Sticky Situation: Nonstick surfaces can turn toxic at high heat

Teflon and related nonstick materials are made from an ultraslippery compound, polytetrafluoroethylene (PTFE). Studies conducted during the past 40 years by many research groups demonstrate that at high temperatures, the polymer can emit airborne poisons, an environmental group reported in a self-published review last week. The fumes can kill birds, and people breathing the emissions can develop flulike “polymer-fume fever,” the reviewers find.

HOT STUFF. A researcher uses a gun-style, noncontact thermometer to take the temperature of a PTFE-coated pan. Environmental Working Group

With widespread use of nonstick cookware, it’s likely “there is a fair amount of polymer-fume fever” each year, says Richard Wiles of the Environmental Working Group in Washington, D.C. Because the symptoms in people resemble those of a viral infection, they simply “go unrecognized,” he suspects. The group has just petitioned the Consumer Product Safety Commission to require mandatory warning labels on PTFE-bearing products that are expected to get hot.

For their analysis, the Environmental Working Group amassed 50,000 pages of peer-reviewed papers, reports, and internal company investigations of PTFE and related compounds. To date, much of this information escaped notice, Wiles says, because it was published in obscure journals and reports, many of which appeared before the federal government got tough on toxic pollutants in the mid-1970s.

As far back as the 1960s, workers in factories making polymer products were getting sick from hot PTFE, says Jane Houlihan of the Environmental Working Group. Manufacturers responded by requiring the use of respirators wherever PTFE reached 400F or hotter. In tests just last month, Houlihan’s group demonstrated that an empty nonstick pan on a home-kitchen stovetop can reach 400F within 2 minutes and 730F in 5 minutes.

At DuPont Co. in Wilmington, Del., a major U.S. maker of PTFE products under its Teflon trademark, employees wear respirators–but not from any concern about Teflon-degradation products or polymer-fume fever, says company spokesman R. Clifton Webb.

He maintains that even at 500F, PTFE-coated cookware won’t release material harmful to human health. “DuPont is aware of one published incident of a [cook] pan left unattended which resulted in a case of polymer-fume fever,” says Webb.

The Environmental Working Group says it turned up many reports linking overheated PTFE to accidental poisonings. For instance, a 1964 Aerospace Medicine paper recounted polymer-fume fever in 39 of 40 people on a plane where insulation containing PTFE overheated. A 1975 report in the Veterinary Record described polymer-fume fever in a man–and the death of five cockatiels–after a PTFE-coated fry pan overheated. And a 2000 paper in Avian Diseases traced more than 1,200 broiler-chick deaths in 3 days to the use of new heat lamps coated with PTFE.

An empty pan on a hot stovetop “can reach temperatures that would break down PTFE,” says inhalation toxicologist Günter Oberdörster of the University of Rochester (N.Y.) Medical School.

His studies have shown that at 900F (486C), PTFE emits a mix of gases and ultrafine particles that quickly kills rats. However, neither the particles nor the gases proved toxic alone.

Oberdörster suspects the fine particles, which are emitted at the higher temperatures, carried toxic gases such as hydrogen fluoride deep into the lungs.

Most intriguing, he says, is that rats inhaling nontoxic quantities of PTFE fumes for a few minutes on several days, and later exposed to typically lethal concentrations, weren’t harmed.

Oberdörster notes that with food in it, a pan will never reach temperatures that produce toxic PTFE-derived gases. In fact, he says, “you have to put it in perspective . . . . Cooking with such pans is less dangerous than driving a car.”


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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