Quote Originally Posted by Reefer Rogue
No wonder you have so many posts ;O
I know. It started last summer, back in the Spirituallity forums.

I know that anyone can say that anything foreign is harmful to your body. But, when the same harmful, foreign substance counteracts it's harmful effects, I'd rather not consider them. No one can say that marijuana smoke harms the lungs, because when it enters, it either passes through the large-flat part into the bloodstream, or you expel it.

These are the kind of studies to prove that it harms your lungs:
Quote Originally Posted by www.jointogether.org/news/headlines/inthenews/2002/marijuana-smoking-bad-for.html
Marijuana Smoking Bad for Lungs
(2002)
A new study found that smoking marijuana is just as bad for the lungs as smoking cigarettes, the New Zealand Herald reported Aug. 13.

"You can't say cannabis is safe any more than you can say tobacco is safe. The health message is clear - don't be burning vegetable matter and inhaling it," said study author Robin Taylor, associated professor at the Dunedin School of Medicine in New Zealand.

For the study, researchers examined 900 people between the ages of 18 to 26 to see how much breath they could expel forcefully from their lungs.

The researchers found that people who smoked either marijuana or tobacco expelled less air in one second than non-smokers. Furthermore, it took smokers longer to expel all the air from their lungs because their airways had narrowed slightly.

The researchers also found that participants who smoked marijuana and tobacco had even narrower airways and greater decrease in airflow.

Researchers plan to conduct a follow-up study when the participants are aged 32 to 37.
Quote Originally Posted by http://www.drugprevent.demon.co.uk/New%20look%20of%20Website/research_items/Vol2_%20Issue6.html#MJ%20Lung%20Disease
Doctors in Scotland said that smoking marijuana just once or twice a day for a number of years could lead to serious lung disease, Reuters reported March 21.
??It might be that the psychoactive part of cannabis is harmless but the actual process of smoking, whatever you are smoking, can do your lungs harm,? said Dr Martin Johnson of Glasgow Royal Infirmary.
As part of the study, Johnson and fellow scientists studied four men with a type of emphysema. There was no other genetic susceptibility or explanation for the lung disease except that all four men were heavy cannabis smokers.

But, here's the facts:

Quote Originally Posted by Tashkin, D.P. et al, "Longitudinal Changes in Respiratory Symptoms and Lung Function in Non-smokers, Tobacco Smokers, and Heavy, Habitual Smokers of Marijuana With or Without Tobacco," pp 25-36 in G. Chesher et al (eds), Marijuana: an International Research Report, Canberra: Australian Government Publishing Service (1988)
Since 1982, UCLA researchers have evaluated pulmonary function and bronchial cell characteristics in marijuana-only smokers, tobacco-only smokers, smokers of both, and non-smokers. Although they have found changes in marijuana-only smokers, the changes are much less pronounced than those found in tobacco smokers.

The nature of the marijuana-induced changes were also different, occurring primarily in the lung's large airways - not the small peripheral airways affected by tobacco smoke. Since it is small-airway inflammation that causes chronic bronchitis and emphysema, marijuana smokers may not develop these diseases.