Pubdate: Thu, 20 Oct 2005
Source: Windsor Star (CN ON)
Copyright: 2005 The Windsor Star
Author: Andre Picard, Canadian Press
Bookmark: (Cannabis - Medicinal - Canada)
Bookmark: (Harm Reduction)


TORONTO - Marijuana smokers are less likely to get 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 new study, published in Tuesday's edition of the medical journal Harm 
Reduction, is a review and analysis of research that has already been 

The research has important political implications in the 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 that 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 chemically, 
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 very much," she said.

Ferrence said that most carcinogens are a byproduct of combustion, so 
"anything you burn and inhale is going to be carcinogenic -- including 
tobacco and cannabis. There is no way, based on this research, that you can 
say that smoking cannabis is safe." 
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