# Cancer from Marijuana **URL:** \ **Category:** Factual Questions\ **Created:** [February 27, 2001, 7:01am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033 "2001-02-27T07:01:32Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Homer](https://avatars.discourse-cdn.com/v4/letter/h/df788c/32.png) [@Homer](https://boards.straightdope.com/u/Homer)\ **Post date:** [February 27, 2001, 7:01am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/1 "2001-02-27T07:01:32Z")
A friend asked me what I always do on the SDMB and I told him that the people here could answer any question, regardless of content. He doesn’t believe me, so he posed this question to me for an answer. Let’s say that he smokes an ounce of weed a week using mainly a single chamber water bong with ice, and occassionally glass pipes, joints, blunts, etc. Let’s also say that he’s been smoking for 5 years, and has maintained his current dosage for about 2 years. Let’s also say that he has no plans to quit in the near future. What are the chances of lung cancer forming after X many years? I suppose the basic question is, how carcinogenic is marijuana? –Tim ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [February 27, 2001, 7:25am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/2 "2001-02-27T07:25:49Z")
Marijuana is very carcenogenic indeed, but nobody smokes it anywhere _near_ the quantities that they do cigarrettes, so the chances of lung cancer as a direct result are probably not very high. I am not a scientist. ---
**Author:** ![Pjen](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Pjen](https://boards.straightdope.com/u/Pjen)\ **Post date:** [February 27, 2001, 7:50am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/3 "2001-02-27T07:50:55Z")
Bob Marley! ---
**Author:** ![Steve\_Wright](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@Steve\_Wright](https://boards.straightdope.com/u/Steve_Wright)\ **Post date:** [February 27, 2001, 8:55am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/4 "2001-02-27T08:55:17Z")
Um. A survey was published in the UK last year, I think September, but I don’t have the details to hand. The risk of cancer from marijuana smoking was assessed at about seven times greater than that of smoking normal tobacco cigarettes. I think this was mostly down to different smoking habits - smoke retained in the lungs longer, filters not used, that sort of thing - rather than any higher inherent carcinogenicity of the chemicals involved. So…um. That’s why I don’t smoke. (Anything) ---
**Author:** ![Dani\_Filth](https://avatars.discourse-cdn.com/v4/letter/d/f07891/32.png) [@Dani\_Filth](https://boards.straightdope.com/u/Dani_Filth)\ **Post date:** [February 27, 2001, 9:27am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/5 "2001-02-27T09:27:32Z")
Most of the studies i’ve heard of that try to determine whether or not marijuana causes cancer fail to take one thing into account… the test subjects smoked cigarettes! But, my guess is that smoke (of any kind) is carbon monoxide. Carbon monoxide is a carcenogen. So, enough smoke of any kind _could_ give you cancer. But as Bill Maher said, “Hey, sometimes fun costs ya…” -Dani ---
**Author:** ![Maxwell\_Edison](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Maxwell\_Edison](https://boards.straightdope.com/u/Maxwell_Edison)\ **Post date:** [February 27, 2001, 3:18pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/6 "2001-02-27T15:18:00Z")
Yep, smoking anything is bad for you, but how about eating MJ in brownies or cookies? ---
**Author:** ![idiotboy](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@idiotboy](https://boards.straightdope.com/u/idiotboy)\ **Post date:** [February 27, 2001, 4:17pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/7 "2001-02-27T16:17:13Z")
> [@](#): > > \*Originally posted by Maxwell Edison \* > \*\*Yep, smoking anything is bad for you, but how about eating MJ in brownies or cookies? \*\* Well, since you’re not burning the plant, the carbon dioxide smoke doesn’t form. If you ingest the MJ, it would be like eating a salad. There’s no carcinogens in plants, unless you change their chemical properties (i.e., burning it). I’m sure you’d get cancer from smoking broccoli or lettuce as well. But in this new line of thought, **my** question would be, if you’re not burning chewing tobacco, why does it still cause cancer in the mouth? ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [February 27, 2001, 4:27pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/8 "2001-02-27T16:27:26Z")
The master himself has addressed this question: [What are the long term health effects of marijuana?](http://www.straightdope.com/classics/a2_225.html) Arjuna34 ---
**Author:** ![sqweels](https://avatars.discourse-cdn.com/v4/letter/s/f19dbf/32.png) [@sqweels](https://boards.straightdope.com/u/sqweels)\ **Post date:** [February 27, 2001, 4:30pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/9 "2001-02-27T16:30:46Z")
I think a more realistic level of marijuana use would be an average of 1 or 2 joints a week for about 20 years. Assuming that no tobacco is being used, and acknowleging that, although smaller quatities are being smoked, the smoke is held in longer, no filters, etc., what are the cancer risks? ---
**Author:** ![Steve\_Wright](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@Steve\_Wright](https://boards.straightdope.com/u/Steve_Wright)\ **Post date:** [February 27, 2001, 4:34pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/10 "2001-02-27T16:34:31Z")
Um again. I think different plants contain all sorts of different chemicals, some of which will do you good, and some of which will do you all sorts of harm. So I think “there’s no carcinogens in plants” is, um, so overly broad a generalization that somebody will be along with a counterexample. In fact, I suspect that chewing tobacco is linked to mouth cancers precisely because some plants _do_ contain carcinogens… IIRC, the chemicals which cause problems for smokers are more complex than just carbon monoxide - they are all sorts of tars, incomplete combustion products, and so on, which I, not being a chemist, would classify as “icky stuff”. If you don’t burn stuff, you don’t get combustion products (he says, stating the obvious). And if you don’t inhale it, it doesn’t get into your lungs (strikes again). So, any health risks would depend on whether marijuana contains carcinogens which (a) survive the cooking process and (b) can be absorbed by (or can in passing affect) the digestive organs. To which I confidently answer: I haven’t a clue. ---
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [February 27, 2001, 8:59pm UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/11 "2001-02-27T20:59:46Z")
> [@](#): > > \*Originally posted by sqweels \* > **I think a more realistic level of marijuana use would be an average of 1 or 2 joints a week for about 20 years.** Yeah, realistic if you’re a lightweight weenis! Although an ounce a week is awful hardcore… Anyway, I would like to chime into the chorus of "I don’t Know"s. I haven’t the foggiest. I doubt much research has been done, especially not here in the States. jb p.s.- carbon monoxide isn’t a carcinogen, right? ---
**Author:** ![Homer](https://avatars.discourse-cdn.com/v4/letter/h/df788c/32.png) [@Homer](https://boards.straightdope.com/u/Homer)\ **Post date:** [February 28, 2001, 12:55am UTC](https://boards.straightdope.com/t/cancer-from-marijuana/56033/12 "2001-02-28T00:55:39Z")
Those were his figures, and having hung around him, I believe them. Thanks for the answers. I think the column will be enough to sate him. “Ha! Not only did they know the answer, but it had _already been answered_ before you even asked it!” –Tim