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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
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The study results are obviously discomforting to waterpipe enthusiasts, many of whom prefer the cooler, milder smoke they produce, and have naturally assumed it is also more healthful. Unfortunately, however, the study indicates that waterpipes may actually be counterproductive in increasing consumption of carcinogenic tars.
Nonetheless, it is still premature to judge that waterpipes are actually unhealthful, since they may filter out other, non-solid smoke toxins occurring in the gas phase of the smoke, which was not analyzed in the study. Noxious gases known to occur in marijuana smoke include hydrogen cyanide, which incapacitates the lung's defensive cilia; volatile phenols, which contribute to the harshness of the taste; aldehydes, which promote cancer; and carbon monoxide, a known risk factor in heart disease. Previous studies indicate that water filtration may be quite effective in absorbing some of these [Nicholas Cozzi, Effects of Water Filtration on Marijuana Smoke: A Literature Review, MAPS Newsletter, Vol. IV #2, 1993]. If so, waterpipes might still turn out to have net health benefits.
MAPS and California NORML are planning to undertake a second phase of the waterpipe study for the purpose of analyzing the gaseous phase of marijuana smoke.
In the meantime, the easiest way for most smokers to avoid harmful smoke toxins may be simply to smoke stronger marijuana. This strategy is apt to be more effective than any smoke filtration device. By simply replacing the low, 2.3% potency NIDA marijuana used in this study with high-quality 12%-sinsemilla, smokers could presumably reduce their tar intake by a factor of five while still achieving the same effect. Further improvements could be had by using pure THC or hash oil, which has been tested at potencies of 60%.
The notion that high-potency marijuana is less harmful directly contradicts official government propaganda, which maintains that marijuana has become more dangerous since the '60s due to increased potency. This claim appears to rest less on scientific evidence than on the desire to frighten the public. A careful analysis of government data by Dr. John Morgan has shown that the supposed increase in potency has been greatly exaggerated [American Marijuana Potency: Data Versus Conventional Wisdom, NORML Reports (1994)]. In any case, however, there is no good reason to presume that higher potency marijuana is more harmful, given the potential respiratory benefits of reduced smoke consumption. The hazards of excessive potency are purported to be an increased risk of acute overdose and greater susceptibility to dependency. However, both problems can be avoided if users adjust their dosage to potency. For most users, such hazards may well be outweighed by the benefits of reduced smoke consumption.
Research in Australia
The Australian government is currently conducting another study that may cast further light on the effects of potency variations. The study is designed to determine baseline THC, tar, and carbon monoxide levels from marijuana and marijuana-tobacco mixtures smoked through joints and waterpipes. The samples being tested come from police seizures in six different Australian states. Researchers say that they have observed "incredible" variations in tar and THC potency among different samples. Their report is expected shortly.
THC Transfer Rate
The MAPS-NORML study provides new information on the efficiency of different devices in delivering THC from marijuana to the user. Previous studies have shown that 60% - 80% of the THC burned in joints or waterpipes is lost in slipstream smoke, adhesion to the pipestem and bowl, pyrolysis, etc. [Mario Perez-Reyes, Marijuana Smoking: Factors that Influence the Bioavailability of Tetrahydrocannabinol, in C. Nora Chiang and Richard Hawks, ed., Research Findings on Smoking of Abused Substances, NIDA Research Monograph 99, 1990]. The percentage of total THC delivered to the user is called the THC transfer rate. The unfiltered joint scored surprisingly well in smoking efficiency, coming in second place with a transfer rate close to 20%. The portable waterpipe did slightly better, and the bong slightly worse. The other devices did notably worse. The vaporizers and electric waterpipe did especially poorly, with transfer rates less than one-third that of the top three devices. Thus, heavy smokers could literally be blowing most of their stash away with bad pipes.
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Contrary to the initial version of this article, which erroneously stated that THC vaporizes at 155º C, the Merck Manual lists the vaporization point of THC as 200º in vacuum. The vaporization point at normal atmospheric pressure appears to be unknown, but is thought to be in the range 250-400º.