Frying Pans Could Be Toxic
(Note - As bird owners will attest, teflon and non-stick pan coatings can kill pet birds quickly. The toxins that kill birds can't be considered beneficial for humans. The basic rule is: if you have a pet bird, throw out ALL teflon cookware. -ed)
PARIS (AFP) - Teflon and similar coatings used to make non-stick frying pans and ovens degrade at high temperatures, yielding chemicals that are potentially toxic for plants and help to destroy the ozone layer, a study published Thursday says.
These coatings, called fluorinated polymers, are liable to break down under heat to produce a nasty cocktail, according to a team of Canadian chemists and environmental biologists.
The compounds include the persistent pollutant trifluoroacetate, which is mildly toxic to plants, and types of perfluorocarboxylate which also degrade only very slowly and accumulate in animal tissues, they say.
Other substances are small quantities of chlorofluorocarbons (CFCs) and fluorocarbons, which degrade the Earth's protective ozone layer and are also greenhouse gases that stoke climate change, they add.
"We're using compounds that will persist in the environment for very long periods of time," said researcher Scott Mabury of the University of Toronto's chemistry department.
The team first placed a pure sample of fluorinated polymer in a glass tube and passed a stream of air over it.
The sample was heated to 500 degrees C. (932 F) and the resultant gases examined. It was also heated to 360 C. (680 F), a temperature that replicates the conditions at which domestic rubbish is burned in municipal incinerators.
At both temperatures, the backbone of the polymer chain split open, causing its components to rearrange into other compounds.
Tests were then carried out on commercial products with fluoropolymers that are exposed to high temperatures, such as teflonised frying pans and surgical syringes and a lubricating engine additive.
The polymers incorporated in these products decomposed in the same way as the pure sample.
The amount of potentially dangerous compounds is relatively small, but this is no cause for complacency because of the growing volume of fluorinated polymers in daily use and their unknown effects on the environment, the researchers say.
They speculate that burnt fluoropolymers are to blame for higher concentrations of trifluoroacetates that have been found in rainwater in some urban areas.
"Although the significance of any single source may be small, the incorporation of fluorinated polymers into commercial materials continues to increase, and could result in the accumulation of these compounds in the environment," they warn.
In 1988, the average annual global consumption of fluorinated polymers was 40,000 tonnes, but by 1997, this had risen by almost 220 percent, with a projected annual increase of seven percent, they say.
The study is published in Nature, the British science weekly.