Kind of depends on where you measure I think
I don't see lead as an ingredient or reaction product in burning gun powder if that is the question - no transmutation of elements, it's not a nuclear reaction. I think the problem is dispersal of existing lead and encapsulating works as well for lead as for asbestos - which may be not very but I can't do more myself - I do prefer to shoot outdoors where I hope the lead is scattered more but that may as much taste as health.
My information is nowhere near current but for indoor .22 intercollegiate competition the lead around the firing line was priming compound type - lead styphenate and such.
Downrange the priming compound decreased and spray then backspray increased. Many of us have seen indications on paper of lead or lube or both coming off cast bullets like a spiral galaxy.
I haven't tested it myself but I'd expect that lacking a water curtain successive shots on a bullet trap would grind ever smaller particles and disperse them regardless of plating
(I'd think even the best snail would shake a little bit on each shot and pieces or the whole of each bullet would impact the ones that came before)
but with proper from the firing line to the target airflow and then scrubbers before the exhaust I'd hope environmental lead is minimized.
I may disagree with Mas Ayoob on a few things, likely because I'm ignorant, but I agree with him on always shoot outdoors (I have to add if you can because I don't have his resources either)