Non-smoker exposure to secondhand cannabis smoke II: Effect of room ventilation on the physiological, subjective, and behavioral/cognitive effects

Drug Alcohol Depend. 2015 Jun 1:151:194-202. doi: 10.1016/j.drugalcdep.2015.03.019. Epub 2015 Apr 6.


Introduction: Cannabis is the most widely used illicit drug. Many individuals are incidentally exposed to secondhand cannabis smoke, but little is known about the effects of this exposure. This report examines the physiological, subjective, and behavioral/cognitive effects of secondhand cannabis exposure, and the influence of room ventilation on these effects.

Methods: Non-cannabis-using individuals were exposed to secondhand cannabis smoke from six individuals smoking cannabis (11.3% THC) ad libitum in a specially constructed chamber for 1h. Chamber ventilation was experimentally manipulated so that participants were exposed under unventilated conditions or with ventilation at a rate of 11 air exchanges/h. Physiological, subjective and behavioral/cognitive measures of cannabis exposure assessed after exposure sessions were compared to baseline measures.

Results: Exposure to secondhand cannabis smoke under unventilated conditions produced detectable cannabinoid levels in blood and urine, minor increases in heart rate, mild to moderate self-reported sedative drug effects, and impaired performance on the digit symbol substitution task (DSST). One urine specimen tested positive at using a 50 ng/ml cut-off and several specimens were positive at 20 ng/ml. Exposure under ventilated conditions resulted in much lower blood cannabinoid levels, and did not produce sedative drug effects, impairments in performance, or positive urine screen results.

Conclusions: Room ventilation has a pronounced effect on exposure to secondhand cannabis smoke. Under extreme, unventilated conditions, secondhand cannabis smoke exposure can produce detectable levels of THC in blood and urine, minor physiological and subjective drug effects, and minor impairment on a task requiring psychomotor ability and working memory.

Keywords: Cannabis; Cognitive; Exposure; Marijuana; Secondhand; THC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Attention / drug effects
  • Behavior / drug effects*
  • Blood Pressure / drug effects
  • Cannabis / adverse effects*
  • Cognition / drug effects*
  • Dronabinol / blood
  • Dronabinol / pharmacology
  • Environmental Exposure / statistics & numerical data*
  • Female
  • Hallucinogens / blood
  • Hallucinogens / pharmacology
  • Heart Rate / drug effects
  • Humans
  • Male
  • Marijuana Smoking / psychology*
  • Middle Aged
  • Psychomotor Performance / drug effects
  • Ventilation / statistics & numerical data*
  • Young Adult


  • Hallucinogens
  • Dronabinol