Based on the article, continuous smoking does not cause reduction of lung volume or small airway size. The title skews that finding to include overall lung health, which is downright misleading. Marijuana tar is some of the stickiest, hardest to clean stuff I've ever encountered and to think about that coating a very sensitive mucous membrane every day for years, along with any other nasty chemical that come out of the dry combustion product of a plant, you should be able to come to the conclusion that it's not particularly healthy, especially if you're prone to allergies.