Pubdate: Thu, 20 Oct 2005 Source: Windsor Star (CN ON) Copyright: 2005 The Windsor Star Contact: http://www.canada.com/windsor/windsorstar/ Details: http://www.mapinc.org/media/501 Author: Andre Picard, Canadian Press Bookmark: http://www.mapinc.org/mmjcn.htm (Cannabis - Medicinal - Canada) Bookmark: http://www.mapinc.org/hr.htm (Harm Reduction) LESS CANCER RISK IN POT THAN TOBACCO, SAYS STUDY 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 published. 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." - --- MAP posted-by: Jo-D