The Chofetz Chaim said that it’s assur to smoke (I believe it’s in “Zechor L’Miriam). He gives two reasons: 1. health & 2. bitul Torah (in those days it took at least half an hour to roll the cigars).
And that was way before the surgeon general came out against it.
But, I still don’t think it’s “assur” the way that being mechalel Shabbos is assur. And he doesn’t bring it down in a halacha sefer like the Mishna Berurah.