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2nd-hand cannabis exposure has same effects as smoking

Updated: Sep 27, 2020

This study evaluated human toxicological and subjective effects after passive (second-hand) exposure to cannabis smoke and concluded


  • In extreme cases, the effects of passive exposure mimicked active smoking effects though to a lesser extent than in active smokers.

  • The rapid absorption of THC into blood led to functional pharmacologic effects in nonsmokers as a result of second-hand exposure.

  • Extreme exposure of nonsmokers could lead to positive drug tests and drug-induced behavioral changes not unlike those produced by active cannabis smoking.

  • Extreme exposure to second-hand cannabis smoke by nonsmokers led to presence of THC in oral fluid for up to 3 hours after end of exposure.

  • Indication was found of rapid absorption and metabolism of THC having occurred as a result of second-hand exposure.

  • Evidence suggests that respiratory and transmucosal absorption were key in linking THC concentration in oral fluid to blood as seen in both nonsmokers and smokers.

  • Data from the study suggest that second-hand exposure to cannabis smoke should be avoided by nonsmokers and may have implications for those who undergo drug testing and who are engaged in “safety-sensitive activities” (e.g., driving).


Authors: Edward J. Cone, George E. Bigelow, Evan S. Herrmann, John M. Mitchell, Charles LoDico, Ronald Flegel, and Ryan Vandrey


Published in:

Journal of Analytical Toxicology

2015;39:497–509


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