PTFE (Polytetrafluoroethylene) is a synthetic compound with many applications, the most well know is Teflon. So what's the worry? Well at low temperatures, Teflon is stable and nonreactive. But when you heat it up toxic fumes are released at high temperatures. These fumes can kill pet birds and can even cause flu-like symptoms in people!
The non-stick coating is made with PFOA (Perfluorooctanoic acid) which is a carcinogenic chemical. And when heated it too can emit toxic fumes while you cook.
What's considered 'high heat' you ask? Well, here's what they say: “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.
Now, you say you don't cook at that high heat, so I must be OK, right? Well check out this little test that Good Housekeeping did comparing a lightweight, medium weight and heavier non-stick pans under various cooking conditions. You might be surprised by the results, I sure was!