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Administrative data

Link to relevant study record(s)

Description of key information

Absorption was demonstrated for the oral and dermal route (acute toxicity) and is expected for the inhalation route. A distribution through extracellular body fluids is likely. The formation of reactive metabolites is unlikely. Excretion will most likely occur via the urine. No bioaccumulation is expected.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

The main toxicokinetic properties of 1-Ethynylcyclohexanol (EC-No. 201-100-9) are assessed on the basis of its physico-chemical properties and with special regard to the results of the standard toxicity studies performed with this substance.

Specific toxicokinetics or dermal absorption studies are not available for the test item.

 

1. Relevant physico-chemical properties of 1 -Ethynylcyclohexanol

1-Ethynylcyclohexanol is a clear, colorless melted solid with a density of 0.976 g/cm³, a boiling point of 179.75 °C and a molecular weight of 124.18 g/mol. The log octanol/water partition coefficient (logPow) is 1.49 (at 25 °C). The test item has a vapor pressure of 0.4 hPa (20°C) and is of good water solubility (24.5 g/L).

 

2. Absorption:

Based on its low molecular weight, moderate logPow and relatively high water solubility 1-Ethynylcyclohexanol is likely to be absorbed in the GI tract. The moderate logPow value of 1.49 (at 25°C) indicates that the substance is lipophilic, i.e. in the logPow range between -1 and 4, and will thus diffuse well across plasma membranes. In addition, gastrointestinal absorption of 1-Ethynylcyclohexanol is considered to be triggered by passage through aqueous membrane pores or carriage with the bulk passage of water, which is favoured for small (molecular weight < 200 g/mol), water soluble substances. It is unclear whether an active transport for 1 -Ethynylcyclohexanol exists.

Overall, quantitative gastrointestinal absorption is expected for 1-Ethynylcyclohexanol, based on its physicochemical properties.

 

In view of the above considerations for the oral route of exposure, 1 -Ethynylcyclohexanol is considered to be absorbed directly across the respiratory tract epithelium by passive diffusion when its vapour or particles reach the alveolar regions of the lungs. However, based on the relative low volatility and the high boiling point exhibited by 1-Ethynylcyclohexanol, generally only low amounts of the substance will be available for inhalation under ambient conditions.

 

With respect to the physicochemical properties (molecular weight, logPow and water solubility and in view of the acute dermal toxicity data), it is concluded that dermal absorption occurred.

 

3. Distribution/Metabolism:

Distribution of 1-Ethynylcyclohexanol to CNS could be demonstrated by the clinical signs (here: anaesthesia, paralysis) observed in an acute oral toxicity study in rats.

The logPow and the good water solubility of 1 -Ethynylcyclohexanol support this conclusion.

Generally, metabolism will render a xenobiotic molecule more polar and harmless, leading to fast and quantitative excretion.

There were no indications of genotoxicity of 1-Ethynylcyclohexanol from the present mutation and cytogenetic tests (Ames-test +/- S9; BASF AG, 1999; in vitro HPRT assay & in vitro CA test; Harlan CCR, 2012). For 1 -Ethynylcyclohexanol, no conversion into a metabolite that was more cytotoxic or more genotoxic than the parent substance was noted when comparing in vitro genotoxicity test results with metabolic activation to in vitro test results without metabolic activation system. Based on this, a clear indication is given that the formation of reactive metabolites is unlikely.

 

4. Excretion:

The low molecular weight (below 300 g/molt) and good water solubility of 1-Ethynylcyclohexanol lead to the conclusion that urinary excretion will be the most relevant route of excretion in the rat. This is considered to apply also to the potential polar metabolites of 1-Ethynylcyclohexanol. The logPow indicates no potential for accumulation in the tissues.

Summary

Based on the available data on the structure, the molecular weight and the phys./chem. properties, 1-Ethynylcyclohexanol is considered to be bioavailable. Due to the low molecular weight, the chemical structure and the vapor pressure, 1 -Ethynylcyclohexanol is expected to be excreted via the urine. Based on the overall assessment of the present data, there is no indication for a bioaccumulation potential.