Q: Is cannabis more damaging to the lungs than tobacco?

A: The BMA has stressed that cannabis smokers are at a high risk of developing lung cancer, bronchitis and emphysema. However, research suggests that moderate smoking of cannabis appears to pose minimal danger to the lungs. Like tobacco smoke, cannabis smoke contains a number of irritants and carcinogens. But marijuana users typically smoke much less often than tobacco smokers, and inhale less smoke.

There have been no reports of lung cancer related solely to cannabis. However, because researchers have found pre-cancerous changes in cells taken from the lungs of heavy cannabis smokers, the possibility of lung cancer from cannabis cannot be ruled out.

Unlike heavy tobacco users, heavy cannabis smokers exhibit no obstruction of the lungs' air ways, indicating that people will not develop emphysema from cannabis.

Taken from 'Marijuana Myths, Marijuana Facts', by Professors Lynn Zimmer and John P Morgan, published by the Lindesmith Centre, New York, and available from Compendium Books at pounds 12.99.