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Marijuana Smoke Constituents and Hazard Reduction Methods to be Studied: The MAPS/California NORML Water Pipe/Vaporizer Study


December 1994

by Rick Doblin, president and founder of the Multidisciplinary Association for Psychedelic Studies

The long-awaited MAPS/California NORML marijuana smoke filtration study is finally underway. After six months of trying and failing to import high-potency marijuana from the Netherlands for this study, MAPS has succeeded in obtaining 250 grams of marijuana from the National Institute on Drug Abuse (NIDA). NIDA has kindly agreed to supply the research project with the same variety of marijuana that they supply to the eight patients who receive marijuana legally for their medicinal use.


The smoke filtration study is aimed at gathering scientific data about several possible methods of reducing the amount of harmful constituents of marijuana smoke. The researchers will conduct a thorough analysis of the chemical constituents of marijuana smoke both before and after it has been filtered by a variety of methods. Researchers will quantify the total emissions of tar, various cannabinoids (the THC and other chemically similar therapeutic ingredients), volatile aldehydes (which inhibit lung function), and carbon monoxide (which is highly toxic). If the results of the initial study are promising and if funds can be obtained, a subsequent study will analyze marijuana smoke for tumor-promoting compounds like benzene, volatile phenols, benzo(a)pyrene, and volatile N-nitrosamines. These studies are part of an overall clinical plan to evaluate marijuana's safety and efficacy for the treatment of the HIV-related Wasting Syndrome.

This study is needed because there are no scientific data currently available describing the filtration effects of water pipes and vaporizers on marijuana smoke. Data about the filtration effects of water pipes for tobacco smoke are encouraging (contact MAPS for more information), so it may well be that with marijuana smoke these devices would substantially reduce the proportion of tars and particulate matter inhaled along with the THC and other cannabinoids. This study is especially important since the patient population in which the medicinal use of marijuana will soon (we hope) be tested is comprised of AIDS patients, who already have compromised immune systems. If delivery systems can be developed that minimize marijuana smoke's potentially stressful effect on the immune system, the risk/benefit ratio for the medical use of marijuana may decrease dramatically. This research will help the FDA balance the harmful effects of marijuana against its beneficial effects. Of particular interest in this regard is a recent scientific study at the University of Florida which demonstrated that THC itself seems to stimulate some parts of the immune system. The more that the non-therapeutic ingredients in marijuana smoke can be filtered out, the greater the beneficial effect of smoked marijuana.

Some critics of this study suggest that it will provide ammunition for the argument that marijuana is not safe enough for medicinal use when its smoke is not filtered. They fear that this study will thus undermine the effort to secure approval for unfiltered marijuana smoke as a medicine, and place people who claim a medical necessity defense at greater risk of losing their cases.

I think it is irresponsible to ignore the risks of marijuana smoke. The search for safer and more effective methods of helping severely ill patients must be conducted in the most comprehensive and highly scientific manner. Marijuana, like any other drug, has its risks. It behooves those who believe it has benefits to seek ways to minimize those risks. I personally believe that fears that medical necessity cases will be weakened by scientific research into the safest ways to smoke marijuana are unfounded.


This study is an excellent example of a harm-reduction strategy in action, a rising-star strategy in the world of drug policy analysis. Rather than pretending that marijuana has no harmful effects, MAPS continues to explore ways to clarify and minimize those harms.

MAPS' approach to the risks associated with marijuana smoking contrasts dramatically with the approach taken by the tobacco industry regarding the health risks of the cigarette. In a fascinating series of articles in the New York Times (June 16-18, 1994), the secret research projects of the tobacco industry were described. A major direction of research was called Project Ariel, which was a series of studies in the 1960s intended to produce a safer nicotine delivery device than the cigarette. Project Ariel was abandoned after initial prototypes were unsuccessful, in part because they delivered too much nicotine in too short a time. After Project Ariel was closed down, all reports about this direction of research were kept secret.

In the effort to develop safer methods of smoking marijuana, MAPS will report all the data that are gathered, whatever the results.


The water pipe/vaporization study will take place at a respected research center which has been at the forefront of tobacco smoke analysis, so much so that when the tobacco companies recently released their top-secret list of tobacco ingredients, the main person quoted by the media about the health risks of those ingredients was the research director of MAPS' study. As always, MAPS seeks out the most respected scientists in their fields to conduct its research. Since MAPS' research agenda is so controversial, it is essential that the scientists who conduct the research have the respect of their peers across the political spectrum. Otherwise, the results of the studies will not be given much credence and MAPS' limited resources will have been wasted.


Whether water pipes and vaporizers will actually prove useful is an open scientific question. Combustion gases like carbon monoxide are water soluble, making water an effective filter medium for these kinds of components in marijuana smoke. On the other hand, THC and other cannabinoids are not water soluble, permitting them to pass through water to be inhaled. While tars and particulate matter are not water soluble, water nevertheless does seem to retain some of them. On the other hand, the cannabinoids have certain chemical properties that make them "sticky." The practical implication of this chemical property is that the cannabinoid molecules tend to adhere tightly to the tars (particulate matters) produced when marijuana is burned. Therefore, when marijuana smoke is filtered through a water medium, some of the cannabinoids will be filtered out along with the tars to which they are chemically bonded.

The key question is whether the tars will be selectively filtered out to a greater degree than the cannabinoids, resulting in a smoke that has a higher proportion of cannabinoids than before it passed through the water. If the cannabinoids and tars are filtered out equally, smokers will still end up inhaling the same proportion of each to reach the desired therapeutic levels of the cannabinoids.

Water pipes do reduce the temperature of the smoke. Since heat is an important co-factor for carcinogenicity, water pipes offer at least this safety advantage.


Vaporizers are another story entirely. Vaporizers theoretically permit the cannabinoids to be inhaled virtually without any tars and particulate matter. Vaporizers work by heating the marijuana to a temperature at which the cannabinoids boil out from the marijuana, creating a vapor that can be inhaled. The temperature at which the cannabinoids turn to vapor is below that at which the marijuana leaf combusts, so there are presumably few or no combustion products such as carbon monoxide and tars. This is the theory this study will put to the test.

Vaporizers also have another extremely useful property; they are extraordinarily efficient. When the marijuana plant components are burned, only a fraction of the cannabinoid constituents are turned into a vapor and inaled with the marijuana smoke. Cannabinoids are highly combustible, so much so that a large proportion of them in a marijuana joint are burned up and destroyed. With a vaporizer, the same amount of marijuana can produce at least twice as many inhaled cannabinoids, and probably much more. Given that AIDS patients in the final stages of their disease have usually exhausted all financial resources, the efficiency of the vaporizer can dramatically reduce the cost of the medicinal use of marijuana.

Whether vaporizers will work as they theoretically should is an open scientific question not previously tested. Some anecdotal reports indicate that the subjective experience of marijuana smoke that has been vaporized is somewhat different than when the same marijuana is smoked in a joint. What these differences are, and what implications, if any, they have for the therapeutic effects of the vaporizer, remains to be determined.


A unique collection of water pipes will be used in this experiment. One factor that may influence the filtration potential of a water pipe is the volume of water that the marijuana smoke is forced to pass through. Common sense suggests that the more water the marijuana smoke passes through, the more filtration will take place. However, this may not be the case, especially if the tars and cannabinoids are filtered out at an equal rate. To evaluate this, the study will test a water pipe especially designed to prolong the mixing time of the smoke and the water. This water pipe, called the HealthPipe, was manufactured in the 1970s. Thousands were sold before it was driven off the market by aggressive paraphernalia laws. The pipe is ingenious. It looks like a fairly small, traditional water pipe, except that it has a battery-operated paddle blade extending down into the water. When activated by a push button, the paddle blade spins and creates turbulence in the water. This turbulence promotes a more thorough and vigorous mixing between the smoke and water, thus breaking up the smoke into smaller bubbles, and increasing the surface area of the smoke that is placed in contact with the water. These pipes are not inexpensive, and would cost about $40 each to manufacture. However, if they do reduce the amount of particulate matter that an AIDS patient might otherwise inhale, they will be well worth the cost.

The second water pipe that will be tested was manufactured by a MAPS member and donated to the project. This pipe is basically a hookah, with a long plastic hose attached to a bowl. It may be that the passage of marijuana smoke through a line hose will cause some of the heavier particles and tars to become deposited on the hose, leaving smoke with a higher concentration of cannabinoids. This pipe is also designed to release the smoke at the bottom of the water bowl, for maximum contact with the water.

The third pipe to be studied will be a standard water pipe, just like the varieties commercially available in some stores (usually with a note saying that they are for tobacco use only). This water pipe is simply a long plastic cylinder about a foot long and several inches in diameter. A short air tube is positioned near the bottom of the cylinder so that it lies under a few inches of water. I imagine that most water pipes in use in the United States today are of this variety.


The vaporizer we will use in this study is an ingenious combination of a vaporizer and a water pipe, and was designed by members of San Francisco's Cannabis Buyers Club to get the benefits of both devices. (The Cannabis Buyers Club is an organization of thousands of AIDS and cancer patients who have formed a co-op to obtain marijuana for medicinal purposes.) Rather than using a hot plate for the heating element as most vaporizers do, this vaporizer uses hot air. The hot air is generated by a commercially available paint stripper gun available at hardware stores, at a cost of about $40. The tool blows a stream of hot air through the interior of a round metal tube with a diameter of about an inch, at a range of temperatures from several hundred degrees up to and exceeding 1000 degrees F. When used as a marijuana vaporizer, the temperature is set at about 450 degrees F. The end o the tube is positioned about an inch above a small pipe bowl which has a hole at the bottom, just like a standard pipe bowl. That small bowl is placed on top of a much larger beaker of water. A small tube for inhaling the vapor has been inserted into the larger beaker beneath the level of the water.

The vaporizer/water pipe works rather simply. The hot air blows down on the marijuana that is in the first bowl. A screen is secured on both the top and the bottom of the bowl so that the marijuana stays in place. As the temperature of the marijuana increases, the cannabinoids start to vaporize. The downward pressure of the hot air pushes the vapor down into the beaker below. When enough vapor has collected in the beaker, the smoker inhales on the tube. This draws the vapor through the water, cooling it before it goes into the lungs. At no time does the marijuana burn. One disadvantage of this system is that it requires an electric outlet, and is not portable. Another is that the paint stripper gets extremely hot and can inflict pain and burn skin if touched. If this technology proves useful after scientific analysis of the smokestream, further modifications of the prototype will be made. (It is difficult to standardize the output of simpler vaporizer models, and so this more complex combination vaporizer/water pipe will be used in the study.)


The scientists conducting the experiment have a great deal of experience studying the effects of cigarette filters. I have therefore requested that they design a filter for a marijuana cigarette, and test its effectiveness. Their initial impression was that a standard tobacco filter would not work well for marijuana, since it would filter out the cannabinoids as well as the particulate matter. The filter that may be used in this study will be designed to filter out harmful combustion gases rather than tars, particularly removing carbon monoxide. The filter will probably be a short thin empty tube with perforations which increase the amount of oxygen getting into the smoke stream, converting some of the carbon monoxide to the safer carbon dioxide.


This study will take six months and will cost $25,000. MAPS is providing $18,000 for the study and $7,000 is being provided by California NORML. These funds have already been raised. MAPS' support for the study was made possible by a donation of $18,000 from one donor, $14,000 of which was donated directly to the study and $4,000 of which was donated by the same person for two original art drawings from the Doonesbury Brownie Mary/medicinal marijuana series, donated to MAPS by Garry Trudeau.

MAPS has made an initial $17,000 payment toward the study's cost. The final $8,000 will be paid upon receipt of the final report, in part by MAPS and in part by California NORML. In addition to its report to MAPS and California NORML, the scientists conducting the experiment have agreed to prepare a scientific paper describing their results which will be submitted to a peer-reviewed scientific journal for publication.

If this initial study is promising, it would be desirable to conduct a subsequent study to further analyze the constituents of marijuana smoke. This study would include the vaporizer, the most effective of the different water pipes tested, and both a filter-tipped and a nonfilter marijuana cigarette. The cost of this study has been already negotiated with the research team, and would be $15,000. This sum has not yet been raised.


Out of all the tens of millions of dollars that have been spent by the U.S. government on marijuana research, not one penny that I know of has gone toward studies designed to see if the health risks of marijuana smoke could be reduced. One of the primary functions of MAPS is to identify strategic gaps in the scientific literature, and to ensure that those gaps are filled. For a relatively small investment of $25,000, MAPS and California NORML might help identify several methods for reducing what is probably the greatest health risk of marijuana, its harmful effects on the lungs. In terms of the medical use of marijuana, this study may fundamentally change the risk profile of smoked marijuana, and provide data to the FDA that makes is approval of the prescription use of marijuana much more likely. Our results are expected in spring of 1995.

Rick Doblin is a Public Policy Ph.D. student at Harvard's Kennedy School of Government and president and founder of the Multidisciplinary Association for Psychedelic Studies. MAPS is a tax-exempt public charity under section 501 (c)(3) of the Internal Revenue Code. For more information about this study and other MAPS work contact: MAPS, 1801 Tippah Avenue, Charlotte, NC 28205, phone (704) 358-9830, fax (704) 358-1650. E-mail: MAPS@MAPS.ORG.