Lead is not exactly plutonium. You will not become a nerve-jangled moron after one exposure. But, if you're concerned about a lifetime of risk, being cautious around any dusts, fumes and or gases is prudent. Acquiring an OSHA approved cartridge mask for your tool box will ensure that you are always prepared when using paints and working around dusts. Just be sure to use the cartridge types approved for the specific agent — dust and chemical types. Personally speaking, if I were wet-sanding with emery paper and using lots of water, I'd not worry about it. Just don't grab a sandwich before you wash your hands.