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Key value for chemical safety assessment

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There are no data on the toxicokinetics of triethylsilane.

The following summary has therefore been prepared based on validated predictions of the physicochemical properties of the substance itself 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 predictions 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 triethylsilane, reasonable predictions or statements may be made about the potential absorption, distribution, metabolism and excretion (ADME) properties of triethylsilane.

Triethylsilane is hydrolytically stable. The hydrolysis half-lives of triethylsilane are pH 4.0 = 53.8 hours (at time period 0 -53.8 hours), 250 hours (at time period 0 -269 hours) at 20°C; 26.3 hours (at time period 0 -30.9 hours), 199 hours (at time period 0 -245 hours) at 30°C and 16.6 hours (at time period 0 -30 hours), 94.8 hours (at time period 0 -221 hours) at 50°C; 218 hours at 25°C.

pH 7.0 = 377 hours at 20°C, 314 hours at 25°C, 279 hours at 30°C and 60.7 hours at 50°C

pH 9.0 = 56.8 hours at 20°C, 39.9 hours at 30°C and 8.67 hours at 50°C

Absorption

Oral

Significant oral exposure is not expected for this 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).

Therefore, if oral exposure did occur, the molecular weight of triethylsilane (116.28) is in the favourable range and the water solubility (2 mg/mL) means that some absorption would occur.

Dermal

The fat solubility and the 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.

Although the log Kow (3.6) is in the favourable range for dermal absorption, because of the relatively low water solubility dermal absorption is likely to be minimal.

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.

Using these values for triethylsilane predicts a blood:air partition coefficient of approximately 0.05:1 meaning that, if lung exposure occurred, there would be minimal uptake into the systemic circulation.

 

Distribution

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 triethylsilane predicts that, should systemic exposure occur, potential distribution into the main body compartments would be primarily into the lipid compartment, and to a much lesser extent to the other tissues.

Tissue:blood partition coefficients

 

Log Kow

Kow

Liver

Muscle

Fat

Brain

Kidney

triethylsilane

3.6

3981.1

7.7

4.8

110.8

6.1

4.1

 

Metabolism

There are no data on the metabolism of triethylsilane. 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 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 the algorithm, the soluble fraction of triethylsilane in blood is approximately 4%. This means that once absorbed the potential for the substance to be eliminated via the kidneys in urine is low.

                                                                                  

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.