This has been known about for a long time. Apparently with cannabis the cancer causing enzyme (p450 if I remember rightly) is still produced as it is with smoking tobacco but thc itself works in competition with said enzyme and protects the cells from being damaged. Of course this means that the higher the thc levels the greater the protection from harm as with skin cancer and head tumurs et al which unfortunately is getting bad press from the pharma companies quacks.
Trychs Reviewed by Trychs on . Marijuana: THC Counters Cancer-Causing Chemicals? A new report says that Marijuana is not a cancer risk since the THC acts to counter the cancer-causing chemicals produced by it's smoke unlike tobacco where the nicotine does the opposite. The report is by Dr Robert Melamede of the Univ. of Colorado. "THC turns down the carcinogenic potential," he said stating that in studies on mice THC seems to block the enzyme that turns chemicals in smoke to their cancer promoting form. Also cannabinoids help to reduce immune regulated responses to Rating: 5