This article was originally published on Leafly and appears here with permission.

In 1998, Ross Rebagliati took the gold medal for the men’s giant slalom snowboarding event at the Winter Olympics in Nagano, Japan. The day after his victory, he was stripped of his medal following a positive test for marijuana. Rebagliati’s urine test showed 17.8 nanograms in his system, while the limit at the time was 15 nanograms. 

Rebagliati maintained that the positive test was caused by secondhand smoke he inhaled at a party the night before he left for the Olympics, and a contentious appeal saw Rebagliati reinstated with his gold. Still, the event left many wondering—just how potent is secondhand cannabis smoke?

Beyond the issue of accidentally getting high, there are respiratory risks associated with secondhand weed smoke. Let’s look at the effects of secondhand cannabis smoke, how it compares with secondhand tobacco smoke, and also whether secondhand cannabis vapor poses any health problems.

Risks associated with secondhand cannabis smoke

Research tells us that secondhand cannabis smoke presents two significant risks for non-smokers. For starters, individuals who are not actively smoking but inhale secondhand weed smoke may become mildly intoxicated from THC. The other issue is that cannabis smoke contains hundreds of different types of chemicals and particulates (tiny particles of matter) that can be toxic to those who inhale it—secondhand or not.

Does Secondhand Smoke Lead To A Contact High?

Back in 2014, a group of Johns Hopkins researchers carried out a study to learn more about the effects of secondhand weed smoke on non-smokers. 

The researchers placed six cannabis smokers and six non-smokers in a small sealed chamber for three one-hour sessions.

The findings revealed two critical factors: Ventilation and THC potency both play a part in determining whether non-smokers returned positive marijuana drug tests. 

In the first session, one non-smoker produced a positive drug test with THC levels around the 20 nanograms/mL cutoff (although, this is significantly lower than the federal cutoff for a positive screen, which is 50 nanograms/mL). In the second session, four non-smokers produced positive tests up to 22 hours after exposure. 

No participants in session three (the …

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