I'm one of many who have tried to reduce plastic 'ingestion', for want of a better word. Some leach chemicals when in contact with acidic or fatty foods/beverages, some leach when exposed to heat, and others just by repeated use.I like the PTB mod, it works great--and I realize they're designed to be exposed to heat--but then, so is styrofoam and that is unsafe.So my questions are: is there a natural wicking material (wool?) that does well exposed to heat? How safe *is* the nylon(?) in the PTB? Does anyone know of a non-plastic cartridge and are any in the works? What type of plastic are the cartridges made of? I'm assuming #7. And what about the little cups inside the cartridges?Are metal cartridges even advisable? It would seem that would make them more 're-usable friendly'.