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FC-72 is a member of the Perfluorinated Organic Chemicals, C5-C18 category. It is a liquid at room temperature with a vapor pressure of 23.77 kPa (178.3 mm Hg) at 20 °C. FC-72 water solubility is 84.1 µg/L at 23.7 °C. Its measured Henry’s law constant is 1021 atm∙m³/mol at 22.9 °C. Releases of FC-72 are expected to be to the atmosphere based upon its intended uses. Fugitive emissions may occur at transfer points. During routine use, there is no anticipated release to water or wastewater in the EU. The vapor pressure, low water solubility and high Henry’s law constant combine to move FC-72 from any terrestrial compartment into the atmosphere. Evaporation of FC-72 from surfaces is rapid. Fugacity modeling indicates that distribution from soil to air dominates over all other processes, and therefore that release to soils would result in rapid volatilization to the atmospheric compartment. With 100% of FC-72 emission directed to the atmospheric compartment, 99.996% of FC-72 was predicted to be in the gas phase in the air compartment, whereas 0.0036% was predicted to be in the gas-filled pore spaces in the soil, and 0.00014% sorbed to soil solids. The best available estimates of soil volatilization half-life are 9.0 hours for agricultural soils, 36 minutes for grassland (natural) soils, and 36 minutes for industrial soils. Once in the atmospheric compartment, this compound will not partition to terrestrial or aquatic compartments based on the same properties. Therefore, this compound will remain in the atmosphere when released from industrial applications. FC-72 contains no hydrolysable groups and is not biodegradable. Degradation in the environment is expected to be by solely by direct photolysis in the upper atmosphere. An overall half-life of 2200 years is expected through these processes. The ultimate degradation products are hydrofluoric acid (HF, CAS# 7664-39-3) and carbon dioxide. These materials are miscible in water and are completely ionized in rainwater. They are expected to undergo wet deposition with no further significant transformation upon return to the troposphere.

As FC-72 is a highly fluorinated substance, global warming and ozone depletion potentials may be of interest. USEPA states flatly that hydrofluorocarbons do not deplete ozone because they lack chlorine or bromine. Fluorine radicals do not contribute to ozone depletion because of fast quenching of F* by water or hydrogen donors, slow reaction of FO* radicals with oxygen, and obligate reformation of F* in the pathway (1). F* radicals are rapidly and irreversibly removed from the atmosphere after quenching as HF. Therefore, neither FC-72 nor any of its acidic photodegradation products contribute to ozone depletion. Global warming potential depends on three factors: absorption of infrared radiation, area of the spectrum the absorption occurs and lifetime of the material in the atmosphere. FC-72 has an estimated GWP of 9300 over a 100-year integrated time horizon.

FC-72 is not expected to partition to moist soils or surface waters. Upon accidental, direct release of FC-72 to the aquatic compartment, the chemical is expected to volatilize rapidly. In the aforementioned distribution modeling, 0.0037% of released FC-72 was predicted to be in soil, but only 0.0000088% was predicted to be in sediment and 0.0000039% in water. Members of the Perfluorinated Organic Chemicals, C5-C18 category did not show signs of biodegradation in reliable Closed Bottle (BOD) tests. In particular, a headspace biodegradation (OECD310) assay of category member FC-770 (perfluoro-N-C1,3-alkyl morpholines) showed no biodegradation. However, non-biodegradability of FC-72 in aquatic or terrestrial compartments is expected to be not relevant due to rapid volatilization from aquatic systems.

FC-72 is expected to have little potential to bioaccumulate. Given its extremely short half-life in the aquatic compartment due to volatilization, it will not exist in aquatic environments or organisms for a sufficient time to allow partitioning into lipid tissues or testing of bioconcentration under relevant conditions. The calculated log Koa of FC-72 is 0.39. This log Koa value indicates that FC-72 has a low potential to partition from air to the lipid rich tissues of air-breathing organisms.

References: 1) A.J. Colussi, M.A. Crela. 1994. Rate of the reaction between oxygen monofluoride and ozone. Implications for the atmospheric role of fluorine. Chem. Phys. Lett. Vol. 229, pp. 134-138.