Scientific studies of Herbal Vaporizers
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At least five scientific studies have examined vaporizers. Studies have found the release of harmful constituents dramatically reduced or completely eliminated. Substantial reductions were also found for the M1-volatizer. However, a 1996 study including two simple vaporizers still found ten times more tar in the vapor than THC, although this was nevertheless up to a 30% improvement compared to the best alternative smoking method.
In 2007, a study by University of California, San Francisco published in the Official Journal of the American Academy of Neurology examined the effectiveness of a vaporizer that heats cannabis to a temperature between 180 and 200 degrees and found:
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Using CO as an indicator, there was virtually no exposure to harmful combustion products using the vaporizing device. Since it replicates smoking's efficiency at producing the desired THC effect using smaller amounts of the active ingredient as opposed to pill forms, this device has great potential for improving the therapeutic utility of THC |
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In 2006, a study performed by researchers at Leiden University, tested a Volcano Vaporizer with preparations of pure THC and found that:
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Our results show that a safe and effective cannabinoid delivery system seems to be available to patients. The final pulmonal uptake of THC is comparable to the smoking of cannabis, while avoiding the respiratory disadvantages of smoking. |
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When using plant material (crude flower tops), besides THC, several other cannabinoids as well as a range of other plant components including terpenoids were detected in the plant material. However, using pure THC in the Volcano, no degradation products (delta-8-THC (D8-THC), cannabinol (CBN), or unknown compounds) were detected by HPLC analysis. Also, a substantially larger fraction of the THC was delivered to the vapor by using pure THC.
Analysis of the vapor from the Volcano found that using multiple passes it delivered 36% - 61% of the THC in the sample - a more recent study using pure cannabinoid preparations achieved a maximum of 54%. For comparison, studies of cannabis cigarettes smoked via a smoking machine under varying conditions of puff duration and air speed found very similar efficiencies of 34% to 61%. Consequently, users can achieve the desired effect with a similar amount of material as when smoking.
In a 2001 study testing a device called the M1 Volatizer®, the researchers found that "it is possible to vaporize medically active THC by heating marijuana to a temperature short of the point of combustion, thereby eliminating or substantially reducing harmful smoke toxins that are normally present in marijuana smoke." The M1 Volatizer, produced THC at a temperature of 365 degrees Fahrenheit (185 degrees Celsius), while completely eliminating three measured combustion products, benzene, toluene and naphthalene. Carbon monoxide and smoke tars were also reduced, but not quantified.
These positive results are in contrast to MAPS/NORML's previous studies into vaporizers which found less encouraging results, leading one to the conclusion that the effectiveness of vaporization varies greatly from vaporizer to vaporizer. See Factors affecting vaporizer output for possible causes of variation.
A 1996 MAPS study tested two simple vaporizer models against water pipes and filtered and unfiltered cannabis cigarettes (joints). The smoke produced by each was analyzed for solid particulates (tars) and 3 major cannabinoids. The various smoking methods were then rated based on their cannabinoid-to-tar ratio. The two tested vaporizers performed up to 25% better than unfiltered cannabis cigarettes (second best) in terms of tar delivery. However, both vaporizers produced more than ten times more tars than cannabinoids, which may partly be attributable to the low potency (2.3%) of the NIDA-supplied cannabis used in the study. Surprisingly, the same study found that water pipes (bongs) and filtered cigarettes performed 30% worse than regular, unfiltered joints. The reason was that waterpipes and filters filter out psychoactive THC with the tars, thereby requiring users to smoke more to reach their desired effect. The study did not, however, rule out the possibility that waterpipes could have other benefits, such as filtering out harmful gases such as carbon monoxide.
These studies have not measured the presence of toxic gases, such as ammonia, hydrogen cyanide and carbon monoxide, though previous studies have indicated unquantified decreases in carbon monoxide with vaporization.
Although vaporizers produce cleaner vapors than smoking, they do not completely eliminate respiratory irritation. A puff of strong vaporized cannabis will occasionally cause coughing. This however, could be due to THC itself, which is known to have a strong expectorant effect.
