Marijuana causing cancer

In the column What are the long term health effects of marijuana?, Cecil writes

A little further down, he writes

This seems to be a flat-out contradiction. What have I missed?

It isn’t a “flat-out contradiction”, because the one sentence speaks of carcinogenic hydrocarbons and the other speaks of carcinogenic properties generally.

But there may be more to it than that.

It might just be a consequence of the fact that tobacco smokers generally smoke more than marijuana smokers. A tobacco smoker might take several cigarette breaks over the course of a day, and I don’t know how many at home. But it’s my impression that the typical marijuana smoker will have perhaps a couple of joints a weekend. If smoke is carcinogenic, then more smoke will be more carcinogenic.

In regions where marijuana use is more acceptable than the US, have there ever been studies of lung cancer incidence in marijuana users as compared to tobacco users?

while it may have more carcenogens in general, you have to look at the bigger picture. cigarettes may have less in quantity than pot; however, the real question is how many you smoke a day. while estimates are on a ratio of about 5 to 1, cigarettes to dubbies, hazardwise. how many people do you know who smoke 20 or so dub’s a day? i would think those people have much larger issues than carcenogens, ya know? it’s not really that much more hazardous when taken in a relative context. by the way, what day is it? and more puzzling; where did i put my stash?

Chronos, that possibility occurred to me too, but if that’s what Cecil means, I think the phrasing is rather odd. That doesn’t mean marijuana in itself pales in comparison to tobacco, just that you’re unlikely to smoke so much marijuana that the risk of cancer gets to a tobacco level.

In general- inhaling smoke from burning plants is NOT good for your lungs.

It could be due to other carcinogens in Tobacco that aren’t in Marijuana or are higher in marijuana. Cadmium is a caricnogenic metal found in soil and the Tobacco plant has a rather high affinity for it, though no doubt some will be found in Marijuana. I believe there is also a Polonium isotope that is radioactive in tobacco. There is also chlorform found in manufactured cigarettes, I’m not sure if Cecil is including this, for while it is a hydrocarbon it isn’t a naturally occuring one. There’s a whole mess of other chemicals added to cigarettes. I’m with DrDeth, inhaling smoke should be avoided as much as reasonable.

Only if carcinogenic hydrocarbons are the only carcinogens found in tobacco.

I have no idea if that’s the case.

Although from the context it almost seemed that he was saying “marajuana as a carcinogen pales in comparison to tobacco” because there are fewer cases of cancer caused by marajuana. As has been pointed out, that could be due to the fact that tobacco is used more heavily. If so, though, I don’t think it makes sense to say "marajuana as a carcinogen pales . . . " Maybe "marajuana as a cause of cancer pales . . . " would be better. Yes, I know a carcinogen is something that causes cancer, but when one discusses how carcinogenic something is, one generally means how likely is a given quantity of that substance to cause cancer relative to the same quantity of other substances, not how many cases of cancer in the world are caused by that substance.

So if Cecil just meant “there are more cases of cancer caused by cigarettes than marajuana”, or if he meant “a typical cigarette smoker is more likely to get cancer than a typical marajuana smoker”, then I agree with Priceguy – he chose a rather odd way to say this. It’s not clear to me that that’s what he meant, though.

tim314, what’s the deal with changing “marijuana” to “marajuana” in Cecil’s quotes? Fair enough if that’s how* you* spell it, but that’s not how Cecil spelt it, and you’re misquoting.

book antiqua7 ptblack :cool: There are no, repeat NO, studies which definitively link marijuana smoking to cancer. The link that is espoused is theoretical and may have some truth, but it has not been proved empirically. I’m sure it depends on how much you smoke, what it is, and how hot or irritating is to you. Take the placebo; believe that it won’t hurt you. If you live in LA or a major city, there are plenty of carcinogens emitted by cars, buses, ships, BBQ’s etc. to worry about. Smoke a dubie and relax. Mind over matter. If you don’t mind, it doesn’t matter. Peace and Love

I happen to have heard this discussion, at some length, by people who could be called among the world’s leading experts in the field. I will try to summarize the consensus I heard.

First, on the relative carcinogens of the smoke, the consensus was that burned vegetable is burned vegetable matter and – given equivalent samples of tobacco and marijuana – it would be expected that they would produce similar smoke, except for a few key ingredients.

Marijuana would produce THC and other cannabinoids, most of which have amazingly low toxicity.

Tobacco would produce nicotine and other things such as polonium, which come from the commercial fertilizers used.

On balance, tobacco would probably get the nod as the more dangerous in all respects – especially if you look up the effects of nicotine.
As far as overall health effects go, the negative effects of tobacco on health have been pretty well documented. It is associated with a lot of bad stuff, from premature aging to cancer.

The biggest research study on the health effects of marijuana users was one done by Kaiser Permanente. They compared the long-term health records of 65,000 patients. They found no significant differences in the health histories of pot smokers versus non-smokers.

The lack of difference in the health records may be due to a number of things.

– Marijuana smokers may not smoke very much on average.
– In addition to carcinogens, the active ingredients in marijuana have also been shown to inhibit tumors.
– Marijuana may be consumed in other, less harmful ways than smoking.
– Marijuana just isn’t that toxic overall. According to which US Government authority you want to believe, the lethal dose of marijuana is either one-third your body weight, or 1,500 pounds, consumed in about fifteen minutes.
– There is some evidence that, when marijuana is available, some people will use marijuana instead of more harmful substances like alcohol. Marijuana might have a harmful effect, but the effect might not be seen in research because it substitutes for something that had a worse effect.

The Kaiser Permanente study can be found at

This just in:

The conclusion by Dr. Donald Tashkin, the
leading expert on respiratory effects of
marijuana smoking, that marijuana smoking does
not cause lung cancer, is a bombshell, given Dr.
Tashkin’s long history of warnings to the
- D. Gieringer, Cal NORML

Topics: MJ & Lung Cancer, Sativex, Ca DEA Raids

C-Notes July 1st 2005
by Fred Gardner

Marijuana Smoking Does Not Cause Lung Cancer, Tashkin Concludes;
Protective Effect “Not Unreasonable”

wolfman97, it seemed to me that you had reposted at our message board the text of an article under copyright, so I edited your post to remove the article. We ask that instead of posting the exact text of an article you rephrase it in your own words or condense it.
If I was in error, please e-mail me. I saved the original text of your post.

One thing I do know about tobacco is that it tends to pick up a lot of things from the surrounding soil, moreso than other plants (including MJ). Someone mentioned polonium from fertilizers, and another really big one is radium found naturally in the soil in some areas.

Almost 99% of naturally occuring radium is Radium-226 (T.5 = 1600y) which can stay in the lungs for years after being deposited there in particulate form (usually as a radium salt). Radium-226 decays into Radon-222 gas (T.5 = 3.8d) which is a pretty potent alpha particle emitter. Alpha particles usually arent much of a problem unless they get inside your body where you have no protective layers of dead skin cells. Lung epithelium is particularly succesptible to damage from radiation, a fact not helped by the usually protective surface moisture and mucous which can trap and concentrate particulate carcinogens.

The two main types of non-small cell lung carcinoma also represent the two major divisions of lung cancer demographics:

a) The long time habitual smoker or previous-smoker-turned-nonsmoker who presents with a squamous cell carcinoma usually in or near the mainstem bronchi. The current theory on why they develop tumors near the midline is that smokers tend to have more productive mucous which is flowing towards the bronchi and trachea – thus concentrating radioactive carcinogens in those areas.

b) The ‘never smoked a cigarette in their life’ type who present with an adenocarcinoma (or another rarer type such as a oat cell carcinoma) in the periphery of the lung. Less mucous flowing towards the bronchi tends to keep carcingoens deeper in the lungs.

I wont comment on the nature of second hand smoke here.

I don’t doubt that the hydrocarbons in both tobacco and MJ smoke contribute to the carcinogenic effects of both plants – what may push tobacco over the top is it’s ability to concentrate more than just hydrocarbons.

Ok, here is a breakdown of the smoke of both marijuana and tobacco. This is page 17 of Marijuana and Health, a study conduct by the Institue of Medicine and funded by the NIH (printed in 1982).

Can someone with a better scientific background than myself please point out the carcinogenic hydrocarbons in both marijuana and tobacco, as well as any other carcinogens present in one or both?

I thought instead of supposition, perhaps we could talk about what is actually there.

Good link, Bo. Note that the footnote identifies which compounds are known carcinogens.

Or, I should say, it identifies those compounds which were known carcinogens at the time. This appears to be a fairly old study, yes?

Hat trick! 1982!

I would not be suprised if Pot was found to cause lung cancer- if smoked at two packs a day. (Of course, if it did, you’d die so mellow that, well… :smiley: )

I sincerely doubt if the good Doctor Tashkin’s study had anyone who smoked one to two packs (that’s 20- 40 reefers) of Marijuana cigs every day- over a ten to twenty year period! But that is the kind of tobacco smoking that triggers lung cancer- in the vast majority of victims. (Others, especially those who have lungs damaged by coal dust, or heavy air pollution, may get unlucky even if not long term heavy smokers). In tohers words- I would be suprised if his study did find anyone who had lung cancer due to smoking pot.

The heaviest Pot user I know (who cheerfully admitted he was “addicted to the stuff”) smoked 4 joints a day . Nearly every day, sure. (maybe 6 if in “party mode”). I know he smoked for 10 years. If we took a study of tobacco users who only smoked 4 cigs a day for ten years- how many would have succumbed to Lung cancer? :dubious:

Thus, I agree with Chronos. I think it is more a matter of amount than risk. Not that I’d be surprised to find out that Pot was “less risky” than tobacco, sure. If so, then we’d expect it to be risky only if smoked for 3-4+ decades and at a pack- 3 packs a day. But I am simply not going to believe that inhaling ANY burning plant smoke into your lungs isn’t dangerous at some level. Even if it isn’t cancer, perhaps other lung problems, like those linked to SHS- brochitus, etc.

wolfman97- in your post below, you seem to blame "commercial fertilizers’- you know for a certainly that NO Pot growers use such fertilizers? :dubious: