BCFred, your experience from shooting indoors is nothing comparable to shotgunning. The problem with lead indoors is that it's being breathed in as you say, partly from disintegrating bullets, but mostly from the primers. Changing to steel shot doesn't change what is in the primer anyway, and it's outdoors.
None of your experience from indoor ranges has anything to do with how lead acts laying on the dirt on a trap range.
About the only environmental damage I've seen around our trap range, is the gophers, and I guarantee it's lead poisoning getting to them, but it's not from the shot on the ground.
I agree that the indoor experience doesn't apply to lead laying on the dirt as you say and the gopher type of poisoning is one that would be directly obvious if it applied to human beings and would probably have been frowned upon quite some time ago. I apologize if I got off track. Fred