Although marijuana smokers generally consume their cigarettes (joints) at a fraction of the quantity seen in tobacco smokers, legitimate concerns persist about the pulmonary effects of cannabis smoke, especially given that some evidence suggests higher levels of carcinogens and tars in cannabis cigarettes than in tobacco cigarettes (89). After adjusting for tobacco use and other potential confounders, some (90, 91) but not all (92) studies implicate cannabis consumption as a risk factor for lung cancer. Chronic cannabis use may lead to symptoms of bronchitis (93), although moderate marijuana use does not seem to be associated with these symptoms (94). Cannabis vaporizers are becoming increasingly popular and have been purported to decrease the amount of toxins delivered; thorough research investigating the comparative safety of marijuana smoking versus vaporization has not been done.
