I have 6-7 rolls of slide film (Kodak, Kodachrome 64) that I shot back
in 1984. They slides were stored in the carousel's I use with the
projector. (My bad.) Recently I dug up the slides and decided to scan
them into my computer for archive and enhancement. Much to my surprise,
what looked fine when projected on a wall or screen, actually had a fine
  blue & green grit covering the entire slide which was picked up by my
scanner. (HP_Scanjet 5370C with transparency adapter.) I called Kodak
customer support and they have told me that Kodachrome from that period
in time was highly susceptible to growing a fungus, which is what I am
seeing in my scanned images. The suggestion was to use a strong
Isopropyl solution and a cotton ball to clean. Haven't found anything
stronger than rubbing alcohol which is about a 4% solution. I've tried
using PEC-12, a film cleaning solution and haven't seen much of an
improvement.