The next time you reach for your nonstick frying pan to fry some onions, you may want to think again, say researchers at the University of Toronto, Environment Canada, and University of Guelph. They have discovered that using cookware containing teflon and other fluorinated polymers releases a host of chemicals into the environment. In a study published in the July 19 issue of the journal Nature, the researchers explain 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.
Trifluoroacetic acid is widely used in the chemical industry in processes where it is either consumed or becomes part of a chemical waste stream.
Also emitted are trace amounts of ozone-destroying chlorofluorocarbons (CFCs) and longer chain perfluorocarboxylates, which accumulate in animal tissues, said David Ellis, lead author of the study and a pH.D. candidate in the University of Toronto´s chemistry department.
The use of CFCs can contribute to ozone depletion. Once widely used in refrigeration systems, aerosols, styrofoam, and other products in the 1960s and 1970s, under international agreement CFCs have been replaced by hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbon (HFCs) gases.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 rain water. 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," said Ellis. "We unexpectedly discovered the TFA levels have far exceeded that amount and we wanted to know why," he said.
The researchers hypothesized that fluorinated polymers like teflon were to blame. They heated a variety of products containing fluoropolymers at various temperatures and found they emitted up to 10 percent of trifluoroacetic acid, TFA.
They discovered the average annual global production of fluorinated polymers was 44,000 tons in 1988. Ten years later, that figure had increased by more than 200 percent.
While research has not uncovered harmful effects of TFA on people, there is cause for concern, said Scott Mabury, University of Toronto assistant professor of analytical and environmental chemistry who supervised the study.
"High concentrations of TFA in water can be mildly phytotoxic (toxic to plants), but more importantly, it will take decades for TFA to degrade," said Mabury. "We don´t know what the long-term environmental impacts are."
Water bodies characterized by little or no outflow and high evaporation rates may have the potential to accumulate TFA, according to the U.S. Global Change Research Information Office.
"High concentrations of TFA have been observed in contemporary water and air samples, suggesting the existence of one or more large unknown sources," the Global Change Research office said. "Samples of rain and surface waters (oceans, rivers, lakes, and springs) have been obtained from many geographical areas (USA, Canada, Australia, South Africa, Germany, Israel, Ireland, France, Switzerland, Finland) and show that TFA is a ubiquitous contaminant of the hydrosphere."
There is little likelihood that TFA accumulates in the tissues of animals, the U.S. researchers said, but TFA can accumulate in plants via roots´ uptake of water, they confirmed.
To reduce emissions of these gases, nonstick cookware should not be preheated empty for longer than three minutes. The fumes can be fatal to pet birds or cause illness in people, some scientists say.
"Toxic fumes from overheated cooking pans lined with polytetrafluoroetheylene (PTFE), commonly sold under the trade names teflon and Silverstone, are a little known but increasingly frequent cause of sudden death in caged pet birds, said a Chicago-area veterinarian specializing in avian medicine. Dr. Peter Sakas of Niles Animal Hospital told the Chicago Tribune newspaper, "It is a real problem thats been going on a while, and I have been getting more and more frustrated because it is becoming more frequent, and people don´t know about it."
The University of Toronto study was funded by the Natural Sciences and Engineering Research Council of Canada. The equipment used in experiments was donated by Perkin Elmer Canada.
Chemist Dr. Roy Plunkett discovered tetrafluoroethylene resin while researching refrigerants at DuPont research laboratories. Known by its trade name, teflon, Plunkett´s discovery was found to be heat tolerant and stick resistant. After 10 years of research, teflon was introduced in 1949. Since then, it has become a coating for everything from satellite components to cookware.