How does marijuana affect the lungs?
Scientists believe that marijuana can be especially harmful to the lungs because users often inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Therefore, the smoke is in contact with lung tissues for long periods of time, which irritates the lungs and damages the way they work. Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause emphysema and cancer. In addition, many marijuana users also smoke cigarettes; the combined effects of smoking these two substances creates an increased health risk.
Can marijuana cause cancer?
Marijuana smoke has been found to contain more cancer-causing agents than is found in tobacco smoke. 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 suggest that it is likely that marijuana may cause cancer if used for a number of years.
How does marijuana affect the heart?
Marijuana use increases the heart rate as much as 50 percent, depending on the amount of THC. It can cause chest pain in people who have a poor blood supply to the heart - and it produces these effects more rapidly than tobacco smoke does.
Please Scroll Down to See Forums Below 
