Many people feel that because marijuana is a plant, that it is “all natural” and good for them. But marijuana can have similar health consequences to tobacco, especially among those who use it regularly. Frequent marijuana users have been found to suffer from chronic bronchitis, coughing on most days, excess phlegm production, shortness of breath, wheezing, and chest sounds without a cold, according to one US study. Marijuana plants can also have mold and fungi on them, as well as remnants of any chemicals used to grow them, and it is possible for users to ingest up to 70 percent of these while smoking, creating increased risks of infection and poisoning. Marijuana, like tobacco, also carries tar, which is associated with lung cancer, though this link has not been definitively proven for marijuana users. Because marijuana smokers keep smoke in their lungs longer than tobacco smokers, their lungs actually face greater exposure to tars, chemicals, and contaminants. In addition, smoking marijuana compromises the overall resistance of the lungs to disease, increasing rates of infection. For a good summary of all the potential health hazards of marijuana, see this article from the National Institute of Drug Abuse.