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Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

There are no data on the toxicokinetics of 3-[tris(acetoxy)silyl]propyl methacrylate.

The following summary has therefore been prepared based on validated predictions of 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. 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-[tris(acetoxy)silyl]propyl methacrylate or its hydrolysis products, reasonable predictions or statements can be made about their potential absorption, distribution, metabolism and excretion (ADME) properties.

3-[tris(acetoxy)silylpropyl methacrylate hydrolyses in contact with water (predicted hydrolysis half-lives <1 minute at 25oC and pH 4, 7 and 9), generating 3-(trihydroxysilyl)propyl methacrylate and acetic acid. Human exposure can occur via the inhalation or dermal routes. Relevant inhalation and dermal exposure would be to the hydrolysis products, due to the rapid hydrolysis rate.

The toxicokinetics of acetic acid have been reviewed in other major reviews (OECD SIDS, 2005) and are not considered further here.

Absorption

Oral

Significant oral exposure is not expected for this corrosive substance.

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 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).

The hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate has a favourable molecular weight (206.27) and water solubility for absorption so should oral exposure occur then systemic exposure is likely.

Dermal

Dermal exposure would be to the hydrolysis products. Corrosive effects would be predominant due to the properties of the acetic acid.

The fat solubility and therefore potential dermal penetration of the hydrolysis product 3-(trihydroxysilyl)propyl 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.

For the hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, although it is highly soluble (predicted solubility 1E+06 mg/L), the log Kow value (-0.9) indicates it is not likely to be sufficiently lipophilic to cross the stratum corneum and therefore dermal absorption into the systemic circulation is likely to be minimal. However, as the registered substance is corrosive to skin, due to the production of acetic acid, damage to the skin may increase the potential penetration.

Inhalation

There is a Quantitative Structure-Property Relationship (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.

For the hydrolysis product 3-(trihydroxysilyl)propyl methacrylate the predicted blood:air partition coefficient is approximately 5E+11:1 meaning that significant uptake in to the systemic circulation is likely. However, the high water solubility may result in some of the hydrolysis product being retained in the mucus of the lungs so once hydrolysis has occurred, absorption is likely to slow down.

Distribution

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. No information on the log Kowand water solubility of the parent compound are available, due to the rapid hydrolysis which takes place.

For the hydrolysis product 3-(trihydroxysilyl)propyl methacrylate, distribution into the main body compartments is predicted to be minimal.

Table: Tissue:blood partition coefficients

 

Log Kow

Kow

Liver

Muscle

Fat

Brain

Kidney

3-[tris(acetoxy)silyl]propyl methacrylate

n/a

n/a

n/a

n/a

n/a

n/a

n/a

3-(trihydroxysilyl)propyl
methacrylate

-0.9

0.13

0.6

0.7

0.0

0.7

0.8

Metabolism

There are no data on the metabolism of 3-[tris(acetoxy)silyl]propyl methacrylate. However, it will hydrolyse immediately when in contact with moisture to form acetic acid and 3-(trihydroxysilyl)propyl methacrylate. Genetic toxicity tests in vitro showed no observable differences in effects with and without metabolic activation.

Excretion

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 the algorithm, the soluble fraction of the hydrolysis product 3-(trihydroxysilyl)propyl
methacrylate in blood is >99% meaning that once absorbed the hydrolysis product is likely to be eliminated via the kidneys in urine and accumulation is unlikely.

 

References

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.

OECD (2005): SIDS Initial Assessment Report for SIAM 21, Washington DC, USA, 18-21 October 2005, Methyltriacetoxysilane, CAS 4253-34-3