I’d be careful with emitters that are primarily alpha radiation like U238. It’s easy to dismiss them because they’re fat diabeetus particles that are simple to stop, but the flip side of that is that they are nasty when they’re not stopped. They’re a big fat thing going really, really fast, and whatever they hit is going to take a lot of damage.

Maybe the saliva on your tongue will stop it? If your tongue is relatively dry, though, you could very easily get tongue cancer.