When someone smokes a cigarette, tiny little wounds are created inside the fragile pink tissue of the lung. Into the lungs pour several thousand chemicals, including a number of them that not only damage the DNA but that interfere with repair of DNA. Meanwhile, the police and fire brigade of the immune system shows up, and the process of wound healing begins. New cells are created. Over and over and over, cigarette after cigarette, year after year. (Smoking is a chronic activity, as opposed to, say, inhaling fewer chemicals less directly at the occasional campfire.) In the case of smoking, the
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