A newly published review in the Archives of Internal Medicine confirms what has been known since 1988. Epidemiological and clinical data do not show a direct cause and effect relationship between marijuana smoking and the development of lung cancer.

Possible reasons that studies detect lung damage but not cancer in marijuana smokers include the young age of the smokers studied, the small number of people included in each study, and the lack of long-term monitoring.

What was found in marijuana smokers included the following:

• The lungs are exposed to tar (the solid residue of tobacco smoke containing byproducts of combustion)
• The macrophage cells in the alveoli (the oxygen exchange cells) that should protect against noxious substances do not work properly
• There is increased oxidative stress
• Cells in the bronchi (the air passages) show an increase in abnormal and precancerous findings

Since some bronchial cell changes appear to be precancerous, an increased risk of cancer among frequent marijuana smokers is possible.

7/15/06 14:20 JR