I've read a lot on this subject and the "official" answer has always been: No real threat to humans. Keep in mind our forefathers and how all game thy harvested was using led - softer than the lead we use today in most cases and they lived long enough to perpetuate the species.

There are always lots of examples given by past middle-aged folks who've dined on lots of lead shot animals their entire lives and have no health issues.

If you still have concerns, follow snipers suggestions - that should eliminate all uncertainty.