Pubdate: Wed, 19 Oct 2005
Source: Chronicle Herald (CN NS)
Copyright: 2005 The Halifax Herald Limited
Author: Andre Picard, Globe and Mail
Note: Robert Melamede's study is at
Bookmark: (Cannabis - Popular)


TORONTO - Marijuana smokers are less likely to contract cancer than
cigarette smokers, new research suggests.

While cannabis and tobacco smoke are chemically similar, the key
difference is that cigarettes contain nicotine, which appears to
bolster the cancer-causing properties of tobacco, while cannabis
contains tetrahydrocannabinol (THC, the active ingredient in pot),
which may actually reduce the carcinogenic properties of some chemicals.

"Current knowledge does not suggest that cannabis smoke will have a
carcinogenic potential comparable to that resulting from exposure to
tobacco smoke," said Robert Melamede, chairman of the department of
biology at the University of Colorado at Colorado Springs.

The study, published in Tuesday's edition of the medical journal Harm
Reduction, is a review and analysis of previously published research.
The research has important political implications in the ongoing
debate about medical marijuana.

One of the principal reasons public-health officials and medical
experts oppose the use of marijuana as a prescription drug is the
belief that the risks outweigh the benefits, and the fear that
endorsing medical marijuana undermines anti-smoking campaigns.

Marijuana contains about four times the level of tar found in
cigarettes, and is believed to place smokers at risk of lung cancer
and other cancers related to smoking.

But Melamede said there is no solid evidence cannabis smoking
increases the risk of lung cancer or other cancers related to tobacco
smoking such as breast, colon and rectal cancer.

He said there is evidence from studies done on laboratory rats that
the THC in cannabis smoke "exerts a protective effect" against
potential carcinogens and evidence that nicotine found in cigarettes
activates the growth of tumours. "While both tobacco and cannabis
smoke have similar properties their pharmacological activities differ
greatly," Melamede said.

But Roberta Ferrence, director of the Ontario Tobacco Research Unit
and professor of public health at the University of Toronto, expressed
grave doubts about the research, likening it to splitting hairs.

"It may be that cannabis is slightly less carcinogenic but tobacco
smoke is extremely carcinogenic so that doesn't tell us much," she
said. Ferrence said most carcinogens are a byproduct of combustion, so
"anything you burn and inhale is going to be carcinogenic. There is no
way, based on this research, that you can say that smoking cannabis is

She also noted that many people who smoke marijuana mix it with
tobacco, and that makes the chemical distinctions moot. "From a
public-health perspective, smoking is smoking," Ferrence said.
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