I recently came across a crate of sealed games for the Saturn and Dreamcast via a good friend. The games all came from various game stores that were getting rid of over stocks.
Now being the type of guy who likes to see games in motion I proceeded to open them to see what they were like. True enough most were crap as expected but what I didn't find to expect was white mold spots on three of the discs. 1 Dreamcast game and 2 Saturn games were effected out of 60 odd discs. Luckily the mold cleaned off with glasses cleaning fluid I use to clean all my discs. The worrying thing is has the mold effected the discs so much that it will re-appear? Then I though about all those collectors who keep everything sealed. It's possible that some of your games may contain mold as well!
I guess CD printing factories are not as sterile as I though.