Why Is Smoking Bad For Your Lungs / Heart?

Hi. These tobacco companies for some reason have been putting up to 4000 chemicals that are said to be i neach cigarette and this is the reason it is so bad for the heart and lungs, that is not natural. I can hardly believe that there could even be so many chemicals like that but apparently it's been said more than once throughout major news stream media so I am going to give it a proper account. But people like Bob Marley from Jamaica smoked green herb his ENTIRE life from a boy to adulthood and was part of his religion and he never had a hint of lung fatigue because of that dense green smoke filling his lungs into the tons of buildup if you could find a way of accumulating an entire amount throughout ones life. He ended up getting cancer in his foot from the sun always beating down on the body in a sun scorched land and they never found cancer in his lungs when he died. The tobacco companies have advertised smoking 1 green herb smoke roll as an equivalent as to an entire pack of cigarettes with their 4000 chemicals. What do you think?