Regardless of the health concerns that arise from using Teflon, the industrial process used to produce it has caused significant issues that were covered in the documentary "The Devil We Know"[0].
Teflon itself is not the issue (unless it goes over about 260°C), but the PFAs which should have been phased out of modern non-stick coatings. The problem is if the surface is scratched from using metal utensils or scourers as this can cause PFAs to leach into the food.
It's not possible to fry in a safe range. The safe range is <500F. I use pans at a greater temperature than that for frying. Additionally, when the pans wear the surface degrades and becomes your food. This probably always occurs, but more when the products wear.
Also the vaporization of teflon is probably not a step function but a curve, and they set the safety range at some threshold. So in all likelihood you are inhaling who knows what at even the safe ranges.
