MARIJUANA SMOKE AND CANCER RISK

Health Mailbox Columnist Tara Parker-Pope answers readers' questions.

Q: Your recent article about lung cancer in people who have never
smoked begs the simple question: who never smoked what? One might
assume you are referring to tobacco. May I remind you that marijuana
is well into a third generation of mainstream population users.

- --H.B.

A: It's true that marijuana smoke contains several of the same
carcinogens as the tar from tobacco, but two recent reviews of the
scientific research have concluded that smoking marijuana probably
doesn't pose the same lung-cancer risk as smoking tobacco. This
month, the scientific journal Harm Reduction reported that although
tobacco and marijuana smoke have similar chemical properties, they
interact with the body in different ways. While the nicotine in
tobacco is known to promote lung and other cancers, the active
ingredient in marijuana, THC, appears to counter the cancer-causing
chemicals in marijuana smoke. The complete report in Harm Reduction
is available free at www.harmreductionjournal.com/content/2/1/21.

This doesn't mean marijuana smoke is risk-free. In April, the medical
journal Alcohol reviewed 16 studies of marijuana and cancer risk. The
research showed that marijuana smoke doesn't appear to increase risk
of lung, colon or oral cancers, but it may increase risk for prostate
and cervical cancers and head and neck cancers. Marijuana use during
pregnancy was linked with increased risks of childhood leukemia and
other diseases. However, the report noted that most of the studies
weren't sufficient to adequately evaluate the impact of marijuana on
cancer risk.