Trifluoro(trifluoromethoxy)ethylene

Endpoint summary

Description of key information

Basing on its physico-chemical properties PMVE is expected to primarily and rapidly distribute to the atmosphere. Only negligible amount is expected to distribute to water, sediment and soil.

Additional information

Perfluoromethyl vinyl ether (PMVE) is a gas at ambient conditions (boiling point is equal to -26 °C) and it is characterized by a limited water solubility. The value of water solubility of 31.5 mg/l was experimental determined in a completely sealed system with an atmosphere saturated with PMVE, therefore, although the value of 31.5 mg/l itself reveals a slight water solubility, it represents an overestimation of the actual water solubility of PMVE in the natural system since the experimental conditions did not represent the natural conditions.

The Henry’s Law constant of PMVE was calculated to be 32100 Pa m3/mol (HENRYWIN v3.20, EPI Suite v4.0) indicating that the substance rapidly volatizes from water to the air. In fact the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1-4 indicates that substances with a Henry's Law constant of around 1 hPa m3/mole rapidly volatilise from water.

Due to the gaseous nature of the substance and its distribution to the atmosphere, as well as the consequent difficulty to appropriately test PMVE and provide meaningful results, no experimental adsorption/desorption data are reported. However, in order to evaluate the potential adsorption to soil and sediment of PMVE despite the fact that it is expected to rapidly distribute to the atmosphere, QSAR calculation have been performed (KOCWIN model, v.2.0, EPI Suite v 4.0) resulting in Koc = 96.38 L/Kg (calculated by MCI method) and Koc = 41.68 L/Kg (calculated from log Kow). As indicated in the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7a: Endpoint Specific Guidance, Appendix R.7.1.15 (Adsorption/Desorption), substances with a Koc below 500 - 1,000 L/Kg are generally unlikely to adsorb to sediment. The estimated Koc values of PMVE indicates that the potential adsorption of PMVE to soil and sediment is low.

Basing on its physico-chemical properties PMVE is expected to primarily and rapidly distribute to the atmosphere.

This tendency is also confirmed by the results from the EQC Fugacity III Model (Version 2.02, The Canadian Centre for Environmental Modelling and Chemistry, May 2003).The Level III fugacity model predicts partitioning between four environmental compartments (air, soil, sediment and water) using a combination of default parameters and various physico-chemical parameters as input. The model was run assuming emissions only to air as no significant emissions to water are expected and considering that in case of an accidental emissions, due to its gaseous nature, PMVE would be released to air only. The environmental fate of the substance, assessed through the model, confirmed that, following emissions in air, PMVE remains in this compartment. The rates of transfer to soil and water are very low and only negligible amounts of the total emission remain in these media and in sediment.