In the following video we look at a typical “dirty electricity” example where a mains adapter powering an electronic device (the home broadband router) is adding copious amounts of current spikes to the household wiring.
This adapter is a common 240v to 12v adapter. It has a CE mark and various “Safety Marks” claiming to be in compliance with UK regulation. It could just be a faulty component in this power supply. Notice that the oscilloscope was showing current spikes at the main breaker box. When current spikes are introduced at any point in the house they will be present throughout the whole house. So the wiring in the floor under your bed, and in the sockets which are turned off next to your bed, the current spikes will be present even if you have an adapter that is charging a phone downstairs.
The example in this video is of a particularly bad power adapter, but to one degree or another every switched-mode power supply I have come across adds current spikes to the household mains.
As part of the House EMF Survey I check for bad power supplies like this.
For more information on the health implications see Dirty Electricity — Stealth Trigger of Disease Epidemics and Lowered Life Expectancy.