Cadmium oxide electrical switch ban and house fires

Silver–cadmium-oxide contacts (~1% CdO) double the current-carrying capacity of light-switch contacts and prevent sustained arcing on switch-off. Sweden banned cadmium on toxicity grounds ~30 years prior to the lecture and within three years had to reverse the ban after house fires from un-extinguished switch arcs. Paracelsus's "the dose makes the poison" framing invoked.

That's true when we turn the lights off here. You break that circuit and you always get a little arc in that switch. The reason you have to pay two or three dollars, or four or five dollars, for your light switch is that there are two silver contacts in there, and the silver contacts are silver-cadmium oxide. They have about one percent cadmium oxide. Cadmium is not like thorium or cerium oxide in tungsten where you have an easy electron emitter — although to a certain extent, cadmium is an easier electron emitter than silver or any other metal. But silver has very good thermal conductivity. Cadmium, for reasons that are still not completely understood, will double the amount of current.