Effects of water filtration on marijuana smoke

Effects of water filtration on marijuana smoke: a literature review.


Nicholas V. Cozzi, Ph.D.

--------------------------------------------------------------------------------

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 thetreatment of two diseases or conditions. It is indicated for thetreatment 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 inthe United States for disorders such as glaucoma, spasticity, and thewasting syndrome. Each of these drug delivery systems, oral capsulesand smokeable plant, has advantages and disadvantages, and each may beappropriate in particular circumstances. However, a drug deliverysystem that combines the rapid and reliable onset and ability to easilytitrate an ingested dose (such as occurs by smoking marijuanacigarettes) with the least health risk (such as occurs by oralingestion of capsules) would also be desirable. The use ofwater-filtered marijuana smoke, as produced by a water pipe, is onelittle-explored alternative. This article reviews some of thescientific work that has been done regarding the effects of waterfiltration on the composition and effects of marijuana and tobaccosmoke.

While most of the research on water filtration has focused on tobaccosmoke, the work with marijuana smoke has revealed that, except fortheir 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 areapplicable to marijuana smoke.

In the late 1970's, a group based at the University of Athens MedicalSchool (Greece) conducted a series of chemical and pharmacologicalstudies on marijuana and tobacco smoke.1-4 These scientists testedsmoke that had been filtered through a water pipe and also tested thewater itself, which contained both soluble and insoluble compounds.Chemical analysis revealed many different compounds in the smoke and inthe water, as expected from the combustion of plant materials.

The water did trap some THC, as well as other psychoactivecompounds, however, most of the THC present in the marijuana passedthrough the water pipe unchanged. Pharmacological tests (in mice)revealed that some of the water-trapped marijuana compounds wereresponsible for producing catatonia and for suppressing spontaneousmotor activity. In contrast, the water-filtered smoke itself did notaffect spontaneous motor activity and did not induce catatonia, thoughit was richer in THC. These results indicate that water filtrationremoves some behaviorally active compounds in preference to others;this may be important when comparing the therapeutic effects of wholemarijuana smoke to water-filtered smoke.

Research has shown that water filtration reduces both the amount ofparticulate matter and the number and quantity of toxic substances inthe smoke that passes through it. In a 1963 study by Hoffman et al.,5the water pipe was found to retain 90% of the phenol and 50% of theparticulate matter and benzo-a-pyrene of the original tobacco smoke. Inanother study,6 tobacco smoke components that were passed through awater pipe showed only a minor hyperplasic reaction and no sebaceousgland destruction when they were painted onto mouse skin. (Theapplication of substances to mouse skin to assess carcinogenicpotential is a classic toxicological test; the induction of abnormalcell proliferation [hyperplasia] is a red flag.)

In contrast, tobacco smoke condensate that was not water-filteredinduced strong hyperplasia and complete sebaceous gland destructionwhen applied to mouse skin in the same concentration. Salem and Sami,7also using the mouse skin test, showed that there was a significantreduction of carcinogenic potential in water-filtered smoke compared tothe water remaining in the pipe i.e., the water-trapped material wasmore carcinogenic than the smoke that passed through it. Indeed, whenanalyzed by thin layer chromatography, two carcinogenic agents wereidentified in the water itself, while only one was identified in thewater filtered smoke. Therefore, water filtration removes at least twoknown carcinogens that would normally be found in the smoke.

Recently, Dr. Gary Huber at the University of Texas and colleagues fromHarvard's School of Public Health conducted a cellular toxicity studyof marijuana and tobacco smoke.8 This research group showed thatpassing marijuana or tobacco smoke through water, or even exposing thesmoke to a wetted surface of about 48 square inches, effectivelyremoved substances (acrolein and acetaldehyde) which are toxic toalveolar macrophages.

Alveolar macrophages are one of the major defense cells of the lungand are an important component of the immune system. When themacrophages were exposed to smoke that was not water filtered, therewas a marked impairment of their capacity to kill bacteria. When thesmoke was water-filtered, however, there was no reduction in thebactericidal ability of the macrophages, suggesting that marijuanasmoke that has been passed through sufficient water will have lessimpact on the immune system than marijuana smoke that has not beenwater-filtered. This intriguing finding would be of particularimportance when treating patients with the AIDS wasting syndrome.


The laboratory results discussed above parallel what is known fromstudying human tobacco-smoking populations. Thus, there is substantialepidemiological evidence that among tobacco smokers, those who smokethrough a water pipe have a much lower incidence of carcinoma thanthose who smoke cigarettes or smoke a "regular" pipe or cigars.6,7,9,10

In summary, it appears that water filtration can be effective inremoving components from marijuana smoke that are known toxicants,while allowing the THC to pass through relatively intact. Theeffectiveness of toxicant removal is related to the smoke's watercontact area. Specially designed water pipes, incorporating particulatefilters and gas dispersion frits would likely be most effective in thisregard; the gas dispersion frit serves to break up the smoke into veryfine bubbles, thereby increasing its water contact area. Whileindividuals vary greatly in their smoking technique, state of health,dosing regimen, and so on, it seems that many patients could benefitfrom the use of water pipes to deliver THC. This would allow patientsto titrate their dose easily while reducing the health hazardassociated with smoke.