[Passive inhalation of cannabis smoke--is it detectable?]

It is frequently questioned whether cannabinoids are detectable in urine from individuals having been passively exposed to hashish or marihuana smoke. Literature was reviewed to shed light on an issue that is often debated in the health services, judicial system and in sports.

A Medline search with the index terms "cannabis", "hashish", "marihuana" was conducted in September 2007. Summaries, abstracts and reference lists of selected articles were screened for relevancy.

Seven experimental studies with humans were identified. Cannabinoids were detected in urine in two studies where the subjects had been exposed to high smoke levels. In studies conducted under less extreme conditions no urine samples were positive for more than a few hours after exposure and the measured cannabinoid levels were low.

When cannabinoids are detected in urine with conventional methods and limits of quantification the results are commensurate with active smoking.