Why shouldn't you change out your brass doorknobs?
Although brass doorknobs have fallen out of demand lately, they do carry an interesting (and healthy) benefit! It's called the oligodynamic effect: the ions in the metal have a toxic effect on spores, fungi, viruses, and other germs. Imagine a doorknob that disinfects itself within 8 hours! Other such materials include copper, iron, lead and silver; on the other hand, aluminum and stainless steel have no such effect.