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Description of key information

No repeat-dose toxicity data are available for trichloro(3-chloropropyl)silane, therefore good quality data for the related substance trimethoxy(3-chloropropyl)silane have been read-across.
Trimethoxy(3-chloropropyl)silane was tested in an inhalation OECD 422 study, whole-body in rats, up to and including the highest concentration of 100 ppm. In this study there were no signs of general toxicity. Therefore based on these results the NOAEC was established to be at least 100 ppm (867 mg/m3).
In a 90-day inhalation study in rats, conducted in accordance with OECD 413, the NOEC for trimethoxy(3-chloropropyl)silane was determined to be 5 ppm (41 mg/m3) based on treatment-related histopathological effects observed in animals in 100 ppm treatment group. These were minimal/mild hyperplasia of the urinary bladder epithelium in both sexes (Dow Corning, 1993) and species specific changes in the kidneys. It is not known whether the urinary bladder was inflated by a fixative before microscopic examination; without inflation of the urinary bladder the relevance of the hyperplasia is questionable (Wanda M, 1991). There is no evidence for genotoxicity of CPTMO. Therefore, it is highly unlikely that the minimal /mild proliferative changes of the bladder are caused by a urinary bladder carcinogen. Based on the fact that the hyperplasia of the bladder was mild / minimal and associated with a minimal inflammation (cystitis) it can presumed that if the stimulus for the inflammation is removed the hyperplasia will resolve within a matter of weeks and the urinary bladder will return to a normal histological appearance (Wanda M, 1991). A minimal / mild reversible effect is not adverse. Therefore the NOAEC is considered to be greater than or equal to 100 ppm (867 mg/m3).
The 90-day study was selected as the key study as it tested over the longest duration.
Wanda M (1991). Handbook of Toxicologic Pathology, Edited by Wanda M. Haschek and Colin G. Rousseaux, Academic Press, INC., 1991

Key value for chemical safety assessment

Additional information

There are no repeated dose toxicity data on trichloro(3-chloropropyl)silane or its hydrolysis product, 3-chloropropylsilanetriol, so good quality data for the related substance trimethoxy(3-chloropropyl)silane have been used to assess the general systemic toxicity of trichloro(3-chloropropyl)silane. Local effects from the other hydrolysis product (hydrogen chloride) are not addressed by these data.

Trichloro(3-chloropropyl)silane hydrolyses rapidly in contact with water (half-life <1 minute at pH 7), generating hydrogen chloride and 3-chloropropylsilanetriol. Trimethoxy(3-chloropropyl)silane (CAS 2530-87-2) hydrolyses more slowly at pH 7 (half-life approx. 1 hours), but under acidic conditions such as in the stomach following ingestion, much more rapid hydrolysis can be expected based on experience with other methoxysilanes. The relevant hydrolysis products are methanol and 3-chloropropylsilanetriol. Both parent materials therefore generate a common silanol hydrolysis product.

For the inhalation route, the hydrolysis rate of trimethoxy(3-chloropropyl)silane in the respiratory tract and lungs is unknown, but is likely to be slower than that of the corresponding chlorosilane. For trichloro(3-chloropropyl)silane, the species absorbed following inhalation exposure are mainly hydrolysis products, whereas for the trimethoxy substance, absorption of the parent substance may be more significant. Trimethoxy(3-chloropropyl)silane has a higher log Kowvalue (1.96) than the silanol (-1.1) therefore the proportion of inhaled material which is systemically absorbed is likely to be greater for the trimethoxy analogue than for the chlorosilane. Nevertheless, in the absence of other data, the inhalatory NOAEC for trimethoxy(3-chloropropyl)silane is considered to represent a reasonable worst-case for read-across to trichloro(3-chloropropyl)silane.

For the inhalation route, the NOEL (rat) for methanol was 0.13 mg/l (10 ppm) based on slight body weight and organ weight changes, but even effects at 1000 ppm were not considered to be toxicologically relevant. Effects for trimethoxy(3-chloropropyl)silane occurred at doses of 100 ppm and above, and were more significant than those of methanol. Therefore, the observed effects of trimethoxy(3-chloropropyl)silane cannot be attributed to methanol.

Justification for classification or non-classification

It is not considered appropriate to classify trichloro(3-chloropropyl)silane for repeated dose toxicity.