content: Qi is an air-core transformer, the same as any Tesla coil; As opposed to Tesla's designs (unlimited free energy, everywhere at all times), Qi provides only as much power as you need exactly where you need it; Qi field is only active when a Qi-compliant receiver is in proximity to the device; Qi charging is near-field - that is to say that the EM fields generated by the charger can not be detected more than a couple inches from the device, and then, only by specifically designed, highly sensitive equipment used in a controlled environment; Through use of shielding and the shape of the coils themselves, the magnetic field created by the charger is "shaped" such that it extends only into the designated charging area for the mating device; With the primary coil (charger) being magnetically coupled to the secondary (receiver), leakage is minimal;  Source: I work for an automotive supplier in an R&D facility where we are developing Qi charging for current (2018) higher-end model cars, and for general roll-out in most vehicles by the 2020s.  Qi charging is certainly less polluting than, say, wi-fi or cell signals. The frequencies used do not lend well to EM propagation (kilohertz instead of mega- or gigahertz). A Qi charger probably emits less EM noise than plugging a 5V USB charger into your wall and hooking your phone up to that. Most rechargeable devices are going to be using the Qi specification in the not-too-distant future, and by 2030, the concept of having to carry around (or otherwise keep available) various cords and adaptors in order to charge a phone will seem as quaint as we consider carrying a lantern.