Cannabis Exposure and Lung Health

Cannabis smoke and tobacco smoke are not equally carcinogenic

Unlike tobacco smoke exposure, cannabis smoke exposure - even long-term - is not positively associated with cancers of the lung or upper aerodigestive tract

  • "We conducted a population-based case-control study of the association between marijuana use and the risk of lung and upper aerodigestive tract cancers in Los Angeles. ... Although using marijuana for > or =30 joint-years was positively associated in the crude analyses with each cancer type (except pharyngeal cancer), no positive associations were observed when adjusting for several confounders including cigarette smoking. ... Our results ... suggest that the association of these cancers with marijuana, even long-term or heavy use, is not strong and may be below practically detectable limits."
  • "We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use. What we found instead was no association at all, and even a suggestion of some protective effect."
  • "The purpose of this retrospective cohort study was to examine the relationship of marijuana use to cancer incidence. The study population consisted of 64,855 examinees in the Kaiser Permanente multiphasic health checkup in San Francisco and Oakland (California, United States), between 1979-85. ... Follow-up for cancer incidence was conducted through 1993 (mean length 8.6 years). Compared with nonusers/experimenters (lifetime use of less than seven times), ever- and current use of marijuana were not associated with increased risk of cancer of all sites in analyses adjusted for sociodemographic factors, cigarette smoking, and alcohol use. Marijuana use also was not associated with tobacco-related cancers or with cancer of the following sites: colorectal, lung, melanoma, prostate, breast, cervix. ... We conclude that, in this relatively young study cohort, marijuana use and cancer were not associated in overall analyses."

Cannabis smoke exposure, even long-term, is not associated with the sort of significant adverse pulmonary effects associated with tobacco - such as COPD.

  • "[H]abitual use of marijuana alone does not appear to lead to significant abnormalities in lung function. Findings from a limited number of well-designed epidemiological studies do not suggest an increased risk of either lung or upper airway cancer from light or moderate use. ... Overall, the risks of pulmonary complications of regular use of marijuana appear to be relatively small and far lower than those of tobacco smoking."
  • "Cannabis smoking is not equivalent to tobacco smoking in terms of respiratory risk. ... [C]annabis smoking does not seem to increase risk of chronic obstructive pulmonary disease (COPD) or airway cancers. In fact, there is even a suggestion that at low doses cannabis may be protective for both conditions."
  • "In this 20-year study of marijuana and pulmonary function, we confirmed the expected reductions in FEV1 (first second of expiration) and FVC (forced vital capacity) from tobacco use. In contrast, marijuana use was associated with higher FEV1 and FVC at the low levels of exposure typical for most marijuana users. With up to 7 joint-years of lifetime exposure (e.g., 1 joint/d for 7 years or 1 joint/wk for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function. ... Occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function."
  • "On the basis of my own work and a systematic and thorough review of the relevant literature on this subject, I have come to the conclusion that regular marijuana smoking does not lead to COPD and is not a significant risk factor in the development of lung or aerodigestive tract (head and neck) cancer, in contrast to the wealth of evidence implicating tobacco smoking as the major risk factor for both COPD and respiratory cancer."

Vaporization -- which heats marijuana to a point where cannabinoid vapors form - mitigates consumers exposure to potential respiratory hazards, such as the inhalation of combustive smoke or exposure to unwanted particulate matter