Teflon products, including nonstick cookware, are probable sources of pollutants called trifluoracetate, or TFA, that accumulate in seasonal wetlands in California and Nevada, according to a report in today's issue of the journal Nature.
While researchers stress that TFA, a salt, is not toxic to humans and urge people not to throw away their Teflon pots and pans, they do argue that their findings explain a mysterious surplus of the contaminant.
"We asked, 'Where is this extra stuff coming from?' said research team leader Scott Mabury of the University of Toronto. "We think we have it."
In the study, Mabury heated pure Teflon resin to 932 degrees, collected the resulting gas and then analyzed it.
Besides cookware, Teflon products include water repellents and combustion engine additives.
TFA came under scrutiny after the 1987 Montreal protocol to protect the Earth's fragmenting ozone layer. Industrialized nations phased out refrigerants containing chlorofluorocarbons, which deplete the ozone layer. Ozone-friendlier replacements called hydrochlorofluorocarbons and hydrofluorocarbons were introduced.
However, the replacements were soon recognized as sources of TFA. Once released into the atmosphere, TFA washes back to land with rainfall. So the Montreal protocol called for TFA monitoring.
By 1995, researchers in Cambridge, Mass., speculated in Nature that TFA would concentrate in landlocked lakes and seasonal wetlands where the salt is deposited each year with rains. With no outflow from these places, TFA concentrations accumulate.
International chemical companies, including Asahi Glass Co., Ausimont, Celanese AG, Daikin Industries Ltd., DuPont Co., Elf Atochem, Honeywell International Inc., Imperial Chemical Industries, LaRoche Industries Inc., Rhodia and Solvay, commissioned an industry expert group, the Alternative Fluorocarbons Environmental Acceptability Study, to report on TFA.
In 1999, the panel concluded in the journal Human and Ecological Risk Assessment that seasonal wetland concentration of TFA would only occur "if a number of low probability events occur at the same time and endure for a long period of time." It concluded that "accumulation over several orders of magnitude appears to be highly improbable."
Thomas M. Cahill, an environmental chemist at Trent University in Ontario, has studied TFA concentration in California and Nevada and disagrees. Cahill, a former doctoral student at the University of Nevada and collaborator with the Sacramento office of the U.S. Fish and Wildlife Service, said that the Great Basin of the West has many of the most vulnerable ecosystems.
"Mono Lake in California hasn't had an outflow in recent geological times," he said. The streams flowing into it have roughly one-fourth the concentration of TFA as the lake itself, he said. This is not consistent, Cahill said, with industry assumptions that the sources of existing TFA levels are natural.
The effects of TFA in the environment are unknown. "It's only important because it's so persistent," said Mabury, the Teflon study's author.
Cahill agreed. "These compounds will not degrade in 10 or 15 years. The long-term implications are hard to tell."
Toxicity studies have shown TFA to retard the growth of certain forms of algae and some plants, including sunflowers. However, the compound has few human health ramifications. "In acute dosing experiments, it is about as toxic as table salt and about 5,000 times less toxic than nicotine," Cahill said.
So far, he said, toxic concentrations in plants have not occurred in the wild. If they do, he said, it may have implications up the food chain. "In Mono Lake, shrimp eat the algae, then birds eat the shrimp."
Cahill and Mabury--independent of one another--advised a wait-and-watch approach. "This is a new class of pollutant," Cahill said. "We don't know if it's going to have a harmful effect. The identification of another source of TFA is significant because it gives you the ability to regulate it if it does become a problem."