teflon is made of a synthetic polymer called polytetrafluoroethylene, or PTFE. It's a class of plastics known as fluoropolymers and it has many useful properties, making it very popular in scores of applications. You can find it in coatings on nonstick cookware, for example. It's also used in electronics, plumbing, and even as membranes in outdoor jackets.
PTFE has special chemical properties because it contains both carbon and fluorine atoms. Because the carbon atoms have more energy, they can form chemical bonds with other materials. However, the fluorine atoms are much larger than the carbon atoms, so they "hide" the carbon atoms from other molecules and reduce the chances of a chemical reaction.
Another reason PTFE is chemically inert is because it has a negative electrical charge, which means that it doesn't attract or repel charged particles. This also gives PTFE its nonreactive and water-resistant properties.
The problem with PTFE is that it can break down under high heat. When a PTFE-coated pan is heated to more than about 570 degrees Fahrenheit (300 degrees Celsius), the PTFE coating starts to degrade and releases toxic fumes into the air. This can lead to a medical condition called polymer fume fever.
The long-term effects of PFOAs are unknown, but there is enough concern to cause a few companies that still make Teflon to phase out the chemical by 2020. PFOAs are long-lived chemicals that build up in animal tissues, and they can stay in the body for years after exposure.