M.M.
Oh hon, it's going to get FAR worse than sharing chew toys. Seriously, wait till he's a toddler and eating cedar chips at the play ground, playing in toilet water, or licking a bus window. (all have happened with DS, and that's just the tip of the iceberg...)
Unless it's medical waste, I don't worry about it.
And you know what? My son is RARELY sick. He's 2.5 and has had maybe 5 colds total. So I tend to fall into the "it builds his immune system" side.
Really, don't worry about it. You simply can't prevent all the stuff he's going to get into.