Out of the frying pan

Research from Canada suggests that products containing Teflon and other fluorinated polymers can release a cocktail of harmful chemicals into the environment.

In a study to be published in the July 19 issue of Nature, researchers from at the University of Toronto, Environment Canada and University of Guelph found that fluorinated polymers degrade when heated.

They produce, among other chemicals, trifluoroacetic acid (TFA), a persistent compound whose long-term effects on the environment are unknown, trace amounts of ozone-destroying chlorofluorocarbons (CFCs) and longer-chain perfluorocarboxylates, which accumulate in animal tissues.

The use of CFCs — widely used in refrigeration systems, aerosols, styrofoam and other products in the 1960s and 70s — has been replaced by hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbon (HFCs) gases.

Unlike CFCs, these gases break down in the atmosphere and return to Earth in the form of rainwater. However, the rainwater can contain TFA, an acidic by-product that takes many decades to degrade.

‘By measuring TFA levels in rainwater over the last three to four years, researchers estimated there should be 100 to 120 parts per trillion in the water by the year 2020,’ said David Ellis, lead author of the study. ‘We unexpectedly discovered the TFA levels have far exceeded that amount and we wanted to know why.’

The researchers hypothesised that fluorinated polymers like Teflon were to blame. They heated various products containing fluoropolymers at various temperatures and found they emitted up to 10 per cent of TFA.

They also discovered the average annual global production of fluorinated polymers was 40,000 tonnes in 1988, a figure that had increased by more than 200 per cent in 1997.

While research has not uncovered harmful effects of TFA on people, there is cause for concern, said Scott Mabury, who supervised the study and is a U of T chemistry professor. ‘High concentrations of TFA in water can be mildly phytotoxic (toxic to plants) but, more importantly, it will take decades for TFA to degrade. We don’t know what the long-term environmental impacts are.’

The scientists also found that fluoropolymer material releases small amounts of CFCs into the atmosphere that can contribute to ozone depletion.

DuPont, creators of Teflon, point out that non-stick coatings will not begin to deteriorate until the temperature of the cookware reaches about 500 degrees F, (260 degrees C), and significant decomposition of the coating will occur only when temperatures exceed about 660 degrees F (340 degrees C).

They add that these temperatures alone are well above the normal cooking range and that the study referred to in the Nature magazine article involved heating the fluoropolymers to temperatures as high as 932 degrees F, hundreds of degrees higher than would be realised in a kitchen environment.