Who said you had to smoke it? I've always acknowledged it is SLIGHTLY damaging to the lungs when smoked, but that is the fault of combustion. It pales in comparison to cigarettes and the damage is temporary and easily reversible. Vaporizers and edibles easily counter than but no, an occasional bong hit is not going to kill your lungs or give you cancer. "Other research suggests that marijuana smokers, compared to cigarette smokers, inhale more deeply and hold their breath longer." Nice.