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EC number: 219-637-2 | CAS number: 2487-90-3
- 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
Hazard for air
Hazard for terrestrial organisms
Hazard for predators
Additional information
The hydrolysis half-life of trimethoxysilane (CAS 2487-90-3) is =0.2 minutes at pH 4 and pH 9, =0.3 minutes at pH 7 and 2°C; the substance will therefore undergo very rapid hydrolysis in contact with water. This half-life relates to hydrolysis of the Si-OMe bonds to give silanetriol and methanol. The Si-H bond of silanetriol reacts in water, forming monosilicic acid (Si(OH)4) as the ultimate hydrolysis product. The precise rate of this reaction is uncertain but the half-life for Si-H reactivity of trimethoxysilane is estimated as <12 hours (possibly much less than 12 hours) at pH 7 and 25°C.
Methanol will not significantly influence the hydrolysis and condensation reactions of the silanetriol species formed by initial hydrolysis of trimethoxysilane.
Monosilicic acid (Si(OH)4) condenses at concentrations above approximately 100-150 mg/L as SiO2 to give insoluble amorphous polysilicic acid.
The log Kow of monosilicic acid (Si(OH)4) is -4 and the water solubility is approximately 1.0E+6 mg/L (OECD 2004). Above 100-150 mg/L, monosilicic acid condenses to give insoluble amorphous polysilicic acid (see Section 4.8 of IUCLID for further discussion).
Methanol is miscible in water and has log Kow -0.82 to -0.64 (OECD 2004a).
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”. ECHA Guidance Chapter R.7b (ECHA 2017) states that where degradation rates fall between >1 hour and <72 hours, testing of parent and/or degradation product(s) should be considered on a case-by-case basis.
The environmental hazard assessment is therefore based on the properties of the silanol hydrolysis product, in accordance with REACH guidance.
As described below, condensation reactions of the silicic acid are possible.
The registered substance is part of a class of alkoxysilane compounds which hydrolyse rapidly or moderately rapidly to produce monosilicic acid (Si(OH)4) and another non-Si hydrolysis product. Si(OH)4 has not been isolated and only exists in dilute aqueous solution. It readily and rapidly (within minutes) condenses to give amorphous polysilicic acid at concentrations above 100 - 150 mg SiO2 / L. Depending on the pH and concentration, solutions will contain varying proportions of monosilicic acid, cyclic and linear oligomers and polysilicic acid of three-dimensional structure. Further details are given in supporting reports (PFA 2015ao and PFA 2013x) attached in Section 13.
Measured short-term toxicity to fish, Daphnia and algae data are available with the registered substance. LC50 or EC50 values for the three organisms are all >100 mg/L indicating that the substance is not acutely toxic to aquatic organisms.
References
ECHA (2016). REACH Guidance on Information Requirements and Chemical Safety Assessment Chapter R16: Environmental Exposure Assessment Version: 3.0. February 2016.
ECHA (2017). European Chemicals Agency. Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7b: Endpoint specific guidance. Version 4.0 June 2017.
OECD SIDS (2004). SIDS Initial Assessment Report for SIAM 18, Paris, France, 20-23 April, 2004, Soluble Silicates, CAS 1344-09-8 Silicic acid, sodium salt; CAS 6834-92-0 Silicic acid (H2SiO3), disodium salt; CAS 10213-79-3 Silicic acid (H2SiO3), disodium salt, pentahydrate; CAS 13517-24-3 Silicic acid (H2SiO3), disodium salt, nonahydrate; CAS 1312-76-1 Silicic acid, potassium salt.
OECD (2004a). SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1
PFA (2013x). Peter Fisk Associates. Analogue report - Ecotoxicity of (poly)silicic acid generating compounds, PFA.300.003.001.
PFA (2015ao). Peter Fisk Associates. The aquatic chemistry of inorganic silicic acid generators, PFA.404.001.001.
Conclusion on classification
The substance very rapidly hydrolyses to methanol and inorganic silicate moieties. Hydrolysis product methanol has a harmonised classification in Annex VI of Regulation No 1272/2008 and does not require classification for the environment. Hydrolysis product monosilicic acid is a naturally-occuring substance which is not harmful to aquatic organisms at relevant concentrations. All available studies with aquatic organisms report no effects at 100 mg/L in short-term toxicity studies (reference PFA 2013x).
The substance has reliable short-term E(L)C50 values of >100 mg/L in fish, >100 mg/L in invertebrates and >100 mg/L in algae. It has reliable NOEC <6.3 mg/L in algae based on biomass and growth effects.
The substance hydrolyses very rapidly in water.
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.
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