Like anything, it depends on the quantities involved.What is the difference between long term lead pollution and rust pollution, I can't find anything about it?
Are we better off ingesting lead or steel in our game birds?
The digestion process can convert small amounts of iron oxide back to iron, which we need in our diets.
Whether the steel pellets would rust significantly while in the birds is the main question. Apart from anything, it depends on the composition, whereas lead is lead. It’s there and harmful from day one.
I also think we shouldn’t ignore the pressure that’s come from the naturalists and environmentalists. Personally I believe that’s more pressing than the danger to humans from lead shot in birds and has been the biggest pressure to ban lead.