Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment

Following the introduction of hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbon (HFCs) gases as replacements for the ozone-destroying chlorofluorocarbons (CFCs), it has been discovered that HCFCs/HFCs can degrade in the atmosphere to produce trifluoroacetic acid 1 , a compound with no known loss mechanisms in the environment 2 , 3 , and higher concentrations in natural waters 4 have been shown to be mildly phytotoxic 5 . Present environmental levels of trifluooracetic acid are not accounted by HCFC/HFC degradation alone 8 , 9 , 10 . Here we report that thermolysis of fluorinated polymers, such as the commercial polymers Teflon and Kel-F, can also produce trifluoroacetate and the similar compound chlorodifluoroacetate. This can occur either directly, or indirectly via products that are known to degrade to these haloacetates in the atmosphere 11 . The environmental significance of these findings is confirmed by modelling, which indicates that the thermolysis of fluoropolymers in industrial and consumer high-temperature applications (ovens, non-stick cooking utensils and combustion engines) is likely to be a significant source of trifluoroacetate in urban rain water (∼25 ng l -1 , as estimated for Toronto). Thermolysis also leads to longer chain polyfluoro- and/or polychlorofluoro- (C3–C14) carboxylic acids which may be equally persistent. Some of these products have recently been linked with possible adverse health 6 and environmental impacts and are being phased out of the US market 7 . Furthermore, we detected CFCs and fluorocarbons—groups that can destroy ozone and act as greenhouse gases, respectively—among the other thermal degradation products, suggesting that continued use of fluoropolymers may also exacerbate stratospheric ozone-depletion and global warming.