If non-stick coatings such as Teflon are overheated, the give off fumes that have been proven to be poisonous to small birds such a canaries. There is no evidence that these fumes are harmful to humans.
There is a chemical used in the manufacturing process that is a known carcinogen. That chemical is not present in the finished product. The real cancer danger is in the factories. They do not allow pregnant woman to work there as there is a danger to them in the factory.
The carcinogenic chemical is much more prevalent in products such as pizza and food boxes to prevent grease from soaking through, and in clothing for its stain preventing properties.
Non-stick cookware is perfectly safe to cook with.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan