3rd January 2020:

Marijuana smoke contains several thousand different compounds. Some are released unchanged from the plant material as it burns, and the rest are products of either pyrolysis or incomplete combustion. Marijuana smoke consists of some chemicals present in the gas phase, some present in particulate matter, and some semi-volatile compounds that transition between the gas and particulate phase

Marijuana smoke includes a large variety of organic and inorganic chemicals, including amines, aromatic amines, aza-arenes, polycyclic aromatic hydrocarbons (PAHs), carbonyls, phenolics, pyrazines, pyrimidines, pyrroles, pyridines, isoxazoles, metals (arsenic, cadmium, chromium, lead, nickel, and selenium), hydrogen cyanide, carbon monoxide (CO), nitric oxide (NO), other nitrogen oxides (NOx), ammonia, and over 60 cannabinoid compounds

Issues of validity among studies of cancer and marijuana smoking

Validity issues that have been particularly important in the epidemiological studies reporting results for cancer and marijuana smoking have included:

    • Under-reporting of marijuana use due to illegality and social stigma, lack of privacy during interviews, and lack of assurance of data confidentiality.
    • Confounding bias from other risk factors for cancer (e.g., tobacco smoke).
    • Selection bias from non participation.
    • Reporting bias within articles when authors present associations that were found rather than all results.
    • Categorizing people with very little exposure (and thus little potential cancer risk) as exposed. Often, ever/never was the only marijuana exposure quantification in the epidemiologic studies.

Reference: https://oehha.ca.gov/proposition-65/chemicals/marijuana-cannabis-smoke