Amount of food: see above

RENEWAL OF OVERLYING WATER

- Details on volume additions: two volume additions (i.e., 350 mL) per test vessel per day using an intermittent delivery system in combination with a calibrated water-distribution system

- Flow-rate: not reported


OVERLYING WATER CHARACTERISTCS

- Type of water: laboratory well water, amphipod cultures are successfully maintained in this water

- Alkalinity: 21 to 23 mg/L as CaCO3

- Conductivity: 320 to 350 µS/cm

- Particulate matter: not reported

- Total organic carbon: 0.66 and 0.38 mg/L

- Representative samples of the overlying water source were analyzed for the presence of pesticides, PCBs and metals by GeoLabs, Inc., Braintree, Massachusetts. None of these compounds were detected in any of the water samples analyzed in agreement with ASTM guidelines (2002)


SOURCE OF NATURAL SEDIMENT
- Location and description of sampling site: Natural, freshwater sediment collected from Glen Charlie Pond, Wareham, Massachusetts, USA
- Contamination history of site: not reported

HANDLING OF NATURAL SEDIMENT: The sediment was obtained by removing the top 10 to 15 cm of sediment beneath a water depth of approximately 60 cm. The sediment was transferred from the collection site to Smithers Viscient in multiple 20-liter, sealed, polyethylene buckets where it was stored in a refrigerator at approximately 4 oC for 5 weeks prior to testing.

CHARACTERIZATION OF SEDIMENT

- Particle size distribution
- % sand: 93%
- % silt: 4%
- % clay:3%

- Moisture: 21.5%

- Presence of macrophytes/animals: not reported

- Other: percent solids 43.4%. The sediment matrix to be used in testing was analyzed to confirm that the test substance was not present.

- Sediment sieved: yes, through a 2.0 mm sieve

- pH whole sediment: 5.6

- Ammonia content of pore water: 7.9 mg/l as N

- Total organic carbon (%): 3.7%

- Proof of absence of chemical contaminants: A representative sample of the sediment source was analyzed for the presence of pesticides, PCBs and toxic metals by GeoLabs, Inc., Braintree, Massachusetts. None of these compounds were detected at concentrations that would be considered to have an adverse impact on the results of the test.


OTHER TEST CONDITIONS
- Light quality: fluorescent light bulbs
- Photoperiod: 16 h daylight, 8 h darkness
- Light intensity: 520 to 790 lux


EFFECT PARAMETERS MEASURED: All vessels were examined at test initiation and at 24-hour intervals thereafter, until test termination (day 28). Observations of mortality and abnormal behavior were made and the physical characteristics of the test samples were recorded. At test termination (day 28), the total number of surviving amphipods and dry weight of surviving amphipods was determined in each test vessel.


VEHICLE CONTROL PERFORMED: yes


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

- Range finding study

- Test concentrations: 0, 0.010, 0.10, 1.0, 10 and 100 mg/kg dwt

- Results used to determine the conditions for the definitive study: no effects at the highest concentration tested

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: survival and growth

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: survival and growth

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

> 100 mg/kg sediment dw

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: survival and growth

Reported statistics and error estimates:

Wilcoxon's Rank Sum Two-Sample Test (U.S. EPA, 2002) and Equal Variance Two Sample t-Test (U.S. EPA, 2002) were conducted on the survival and dry weight data to compare the performance of the control organisms with that of the solvent control organisms. During this study, the t-Test indicated no significant difference between control and solvent control data. Shapiro-Wilks’ Test (U.S. EPA, 2002) for normality was conducted. Bartlett’s Test (U.S. EPA, 2002) was conducted to check assumption of homogenity. Both dry weight and survival met the assumption for homogeneity of variance.
Survival data did not meet the assumption for normality, therefore treatment related effects were tested with Wilcoxon's Test with Bonferroni's Adjustment (U.S. EPA, 2002). Dry weight treatment related effects were tested with Bonferroni's Adjusted t-Test (U.S. EPA, 2002).
CETISTM Version 1.8.4.20 (Ives, 2011) was used to perform the computations.

Table 1.             Meanpercent survival and mean dry weight during the28-day static-renewal exposure of freshwater amphipods (Hyalella azteca) tothe test substanceapplied to sediment.

 

Mean Measured Sediment Concentration (mg/kg)	Test Day 28
	Mean Percent Survival (SD^a)	Mean Dry Weight Per Amphipod in mg (SD)
Control	99 (4)	0.69 (0.08)
Solvent Control	95 (5)	0.78 (0.14)
Pooled Control	97 (5)	0.73 (0.12)
4.6	99 (4)	0.96 (0.13)
12	96 (11)	0.89 (0.20)
24	99 (4)	0.77 (0.09)
50	98 (7)	0.85 (0.12)
100	94 (9)	0.72 (0.09)

 

^a         SD = Standard Deviation.

Table 2.             Concentrations ofthe test substancemeasured in sediment samples duringthe 28‑day static-renewal exposure of freshwater amphipods (Hyalella azteca).

Nominal Concentration (mg/kg)	Measured Concentration (mg/kg)			Mean^d	Percent of Nominal^d
	Day 0^a	Day 7^b	Day 28^c
Control	< 0.36^e	< 0.35	< 0.43	NA^f	NA
Solvent Control	< 0.36	< 0.35	< 0.43	NA	NA
6.3	5.6	5.0	3.3	4.6	73
13	13	13	9.4	12	90
25	32	23	16	24	96
50	52	52	47	50	100
100	110	110	81	100	100
QC^g#1 1.00	1.07 (107)	0.954 (95.4)	0.771 (77.1)
QC#2 10.0	< 0.596 (NA)^h	10.1 (101)	6.98 (69.8)^h
QC#3 100	97.7 (97.7)	103 (103)	73.2 (73.2)

^a      Analytical samples were removed from replicate I.

^b      Analytical samples were removed from replicate J.

^c      Analytical samples were removed from replicate K.

^d      Mean measured and percent recovery values were calculated using the actual analytical results and not the rounded values (two significant figures) presented in this table.

^e      Concentrations expressed as less than values were below the limit of quantitation (LOQ). The LOQ for each analysis is dependent upon the regression, the area of the low standards and the dilution factor of the controls.

^f      NA = Not Applicable.

^g      QC = Quality Control sample. Percent of nominal is presented in parentheses below the measured results.

^h              Percent recovery for this QC sample is outside of the acceptable range (i.e., 70 to 120%,

Validity criteria fulfilled:

yes

Conclusions:

A 28-day LC50 and NOEC values of >100 and ≥100 mg/kg dry weight of sediment respectively, have been determined for the effects of the test substance on survival and growth of the freshwater amphipod Hyallela azteca.

Reference 5

Endpoint:

sediment toxicity: short-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

third final test, from 2000-07-07 to 2000-07-17

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to an appropriate EU test method. It was compliant with GLP but no analytical monitoring was carried out. PARCOM does not require chemical analysis of the test substance in the test media.

Qualifier:

according to guideline

Guideline:

other: PARCOM Guideline, 1995

Deviations:

yes

Remarks:

the base sediment was a mixture of two sediments and had a media grain-size of between 90 and 180 um.

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 850.1735 (Whole Sediment Acute Toxicity of Invertebrates, freshwater)

Deviations:

not applicable

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT

- Pooling or mixing of different substrates: 1:1 on dry basis

- Method of mixing: not reported

- Details of spiking: The test medium (natural sediment + test substance) was separately prepared for each test substance concentration by adding the appropriate amount of test substance to ca. 400 g (dry weight) of natural sediment followed by mixing for at least 11 hours ( 3.5 h at 15°C on a roller bank and 7.5 h at room temperature by hand because of a technical failure with the roller bank). Throughout the 7.5 h the jars were shaken thoroughly every half hour. The authors state that it is unlikely that the technical failure had an impact on the toxicity measurement the study results. 50 ml of seawater was added to ensure thorough mixing.

- Equilibration time: overnight, ca. 17 h, then the sediments were topped with 200 ml seawater

- Equilibration conditions: roller bank

- Controls: treated in the same way as spiked sediment


PREPARATION OF SPIKED WATER
not applicable

Test organisms (species):

Corophium volutator

Details on test organisms:

TEST ORGANISM

- Source: Eastern Scheldt, The Netherlands.

- Details on collection: not reported

- Age of animals at beginning of exposure: >5 mm (excluding antennae)

- Feeding during test: no


ACCLIMATION

- Acclimation period: 8 days

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

- Type and amount of food: not reported

- Health during acclimation (any mortality observed): no significant mortality is reported (visually assessed)

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

no

Duration:

10 d

Exposure phase:

total exposure duration

Hardness:

not reported

Test temperature:

range: 14.8 to 15.1 ⁰C

pH:

range: 8.0 to 8.2

Dissolved oxygen:

lowest measured value was 7.2 mg/l

Salinity:

range: 32.4 to 32.8 ‰

Ammonia:

not reported

Nominal and measured concentrations:

Nominal concentrations: 3.2, 10, 32, 100 and 320 mg/kg (test substance, not active ingredient).

Details on test conditions:

TEST SYSTEM

- Test container (material, size): 250 ml glass beakers

- Sediment volume: 75 ml

- Weight of wet sediment with and without pore water:

- Depth of sediment and overlying water: 75 ml sediment, topped up to 200 ml with seawater, then after introduction of animals to 225 ml with seawater

- Aeration: yes

- Aeration frequency and intensity: gentle continuous aeration

- Replacement of evaporated test water, if any: to make up for evaporation losses, the sailinity was adjusted by adding demineralised water each day


EXPOSURE REGIME

- No. of organisms per container (treatment): 5

- No. of replicates per treatment group: 4

- No. of replicates per control / vehicle control: 4

- Feeding regime: animals were not fed during the test


OVERLYING WATER CHARACTERISTCS

- Type of water (e.g. deionized, ground water, sea water, Elendt medium acc. to OECD 219): sea water, normally 32%o

- Source of water (if non-standard medium): sea

- Location: from Eastern Scheldt, The Netherlands

- Description of sampling site: relatively unpolluted area

- Filtration: before entering the supply tank the seawater was filtered through a sand filter and was continuously recirculated (filtered) over a carbon filter and a 5 um membrane filter before use.

- Alkalinity:
- Salinity: 32‰

- Conductivity:
- Particulate matter:

- Total organic carbon: 0.47 mg/l

- Chemical oxygen demand:
- Unionized ammonia:
- Residual chlorine:
- Total organic chlorine compounds and PCBs:
- Total organophosphorous compounds:
- Total organic chlorine:


SOURCE OF NATURAL SEDIMENT

- Location and description of sampling site: from Eastern Scheldt, The Netherlands

- Contamination history of site: relatively unpolluted area, no futher details given


HANDLING OF NATURAL SEDIMENT

- Time of collection: not reported, on June 9, 1998

- Core depth: not reported

- Water depth: not reported

- Storage conditions: not reported


CHARACTERIZATION OF SEDIMENT
The base sediment was a mixture of two sediments and had a measured median grain-size of between 90 and 180 um (78%), a silt clay (<63 um) fraction of 6.0%.

- Presence of macrophytes/animals: the sediment were sieved at 0.5 mm within one week of arrival to remove predators, broken shells and larger particles

- Sediment sieved: yes/no

- Total organic carbon (%): 0.62% (weight loss on ignition)


OTHER TEST CONDITIONS

- Light quality: not reported

- Photoperiod: 16 h light, 8 h darkness with a transition period of 30 minutes

- Light intensity: not reported


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : on day 5, remains of dead test animals and moulting skins were removed. On day 10 all surviving animals were counted before and after sieving and their behaviour recorded. Animals which were not recovered at the end of the test are assumed to be dead.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3.2

- Range finding study: not conducted, however a study was conducted with concentrations from 300, 10 000 mg/kg where it was not possible to calculate NOEC, therefore the study was conducted with lower test concentrations range.

Reference substance (positive control):

no

Duration:

10 d

Dose descriptor:

LC50

Effect conc.:

124 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: (84.1-184)

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

32 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/kg sediment dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

behaviour

Details on results:

- Mortality of test animals at end of exposure period: see Table 1 for details

- Behavioural abnormalities:
- Other biological observations:

Reported statistics and error estimates:

LC50 values and its confidence intervals were calculated by means of a parametric model developed by Koojman. The NOEC was determined as the highest concentration tested at which at least 90% of animals survived and did not show any signs of harm with respect to behaviour.

Table 1. Number of surviving animals.

Time	Nominal concentration (mg/kg dry weight sediment)
days	0	3.2	10	32	100	320
0	20	20	20	20	20	20
10	20	20	19	19	12	3

Validity criteria fulfilled:

yes

Conclusions:

A reliable short-term (10-day) LC50 value of 124 mg/kg has been determined for the effects of the registered substance on mortality of Corophium volutator in a sediment containing 0.62% of organic carbon.

Description of key information

NOEC for freshwater sediment: 13 mg/kg dwt (30 mg/kg dwt normalised to 5% OC), growth rate of Lumbriculus variegatus, read across from D4.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

30 mg/kg sediment dw

Additional information

A category approach is applied to this endpoint and is detailed in the Reconsile Siloxane Category report (PFA, 2017) attached in Section 13 of IUCLID. The hypothesis for read-across of sediment ecotoxicity evidence within the Siloxanes Category is that no structure-based or property-based pattern is evident from the category dataset of existing studies, although patterns are identifiable associated with extrinsic aspects of test design to which effects may be attributed. The approach will be revisited in the event that reliable new data become available. With this in mind, a single overall interpretation is made across the category. To fulfil the requirements of REACH, a conservative approach is made by reading across on a nearest-neighbour basis the reliable data within the category.

In the context of the RAAF, Scenario 6 is expected to apply to this endpoint. It is considered that effects observed in benthic organisms are associated primarily with extrinsic factors associated with test design and not to structural similarities as such. The Reconsile Siloxane Category report (PFA, 2017) addresses the Assessment Elements of the RAAF and, in addition to describing the siloxanes category, forms the RAAF justification report.

A total of twenty-four sediment toxicity studies for siloxanes are available and nineteen results from studies of standard duration in standard test species have been reviewed in detail. There is a general trend for studies using natural sediment, which all have pH <~8, to show no effects, or higher NOECs than those with artificial sediment. No significant toxicity (NOEC <100 mg/kg) in any organism is found at pH near 7 with natural sediment. The data suggest that it is possible to read across sediment toxicity data between different siloxane structures, especially where natural sediment data are available, given that the studies which are not suspected to be confounded by extrinsic factors show relatively minimal effects across the dataset.

Data available for the substance:

28 day LC₅₀ and NOEC values of >100 and ≥100 mg/kg dry weight of sediment, respectively, have been determined for the effects of the registration substance on survival and growth of the freshwater amphipod Hyalella azteca, conducted in accordance with test guideline EPA OPPTS 850.1735 (Whole Sediment Acute Toxicity of Invertebrates, freshwater) and in compliance with GLP (Smithers Viscient, 2013). The sediment contained 3.7% organic carbon. This is equivalent to a NOEC of ≥126 mg/kg in sediment containing 5% organic carbon.

It is possible to calculate the solubility of the substance in organic carbon (OC) according to the following formula:

OC solubility mg/kg = K_oc * water solubility

For this substance this is: 1.26E+04 * 0.008 = 100 mg/kg OC.

The sediment in this long-term toxicity study had an OC content of 3.7%, therefore the calculated solubility of the substance in this sediment is 4 mg/kg. This indicates that the substance is not toxic at its solubility in organic carbon.

A short-term (10 day) LC₅₀ value of 124 mg/kg has been determined for the effects of the registration substance on mortality of Corophium volutator in a sediment containing 0.62% of organic carbon (OC), conducted in accordance with PARCOM test Guideline, 1995 and in compliance with GLP (Dow Corning, 2001). This is equivalent to an LC₅₀ value of 230 mg/kg in sediment containing 5% organic carbon. It is possible that the results overestimate toxicity due to the treatments greatly exceeding the substance's solubility in sediment containing 0.62% OC being exceeded.

The registered substance (Vi4-D4) and read-across substance D4 (CAS 556-67-2) are members of the Reconsile Siloxanes Category. Octamethylcyclotetrasiloxane (D4, CAS 556-67-2) is a cyclic siloxane made up of 4 Si with methyl groups, linked by oxygen atoms. Vi4-D4 is a cyclic siloxane made up of 4 Si with methyl and vinyl groups, linked by oxygen atoms. Vi4-D4 and D4 have slow hydrolysis rates (63 h at pH 7 and 20-25°C (predicted) and 69-144 h at pH 7 and 25°C, respectively) and similar physico-chemical properties: high molecular weight (MW 344.7 and 296.6 respectively), low water solubility (0.056 mg/l and 0.0073 – 0.0088 mg/l respectively), high log K_ow (both 6.5) and high log K_oc(both close to 4). The registration and read-across substances are not readily biodegradable and have high potential for adsorption to sediment.

A result for effects in natural sediment on Lumbriculus variegatus is read across from D4 (Springborn Smithers, 2009). The result from that test is a 28 day NOEC of 13 mg/kg sediment dry weight for growth rate (30 mg/kg sediment dry weight, normalised to 5% organic carbon), conducted in accordance with test guideline OECD 225 and in compliance with GLP.

A 28 day NOEC result for Chironomus riparius is also read across from D4 (Wildlife International, 2008). A 28 day NOEC of 44 mg/kg dry weight has been determined for effects on emergence and development rate of Chironomus riparius (54 mg/kg dry weight, normalised to 5% organic carbon), conducted in accordance with test guideline OECD 218 and in compliance with GLP.

The results of all tests are expressed relative to mean measured exposure concentrations in the treated sediment.

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.

Vi5-D5 and D5 are members of the Siloxane Category, and therefore data for Vi5-D5 are read-across from decamethylcyclopentasiloxane D5 (CAS 541-02-6).

Vi3-D3 and D3 have rapid hydrolysis rates (0.6 h at pH 7 and 20-25°C, predicted and 23 minutes at pH 7 and 25°C, measured respectively), and the log K_ow of the hydrolysis products is <3; substances with log K_ow <3 are not likely to be sorbed to sediment and therefore testing for sediment toxicity is not considered necessary. There are therefore no studies available with Vi3-D3 or the surrogate D3.

The lowest sediment NOEC obtained for D5 is 70 mg/kg dry weight for effects of D5 on development rate of Chironomus riparius in artificial sediment, conducted in accordance with test guideline OECD 218 and in complaince with GLP (Wildlife International 2008).