“Marijuana smoke does not damage lungs in the same manner as tobacco smoke, according to a study released Jan. 11. The study found that smoking marijuana on an occasional basis does not appear to significantly damage the lungs.”

“Marijuana Smoke Not as Damaging as Tobacco, Says Study (ABC News)”

http://news.yahoo.com/photos/marijuana-poses-no-threat-to-lungs-1326344236-slideshow/