March 8, 2002 (Ira Pilgrim)

Marijuana and Cancer

The man in the street has unfortunately been sold the idea that the "breakthrough" cure for cancer is just around the corner. So he will see little sense in taking any inconvenient steps now in order to prevent a cancer that he is not going to get for another 10 or 20 years by which time, he has been told, there should be a cure.

John Cairns 1978

There is a lot of information available about tobacco and alcohol. It is possible to find out how many people smoke and how much they smoke. It is relatively simple to also find out the number of people who get cancer and what kinds of cancer. It is well established that smoking cigarettes causes lung cancer and the more you smoke, the greater the risk. There is a lot of information about alcohol. We know that heavy drinking can kill you, but that small and moderate imbibers suffer few, if any, ill effects from it, provided they don't drive when under the influence. As far as cancer is concerned, alcohol is not a factor. I have my doubts about the supposed health benefits of booze.

While it is easy to find out how many cigarettes are smoked and by how many people, that kind of information is not available for marijuana. No one knows how many people smoke pot and how much they smoke. When it comes to illegal drugs, information is hard to come by. When someone ends up in a hospital as a consequence of drug use, you can get some information and some of it may not be reliable. But that's about it.

We know that intravenous drug use is a killer. So are a variety of drugs. But information about marijuana smoking, which is probably the most widely used of the illegal drugs, is very sparse.

It is possible to get the tars from marijuana smoke and test their effect on animals. This has been done and marijuana tars are more potent carcinogens (cancer causers) than tobacco tars. Marijuana tars are potent mutagens(they will change genes), which goes along with their ability to cause cancer. There is ample evidence with most carcinogens, that the greater the exposure, the greater the risk. A good example is that the more cigarettes you smoke, the greater are your chances of getting lung cancer .

The argument has been advanced that, unlike cigarettes, no one has a two pack a day marijuana habit. However, the way that marijuana is usually smoked delivers more tar to the lungs than an equivalent amount of cigarette smoke.

There is very little in the medical literature about marijuana and cancer in people. The only paper that I would consider significant was one where, in a single hospital in Florida, the records were scanned for patients with cancer of the lung and upper respiratory tract in people under 40 years of age. They found 10 cases of respiratory tract cancer. These cancers are extremely rare in people so young. Of those, 7 were marijuana smokers. Five were heavy users and two were "regular users."

That's about it. It is hardly what you would call convincing evidence, but it is enough to make you wonder whether marijuana is as safe as some people think. Remember that we didn't find out that tobacco smoke caused lung cancer until there were a large number of cigarette smokers. Pipe and cigar smokers didn't usually inhale deeply and lung cancer is produced by the deep inhaling of tobacco smoke. Marijuana smoke is inhaled deeper and is held in the lungs for a longer time than tobacco smoke.

What I find most troubling is that accurate information about the use and long term effects of illegal substances is almost impossible to obtain. If a person knew what the probable consequences of his actions were, he could make a choice whether to heed or ignore the potential consequences. As things stand now, by the time reliable information is available, it will probably be too late.

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