Contrary to popular impression, waterpipes don't necessarily protect smokers from harmful tars in marijuana smoke, according to a new study sponsored by MAPS and California NORML (National Organization for the Reform of Marijuana Laws). The reason is that waterpipes filter out more psychoactive THC than they do other tars, thereby requiring users to smoke more to reach their desired effect. The study does not rule out the possibility that waterpipes could have other benefits, such as filtering out gases, but it suggests that other methods, such as the use of high potency marijuana, vaporizers, or oral ingestion are needed to avoid harmful toxins in marijuana smoke.

Seven Devices Tested

The study, which was supported by the Drug Policy Foundation and private donors, was conducted at a research lab with expertise in the analysis of various chemical properties of tobacco and marijuana. Researchers tested the smoke from seven different sources: a regular rolled joint, a joint with a cigarette filter, three different waterpipes, and two vaporizers, designed to heat marijuana to a temperature where psychoactive vapors form without producing smoke. The waterpipes included a standard bong (Picture #1), a small portable device with a folding pipestem (Picture #6), and a battery-operated model with a motorized paddle to thoroughly mix the smoke in the water (Picture #3). The first vaporizer (Picture #5), commercially produced in Canada, consisted of a battery-powered metal hot plate inside a jar to trap the marijuana vapor. The second (Picture #4) was a homemade, hybrid apparatus, in which vapors were produced by a hot air gun and then drawn through a beaker of water, thereby combining vaporization with water filtration. The smoke was produced from standard NIDA-supplied marijuana drawn through a smoking machine adjusted to mimic the puff length of marijuana smokers.

Focus: Cannabinoid/Tar Ratio

The study focused on two key components of the smoke: (1) total solid particulates, or tars, which are noxious waste by-products of burning leaf like those from tobacco; and (2) cannabinoids, the chemicals distinctive to marijuana, including its major psychoactive ingredient, delta-9-tetrahydrocannabinol (THC), and its two commonest chemical relatives, cannabinol (CBN) and cannabidiol (CBD), which are only weakly psychoactive but may have medical benefits.

Like tobacco, marijuana tars are rich in carcinogenic compounds known as polycyclic aromatic hydrocarbons, which are a prime culprit in smoking-related cancers. However, cannabinoids themselves are not carcinogenic. An obvious way to protect smokers' health is therefore to minimize the content of smoke tars relative to cannabinoids.

One way to do this is to increase the THC potency of the marijuana. Assuming smokers adjust their smoke intake to the cannabinoid dosage, the higher the concentration of cannabinoids, the lower the amount of tars they are likely to consume.

Another strategy is to try to reduce the tars in the smoke with some kind of filtering device. Obviously, this is beneficial only to the extent that THC isn't also reduced, thereby inducing users to smoke more to compensate. A major aim of the study was to determine the efficacy of various smoking devices at reducing the concentration of tars relative to cannabinoids. The performance of each device was accordingly rated in terms of the cannabinoid-to-tar ratio in its smokestream.

Joints and Waterpipes

Surprisingly, the unfiltered joint outperformed all devices except the vaporizers, with a ratio of about 1 part cannabinoids to 13 parts tar. This disturbingly poor ratio may be explained by the low potency of the NIDA-supplied marijuana used in the study, which was around 2.3%.

Disappointingly, waterpipes performed uniformly worse than the unfiltered joint. The least bad waterpipe, the bong, produced 30% more tar per cannabinoids than the unfiltered joint. Ironically, the pipe with the electric mixer scored by far the worst of any device. This suggests that water filtration is actually counterproductive, apparently because water tends to absorb THC more readily than noxious tars. Like the waterpipes, the cigarette filter also performed worse than the unfiltered joint, by about 30%. Researchers speculate this is because cannabinoids are exceptionally sticky and adhere to other solids. Hence, any filtration system that picks up particulates is likely also to screen out cannabinoids.

Vaporizers

The vaporizer results appeared more promising, but confusing. The two vaporizers were the only devices to outscore unfiltered joints in terms of raw cannabinoid/tar ratio. The electric hotplate vaporizer did best, with a performance ratio about 25% higher than the unfiltered joint. The hot air gun was just marginally superior, but might have done better had it not been for its water filtration component.

However, the situation was complicated by the fact that the cannabinoids produced by the electric hotplate vaporizer were unusually high in CBN, leaving 30% less THC as a percentage of the total cannabinoids than with the other smoking devices. Since CBN is not psychoactive like THC, recreational users might be expected to consume more smoke to make up for the deficit. (The situation may be different for medical users, who could experience other, medicinal benefits from CBN). For this reason, it seemed advisable to recompute the performance efficiencies of the vaporizers in terms of THC, rather than all cannabinoids. When this was done, the electric hotplate vaporizer turned out to have a lower THC/tar ratio than the unfiltered joint, while the hot air gun was still marginally higher.