Is the amount of lead that airplanes put out actually relevant for lead poisoning?
Yes. It's not the _worst_ thing we're doing to the general populace, by probably a decent margin, but it's not good.
Lead bioaccumulates and causes irreversible damage.
The bioaccumulative effects are well researched in all the places you’d expect to undertake expensive and generational health research.
The Man Who Accidentally Killed The Most People In History - by Veritasium