In the wake of the passage of Vermont's recreational marijuana law, Vermont Edition looked at the health impact of smoking cannabis.
Dr. Garth Garrison, a pulmonary disease specialist at the University of Vermont Medical Center, spoke about what is currently known about smoking, smoking marijuana specifically, and cancer.
Lindholm: Right after the Legislature passed the new marijuana bill. We did a show here that went through the specifics of what is and isn't allowed under the law.
Lindholm: After that show, we received an email from Gordon in Petersburg, New York. He wrote "We have collectively spent about 50 years teaching our children and ourselves that smoking is bad and should stop. There is no longer any cigarette advertising in magazines on radio on television. Smoking pot is smoking, period. Yet advocates for pot are getting a big-time pass. Why? I think this needs to be talked about. Pot is smoke and smoke going into lungs is bad. It is known it is a known carcinogen. Why is everyone getting a pass on this aspect of the use of pot?" Well, Gordon, we thought we'd take up your line of thinking and joining us now to discuss what is known about smoking marijuana and cancer is Dr. Garth Garrison. He's a pulmonary disease specialist at the University of Vermont Medical Center.
Lindholm: Dr. Garrison welcome to Vermont Edition.
Garrison: Hi. Thanks for having me.
Lindholm: So is marijuana a known carcinogen?
Garrison: Well you know studying marijuana has been really challenging. There have been some real barriers to studying its effects — You know it's legal status. The different amounts that people have smoked, the different products that people smoke.
Garrison: What we know right now in terms of the link with cancer is that it is a burned bio biomass product which is going to be harmful to the lungs. There's been several series looking at associations between cannabis smoking and lung cancer. The evidence is a little bit conflicting I think right now we're sort of concerned now that it's becoming more common that we're going to start seeing more and more evidence that there's a link.
Lindholm: We know things like tar and nicotine carbon monoxide in cigarette smoke are bad for our lungs. Are there similar chemicals in marijuana smoke that we're concerned about?
Garrison: Yeah, there are some of the components that are very similar between the two. And again, anytime time you burn biomass and inhale it there's harmful materials that are being brought into the lungs. We know that that smoke is irritating to the lining of the lung. People who smoke chronically have increased risk of having ongoing respiratory symptoms — so having sputum production, airway swelling sometimes wheeze, occasionally shortness of breath — so the sense is definitely there that that a lot of the effects are very similar and really the differences in the effects may be related to that dose of their frequency that people are smoking.
Lindholm: So just to clarify: What we're talking about here is the fact that smoking anything is bad — if you're smoking oregano, if you're smoking a leaf it's that you're turning that material you're combusting it and putting that smoke into your lungs and that is partly where this danger lies.
Garrison: Yeah. When you burn organic material you generate a whole bunch of different kinds of products and a number of those can be carcinogenic. In addition, different plants have to go in different areas may take up things from the soil like cigarette smoking there's cadmium and things that are a part of the smoke that can also be inhaled. So you get a whole sort of toxic mixture of things that enter the lungs and can cause damage.
Lindholm: You mentioned that some of the concerns are about how marijuana is smoked and how often. And you know you think about it compared to smoking cigarettes marijuana you sort of draw it deep into your lungs and hold it there which is a little bit different than how people smoke cigarettes. On the other hand, you know there are cigarette smokers who are smoking a pack or more a day and even with a filter you're still getting some of that carcinogenic material into your lungs and you're still smoking. So when you start to weigh the balances comparing to cigarettes how do you do that with marijuana?
Garrison: It's really challenging and that's been some of the problems. One of the big challenges is that there's no standardized form of marijuana. People smoke different sizes of joints or other ways of inhaling the product. You know there's not a standard you know a standard size that lets you measure how much people are really taking so that's sort of a challenge. One of the other challenges in terms of separating the effects out is that most people who smoke marijuana also smoke cigarettes and so there's a big correlation between the two. And oftentimes people smoke marijuana and tobacco together and so says rating the effects out of in terms of how much worse it is that cigarette smoking is really challenging and we may not really have a complete picture until we're able to study it in an environment where there's less kind of legal repercussions.
Lindholm: Yeah. So to that. Are you advocating or are you pushing or are you hearing people who are really trying to push the federal government to allow more testing even though federally it is still illegal? You know that that really inhibits the ability for doctors to do research on marijuana. So would you like to see more research done regardless of whether the federal prohibition is lifted or not?
Garrison: Yeah I think so. I mean we definitely know that people are smoking marijuana. I mean it's it's the most commonly used illegal substance in the United States. And so a significant portion of the population is doing it and we'd really like to be able to better characterize the risk of smoking marijuana to raise awareness for the public.
Lindholm: I went into a head shop recently to talk to the guy who worked there about what's happening with legalization and what was he thinking and one of the things that he told me was that 'oh nobody smokes anymore, everybody is either vaping or you know using it as butter or they're these tinctures that you can now use and none of that is smoking none of that is putting the same combustible material into your lungs. Now I know, Dr. Garrison, I'm not asking you to advocate in favor of marijuana, but if people are going to use marijuana do you see them turning to ways other than smoking maybe partly because all of that education on cigarettes has had an effect on younger generations. And is that a better way to approach using marijuana?
Garrison: You know, it's really without having a lot of good data about long-term effects of sort of vaping or you know inhaling through a water bong or other methods. It's hard to know for sure how safe those methods are. I think most people would agree that not having the smoke is probably better than having the smoke. And so if this were something that people had had strong reasons to need or use I would certainly favor doing it in a way that doesn't involve inhaling the smoke because we just know that burn biomass generates so many toxic chemicals that you know long-term there are gonna be problems.
Lindholm: So even in the absence of research if people are using marijuana, from a pulmonary perspective it's a better idea to use it in some way other than smoking it?
Garrison: Yeah, I would definitely encourage that.
Lindholm: And for medicinal marijuana users I mean do the benefits outweigh the possible harms of smoking?
Garrison: You know it probably depends on the person you know if someone's got end-stage cancer and they're using it for nausea or some other reason they may not be as concerned with long-term risk. If someone has other reasons they're using it for chronic pain or other reasons that aren't life-threatening those the long-term risks you know may start to add up over time. And so I think you know I wish we had right now some numbers to tell people you know what their risk actually was. But I think the longer you're expected to be using the more important it is to limit the amount of smoking that you're doing.
Listen to the full conversation with Garrison above.
Broadcast live on Thursday, Jan. 25, 2018 at noon; rebroadcast at 7 p.m.