Could a Cadet heater release metallic nanoparticles?
A short or arcing would most likely sound more like a buzzing (but could sound like a hiss, I guess) but would also be accompanied by smoke, a nasty &quot;fried circuitry&quot; ozoneish smell, and black soot marks near the source. I have never heard of this being a common source of danger for anything besides fire and/or shock.
I think it is way more likely that the noise you are hearing is a vibration; one that just happens to happen at a certain point of operation and coincides with a frequency that interferes with the wireless signal from your mouse's transmitter and the receiver unit.
Occam's razor: the most likely solution is almost always the solution. Take the grille off and tighten every screw you can find, whilst also looking for any signs of arcing or electrical failure.Either way, I doubt those little Cadet heaters are the cause of your illness (which I am sorry to hear about and hope you find health and happiness).