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Diss Factsheets

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential

Additional information

There are no in vivo or in vitro data on the toxicokinetics of (3-chloropropyl)triethoxysilane (CAS 5089-70-3; EC 225 -805 -6).

The following summary has therefore been prepared based on the physicochemical properties of the substance itself and its hydrolysis products, using this data in algorithms that are the basis of many computer-based physiologically based pharmacokinetic or toxicokinetic (PBTK) prediction models. Although these algorithms provide a numerical value, for the purposes of this summary only qualitative statements or comparisons will be made. The main input variable for the majority of these algorithms is log Kow so by using this and, where appropriate, other known or predicted physicochemical properties of (3-chloropropyl)triethoxysilane (and its hydrolysis products), reasonable predictions or statements may be made about their potential absorption, distribution, metabolism and excretion (ADME) properties.

(3-Chloropropyl)triethoxysilane is a moisture-sensitive, volatile (30.9 Pa at 25°C) liquid that hydrolyses in contact with water with a hydrolysis half-life of < 24 min at pH 4, 35 hours at pH 7 and 2 hours at pH 9 and 25°C generating ethanol and 3-chloropropylsilanetriol.

Human exposure can occur via the inhalation or dermal routes. Relevant inhalation and dermal exposure would be predominantly to the parent substance. The toxicokinetics of ethanol is discussed elsewhere and is not included in this summary.



Significant oral exposure is not expected for this substance. However, oral exposure to humans via the environment may be relevant for the hydrolysis product, 3-chloropropylsilanetriol. When oral exposure takes place it can be assumed, except for the most extreme of insoluble substances,  that uptake through intestinal walls into the blood takes place. Uptake from intestines can be assumed to be possible for all substances that have appreciable solubility in water or lipid. Other mechanisms by which substances can be absorbed in the gastrointestinal tract include the passage of small water-soluble molecules (molecular weight up to around 200) through aqueous pores or carriage of such molecules across membranes with the bulk passage of water (Renwick, 1993).

As 3-chloropropylsilanetriol is very water soluble (1.0E+06 mg/L at 20°C (QSAR)) and has a molecular weight of approximately 157 it meets both of these criteria, so should oral exposure occur it is reasonable to assume systemic exposure will also occur. Absorption of very hydrophilic substances by passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. However, if the molecular weight is low (less than 200) the substance may pass through aqueous pores or be carried through the epithelial barrier by the bulk passage of water.


The fat solubility and therefore potential dermal penetration of a substance can be estimated by using the water solubility and log Kow values. Substances with log Kow values between 1 and 4 favour dermal absorption (values between 2 and 3 are optimal) particularly if water solubility is high. Due to the likelihood that hydrolysis of (3-chloropropyl)triethoxysilane might occur during contact with skin, exposure via this route is predicted to be to the parent and hydrolysis products. After or during deposition of a liquid on the skin, evaporation of the substance and dermal absorption occur simultaneously so the vapour pressure of a substance is also relevant.  However, (3-chloropropyl)triethoxysilane and its hydrolysis product 3-chloropropylsilanetriol both have low vapour pressures, therefore it is considered that volatilisation would be minimal and would not limit dermal absorption potential.

The predicted log Kow (3.1) of (3-chloropropyl)triethoxysilane suggest that the parent substance could be absorbed very effectively through the skin. The very high predicted water solubility (1E+06 mg/L) and low predicted log Kow of the hydrolysis product, 3-chloropropylsilanetriol, suggest that it is too hydrophilic to cross the lipid rich stratum corneum. Therefore, dermal update is likely to be low; absorption of the test substance might be expected to be significantly reduced once hydrolysis has occurred.

There were no reliable repeated dose toxicity studies to check for signs of systemic availability. There were no signs of systemic toxicity in several skin irritation studies as well as in the three acute dermal studies.


There is a QSPR to estimate the blood:air partition coefficient for human subjects as published by Meulenberg and Vijverberg (2000). The resulting algorithm uses the dimensionless Henry coefficient and the octanol:air partition coefficient (Koct:air) as independent variables.

Using these values for the parent substance, (3-chloropropyl)triethoxysilane predicts a blood:air partition coefficient of approximately 1.0E+01:1 meaning that, if lung exposure occurred there would be some uptake into the systemic circulation. For the hydrolysis product 3-chloropropylsilanetriol the predicted blood:air partition coefficient is very high (approximately 2.6E+4:1 so, once hydrolysis has occurred as it would be expected to in the lungs, then significant uptake would be expected into the systemic circulation. However, the high water solubility of 3-chloropropylsilanetriol may lead to some of it being retained in the mucus of the lungs so once hydrolysis has occurred, absorption is likely to slow down. The water solubility and log Kow of (3-chloropropyl)triethoxysilane suggest that it will be absorbed directly across the respiratory tract lining.

There are no inhalation toxicity studies on (3-chloropropyl)triethoxysilane to check for signs of systemic availability.


The absorbed material may be in the form of the parent and hydrolysis products.

The log Kow of the parent substance means that it is likely to distribute into cells and the intracellular concentration might be higher than the extracellular concentration particularly in fatty tissues. The hydrophilic nature of 3-chloropropylsilanetriol will limit its diffusion across membranes (including the blood-brain and blood-testes barriers) and its accumulation in fatty tissues.

For blood:tissue partitioning a QSPR algorithm has been developed by DeJongh et al. (1997) in which the distribution of compounds between blood and human body tissues as a function of water and lipid content of tissues and the n-octanol:water partition coefficient (Kow) is described.

Using this value for the parent substance and the silanol hydrolysis product predicts that distribution of the parent substance is likely to occur while distribution of the hydrolysis product would be minimal.

Reliable toxicity studies do not provide evidence for distribution to any particular organ or tissue.

Table 1 Tissue:blood partition coefficients


Log  Kow






















There are no data on the metabolism of (3-chloropropyl)triethoxysilane. However, it will hydrolyse gradually to form ethanol and 3-chloropropylsilanetriol once absorbed into the body. Genetic toxicity tests in vitro showed no observable differences in effects with and without metabolic activation for (3-chloropropyl)triethoxysilane.


A determinant of the extent of urinary excretion is the soluble fraction in blood. QPSRs as developed by DeJongh et al. (1997) using log Kow as an input parameter, calculate the solubility in blood based on lipid fractions in the blood assuming that human blood contains 0.7% lipids.

Using this algorithm, the soluble fraction of (3-chloropropyl)triethoxysilane in blood is approximately 10% suggesting it is likely that some of it will be effectively eliminated via the kidneys in urine while accumulation is also likely to occur. The soluble fraction of the hydrolysis product 3-chloropropylsilanetriol in blood is approximately 99% suggesting it is likely to be effectively eliminated via the kidneys in urine and accumulation is very unlikely.


Renwick A. G. (1993) Data-derived safety factors for the evaluation of food additives and environmental contaminants. Fd. Addit. Contam. 10: 275-305.

Meulenberg, C.J. and H.P. Vijverberg, Empirical relations predicting human and rat tissue:air partition coefficients of volatile organic compounds. Toxicol Appl Pharmacol, 2000. 165(3): p. 206-16.

DeJongh, J., H.J. Verhaar, and J.L. Hermens, A quantitative property-property relationship (QPPR) approach to estimate in vitro tissue-blood partition coefficients of organic chemicals in rats and humans. Arch Toxicol, 1997. 72(1): p. 17-25