Dr. Dovvshtein -“From R’ Elyashiv: It’s assur to *start* smoking (because sakana), but once someone is addicted, it is a tzorech for him so then it is not assur.”
This Heter of Tzorech can only be for yourself – it can’t be for Mazik. And that is what a smoker is – A Mazik – because of the second-hand smoke!