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EC number: 220-011-6
CAS number: 2602-34-8
There are no reliable in vivo data on the toxicokinetics of
The following summary has therefore been prepared based on the
physicochemical properties of the substance itself and its hydrolysis
products and using this data in algorithms that are the basis of many
computer-based physiologically based pharmacokinetic or toxicokinetic
(PBTK) prediction models. 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-(2,3-epoxypropoxy)propyl]triethoxysilane, reasonable predictions or
statements may be made about its potential absorption, distribution,
metabolism and excretion (ADME) properties.
[3-(2,3-Epoxypropoxy)propyl]triethoxysilane is a
moisture-sensitive liquid that has a predicted hydrolysis half-life of
12-36 hours at pH 7 and 25°C), generating
2,3-dihydroxypropoxypropylsilanetriol and ethanol. Hydrolysis of the
alkoxy and epoxy groups will happen concurrently and at a similar rate.
Human exposure can occur via the inhalation or dermal routes. Relevant
inhalation and dermal exposure would be predominantly to the parent
The toxicokinetics of ethanol have been reviewed in other major
reviews and are not considered further here.
Significant oral exposure is not expected for this substance.
However, oral exposure to humans via the environment may be
relevant for the hydrolysis product,
2,3-dihydroxypropoxypropylsilanetriol. 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 occurs.
Uptake from intestines must 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).
2,3 -Dihydroxypropoxypropylsilanetriol is highly water soluble
(1E+06 mg/l) but its molecular weight of 242.30 is above the
favourable range. However, it is considered that should oral exposure
occur it is reasonable to assume that resulting systemic exposure is
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. With a log Kow of
2.0 and water solubility of 3300 mg/l, absorption of
[3-(2,3-epoxypropoxy)propyl]triethoxysilane across the skin is likely to
occur. 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 but as
[3-(2,3-Epoxypropoxy)propyl]triethoxysilane has a low vapour pressure
evaporation is not likely to be a factor.
The high water solubility (1E+06 mg/l) of the hydrolysis product,
2,3-dihydroxypropoxypropylsilanetriol, is favourable for absorption
across the skin but the log Kow of -3.8 is not. Therefore
absorption across the skin is not likely to occur as the substance is
likely to be too hydrophilic to cross the lipid-rich environment of the
Therefore absorption might be expected to be significantly reduced
once hydrolysis has occurred. There are no dermal studies to check for
evidence of absorption.
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
Using these values for the parent substance [3-(2,3
-epoxypropoxy)propyl]triethoxysilane, results in a blood:air partition
coefficient of approximately 2E+05:1 meaning that if lung exposure
occurred there would be uptake into the systemic circulation. The high
water solubility of the hydrolysis product,
2,3-dihydroxypropoxypropylsilanetriol, results in a markedly higher
blood:air partition coefficient (approximately 2.6E+13:1) 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
2,3-dihydroxypropoxypropylsilanetriol 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.
There are no inhalation studies to check for evidence of
For blood:tissue partitioning a QSPR algorithm has been developed
by De Jongh 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-(2,3-Epoxypropoxy)propyl]triethoxysilane predicts that, should
systemic exposure occur, distribution would primarily be into fat, with
potential slight distribution into liver, muscle, brain and kidney.
For the hydrolysis product, distribution into the main body
compartments would be minimal with tissue:blood partition coefficients
of less than 1 for all major tissues (zero for fat).
Table 1: tissue:blood partition coefficients
There are no data on the metabolism of
[3-(2,3-epoxypropoxy)propyl]triethoxysilane. However, it will hydrolyse
to form ethanol and 2,3-dihydroxypropoxypropylsilanetriol once absorbed
into the body. Genetic toxicity tests in vitro showed no
observable differences in effects with and without metabolic activation.
A determinant of the extent of urinary excretion is the soluble fraction
in blood. QPSR’s as developed by De Jongh 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-(2,3-epoxypropoxy)propyl]triethoxysilane
in blood is approximately 59% while
the corresponding value for the hydrolysis product, 2,3-dihydroxypropoxypropylsilanetriol,
is > 99%. Therefore these figures suggest that both the parent and the hydrolysis
product are likely to be effectively eliminated via the kidneys in urine
and accumulation is therefore unlikely.
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.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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