Registration Dossier
Registration Dossier
Data platform availability banner - registered substances factsheets
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Diss Factsheets
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 219-863-1 | CAS number: 2554-06-5
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Freshwater
- Hazard assessment conclusion:
- no hazard identified
Marine water
- Hazard assessment conclusion:
- no hazard identified
STP
- Hazard assessment conclusion:
- no hazard identified
Sediment (freshwater)
- Hazard assessment conclusion:
- PNEC sediment (freshwater)
- PNEC value:
- 3 mg/kg sediment dw
- Assessment factor:
- 10
- Extrapolation method:
- assessment factor
Sediment (marine water)
- Hazard assessment conclusion:
- PNEC sediment (marine water)
- PNEC value:
- 0.3 mg/kg sediment dw
- Assessment factor:
- 100
- Extrapolation method:
- assessment factor
Hazard for air
Air
- Hazard assessment conclusion:
- no hazard identified
Hazard for terrestrial organisms
Soil
- Hazard assessment conclusion:
- no hazard identified
Hazard for predators
Secondary poisoning
- Hazard assessment conclusion:
- PNEC oral
- PNEC value:
- 3.33 mg/kg food
- Assessment factor:
- 90
Additional information
2,4,6,8-Tetramethyl-2,4,6,8-tetravinyltetrasiloxane (Vi4-D4, CAS 2554-06-5) hydrolyses slowly to form methylvinylsilanediol. The half-life value of 63 hours at pH 7, 0.8 h at pH 9, and 1.1 h at pH 4 and 20 – 25°C is applicable to hydrolysis of the parent substance but complete reaction to methylvinylsilanediol will take longer. The water solubility of the substance is low (0.0073 – 0.0088 mg/l at 23°C), the measured vapour pressure is 93.5 Pa at 25°C, and the log Kow is high (6.5).
REACH Guidance (ECHA 2017, R.7b) indicates that the parent substance should be tested if the DT50 is greater than 3 days, or on a case by case basis if between 1 hour and 3 days. REACH guidance (ECHA 2016, R.16) states that “for substances where hydrolytic DT50 is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. TGD and REACH guidance (EC 2003) and R.16 (2016) also suggest that when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity.
Due to the slow hydrolysis half-life of the registration substance, the environmental Chemical Safety Assessment is therefore based on the properties of the parent substance rather than the hydrolysis products.
Due to the low water solubility and high log Kow, aquatic organisms are likely to be exposed to only very low dissolved concentrations of the substance in the environment.
In the sediment and soil compartments adsorption to particulate and organic matter will be high.
It is likely that, under the semi-static and flow-through exposure conditions of the long-term Daphnia and long and short-term fish studies, respectively, the test organisms will have predominantly been exposed to the parent substance. In the static short-term invertebrate study and algal test it is likely that exposure will have been initially to the parent substance followed by a mixture of parent substance and its hydrolysis products.
The registration substance has an average purity of >70% 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (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. For each endpoint, the 3 components are considered separately.
READ-ACROSS JUSTIFICATION
In order to reduce testing read-across is proposed to fulfil up to REACH Annex IX requirements for the registered substance from substances that have similar structure and physicochemical properties. Ecotoxicological studies are conducted in aquatic medium or in moist environments; therefore the hydrolysis rate of the substance is particularly important since after hydrolysis occurs the resulting product has different physicochemical properties and structure.
The behaviour of 2,4,6,8-tetramethyl-2,4,6,8-tetravinyltetrasiloxane (Vi4-D4) in the environment is dominated by the high partition coefficient (log Kow 6.5) and adsorption coefficient properties (log Koc 4.1) of the substance.
In the following paragraphs the read-across approach for Vi4-D4 and its impurities are assessed taking into account structure and physico-chemical properties. Vi4-D4 and the substances used as surrogates are siloxanes. Substances in this group tend to have slow hydrolysis rates, low water solubility, high log Kow, high adsorption coefficients and a tendency for high persistence in the sediment compartment.
The physico-chemical and ecotoxicological properties and data of the registered and surrogate substances are summarised in the table below.
Sediment toxicity: Read-across from octamethylcyclotetrasiloxane (D4) to Vi4-D4
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 Kow (both 6.5) and high log Koc (both close to 4). The environmental behaviour and toxicity is driven by the low water solubility, high log Kow and high log Koc, therefore read-across of sediment toxicity data is considered to be appropriate.
Sediment toxicity data with Corophium volutator and Hyalella azteca are available with Vi4-D4. Data with Lumbriculus variegatus are read across from D4. The lowest sediment toxicity value is with L. variegatus where a NOEC of 13 mg/kg dwt in natural sediment is reported.
Aquatic, sediment and terrestrial toxicity: Read-across from decamethylcyclopentasiloxane (D5) to Impurity 1, Vi5-D5
Decamethylcyclopentasiloxane (D5, CAS 541-02-6) is a cyclic siloxane made up of 5 Si with methyl groups, linked by oxygen atoms. Impurity 1, Vi5-D5 is a cyclic siloxane made up of 5 silicon atoms with methyl and vinyl groups, linked by oxygen atoms. Vi5-D5 and D5 have slow hydrolysis rates (1600 h at pH 7 and 20-25°C, predicted and 1590 h at pH 7 and 25°C respectively) and similar physico-chemical properties: high molecular weight (MW 431 and 370.8 respectively), low water solubility (9.1E-06 mg/l and 0.017 mg/l respectively) high log Kow (9.0 and 8.0 respectively) and high log Koc (6 and 5.2 respectively). D5 and Vi5-D5 are structural analogues with very similar properties. The environmental behaviour and toxicity is driven by the water solubility, high log Kow and high log Koc, therefore read-across of aquatic, sediment and terrestrial toxicity data is considered to be appropriate. The aquatic data indicates that D5 is not toxic to aquatic organisms in the long-term up to the limit of solubility. The lowest sediment toxicity study is with C. Riparius where a NOEC of 70 mg/kg dwt in artificial sediment is reported. The lowest terrestrial toxicity study result is with F. candida where a NOEC of 377 mg/kg dry weight is reported.
Aquatic toxicity: Read-across from hexamethylcyclotrisiloxane (D3) to Impurity 2, Vi3-D3
Hexamethylcyclotrisiloxane (D3, CAS 541-05-9) is a cyclic siloxane made up of 3 Si with methyl groups, linked by oxygen atoms. Vi3-D3 is a cyclic siloxane made up of 3 silicon atoms with methyl and vinyl groups, linked by oxygen atoms. 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 similar physico-chemical properties: similar molecular weight (MW 259 and 223 respectively), low water solubility (0.13 mg/l and 2 mg/l respectively) and high log Kow (6.7 and 4.4 respectively). D3 and Vi3-D3 are structural analogues with very similar properties. The environmental behaviour and toxicity is driven by the water solubility and log Kow, therefore read-across of aquatic toxicity data is considered to be appropriate.
Aquatic toxicity: Read-across from trimethoxyvinylsilane to Vi4-D4
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. Data with decamethylcyclopentasiloxane (D5, CAS 541-02-6) and hexamethylcyclotrisiloxane (D3, CAS 541-05-9) are read across to assess the toxicity of the impurities. Vi4-D4, Vi5-D5 and Vi3-D3 contain a vinyl side-chain whereas D5 and D3 do not. To provide evidence that the vinyl side chain does not contribute significantly to the ecotoxicity of the impurities of the registered substance, supporting read-across from trimethoxyvinylsilane (CAS 2768-02-7) has been used. From the available dataset, the vinyl fragment of Vi5-D5 and Vi3-D3 is understood to not have any specific mode of action with respect to ecotoxicity; data with trimethoxyvinylsilane (CAS 2768-02-7) indicate the substance is of low short-term toxicity with L(E)C50 values in the range >89-191 mg/l, which are consistent with non-polar narcosis as seen with other alkoxysilanes.
Trimethoxyvinylsilane is used to read-across to short-term toxicity to fish, invertebrates and algae endpoints. E(L)C50 values of 191, 169 and >89 mg/l, respectively, have been determined.
Consideration of low functionality side chains and reactive groups
Vinyl group: From the available dataset in the whole of the silanes and siloxanes database, vinyl fragments are understood to not have any specific mode of action with respect to ecotoxicity. For example, trimethoxyvinylsilane (CAS 2768-02-7) is an alkoxysilane with vinyl groups and a log Kow 1.1. Short-term toxicity data for the substance report L(E)C50 values in the range >89 - 191 mg/l (MoE Japan 2006, Hüls 1993 and Dow Corning 1979), which are consistent with non-polar narcosis as seen with other alkoxysilanes.
Table: Summary of physicochemical and ecotoxicological properties for the registered substance, its impurities and their surrogate substances.
CAS Number |
2554-06-5 |
556-67-2 |
2768-02-7 |
17704-22-2 |
541-02-6 |
3901-77-7 |
541-05-9 |
Chemical Name |
2,4,6,8 -Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane |
Octamethylcyclotetrasiloxane (D4) |
Trimethoxy(vinyl)silane |
2,4,6,8,10 -Pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane (Impurity 1 (Vi5-D5)) |
Decamethylcyclopentasiloxane (D5) |
2,4,6 -Trimethyl-2,4,6-trivinylcyclotrisiloxane (Impurity 2 (Vi3-D3)) |
Hexamethylcyclotrisiloxane (D3) |
Ultimate Si hydrolysis product |
Methylvinylsilanediol |
Dimethylsilanediol |
Vinylsilanetriol |
Methylvinylsilanediol |
Dimethylsilanediol |
Methylvinylsilanediol |
Dimethylsilanediol |
Molecular weight (parent) |
344.66 |
296.62 |
148.2 |
431 |
370.8 |
259 |
223 |
Molecular weight (hydrolysis product) |
104.18 |
92.17 |
106.2 |
104.18 |
92.17 |
104.18 |
92.17 |
log Kow(parent) |
6.47 |
6.49 |
1.1 |
9.0 |
8.07 |
6.7 |
4.4 |
Water sol (parent) |
0.0073 – 0.0088 mg/l at 23°C |
0.056 mg/l |
l9400 mg/l
|
9.1E-06 mg/l |
0.017 mg/l |
0.13 mg/l |
2 mg/l |
Vapour pressure (parent) |
93.5 Pa |
132 Pa |
1190 Pa |
0.6 Pa |
33 Pa |
67 Pa |
671 Pa |
Hydrolysis t1/2 at pH 7 and 25°C |
approximately 63 hours |
69-144 hours |
0.2 h (at 20⁰C) |
1600 hours |
1590 hours |
0.6 hours |
23 minutes |
Hydrolysis t1/2 at pH 4 and 25°C |
1.1 hours |
1.8 hours |
0.04 h |
3.3 hours (pH5) |
9.3 hours |
0.1 hours |
2 minutes |
Hydrolysis t1/2 at pH 9 and 25°C |
0.8 hours |
0.7-0.8 hours |
0.004 h |
11 hours |
24.8-31.6 hours |
0.02 hours |
0.4 minutes |
Short-term toxicity to fish (LC50) |
LL50 >1000 mg/l loading rate (WAFs), equivalent to >7.3 mg/l* |
10 µg/l |
191 mg/l |
n/a |
>16 µg/l (>LOS) |
n/a |
>1.6 mg/l (>LOS) |
Short-term toxicity to aquatic invertebrates (EC50) |
EL50 272 mg/l loading rate (WAFs) * |
15 μg/l |
169 mg/l |
n/a |
>2.9 µg/l (>LOS) |
n/a |
>1.6 mg/l (>LOS) |
Algal inhibition (ErC50 and NOEC) |
EL50 (70.5 h): >988 mg/l NOELR: ≥988 mg/l* |
>22 µg/l |
ErC50 >89 mg/l; NOEC ≥89 mg/l |
n/a |
96-h EC50 >12 µg/l and 96-h NOEC ≥12 µg/l. (>LOS) |
n/a |
>1.6 mg/l (>LOS) |
Long-term toxicity to fish (NOEC) |
≥0.036 µg/l |
≥4.4 μg/l |
n/a |
n/a |
≥14 µg/l (>LOS) |
n/a |
n/a |
Long-term toxicity to aquatic invertebrates (NOEC) |
0.00378 mg/l |
NOEC 7.9 µg/l |
n/a |
n/a |
≥15 µg/l (>LOS) |
n/a |
n/a |
Sediment toxicity (NOEC) |
≥100 mg/kg dry weight, Hyalella azteca |
13 mg/kg dry weight,Lumbriculus variegatus; 44 mg/kg dry weight,Chironomus riparius |
n/a |
n/a |
Chironomus riparius 70 mg/kg dry weight |
n/a |
n/a |
Terrestrial toxicity (NOEC or EC50) |
n/a |
n/a |
n/a |
n/a |
F. Candida 377 mg/kg dry weight |
n/a |
n/a |
* The studies have been conducted at loading rates above the solubility limit of the substance. The studies indicate that the substance is not toxic at the limit of solubility.
Conclusion on classification
The substance has reliable short-term E(L)L50 values of >1000 mg/l in fish, 272 mg/l in invertebrates and >988 mg/l in algae. It has a reliable NOELR of ≥988 mg/l in algae and reliable long-term NOECs of ≥0.036 µg/l in fish and ≥0.00378 mg/l in Daphnia.
The available short- and long-term aquatic toxicity data indicate that there are no effects on aquatic organisms at the limit of solubility of the substance in water.
The substance hydrolyses slowly in water and is not readily biodegradable.
These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):
Acute toxicity: Not classified.
Chronic toxicity: Not classified.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.