In a study to be published in the July 19 issue of Nature, researchers 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use of CFCs -- widely used in refrigeration systems, aerosols, styrofoam and other products in the 1960s and 70s -- has been replaced by hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbon (HFCs) gases.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 byproduct 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," says David Ellis, lead author of the study and PhD graduate, now working in U of T's chemistry department. "We unexpectedly discovered the TFA levels have far exceeded that amount and we wanted to know why."
The researchers hypothesized 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, says 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 which can contribute to ozone depletion.
This study was funded by the Natural Sciences and Engineering Research Council of Canada; the equipment used in experiments was donated by Perkin Elmer Canada. Additional Contacts:
Department of Chemistry