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EC number: 921-774-4 | CAS number: 13763-19-4
- 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
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
Additional information
There are no in vivo or in vitro data on the toxicokinetics of decachlorotetrasilane. The following summary has therefore been prepared based on physicochemical properties of the substance itself and its hydrolysis products. Decachlorotetrasilane is an inorganic, moisture-sensitive liquid that hydrolyses very rapidly in contact with water (half-life approximately 5 seconds at 25°C and pH 4, 7 and 9 (analogue read-across)). This half-life relates to hydrolysis of the Si-Cl bonds to give decahydroxytetrasilane and hydrochloric acid. Further hydrolysis of the Si-Si bonds in decachlorotetrasilane is expected to occur rapidly, producing monosilicic acid (Si(OH)4), which condenses at concentrations above approximately 100-150 mg/l as SiO2 to give insoluble amorphous polysilicic acid (SAS). Decahydroxytetrasilane is also likely to form condensation products (polyhydroxy-polysilanes) at similar concentrations (in terms of SiO2 equivalents). The structure and predicted properties of the Si-Si containing hydrolysis products (polyhydroxy-polysilanes) and (poly)silicic acid are very similar, and distinguishing between them would be very difficult analytically.
Most, if not all of this hydrolysis and condensation will have occurred before absorption into the body, therefore relevant systemic exposure is limited to the hydrolysis products.
Human exposure can occur via the inhalation or dermal routes. Relevant inhalation exposure would be to the hydrolysis products (hydrolysis would occur rapidly when inhaled, even if a mixture of parent and hydrolysis products were present in air). The substance would also hydrolyse rapidly in contact with moist skin. The resulting HCl hydrolysis product would be severely irritating or corrosive.
Absorption
Oral
Significant oral exposure is not expected for this corrosive substance. Should it occur then gastrointestinal absorption of insoluble condensation products will be insignificant as compared to the absorption of the soluble species (Carlisle, 1986).
Inhalation
The high water solubility of decahydroxytetrasilane and monosilicic acid might lead to some of this hydrolysis product being retained in the mucous of the lungs. Damage to membranes caused by the corrosive nature of the HCl hydrolysis product might enhance the uptake. Absorption of the insoluble condensation products is not expected.
Dermal
The molecular weights of the parent and hydrolysis products favour absorption across the skin. However, the very high water solubility ( 1E+06 mg/l; which is a theoretical value and does not take into account the condensation reaction) and low predicted log Kow (-4) of the silanol hydrolysis products, decahydroxytetrasilane and monosilicic acid, suggest that they are too hydrophilic to cross the lipid rich stratum corneum. Since the other hydrolysis product, HCl is corrosive to the skin, damage to the skin might increase penetration. Absorption of the insoluble condensation products is not expected.
There are no reliable studies to check for signs of dermal toxicity.
Distribution
All absorbed material is likely to be in the form of the hydrolysis products, decahydroxytetrasilane, monosilicic acid and hydrogen chloride. Decahydroxytetrasilane and monosilicic acid are small molecules, and therefore have potential to be widely distributed, but their hydrophilic nature will limit their diffusion across membranes (including the blood-brain and blood-testes barriers) and their accumulation in fatty tissues. Human blood contains 1 mg SiO2/l of monosilicic acid (Iler, 1979). Hydrogen and chloride ions will enter the body's natural homeostatic processes.
Metabolism
Decachlorotetrasilane is rapidly hydrolysed generating HCl and decahydroxytetrasilane, which will then further hydrolyse to monosilicic acid, both will then condense to give an amorphous polydydroxy-polysilane precipitate.There are no data regarding the metabolism of decahydroxytetrasilane. Silicon is an essential trace element participating in the normal metabolism of higher animals. It is required in bone, cartilage and connective tissue formation as well as participating in other important metabolic processes. The silicon is present almost entirely as free soluble monosilicic acid (Carlisle 1986).
Excretion
The low molecular weight and high water solubility of decahydroxytetrasilane and monosilicic acid suggest that they are likely to be rapidly eliminated via the kidneys in urine. There is therefore no evidence to suggest that this substance will accumulate in the body.
Carlisle E.M. (1986) Silicon is an essential trace element in animal nutrition in Silicon Biochemistry, Ciba Foundation Symposium 121, Wiley, p123.
Iler, R.K. (1979) The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica, Wiley, p. 13.
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