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EC number: 213-773-6 | CAS number: 1009-93-4
- 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
Description of key information
In the key acute oral toxicity study in mice, conducted according to a protocol similar to OECD TG 401, but not in compliance with GLP, the LD50 value for the test substance, 2,2,4,4,6,6-hexamethylcyclotrisilazane, was concluded to be 1700 mg/kg bw (Rhône-Poulenc, 1973).
Key value for chemical safety assessment
Acute toxicity: via oral route
Endpoint conclusion
- Endpoint conclusion:
- adverse effect observed
- Dose descriptor:
- LD50
- Value:
- 1 700 mg/kg bw
- Quality of whole database:
- The study was the most recent study available, conducted according to a protocol similar to OECD TG 401 with no clear information on GLP compliance.
Acute toxicity: via inhalation route
Endpoint conclusion
- Endpoint conclusion:
- no study available
Acute toxicity: via dermal route
Endpoint conclusion
- Endpoint conclusion:
- no study available
Additional information
In the key acute oral toxicity study in mice, conducted according to a protocol similar to OECD TG 401, but not in compliance with GLP, the LD50 value for the test substance, 2,2,4,4,6,6-hexamethylcyclotrisilazane, was concluded to be 1700 mg/kg bw (Rhône-Poulenc, 1973).
2,2,4,4,6,6-Hexamethylcyclotrisilazane was administered to three male and three female mice at doses of 670, 1000, 1500, 2250 and 3370 mg/kg bw in peanut oil. No mortalities occurred in any of the test animals treated with 670 and 1000 mg/kg bw of the test substance.
After ten days, the mortalities in the other groups were as follows: 1500 mg/kg bw three out of six; 2250 mg/kg bw four out of six; 3370 mg/kg bw six out of six. At all doses tested the animals showed slight sedation, stiffness and increased sensitivity to sound and touch. At toxic doses death followed tonic convulsions, appearing during the first 24 hours. Animals which survived were symptom-free after two days.
Two supporting acute oral studies were also available. Neither study meets current guideline requirements; they do, however, add weight of evidence for acute toxicity and support the findings of the key study (DCC, 1969; DCC, 1970). The first supporting study (DCC, 1969) reported LD50 value of <500 mg/kg bw in rats, where no mortality was observed after administration of 0.252 g/kg. All animals died after administration of 0.50, 1.00, 2.00, 3.98 g/kg. The second supporting study (DCC, 1970) reported LD50 value of <1000 mg/kg bw in rats, where no deaths occurred following administration of 0.1 g/kg test substance. All animals died after administration of 1.0 and 10.0 g/kg test substance.
Two supporting acute inhalation studies were also available. The first study (DCC, 1989), conducted according to an appropriate OECD test guideline with acceptable restrictions and under GLP, did not report any mortality or clinical signs of toxicity during the 14-day study period, therefore the LC50 value would be greater than the tested concentration (≥4.9 mg/l). The restrictions were that the test concentration was not the maximum test concentration for vapours as stated in the guideline, and analytical verification of the test concentration was not performed. The second study (DCC, 1969), which did not meet current guideline requirements, concluded that the test substance, 2,2,4,4,6,6 -hexamethylcyclotrisilazane caused eye and nose irritation during 7-hour exposure.
The registration substance was also tested in a dose range finding study for skin sensitisation (see Section 7.4). The main study was terminated due to adverse effects observed in the test animals, but it was conducted according to an appropriate OECD test guideline, and in compliance with GLP (Eurofins, 2016).
Following a 6-hour occluded topical application of 25, 50, 75 and 100 % test substance in dry acetone to the flanks of 2 guinea pigs, signs of systemic toxicity and severe skin irritation (necrosis) were observed in all of the animals. One animal, treated with 2.5 and 5.0 % of test substance, showed grade 2 erythema, which was evident after 72 hours. One animal, treated with 0.5 and 1.0 % test substance, showed grade 1 erythema which was fully reversible within 72 hours.
In combination with the results of historical skin irritation studies (refer to Section 7.3), the findings of the sensitisation sighting study were taken as evidence that the registration substance should be classified as corrosive to skin. As such, it is considered that further testing for acute oral toxicity is not appropriate despite the fact that the available acute studies do not meet current guideline standards. There is sufficient evidence to classify the substance as harmful via oral exposure.
Justification for classification or non-classification
Based on the available data for, 2,2,4,4,6,6-hexamethylcyclotrisilazane, classification for Acute Toxicity Category 4, 'H302: Harmful if swallowed' is required according to Regulation (EC) No. 1272/2008.
In addition, classification for Specific Target Organ Toxicity following a single exposure (STOT SE 3) is applicable for respiratory irritation, H335: May cause respiratory irritation.
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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