Thermolysis of fluoropolymers as a potential source of halogenated organicacids in the environment

Following the introduction of hydrochlorofluorocarbon (HCFCs) and hydrofluo rocarbon (HFCs) gases as replacements for the ozone-destroying chlorofluoro carbons (CFCs), it has been discovered that HCFCs/HFCs can degrade in the a tmosphere to produce trifluoroacetic acid(1), a compound with no known loss mechanisms in the environment(2,3), and higher concentrations in natural w aters(4) have been shown to be mildly phytotoxic(5). Present environmental levels of trifluooracetic acid are not accounted by HCFC/HFC degradation al one(8-10). Here we report that thermolysis of fluorinated polymers, such as the commercial polymers Teflon and Kel-F, can also produce trifluoroacetat e and the similar compound chlorodifluoroacetate. This can occur either dir ectly, or indirectly via products that are known to degrade to these haloac etates in the atmosphere(11). The environmental significance of these findi ngs is confirmed by modelling, which indicates that the thermolysis of fluo ropolymers in industrial and consumer high-temperature applications (ovens, nonstick cooking utensils and combustion engines) is likely to be a signif icant source of trifluoroacetate in urban rain water (similar to 25 ng l(-1 ), as estimated for Toronto). Thermolysis also leads to longer chain polyfl uoro- and/or polychlorofluoro- (C3-C14) carboxylic acids which may be equal ly persistent. Some of these products have recently been linked with possib le adverse health(6) and environmental impacts and are being phased out of the US market(7). Furthermore, we detected CFCs and fluorocarbons- groups t hat can destroy ozone and act as greenhouse gases, respectively-among the o ther thermal degradation products, suggesting that continued use of fluorop olymers may also exacerbate stratospheric ozone-depletion and global warmin g.