Registration Dossier
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EC number: 201-251-0 | CAS number: 80-10-4
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
No studies are available. Based on molecular structure, molecular weight, water solibility, and octanol-water partition coefficient it can be expected that the submission substance is likely to be absorbed via the oral, dermal, and inhalation routes. Hydrolysis occurs rapidly, and systemic exposure is expected to both the parent substance and the hydrolysis product. Based on the water solubility, the registered substance and its silanol-containig hydrolysis product are likely to be distributed in the body, and excretion via the renal pathway can be expected. Bioaccumulation is not expected.
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
Additional information
There are no studies available in which the toxicokinetic properties of dichloro(diphenyl)silane have been investigated. Therefore, the toxicokinetic behaviour assessment of the substance and its hydrolysis product was assessed by its physico-chemical properties.
Dichloro(diphenyl)silane hydrolyses rapidly in contact with water (half-life 10 seconds at pH 7 and 1.5°C), generating hydrogen chloride (HCl) and diphenylsilanediol.The substance would also hydrolyse rapidly in contact with moist skin; the resulting HCl hydrolysis product would be severely irritating or corrosive. It is therefore likely that any systemic exposure to the substance will be to the hydrolysis product, diphenylsilanediol, rather than the parent substance, dichloro(diphenyl)silane. Therefore, this toxicokinetic behaviour assessment will try to predict the behaviour of the hydrolysis product diphenylsilanediol.
The molecular weight, predicted water solubility and log Kow of diphenylsilanediol are 216.3 g/mol, 580 mg/l and 2.00, respectively. The moderate log Kow (2.00) and water solubility (580 mg/l) of the hydrolysis product suggest it will have the potential to efficiently pass through biological membranes by passive diffusion.
Absorption
Oral: If ingestion occurs, the hydrolysis of the parent substance at the low pH of the stomach will be very rapid (T1/2 of 6 seconds at pH4), so any absorption of the parent substance is expected to be negligible and it is more likely to be the hydrolysis product that is absorbed. The predicted moderate water solubility (580 mg/l) of the hydrolysis product suggests it will readily dissolve in the gastrointestinal fluids. Also, the low molecular weight (216.3 g/mol) of diphenylsilanediol suggests that it may have the potential to pass through aqueous pores or be carried through the epithelial barrier by the bulk passage of water. Furthermore, the moderate log Kow (2.00) of diphenylsilanediol indicates it is likely to be absorbed by passive diffusion. There are no reliable studies to check for signs of oral toxicity.
Dermal: The moderate water solubility (580 mg/l) and log Kow (2.00) of diphenylsilanediol suggest that absorption via the dermal route is possible. However, the molecular weight of 216.3 g/mol indicates that the potential for absorption by the dermal route will be limited. QSAR based dermal permeability prediction (DERWIN V2.00.2009) using molecular weight, log Kow and water solubility, calculated a dermal penetration rate 1.69E-03 mg/cm2/h for diphenylsilanediol. This suggests that dermal penetration of the hydrolysis product, diphenylsilanediol, will be very low. Since the other hydrolysis product, HCl is corrosive to the skin; damage to the skin might increase penetration. There are no reliable studies to check for signs of dermal toxicity.
Inhalation: The vapour pressure of the parent substance (0.078 Pa) indicates that inhalation of the registered substance as a vapour will be minimal or negligible. The moderate log Kow (2.00) and water solubility (580 mg/l) of the hydrolysis product suggest that absorption from the respiratory tract epithelium by passive diffusion is likely. As with dermal exposure, damage to membranes caused by the corrosive nature of the HCl hydrolysis product might enhance the uptake. There are no reliable studies to check for signs of inhalation toxicity.
Distribution
The low molecular weight (216.3 g/mol) and moderate water solubility of diphenylsilanediol suggest that it will have the potential to diffuse through aqueous channels, pores and will be widely distributed. The log Kow of 2.00 indicates it is likely to be distributed into cells and therefore the intracellular concentration will be higher than the extracellular concentration. Hydrogen and chloride ions will enter the body’s natural homeostatic processes.
Metabolism
Dichloro(diphenyl)silane hydrolyses very rapidly to form diphenylsilanediol and HCl. There are no data regarding the enzymatic metabolism of dichloro(diphenyl)silane or diphenylsilanediol. Genetic toxicity test in vitro showed no observable differences in effects with and without metabolic activation for dichloro(diphenyl)silane and the read-across substance trichloro(phenyl)silane.
Excretion
The low molecular weight and good water solubility of the hydrolysis product suggest that they are likely to be excreted by the kidneys into urine.
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