N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine

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:

weight of evidence

Study period:

1994-02-8 to 1994-02-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP, and was considered to be reliability 1 (reliable without restrictions).

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All concentrations at the start and end of the test.

- Sampling method: Not reported

- Sample storage conditions before analysis: Not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by mixing for 18 h followed by filtration.

- The DOC concentration of the stock solution was determined to be 323 mg/L, equivalent to 722 mg/L of the test substance.

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

Hardness:

202 mg/L as CaCO3

Test temperature:

20+/-1ºC

pH:

6.6-8.5 (The pH values in the control and the lower concentrations showed a larger than 1 unit deviation.  This is not considered to effect  the validity of the study)

Dissolved oxygen:

8.5-8.8

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 13, 18, 25, 26, 51, 72, 101 and 144 mg/L.

The measured concentrations were very close to the nominal values and therefore nominal concentrations were used to present and interpret the test results.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: glass cylinder containing 20 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 prepared with deionized water. The background TOC value  of deionized water is < 1 mg/l (under the detection limit).

- Composition of synthetic water: CaCl2 x 2 H20: 294 mg/L; MgS04 x 7 H20: 123 mg/L; NaHCO3: 63 mg/L; KCl: 5.5 mg/L. The sum of Ca2+ to Mg2 + amounts to 2.5 mmol. The ratio of Ca2+ to mg2+ amounts to 4:1. The ratio of Na+ to K+ amounts to 10:1. 

- Intervals of water quality measurement: end of test

OTHER TEST CONDITIONS

- Photoperiod: Dark

EFFECT PARAMETERS MEASURED: Immobilization after 24 and 48 h exposure

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.4

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

80 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Remarks on result:

other: 70-92

Duration:

48 h

Dose descriptor:

EC100

Effect conc.:

144 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

other: 24 hr EC50

Effect conc.:

89 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

mobility

Details on results:

- Immobilisation of control: 0%

Results with reference substance (positive control):

- Results with reference substance valid?: yes

- EC50: The EC50 value was between 1 and 2 mg/L

Reported statistics and error estimates:

The ECx values were determined by probit analysis

Table 1. Test results

Nominal concentration (mg/L)	Measured concentration at the end of the test (mg/l)	Percentage immobilisation at the end of the test
0 (Control)	-	0
13	15	0
18	19	0
25	25	0
36	36	5
51	51	5
72	72	20
101	103	90
144	142	100

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of 80 mg/L and a NOEC of 25 mg/L have been determined for the effects of the test substance on mobility of Daphnia magna. It is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2004-03-23 to 2004-03-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

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

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 solution) and 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

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Source: Source: Wildlife International, Ltd. cultures

-Age at study initiation: <24 hours old

- Culture: Adult daphnids were cultured in water from the same source and at approximately the same temperature as used during the test. Daphnids in the cultures were held for 14 days prior to collection of the neonates for testing. The adults showed no signs of disease or stress during the holding period.

- Test organisms: Neonate daphnids were obtained for testing from four individual adult daphnids that had already produced at least one previous brood and had produced at least three young per adult per day over the 7-day period prior to the test. At test initiation, the juvenile daphnids were collected from the cultures and indiscriminately transferred one and two at a time to transfer containers until each transfer chamber contained 10 daphnids. Transfer chambers were indiscriminately assigned to test chambers, and then the daphnids were released into the test chambers. All transfers were made below the water surface using wide-bore pipettes.

- Feeding: Daphnids in the cultures were fed daily a mixture of yeast, Cerophyll® and trout chow, as well as a suspension of the freshwater green alga, Selenastrum capricornutum. The adults were fed prior to test initiation, but neonates were not fed during the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

None

Hardness:

126 mg/L as CaCO3

Test temperature:

19.2 to 20.5 ºC

pH:

8.5 to 8.6

Dissolved oxygen:

≥8.6 mg/L (96% of saturation)

Salinity:

Not applicable

Nominal and measured concentrations:

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

Mean measured concentrations:
The results are reported and interpreted with reference to the mean measured concentrations.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: 250 mL glass beakers containing 20 mL of test solution.

- Aeration: none

- Renewal rate of test solution: Daily

- No. of organisms per vessel: 10

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

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

- Biomass loading rate: 1 daphnia/2 ml


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Well water

- Total organic carbon: < 1 mg/L

- Alkalinity: 179 mg/L as CaCO3

- Conductivity: 290 mhos/cm

- Culture medium different from test medium: No

- Intervals of water quality measurement: Daily


OTHER TEST CONDITIONS

- Adjustment of pH: no

- Photoperiod: 16 hours light:8 hours dark

- Light intensity: Wavelength similar to natural sunlight, 131 lux


EFFECT PARAMETERS MEASURED: Mobility daily


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 905 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: mortality and immobilization

Remarks on result:

other: not calculable

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

124 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: mortality and immobilization

Remarks on result:

other: 51-203

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

< 60 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: mortality and immobilization

Details on results:

Biological observations: After 48 hours of exposure, mortality/immobility in the 60, 116, 207, 447 and 905 mg/L treatment groups was 30%, 65%, 45%, 80% and 85%, respectively.

Was control response satisfactory: Yes

Reported statistics and error estimates:

Statistical methods: Probit Analysis

Table 1. Cumulative immobilization:

Mean measured concentration (mg/l)	Number dead/Number immobile 0 hours	Number dead/number immobile/number exposed 24 hours	Number dead/number immobile/number exposed 48 hours
negative control	0/0/20	0/0/20	0/1/20
60	0/0/20	0/0/20	0/6/20
116	0/0/20	0/0/20	7/6/20
207	0/0/20	0/0/20	8/1/20
447	0/0/20	0/2/20	10/6/20
905	0/0/20	0/4/20	8/9/20

Validity criteria fulfilled:

yes

Conclusions:

A 48-hour EC50 value of 124 mg/L and NOEC of <60 mg/L have been determined for the effects of the test substance on mobility/mortality of Daphnia magna based on mean measured concentrations.

Description of key information

(WoE) 48 hr EC₅₀ 80 mg/l (nominal) (EU method C.2), read across from a structurally related substance, 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3). The EC₅₀ is equivalent to 44.7 mg/l when expressed in terms of the silanol hydrolysis product, trimethylsilanol and 8.5 mg/l in terms of NH₃.

(WoE) 48 hr EC₅₀ 124 mg/l (measured) (OECD 202), read across from an analogous substance, trimethylsilanol (CAS 1066-40-6).  

(supporting) 48 hr EC₅₀ 169 mg/l (nominal) (EU method C.2), read across from an analogous substance, trimethoxy(vinyl)silane (CAS 2768-02-7). The EC₅₀ is equivalent to 121 mg/l when expressed in terms of the silanol hydrolysis product, vinylsilanetriol.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

124 mg/L

Additional information

There are no reliable short-term aquatic invertebrate toxicity data for N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, therefore good quality data have been for the effects of the read-across substances 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3) and trimethylsilanol (CAS 1066-40-6) based on structural similarity and production of ammonia, and structural similarity and log K_ow of the silanol hydrolysis product of the registered substance respectively.

In addition, supporting data are presented for trimethoxy(vinyl)silane (CAS 2768-02-7) to demonstrate low toxicity of the vinyl group.

 

48-h EC50 values of 80, 124 and 169 mg/l and NOECs of 25, <60 and (not reported) mg/l (nominal, measured and nominal respectively) have been determined for the effects of the read-across substances 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3), trimethylsilanol (CAS 1066-40-6) and trimethoxy(vinyl)silane (CAS 2768-02-7) respectively, on immobility of Daphnia magna in all three studies.

 

The data on trimethylsilanol (CAS 1066-40-6) are used to derive the PNEC for the silanol hydrolysis product, whereas the data for 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3) are used to establish the classification and labelling of the registered substance due to the presence of the ammonia hydrolysis product, which drives toxicity. The PNECs for ammonia are derived based on literature data.

The study with trimethylsilanol presents a slightly unusual dose-response curve, where at 48-hours the immobility and mortality rates observed at 116 mg/l are higher than those at 207 mg/l concentrations. It is possible this causes the high confidence intervals (51-203) observed in the study. It is the opinion of the reviewer that because at 24 hours no unusual observations were observed and the other study concentrations appear to follow a normal dose-response curve, the study is considered to be valid and the data are used in the risk assessment.

 

Trimethylsilanol (TMS, CAS 1066-40-6) has the potential to condense to form hexamethyldisiloxane (HMDS, CAS 107-46-0), which would then contribute to the species present in the test system. HMDS is classified as Aquatic Acute 1 H400 and Aquatic Chronic 2 H411^[1] and therefore its presence may impact the toxicity 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_owof TMS (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 invertebrate study may be attributable to TMS alone and the study is considered to be conservative and reliable for the purpose of this assessment.

In view of the exposure regime and the fast hydrolysis rates of 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3) and trimethoxy(vinyl)silane (CAS 2768-02-7) it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substances.

 

1,1,1,3,3,3 -Hexamethyldisilazane (CAS 999-97-3)

The results may be expressed in terms of concentration of the hydrolysis product, trimethylsilanol, by applying a molecular weight correction: (MW of silanol = 90.2 / MW of parent = 161.4) * 80 mg/l = 44.7 mg/l. The results may also be expressed in terms of ammonia (NH3), by applying a molecular weight correction: (MW of ammonia 17.03 / MW parent 161.4) * 80 mg/l = 8.5 mg/l. However, data with 1,1,1,3,3,3-hexamethyldisilazane are read across for the purpose of classification and labelling and the relevant values are those determined in terms of the parent substance.

 

Trimethoxy(vinyl)silane (CAS 2768-02-7)

The results may be expressed in terms of concentration of the hydrolysis product, vinylsilanetriol, by applying a molecular weight correction: (MW of silanol = 106.15 / MW of parent = 148.24) * 169 mg/l = 121 mg/l. This value is used as supporting evidence of the lack of effects of dimethylvinylsilanol without further correction.

 

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. Please refer to Section 13 of IUCLID for the read-across justification.

 

Registered substance: N-(Dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine (CAS 7691-02-3)

A study is available with the registered substance (CAS 7691-02-3) in which a 48-h EL50 value of 4.9 mg/l and a NOELR of <0.215 mg/l have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal test substance concentration. The study was severely compromised by significant methodological deficiencies or use of unsuitable test system, which may have adversely influenced the outcome of the study and the results are deemed not fit for the purpose of determining effects on Daphnia magna.

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