While we often hear about the secondhand effects of cigarette smoke, a new study at Johns Hopkins University School of Medicine tested the effects of exposure to cannabis smoke. Non-smoking volunteers were exposed to secondhand smoke and later tested for THC levels in both the blood and the urine. After just an hour of heavy exposure to secondhand cannabis smoke, the volunteers showed a mild sense of intoxication, mild impairment of cognitive markers, and in some cases tested positive for the drug.

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