Fluorinated polymers¿a class of compounds that includes the non-stick novelty Teflon¿may be responsible for an increase in long-lived environmental contaminants, according to new research from Canadian scientists. Their report, published in today's issue of Nature, suggests that the degradation of fluorinated polymers at high temperatures is pumping unexpectedly large amounts of trifluroacetic acid (TFA) into the environment.
TFA enters the atmosphere when hydrochlorofluorocarbons (HCFCs) and hydroflurocarbons (HFCs) break down and it exits in rainwater. (Both HCFCs and HFCs are coolant chemicals that industries now use in place of chlorofluorocarbons (CFCs), compounds that persist longer in the atmosphere and degrade the ozone layer.) When the scientists analyzed rainwater samples, however, they found more TFA than the CFC-replacement gases could explain. "We unexpectedly discovered the TFA levels have far exceeded that amount and we wanted to know why," says David A. Ellis, a University of Toronto chemist and the lead author of the study.
The scientists guessed that the excess TFA came from human activity because there are no naturally occurring compounds that degrade to form TFA. Also, levels of TFA measured near cities were much higher than those in rural areas. The researchers suspected fluoropolymers¿which coat surfaces as varied as frying pans to car engine parts¿as the likely source.
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To test their theory, they subjected small amounts of the pure polymers to temperatures as high as those used to burn domestic waste and then analyzed the products. They discovered a variety of compounds, including TFA and hexafluoropropene (HFP), which can react efficiently with molecules in the troposphere to produce TFA. The scientists also heated commercial products containing fluoropolymers and obtained similar results. They conclude that "further studies are needed to quantify the actual emissions of these compounds from various sources."
In 1997, companies bought more than 80,000 tonnes of fluorinated polymers for commercial uses. That sales figure continues to rise, the scientists say, and could result in the accumulation of compounds in the environment. "High concentrations of TFA in water can be mildly phytotoxic [toxic to plants] but, more importantly, it will take decades for TFA to degrade," notes Scott Mabury, a University of Toronto chemistry professor who supervised the study. "We don¿t know what the long-term environmental impacts are."