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There are no in vivo data on the toxicokinetics of 3-(trimethoxysilyl)propanethiol.

3-(Trimethoxysilyl)propanethiol is a low volatility (predicted vapour pressure 8.1 Pa) liquid that is soluble in water (predicted water solubility 2800 mg/l at 20°C). 3-(Trimethoxysilyl)propanethiol hydrolyses rapidly in contact with water to form 3-(trihydroxysilyl)propanethiol and methanol (predicted half-life approximately 2.6 hours at 25°C and pH7). At 37.5°C and pH 7, the half life is approximately 1 hour.

Human exposure can occur via the oral, inhalation or dermal routes.

The following summary has therefore been prepared based on validated predictions of 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 other where appropriate, known or predicted physicochemical properties of 3-(trimethoxysilyl)propanethiol or its hydrolysis products, reasonable predictions or statements may be made about their potential absorption, distribution, metabolism and excretion (ADME) properties.

The toxicokinetics of methanol have been reviewed in other major reviews and are not considered further here.



When oral exposure takes place it is necessary to assume that 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).

3-(Trimethoxysilyl)propanethiol has a molecular weight of 196.34, which is  within the favourable range, and the substance is water soluble, so should oral exposure occur then it is reasonable to assume systemic exposure to 3-(trimethoxysilyl)propanethiol will occur also.

For the hydrolysis product, 3-(trihydroxysilyl)propanethiol, oral exposure to humans following hydrolysis in the gastro-intestinal tract or via the environment may be relevant. With a significantly higher solubility and lower molecular weight than the parent, then should oral exposure to 3-(trihydroxysilyl)propanethiol occur then it is reasonable to assume systemic exposure will occur also and to a greater extent than the parent.

In an acute oral toxicity study with 3-(trimethoxysilyl)propanethiol clinical signs such as sluggishness and unsteady gait indicated that absorption of test substance-related material had occurred.


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. The water solubility (2800 mg/l at 20°C, predicted) and log Kow (1.7, predicted) of 3-(trimethoxysilyl)propanethiol are therefore favourable for dermal absorption. The water solubility (1E+06 mg/l) of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, is favourable for absorption across the skin but the log Kow of -1.4 is not. Therefore potential absorption of the hydrolysis product is unlikely.

In an acute dermal toxicity study there were indications (sluggishness, unsteady gait, spasmodic movement, diarrhoea and red discharge) that absorption had occurred.


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 3-(trimethoxysilyl)propanethiol results in a blood:air coefficient of approximately 1180:1 meaning that, if lung exposure occurred there would likely be uptake into the systemic circulation. The high water solubility of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, results in a markedly higher blood:air partition coefficient (approximately 3.8E+10:1) 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-(trihydroxysilyl)propanethiol 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.

No systemic effects were observed in the available acute inhalation studies.


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 3-(trimethoxysilyl)propanethiol predicts that, should systemic exposure occur, distribution would primarily be into fat, with potential distribution into liver, muscle, brain and kidney but to a much lesser extent.

For the hydrolysis product, 3-(trihydroxysilyl)propanethiol, it is predicted there would minimal distribution into the main body compartments with tissue:blood partition coefficients of less than 1 (zero for fat).

Table 5.1: Tissue:blood partition coefficients


Log Kow
























3-(trimethoxysilyl)propanethiol is rapidly hydrolysed to 3-(trihydroxysilyl)propanethiol and methanol in the presence of moisture. There are no data regarding the metabolism of the 3-(trimethoxysilyl)propanethiol or 3-(trihydroxysilyl)propanethiol. Genetic toxicity tests in vitro showed no observable differences in effects with and without metabolic activation for 3-(trimethoxysilyl)propanethiol.


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-(trimethoxysilyl)propanethiol in blood is approximately 70% while the corresponding value for the hydrolysis product, 3-(trihydroxysilyl)propanethiol, is > 99%. Therefore these figures suggest that the hydrolysis product is likely to be effectively eliminated via the kidneys in urine whilst the parent substance would be predicted to be eliminated to a slightly lesser extent. However, as the parent is hydrolysed, the hydrolysis product will be excreted via urine, and accumulation is therefore 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.