One adult, who is not a member of the other adult's family, can not be in charge of telling the other adult how to live.
I would take a humorous route to try to help your friend. Promise him a whuppin' or some such thing, while laughing...if he doesn't change his "Redneck habits".
Hand him a brochure for a cardiologist's office, or a brochure showing photos of the different stages of lung cancer and tell him that they were mailed to HIS address but you received them by mistake...and then laugh and say, "Just kidding!"
Eventually, the light approach, with humor, will impress on your friend that you care about his health, and that what he is doing is self harm.
