1,1,3,3-tetramethyldisiloxane

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:

weight of evidence

Study period:

2004-03-15 to 2004-03-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1075 (Freshwater and Saltwater Fish Acute Toxicity Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Negative Control, 63, 125, 250, 500 and 1000 mg/L

- Sampling method: Measurement of test concentrations in each test chamber at test initiation, on Day 1 (old solutions) and at test termination :

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Direct addition of test article to dilution water

- Controls: Dilution water

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): No organic solvent

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trout

- Age at study initiation (mean and range, SD): 77 days

- Length at study initiation: 5.9 cm (Range 5.5 to 6.3 cm)

- Weight at study initiation: 1.7 g (Range 1.4 to 2.3 g)

ACCLIMATION

- Acclimation period: 2 weeks prior to the test.

- Acclimation conditions: same as test

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None

Hardness:

122 mg/L as CaCO3

Test temperature:

11.3 - 12.2 ºC

pH:

8.3-8.7

Dissolved oxygen:

>8.3 mg/L (>77% saturation)

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: Negative Control, 63, 125, 250, 500 and 1000 mg/L in dilution water

Measured concentrations:
Method of Calculating Mean Arithmetic mean
Statistical methods: Binomial Probability, Probit Method

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: 38-L or 54-L stainless steel aquaria containing 30-L of test solution

- Renewal rate of test solution: Daily renewal

- No. of organisms per vessel: 10

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

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

- Biomass loading rate: 0.3-0.5 g/L


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Well water

- Alkalinity: 180 mg/L as CaCO3

- Conductivity: 270 mhos/cm

- Culture medium different from test medium: no

- Intervals of water quality measurement: daily


OTHER TEST CONDITIONS

- Adjustment of pH: no


EFFECT PARAMETERS MEASURED: Mortality observed daily


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

> 949 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: not calculable

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

523 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 250-949

Duration:

72 h

Dose descriptor:

LC50

Effect conc.:

476 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 402-565

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

271 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 128-481

Duration:

96 h

Dose descriptor:

LC0

Effect conc.:

128 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

128 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

Biological observations: After 96 hours of exposure, all surviving fish appeared normal.

Lowest test substance concentration causing 100% mortality: 481 mg/L

Mortality of controls: 5%

Abnormal responses: Surfacing, loss of equilibrium, erratic swimming and lying on bottom

Any observations, such as precipitation that might cause a difference between measured and nominal values: All test solutions appeared clear and colourless.

Sublethal observations / clinical signs:

Table 1. Cumulative mortality:  
Mean Measured 
Concentration    Number Dead/Number Exposed (hours)
(mg/L)             0     24    48    72    96 
0                  0/20  0/20  0/20  0/20  1/20  
65                 0/20  0/20  0/20  0/20  0/20
128                0/20  0/20  0/20  0/20  0/20
250                0/20  0/20  0/20  1/20  8/20
481                0/20  0/20  8/20  9/20  20/20
949                0/20  6/20  20/20 20/20 20/20

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 of 271 mg/L and a NOEC of 128 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss based on mean measured concentrations.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

See Section 13 RAAF reports for the justification of read-across.

Reason / purpose for cross-reference:

read-across source

Remarks:

6.1.1.030

Reason / purpose for cross-reference:

read-across source

Remarks:

6.1.1.144

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

271 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

dimethylsilanol

Basis for effect:

mortality (fish)

Remarks on result:

other: 128-481

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

128 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

dimethylsilanol

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Remarks:

DMSD

Basis for effect:

mortality (fish)

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 of 271 mg/L and a NOEC of 128 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss based on mean measured concentrations.

Reference 3

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2008-06-30 to 2008-07-25

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: The test article concentration was measured in each test chamber at test initiation (before the addition of the fish) and at test termination.

- Sampling method: Water samples (10 mL) were collected from mid-depth of the test chambers using a glass pipette.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The nominal test concentration was 120 mg/L. Appropriate aliquots (3.6 g) of the test article were added directly to 30-L of aerated dilution water in the test chambers. The mixtures were stirred using a glass pipette for approximately 1 minute. The negative control was dilution water only. All test solutions appeared clear and colorless.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trout

- Source: Thomas Fish Company, Anderson, California on June 27, 2008. The identity of the species was verified by the supplier.

- Length at study initiation (length definition, mean, range): 49 mm (46-52 mm)

- Holding conditions: The fish were held at a temperature of 11.6 to 11.7ºC.

- Type and amount of food: During holding, rainbow trout were fed finfish starter #2 obtained from Zeigler Brothers, Gardners, PA. The trout chow is analyzed annually for selected contaminants. No contaminants had been shown to be present in the trout chow at concentrations that might affect the outcome of this study. Feeding was discontinued at least 48 hours prior to test initiation and the fish were not fed during the test.

- Health during acclimation (any mortality observed): no mortality

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

111 mg/L as CaCO3

Test temperature:

12+/-1ºC

pH:

7.6-8.4

Dissolved oxygen:

≥8.7 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control) and 120 mg/L

Measured concentrations at test initiation: 120-126 mg/L

Measured concentrations at test termination: 128-131 mg/L

Mean measured test concentration: 126 mg/L (105% of nominal)

Details on test conditions:

TEST SYSTEM

- Test vessel: Test chambers were 38-L glass aquaria containing approximately 30 L of test solution. Test chambers were impartially placed in a temperature-controlled environmental chamber set to maintain a temperature of 12+/-1ºC. Each test chamber was loosely covered with a piece of Plexiglas. Test chambers were labeled with the study number, test article concentration and replicate.

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 3

- Biomass loading rate: 0.28 g/L


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: The dilution water was municipal water obtained from Bay City, Michigan. The water was dechlorinated using a carbon filter and aerated prior to use.

- Culture medium different from test medium: No

- Intervals of water quality measurement: The laboratory water is monitored weekly for hardness, alkalinity, conductivity, total residual chlorine and pH. . The water is monitored once a year for selected inorganics, total suspended solids (TSS), total organic carbon (TOC) and selected organic compounds. No contaminants have been shown to be present in the water at concentrations that might affect the outcome of this study.


OTHER TEST CONDITIONS

- Light intensity: Lighting used to illuminate the test vessels was provided by cool white fluorescent bulbs with a photoperiod of 16 hours light and 8 hours dark. Light intensity at test initiation was 34 foot-candles.


EFFECT PARAMETERS MEASURED: Mortality after 24, 48, 72 and 96 hours


TEST CONCENTRATIONS

- Spacing factor for test concentrations: Limit test

- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 126 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- Mortality of control: 0

Reported statistics and error estimates:

The 24, 48, 72 and 96-hour LC50 values were estimated by visual inspection of the mortality data. Confidence limits could not be calculated because only one concentration was tested.

Sublethal observations / clinical signs:

No mortality or other effects were observed in the Control or treated test media

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 of >126 mg/L and a NOEC of ≥126 mg/L have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss based on mean measured concentrations.

Description of key information

Short-term toxicity to fish: 96-h LC50: 271 mg/l (measured, arith. mean) (OECD 203), read-across from an analogous/structurally related substance trimethylsilanol (CAS 1066-40-6). 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

271 mg/L

Additional information

There are no reliable short-term toxicity to fish data for 1,1,3,3-tetramethyldisiloxane (CAS 3277-26-7), therefore good quality data have been read across from the following substances: trimethylsilanol (CAS 1066-40-6), based on the substance being an analogue of the intermediate hydrolysis product dimethylsilanol.

Data are also available with dimethylsilanediol (CAS 1066-42-8), registered substance’s ultimate silanol hydrolysis product.

In the tests with trimethylsilanol and dimethylsilanediol, the observations are attributed to the exposure of test organisms to the test substance.

 

Trimethylsilanol (TMS, CAS 1066-40-6) has the potential to condense to form hexamethyldisiloxane (HMDS, CAS 107-46-0), which may be present at low levels in the test system. HMDS is classified as Aquatic Acute 1 H400 and Aquatic Chronic 2 H411[1] and therefore its presence has the possibility to impact the results. However, the estimated concentration of HMDS is 0.04, 0.2, 0.3, 0.6 and 0.9 mg/l at 100, 200, 300, 400 and 500 mg/l of TMS respectively and there was no reporting of undissolved test material or droplets being formed, which would otherwise clearly indicate the formation of HMDS. In addition, the log K_ow of trimethylsilanol (1.62) is such that effects may be observed at high concentrations in short-term studies. Therefore the effects seen in the short-term toxicity to fish study, such as 40% mortality at 250 mg/l test concentration, may be attributable to TMS alone and the study is considered to be conservative and reliable for the purpose of this assessment.

The registered substance also releases hydrogen during its final hydrolysis. Hydrogen is not thought to contribute to the toxicity of the substance and is discussed further in the ecotoxicological information overview endpoint summary (additional information).

 

There results of the studies with the source substance are:

•  A 96-hour LC50 of 271 mg/l has been determined for the effects of trimethylsilanol on mortality of Oncorhynchus mykiss based on mean measured concentrations A 96-hour LC50 of 271 mg/l has been determined for the effects of trimethylsilanol on mortality of Oncorhynchus mykiss based on mean measured concentrations.
•  A 96-hour LC50 of >126 mg/l has been determined for the effects of dimethylsilanediol on mortality of Oncorhynchus mykiss based on mean measured concentrations.

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.

[1] https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/notification-details/32082/948794