radioactive PN junction die wrapped in a few atoms thick of asbestos crystal fibre - in our factory where they are assembled they come in boxes with big red stickers saying DO NOT ABRADE, USE HAZARD KIT IF BROKEN - you're a dead man walking ....
....or it could just be a tiny amount of silicon, dopant, copper wire and glass.
I wouldn't advise deliberately snorting the glass dust or eating the other ingredients but otherwise there is nothing in them except the most abundant materials on the planet so don't worry.
Consider that components involving a particular health risk, e.g. RF power transistors with beryllium oxide case have a clear warning and handling instructions in the datasheet.