From the AP June 19, 2009: “Marijuana smoke has joined tobacco smoke and hundreds of other chemicals on a list of substances California regulators say cause cancer. The listing only applies to marijuana smoke, not the plant itself.
“The state agency found marijuana smoke contains 33 of the same harmful chemicals as tobacco smoke.
The findings came from a review of more than 30 scientific papers.” But does the presence of these chemicals mean more cancer for sure? That’s quite a leap. It carefully ignores human biology. It also overlooks a National Institutes of Health study published three years earlier, and reported in the Washington Post by Marc Kaufman on May 26, 2006, and elsewhere. By the way, if you look at the fine print on practically any glue you use, you’ll see the same ominous warning from the same group. After you read this, you may want to think about fixing those toys, chairs, and cup handles again.
Here are excerpts from the Washington Post article: “The largest study of its kind has unexpectedly concluded that smoking marijuana, even regularly and heavily, does not lead to lung cancer.
“Donald Tashkin of the University of California at Los Angeles, a pulmonologist, expected a positive association between marijuana use and lung cancer. There was no association at all, and even a suggestion of some protective effect.
“Earlier work established that marijuana does contain cancer-causing chemicals as potentially harmful as those in tobacco. However, marijuana also contains the chemical tetrahydrocannabinol (THC), which may kill aging or genetically damaged cells and keep them from becoming cancerous, or prevent the development of new blood vessels that supply cancer cells.” THC, by the way, is what makes marijuana…..marijuana. Could this be a potentially fruitful avenue for cancer research?
Nicotine in tobacco has the opposite effect: it inhibits the destruction of cancer-causing cells.
“The heaviest marijuana smokers had lighted up more than 22,000 times. Tashkin found that even the very heavy marijuana smokers showed no increased incidence of the three cancers studied.
“Tashkin said previous studies found that marijuana tar has a 50 percent higher concentration of chemicals linked to cancer than tobacco cigarette tar, and marijuana is inhaled deeper and held longer in the lungs.”
The study findings, presented to the American Thoracic Society International Conference, did find a 20-fold increase in lung cancer among people who smoked two or more packs of cigarettes a day.
Moral of the story:
To smoke or not to smoke marijuana? No.
That one can not be simplistic about biology? Yes. Yes.
By Robert Schneider, M.D.