Why do exposed magnets on old toys look fucked up even when they havent been touched for years? this tech deck dudes magnets are covered in what looks like iron filling dust.

This has also happened to the hands on my old Megabloks dragons sets, where the dragons hands were supposed to "pick up" the minifigs by using a magnet embeded in each claw. Despite not being disturbed for years, those magnets looks fucked up just like these, covered in iron fillings held in weird shapes by the magnetic field.

Do all magnets in toys do this? or is this a result of being left in a garage that fluctuates in temperature? Should i clean the layer of iron fillings off the effected magnets? Or toss out all toys where the magnet have degraded? I dont need iron dust floating around my house rusting.