A lot of attention is being paid to secondhand cannabis smoke now that cannabis is legal in so many states. People are wondering, can you get high from secondhand smoke? Will it cause me to fail a drug test?
The short answer is, “yes, but you’d have to try.”
It is possible to be affected by cannabis smoke providing you’re in a small, enclosed space with little to no ventilation with the primary smoker. This Johns Hopkins study from 2015 did show participants exposed to secondhand cannabis smoke under very specific conditions could absorb enough THC for it to appear in blood and urine tests for a short time after the event.
However, the study cautions, “the experimental conditions created here do not reflect the full spectrum of secondhand cannabis smoke exposure scenarios that occur outside of the laboratory, and should not be interpreted to reflect normative conditions. This study models two scenarios of acute exposure in an enclosed room. The size of room, amount of cannabis consumed, duration of exposure, and frequency of such exposure are all variables that likely would influence outcomes in the real world.”
The participants in ventilated areas did not achieve any contact high. Basically, you can get high from secondhand smoke in situations where’d you expect to – with 3 stoners in an enclosed compact car, for example. But, if a couple is passing a joint ahead of you on the hiking trail, you’re safe.