Passive inhalation of marijuana smoke and urinary excretion cannabinoids.

To the Editor.— We have performed systematic studies designed to investigate whether the breathing of high concentrations of marijuana smoke by nonsmoking subjects (passive inhalation) could result in the urinary excretion of detectable amounts of cannabinoid material, which could produce positive results by the enzyme multiplied immunoassay technique (EMIT). Three studies in which the exposure to marijuana smoke was progressively increased were conducted. In each study, four experienced marijuana users smoked marijuana cigarettes in the presence of two nonsmoking subjects. They were confined in a closed environment for one hour after the beginning of marijuana smoking. All urine samples voided by the nonsmoking subjects were collected separately for 24 hours after marijuana smoke exposure, and the times of each voiding were recorded. For all the studies, a 15-mL aliquot of each urine sample was coded, immediately frozen, and was sent out for an evaluation of the presence of cannabinoids by