The answer is a qualified one. They're safe, says Robert L. Wolke, Ph.D., a professor emeritus of chemistry at the University of Pittsburgh and the author of What Einstein Told His Cook: Kitchen Science Explained, as long as they're not overheated. When they are, the coating may begin to break down (at the molecular level, so you wouldn't necessarily see it), and toxic particles and gases, some of them carcinogenic, can be released.

"There's a whole chemistry set of compounds that will come off when Teflon is heated high enough to decompose," says Wolke. "Many of these are fluorine-containing compounds, which as a class are generally toxic." But fluoropolymers, the chemicals from which these toxic compounds come, are a big part of the coating formula - and the very reason that foods don't stick to nonstick.

If the danger begins when pans overheat, then how hot is too hot? "At temperatures above 500ºF, the breakdown begins and smaller chemical fragments are released," explains Kurunthachalam Kannan, Ph.D., an environmental toxicologist at the New York State Department of Health's Wadsworth Center. DuPont, inventor and manufacturer of Teflon, agrees that 500 degrees is the recommended maximum for cooking.