The lead left in game from projectiles is a solid. It passes through our digestive tract in a day or so. I doubt it has ever or ever will make anyone sick, raise the lead levels in their blood or kill anyone. What I've always read is, if I get it right, lead oxide, that white powdery substance you see on cast bullets or other lead that has sat for a while, is what is dangerous and, fumes from lead heated over I think 800 or 900 degrees. I think someone has an agenda, (ya think?!?!), to completely ban lead and this is just one more step in the journey.
Now, premium bullets? I believe how quickly the animal is incapacitated and dies is a much better measure of the performance of any bullet than how much the expansion of a bullet or the size of the wound channel. Of the almost 100 head of big game I've killed it's about a 50/50 split with half being cast and the other half cup & core jacketed bullets and a few premium bullets that were available back then, before I went nearly completely cast. I had more game drop in its tracks when using cast bullets than any cup & core or premium bullet. Meat loss was always a heck of a lot less with cast than the other two. That really isn't a very large sampling but it is my experience and I can't ignore what I've seen. A side benefit is my cast bullets cost me less than a penny apiece, any caliber or weight. Shot placement among the two groups of bullets was about equal except that I never did a spine shot with cast and did have two or three with jacketed bullets. Oh, wait, I did break the back, right between the shoulder blades, of a 7 point buck with a 50 cal. flintlock. Shot was maybe 10 feet very nearly straight down.
That isn't to say cast bullets are better than the other two. It IS to say that neither of the other two kill any better than a good cast bullet on thin skinned game. Of course, Forsyth had no issues with taking on the most dangerous game on the planet with hardened lead round balls....in rifles of excruciatingly slow twist and immense powder charges. Definitely not the same thing we're talking about but those hardened lead balls weren't much more than about #15 on today's BHN scale.