Scientists believe that marijuana can be harmful to the lungs because users inhale the unfiltered smoke deeply and keep it in their lungs as long as possible. Therefore, the smoke is in direct contact with lung tissues for long time, which Cause inflammation in the lungs and effects the working process of lungs.And growth of cells are uncontrolled. Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause cancer and emphysema. Many marijuana users also smoke cigarettes, and the combined effects of smoking these two substances ( cigarettes and marijuana ) creates an increased health risk.
Marijuana smoke can contains more cancer-causing agents than tobacco smoke or anything. Examination of human lung tissue that had been exposed to marijuana smoke over a long period of time in a laboratory showed cellular changes called Metaplasia that are considered precancerous. In laboratory test, the tars from marijuana smoke have produced tumors when applied to animal skin. These studies shows that marijuana may cause cancer if used for a number of years.
