Fraser Horton
Fraser Horton
Last Updated on October 5, 2021

The amount of THC in weed nowadays isn’t the same as it was 50 years ago. While THC levels were about 3% in the 1970s, today there are strains with THC levels as high as 30%. Therefore, the effects of marijuana use aren’t the same as they were in the past. 

Recent legalization laws around the US have further affected the popularity of cannabis, and more and more people are becoming marijuana smokers as a result. The coronavirus pandemic has further increased the use of cannabis as people during the said time were even more after the psychoactive effects of tetrahydrocannabinol (THC) and also the sedative effects of cannabidiol (CBD).

But what about the people who are in the same room when a joint is being smoked? Can a non-smoker who’s exposed to marijuana smoke get a positive result when drug testing? To find out more about how secondhand exposure to cannabis smoke affects non-smokers, continue reading.

Cannabis and Drug Testing

After smoking weed, the cannabinoids are absorbed into the bloodstream and are metabolized in the body. The elimination period, which shows how long the metabolites are stored in the body, is different for each metabolite. Some cannabinoids are metabolized pretty fast, while others need a longer time for the body to detox them.

The metabolites are the substances that cannabis drug tests screen for, mainly two metabolites 11-OH-THC (11-hydroxy-delta-9-tetrahydrocannabinol) and THCCOOH (11-nor-9-carboxy-delta-9-tetrahydrocannabinol). They’re the ones that remain even after the effects of THC and CBD have passed, and they can be detected in the blood, saliva, hair, and urine. 

Effects of Secondhand Cannabis Smokе

Мarijuana smokers are the ones who get the full blast of cannabinoids upon inhalation, however, what about the people who are located in the same room but don’t smoke weed? Do they experience the effects of weed, and will they have a positive drug test result?

Similar to tobacco smoke exposure, cannabis smoke can also affect those who are in a room where marijuana is smoked. While there is very little research done on humans, scientists have done studies on rats and secondhand exposure to marijuana smoke. The 2016 study found that cannabis smoke exposure for only 1 minute impairs the vascular endothelial function in rats and impairs the dilatation of the arteries.

Is It Possible to Get a “Contact High” From Secondhand Cannabis Smoke?

A few studies have been done which focus on whether people can get a contact high from being in a room where marijuana is smoked.

  • A 2010 study tested the blood and urine of people staying at a coffee shop in Amsterdam where people were smoking weed. After 3 hours, the tests showed that the nonsmokers didn’t absorb large enough quantities in order to get high.
  • A 2015 study by the Johns Hopkins University School of Medicine did research on 12 participants who sat in a room where 6 people were smoking high-potency cannabis. The results published in the Journal of Analytical Toxicology showed that the nonsmokers didn’t get high as a result of the secondary smoke.
  • The National Institute on Drug Abuse’s (NIDA) report concluded that a “contact high” from secondhand marijuana smoke is unlikely.

Secondhand Marijuana Smoke and Drug Tests

While you can’t get high from secondhand cannabis smoke, some users are wondering whether they will test positive for weed as a result of secondhand cannabis exposure. The urine, blood, hair, and saliva of people who were exposed to secondhand marijuana were tested as a part of a study, and the results are as follows.

Can You Test Positive For Marijuana From Secondhand Smoke?

The systematic study results showed that extreme cannabis smoke exposure resulted in positive urine drug test results. The non-smokers were analyzed at different cutoff concentrations, 20, 50, 75, and 100 ng/mL, and a few non-smokers had a positive result at 20 ng/mL. As the THC potency increased the THC-COOH concentrations, adequate ventilation greatly reduced the exposure levels according to one of the study authors, Herrmann E.

Keep in mind that positive tests are rare, and can happen when the test is done only a few hours after exposure in rooms which aren’t adequately ventilated.

If you’re getting an oral fluid test to check for the presence of cannabis and its metabolites, a 2004 research shows that you’ll get a negative test after 30 minutes of exposure to secondhand cannabis smoke.

Secondhand weed smoke can make you cough, but it’s highly unlikely to get a positive test result from staying in a room where a lot of people smoke weed. (Herrmann et al, 2015)

Secondhand Smoke and Other Health Risks

Even though you won’t get high if you stay in a room where weed is smoked, you may experience other health risks.

  • Secondhand exposure to cannabis smoke when staying in an unventilated room may increase your heart rate.
  • Exposure to secondhand cannabis smoke may result in minor levels of impairment in cognition and performance, which is why people shouldn’t drive a vehicle if they don’t feel good after staying in a stuffy room where people were smoking weed.
  • Passive exposure of cannabis smoke in an unventilated room can affect lung health and cause a cough. (Donald P Tashkin et al, 2013)

Conclusion

The studies we covered in this article have shown that inhaling secondhand smoke won’t get you high, though you may end up with a positive urine test. Therefore, being in a room with cannabis smokers may lead to you getting a positive test result if you take one a few hours after exposure.

Passive exposure to weed smoke may also lead to other unwanted side effects like increased heart rate, minor impairment in cognition and performance, and may even make you cough.

To prevent these negative effects, always stay in a ventilated room when you go to the house of your smoker buddies, or make sure there’s an open window in the room. It can also help you if you stay on the other side of the room, away from the smokers. This way you’ll minimize the chances of being exposed to large quantities of weed smoke, and ensure you have a clean test on your next mandatory drug test at work.

Additional Sources

Tashkin D. P. (2013). Effects of marijuana smoking on the lung. Annals of the American Thoracic Society, 10(3), 239–247. https://doi.org/10.1513/AnnalsATS.201212-127FR

Cone, E. J., Bigelow, G. E., Herrmann, E. S., Mitchell, J. M., LoDico, C., Flegel, R., & Vandrey, R. (2015). Non-smoker exposure to secondhand cannabis smoke. I. Urine screening and confirmation results. Journal of analytical toxicology, 39(1), 1–12. https://doi.org/10.1093/jat/bku116

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