Effects of water filtration on marijuana smoke: a literature review.
Nicholas V. Cozzi, Ph.D.
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A drug derived from marijuana, tetrahydrocannabinol (THC), formulated in sesame oil and encapsulated in soft gelatin capsules (Marinol(R); Roxane), is currently available as a prescription drug for the treatment of two diseases or conditions. It is indicated for the treatment of nausea and vomiting associated with cancer chemotherapy, and for the AIDS wasting syndrome.
The marijuana plant in smokeable form is available to ten patients in the United States for disorders such as glaucoma, spasticity, and the wasting syndrome. Each of these drug delivery systems, oral capsules and smokeable plant, has advantages and disadvantages, and each may be appropriate in particular circumstances. However, a drug delivery system that combines the rapid and reliable onset and ability to easily titrate an ingested dose (such as occurs by smoking marijuana cigarettes) with the least health risk (such as occurs by oral ingestion of capsules) would also be desirable. The use of water-filtered marijuana smoke, as produced by a water pipe, is one little-explored alternative. This article reviews some of the scientific work that has been done regarding the effects of water filtration on the composition and effects of marijuana and tobacco smoke.
While most of the research on water filtration has focused on tobacco smoke, the work with marijuana smoke has revealed that, except for their respective psychoactive components (nicotine and cannabinoids), both smokes share many common constituents and physical properties. Many of the results obtained from studies of tobacco smoke are applicable to marijuana smoke.
In the late 1970's, a group based at the University of Athens Medical School (Greece) conducted a series of chemical and pharmacological studies on marijuana and tobacco smoke.1-4 These scientists tested smoke that had been filtered through a water pipe and also tested the water itself, which contained both soluble and insoluble compounds. Chemical analysis revealed many different compounds in the smoke and in the water, as expected from the combustion of plant materials.
The water did trap some THC, as well as other psychoactive compounds, however, most of the THC present in the marijuana passed through the water pipe unchanged. Pharmacological tests (in mice) revealed that some of the water-trapped marijuana compounds were responsible for producing catatonia and for suppressing spontaneous motor activity. In contrast, the water-filtered smoke itself did not affect spontaneous motor activity and did not induce catatonia, though it was richer in THC. These results indicate that water filtration removes some behaviorally active compounds in preference to others; this may be important when comparing the therapeutic effects of whole marijuana smoke to water-filtered smoke.
Research has shown that water filtration reduces both the amount of particulate matter and the number and quantity of toxic substances in the smoke that passes through it. In a 1963 study by Hoffman et al.,5 the water pipe was found to retain 90% of the phenol and 50% of the particulate matter and benzo-a-pyrene of the original tobacco smoke. In another study,6 tobacco smoke components that were passed through a water pipe showed only a minor hyperplasic reaction and no sebaceous gland destruction when they were painted onto mouse skin. (The application of substances to mouse skin to assess carcinogenic potential is a classic toxicological test; the induction of abnormal cell proliferation [hyperplasia] is a red flag.)
In contrast, tobacco smoke condensate that was not water-filtered induced strong hyperplasia and complete sebaceous gland destruction when applied to mouse skin in the same concentration. Salem and Sami,7 also using the mouse skin test, showed that there was a significant reduction of carcinogenic potential in water-filtered smoke compared to the water remaining in the pipe i.e., the water-trapped material was more carcinogenic than the smoke that passed through it. Indeed, when analyzed by thin layer chromatography, two carcinogenic agents were identified in the water itself, while only one was identified in the water filtered smoke. Therefore, water filtration removes at least two known carcinogens that would normally be found in the smoke.
Recently, Dr. Gary Huber at the University of Texas and colleagues from Harvard's School of Public Health conducted a cellular toxicity study of marijuana and tobacco smoke.8 This research group showed that passing marijuana or tobacco smoke through water, or even exposing the smoke to a wetted surface of about 48 square inches, effectively removed substances (acrolein and acetaldehyde) which are toxic to alveolar macrophages.
Alveolar macrophages are one of the major defense cells of the lung and are an important component of the immune system. When the macrophages were exposed to smoke that was not water filtered, there was a marked impairment of their capacity to kill bacteria. When the smoke was water-filtered, however, there was no reduction in the bactericidal ability of the macrophages, suggesting that marijuana smoke that has been passed through sufficient water will have less impact on the immune system than marijuana smoke that has not been water-filtered. This intriguing finding would be of particular importance when treating patients with the AIDS wasting syndrome.
The laboratory results discussed above parallel what is known from studying human tobacco-smoking populations. Thus, there is substantial epidemiological evidence that among tobacco smokers, those who smoke through a water pipe have a much lower incidence of carcinoma than those who smoke cigarettes or smoke a "regular" pipe or cigars.6,7,9,10
In summary, it appears that water filtration can be effective in removing components from marijuana smoke that are known toxicants, while allowing the THC to pass through relatively intact. The effectiveness of toxicant removal is related to the smoke's water contact area. Specially designed water pipes, incorporating particulate filters and gas dispersion frits would likely be most effective in this regard; the gas dispersion frit serves to break up the smoke into very fine bubbles, thereby increasing its water contact area. While individuals vary greatly in their smoking technique, state of health, dosing regimen, and so on, it seems that many patients could benefit from the use of water pipes to deliver THC. This would allow patients to titrate their dose easily while reducing the health hazard associated with smoke.
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dhwwwooo...shhhhhlllurp.....um, does that mean i should attach the filter from the kitchen sink tap onto the stem below the waterline for better filtration and more Jah-some i-ration? 
