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Key value for chemical safety assessment

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There are no in vivo data on the toxicokinetics of 3-(triethoxysilyl)propiononitrile. The following summary has therefore been prepared based on validated predictions of the physicochemical properties of the substance itself and its hydrolysis products.

3-(triethoxysilyl)propiononitrile is a volatile liquid that hydrolyses in contact with water (half-life 6.5 hours at pH 7), generating ethanol and 3-propionitrilesilanetriol. Human exposure can occur via the inhalation or dermal routes. Relevant inhalation and dermal exposure would be predominantly to the parent substance.

Absorption

Oral: Significant oral exposure is not expected for this substance.

Dermal: Dermal exposure would be to the parent and hydrolysis products. The molecular weights of 3-(triethoxysilyl)propiononitrile and 3-propionitrilesilanetriol are not ideal for dermal absorption, but they would not preclude it. The predicted water solubility (1275 mg/l) and predicted log Kow (1.7) of 3-(triethoxysilyl)propiononitrile suggest that this parent substance will be absorbed effectively through the skin. Conversely, the hydrolysis product has a high water solubility (1.0E+6 mg/l), but with a log Kow of -2.85 it is not likely to be sufficiently lipophilic to cross the stratum corneum and therefore dermal absorption into the blood is likely to be low. Therefore absorption of the test substance might be expected to be significantly reduced once hydrolysis has occurred. In an acute dermal toxicity study there was some systemic toxicity, and therefore evidence of absorption.

Inhalation: The water solubility and log Kow of 3-(triethoxysilyl)propiononitrile suggest that it will be dissolved in the mucous of the respiratory tract lining, but the log Kow is optimal for absorption, so it could be passively absorbed from the mucous. The hydrolysis product is also likely to be dissolved in mucous, but is significantly less likely to be absorbed. There are no reliable inhalation studies to check for signs of systemic toxicity.

Distribution

The absorbed material is likely to be in the form of the parent and hydrolysis products, but predominantly as the parent. 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 hydrolysis product is likely to be widely distributed in the blood. Toxicity studies provide evidence for distribution to various organs, but specifically the kidneys.

Metabolism

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

Excretion

Following dermal exposure 3-(triethoxysilyl)propiononitrile is likely to be sloughed off with skin cells. The high water solubility and molecular weights of the parent and hydrolysis products mean that, once absorbed, they are likely to be excreted by the kidneys into urine.