The bullets I don't understand. Maybe there are many areas of hunting where people miss and the bulles are there to degrade in the environment. The rate at which is happens, I have no idea.
But in fishing, many people do loose their lead sinkers, and lead poisoning in lakes all over the country is a serious problem. It's been a major problem in NY. In New England, a study at Tufts found that 52% of dead loons succumbed to lead poisoning from ingestion of the lead sinkers. MNs loon population has grown from 10,000 to 12,000 in the 80s to to today, but still, over 10% of the loons in MN are dying of lead sinker ingestion. In the Pokjras region of the has the heaviest incidence of lead poisoning in a heavily fished 5-lake region in NH (44%!) - but these are very heavily fished lakes with easy access to Boston.
In WI (Turtle-Flabeau Floweage they found 1.2 sinkers/acre. This compares to 202.4 sinkers/acre in Umbagog Lake on NH-ME border and 404.7 sinkers/acre on the Missiquoi Refuge in VT.
So while it may not be a country-wide problem, it certainly is in certain areas.
Of course, the bigger problem for the loon population is the jet ski