Fears about toxic chemicals put multinational in the dock.
The giant chemicals firm DuPont was hit by lawsuits last week, on behalf of 14 people who say it failed to warn them about possible dangers of chemicals related to Teflon.
The compound receiving most attention, called perfluorooctanoic acid (PFOA), is used in the manufacture of the famous non-stick pan coating, as well as in products such as carpets and clothing.
For many years there have been scientific concerns that PFOA may be toxic, and could potentially cause cancer. On 27 June, the US Environmental Protection Agency (EPA) released a draft report from its Science Advisory Board reviewing the evidence for potential health problems with PFOA. It concluded that previous studies on rats showed the chemical was a "likely" carcinogen, and advised that the EPA should carry out further tests. PFOA is currently categorised as a "possible" carcinogen.
Various studies have found PFOA in human blood and animals around the world, even in remote areas of the Arctic.
The levels needed to induce cancer in rats were much higher than those found in humans, however. And studies of industrially exposed workers have shown no adverse health link. "To date, no human health effects are known to be caused by PFOA even in workers who have significantly higher exposure levels than the general population," Dupont said in a statement on 6 July 2005.
"Consumers using products sold under the Teflon brand are safe," said Cliff Webb, spokesman for DuPont, which is based in Wilmington, Delaware. "Cookware coated with DuPont Teflon non-stick coatings does not contain PFOA," he added.
No one is sure how PFOA is spreading though, atmospheric transport seems the most likely explanation outside urban areas. "At this point we have no indication that the PFOA comes from Teflon products," says Toni Krasnic, a chemist with the EPA who helped to coordinate their review.
Research by Scott Mabury, an environmental chemist from the University of Toronto, Canada, has shown that Teflon products heated to 360 °C, well above normal cooking temperatures, can release traces of PFOA, along with a whole host of related compounds such as trifluoroacetic acid1.
Mabury has also found that there may be an indirect source of PFOA: he says that polyfluorinated alcohols can convert into PFOA in the environment2. These chemicals are produced on a much larger scale than PFOA itself, and are used to coat fabrics and paper. There are several major manufacturers of these chemicals, including DuPont, says Mabury.
Some perfluorinated compounds are at least ten times more common in the environment than PFOA itself, says Mabury. And they seem to be more toxic. These substances are also being investigated by the EPA's advisory board, says Krasnic.
As the family of perfluorinated compounds are made in a variety of different ways, Mabury is trying to use the molecular structure of compounds found in human blood to trace their origin. "It's an area that requires quite a bit more research," he says.
The US$5-billion lawsuits call for DuPont to pay damages to the plaintiffs, put warning labels on Teflon products, and set up a fund to monitor the medical effects of related chemicals.
The lawyers say they intend to argue that DuPont has known for years that chemicals involved in Teflon's manufacture, or released when it is overheated, have been linked to cancer in laboratory studies on rats.
Last year, DuPont reached an out-of-court settlement with residents who live near their chemical plant in West Virginia. The residents claimed that the company contaminated local water supplies with PFOA. DuPont did not accept liability and claims that PFOA poses no danger to the public.
EllisD. A., MaburyS. A., MartinJ. W. & MuirD. C. G. Nature, 412. 312 - 324 (2005).
EllisD. A., et al. Environ. Sci. Technol., 38. 3316 - 3321 (2004).