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EC number: 217-007-1 | CAS number: 1719-58-0
- 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:
- PNEC aqua (freshwater)
- PNEC value:
- 0.12 mg/L
- Assessment factor:
- 1 000
- Extrapolation method:
- assessment factor
- PNEC freshwater (intermittent releases):
- 1.2 mg/L
Marine water
- Hazard assessment conclusion:
- PNEC aqua (marine water)
- PNEC value:
- 0.012 mg/L
- Assessment factor:
- 10 000
- Extrapolation method:
- assessment factor
STP
- Hazard assessment conclusion:
- PNEC STP
- PNEC value:
- 7.4 mg/L
- Assessment factor:
- 10
- Extrapolation method:
- assessment factor
Sediment (freshwater)
- Hazard assessment conclusion:
- PNEC sediment (freshwater)
- PNEC value:
- 1.2 mg/kg sediment dw
- Extrapolation method:
- equilibrium partitioning method
Sediment (marine water)
- Hazard assessment conclusion:
- PNEC sediment (marine water)
- PNEC value:
- 0.12 mg/kg sediment dw
- Extrapolation method:
- equilibrium partitioning method
Hazard for air
Air
- Hazard assessment conclusion:
- no hazard identified
Hazard for terrestrial organisms
Soil
- Hazard assessment conclusion:
- PNEC soil
- PNEC value:
- 0.17 mg/kg soil dw
- Extrapolation method:
- equilibrium partitioning method
Hazard for predators
Secondary poisoning
- Hazard assessment conclusion:
- no potential for bioaccumulation
Additional information
Chloro(dimethyl)vinylsilane hydrolyses rapidly in contact with water or atmospheric moisture (estimated <1 min. at pH and 25°C), to produce dimethyl(vinyl)silanol and hydrochloric acid. The effects of hydrogen chloride on aquatic organisms are limited to those that result from changes to pH in unbuffered media. REACH guidance (ECHA 2012, 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 (2012) 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.Therefore, the environmental hazard assessment (aquatic, sediment and soil) is based on the properties of the silanol hydrolysis product,dimethyl(vinyl)silanol, in accordance with REACH guidance. As described in Section 1.3 of the CSR and Section 4 of the technical dossier, condensation reactions of the silanol are possible.
READ-ACROSS JUSTIFICATION
In order to reduce animal 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.
In moist medium, chloro(dimethy)lvinylsilane hydrolyses very rapidly (half-life < 1 min at 25°C and pH 4, 7 and 9) to dimethyl(vinyl)silanol and hydrochloric acid. Dimethyl(vinyl)silanol is a silanol with a vinyl side chain and a log Kowof 1.5.The effects of hydrochloric acid are related to effects in an unbuffered media and are assessed below.Therefore, the assessment and the read-across are based on the silanol hydrolysis product, dimethyl(vinyl)silanol.
Chloro(dimethyl)vinylsilane, its silanol hydrolysis product and the substances used as surrogates for read-across are part of a class of non-functional compounds which act via a non-polar narcosis mechanism of toxicity. Substances in this group include alkoxy- and chloro- silanes having secondary features that do not affect the toxicity of the substances. The registered substance hydrolyses very rapidly in water and therefore the selection of the surrogate substance is based on log Kow of the silanol hydrolysis product and the vinyl groups present on the side chains. Additional information is given in a supporting report (PFA (2013y) attached in Section 13 of the IUCLID 5 dossier.
In the following paragraphs the read-across approach for chloro(dimethyl)vinylsilane is assessed for each surrogate substance taking into account structure, hydrolysis rate and physico-chemical properties.
· Read-across from trimethylsilanol to chloro(dimethyl)vinylsilane:
The registered substance, chloro(dimethyl)vinylsilane (CAS 1719-58-0) is a monochlorosilane with one vinyl and two methyl groups. Hydroxytrimethylsilane, or trimethylsilanol is a monosilanol containing three methyl groups. Dimethyl(vinyl)silanol, the hydrolysis product of the registered substance on which the hazard assessment is based, and trimethylsilanol are monosilanols, with low molecular weights (102 and 90 respectively) and similar log Kow(1.5 and 1.2). The difference in log Kow is considered to be within normal experimental error and therefore read-across from trimethylsilanol to chloro(dimethyl)vinylsilane is considered valid.
Short-term data available with trimethylsilanol indicate that this substance is of low toxicity to aquatic organisms. The read-across of aquatic effects data from trimethylsilanol to dimethyl(vinyl)silanol is made in terms of the mg/l concentration of silanol without further molecular weight correction.
Read-across from dichloro(methyl)(vinyl)silane to chloro(dimethyl)vinylsilane:
The registered substance, chloro(dimethyl)vinylsilane (CAS 1719-58-0) is a monochlorosilane with one vinyl and two methyl groups. Dichloro(methyl)(vinyl)silane (CAS 124 -70 -9) is a dichlorosilane with one methyl and one vinyl group. Both substances hydrolyse very rapidly and have structurally similar silanol hydrolysis products, dimethyl(vinyl)silanol and methyl(vinyl)silanediol, respectively. In view of the very rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment. Dimethyl(vinyl)silanol and methyl(vinyl)silanediol are silanols with low MW (102 and 104 respectively) and low log Kow(1.5 and -0.05).
This read-across is used for toxicity to microorganisms endpoint.
Chloro(dimethyl)vinylsilane(CAS 1719-58-0) and dichloro(methyl)(vinyl)silane (CAS 124-70-9) are within an analogue group of substances within which, in general, there is no evidence of significant toxicity to microorganisms. The test result is converted to concentration in terms of the silanol hydrolysis product of the tested substance. The read-across from methyl(vinyl)silanediol to dimethyl(vinyl)silanol is made in terms of the mg/l concentration of silanol without further molecular weight correction.
· Read-across from trimethoxy(vinyl)silane to chloro(dimethyl)vinylsilane:
To provide evidence that the vinyl side chain does not contribute to toxicity of the registered substance read-across from trimethoxy(vinyl)silane has been used. From the available dataset, the vinyl fragment of chloro(dimethyl)vinylsilane is understood to not have any specific mode of action with respect to ecotoxicity; trimethoxy(vinyl)silane (CAS 2768-02-7) has E(L)C50 values in the range 169-210 mg/l, which are consistent with non-polar narcosis as seen with other alkoxysilanes.
· Considerations on the non-silanol hydrolysis products:
Effects on aquatic organisms arising from exposure to the other hydrolysis product of chloro(dimethyl)vinylsilane, hydrochloric acid, are thought to result from a reduction in the pH of the ambient environment to a level below their tolerable range. Aquatic ecosystems are characterized by, among other factors, their pH; the organisms of the ecosystem are adapted to these conditions. The pH of aquatic habitats can range from 6 in poorly-buffered ‘soft’ waters to 9 in well-buffered ‘hard’ waters. The tolerance of aquatic ecosystems to natural variations in pH is well understood and has been quantified and reported extensively in ecological publications and handbooks (e.g. OECD SIDS for CAS No. 7647-01-0, hydrogen chloride). It is not considered appropriate or useful to derive a single aquatic PNEC for hydrochloric acid because any effects will not be a consequence of true chemical toxicity and will be a function of, and dependent on, the buffering capacity of the environment. Physical hazards related to pH effects are consideredto be negligible in the environment because the substance and its hydrolysis products will enter the environment through a buffered WWTP before reaching the effluents or will be buffered by the surrounding environment.
Table 1 The key physicochemical parameters and ectoxicological data for the registered and surrogate substances.
CAS Number | 1719-58-0 | 1066-40-6 | 124-70 -9 | 2768-02-7 |
Chemical Name | Chloro(dimethyl)vinysilane | Trimethylsilanol | Dichloro(methyl)(vinyl)silane | Trimethoxy(vinyl)silane |
Si hydrolysis product | Dimethyl(vinyl)silanol | Trimethylsilanol | Methyl(vinyl)silanediol | Vinylsilanetriol |
Molecular weight (parent) | 120.7 | 90.2 | 141.1 | 148.2 |
Molecular weight (silanol hydrolysis product) | 102.2 | 90.2 | 104.2 | 106.2 |
log Kow(parent) | n/a | 1.2 | n/a | 1.1 |
log Kow(silanol hydrolysis product) | 1.5 | 1.2 | -0.05 | -2.0 |
Water sol (parent) | n/a | 995 mg/l | n/a | 9400 mg/l |
Water sol (silanol hydrolysis product)) | 3700 mg/l (Note: condensation reactions can occur over time, limiting the concentration dissolved in water). | 995 mg/l (Note: condensation reactions can occur over time, limiting the concentration dissolved in water). | 146000 mg/l (Note: condensation reactions can occur over time, limiting the concentration dissolved in water). | 1.0E+06 mg/l (Note: condensation reactions can occur over time, limiting the concentration dissolved in water). |
Vapour pressure (parent) | 9500 Pa | 1900 Pa | 5880 Pa | 1190 Pa |
Vapour pressure (silanol hydrolysis product) | 250 Pa | 1900 Pa | 2.11 Pa | 0.02 Pa |
Hydrolysis t1/2at pH 7 and 25°C | <1 min | n/a | <1 min | 0.2 h (at 20°C) |
Hydrolysis t1/2at pH 4 and 25°C | <1 min | n/a | <1 min | 0.04 h |
Hydrolysis t1/2at pH 9 and 25°C | <1 min | n/a | <1 min | 0.004 h |
Short-term toxicity to fish LC50 | No data | 271 mg/l | No data | 191 mg/l |
Short-term toxicity to aquatic invertebrates EC50 | No reliable data | 124 mg/l | No data | 169 mg/l |
Algal inhibition EC50 | No data | >684 mg/l (geometric mean); >750 mg/l (arithmethic mean) | No data | 210 mg/l |
Reference:
ECHA (2012b): European Chemicals Agency. Guidance on information requirements and chemical safety assessment Chapter R.16: Environmental Exposure Estimation. Version: 2.1, October 2012 (Section R.16.5.4.1. Hydrolysis)
Conclusion on classification
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.
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