POT'S LOW CANCER RISK A SURPRISE FINDING

Marijuana Smoke Thought to Be Similar to Tobacco

People who smoke marijuana may be at less risk of developing lung
cancer than tobacco smokers, according to a new study.

The study of 2,200 people in Los Angeles found that even heavy
marijuana smokers were no more likely to develop lung, head or neck
cancer than non-users, in contrast with tobacco users, whose risk
increases the more they smoke.

The findings are a surprise because marijuana smoke has some of the
same cancer-causing substances as tobacco smoke, often in higher
concentrations, said the senior researcher, Donald Tashkin, a
professor at the David Geffen School of Medicine at the University of
California-Los Angeles.

One possible explanation is that THC, a key ingredient in marijuana
not present in tobacco, may inhibit tumor growth, he said in an interview.

"You can't give marijuana a completely clean bill of health," said
Tashkin, who is to present the study to a conference of the American
Thoracic Society. "I wouldn't give any smoke substance a clean bill
of health. All you can say is we haven't been able to confirm our
suspicions that marijuana might be a risk factor for lung and head
and neck cancer."

About 1,200 adults under age 60 with cancer of the lung, tongue,
mouth, throat or esophagus, took part in the study, as well as about
1,000 without cancer, between 1999 and 2003.

Marijuana use was found to be no greater or less in any of the groups
- -- 44 percent of those with lung cancer, 41 percent with head or neck
cancers, and 42 percent of those without cancer, said Tashkin.

Other studies had suggested marijuana smoking was a risk factor for
cancer, Tashkin said. Marijuana smokers inhale more deeply than
tobacco smokers and often hold the smoke in their lungs more than
four times longer, depositing more tar, he said.

The results of Tashkin's study confirm some earlier research, said
Paul Armentano, a senior policy analyst at the National Organization
for the Reform of Marijuana Laws, which advocates legalizing marijuana use.

"It'll be surprising results in light of the way marijuana has been
presented for many years by the government and the media, as a
cancer-causing agent," Armentano said.

Dr. Bertha Madras, deputy director for demand reduction at the White
House's drug policy office, said she couldn't directly comment on the
study without seeing the details.

"There is strong evidence that chronic marijuana use can lead to
adverse effect on lung function such as increased bronchitis and lung
inflammation," Madras said.

The study was funded by the National Institute on Drug Abuse, Tashkin said.