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Effects of Secondhand Smoke on Marijuana Drug Tests

Can being exposed to secondhand marijuana smoke lead to a positive result on a drug test? According to a recent report in the Canadian Medical Association Journal (CMAJ) Open, it can.

With marijuana becoming legal in many places, the researchers of the present study set out to understand what health effects and impacts passive exposure to marijuana had on non-smokers. To do this, they reviewed 15 experimental studies that examined, in a controlled environment, whether THC could be detected in the bodily fluids of non-smokers when sitting near people who were smoking the substance. Additionally, some of the past studies the researchers looked at investigated whether or not secondhand exposure led to a high in non-smokers.

Detectable Levels of THC in Blood and Urine

What the researchers found was that, in all of the studies they reviewed, non-smokers passively exposed to marijuana had detectable levels in their systems. This means that if a person was around someone who was smoking weed, they would test positive for the substance if subjected to a drug test – even though they did not ingest it themselves. Additionally, a higher percentage of THC content resulted in higher levels in urine samples.

Although the THC levels in urine are lower for non-smokers than smokers, various factors affect how much of the substance can be detected in a person who ingested the substance only through secondhand smoke. Two of the past studies the researchers examined found that when non-smokers are in unventilated areas (such as closed rooms in a house or a car) with marijuana smokers, the level of THC in their bodily fluids was higher than in non-smokers in ventilated areas.

Other factors that impacted the effects of THC on non-smokers included:

  • How many other non-smokers were in the room
  • The THC content in the marijuana
  • The number of marijuana cigarettes being smoked
  • The number of people actively smoking

Getting High from Secondhand Smoke

The researchers of the present study also found that, in addition to having detectable levels of THC in blood and urine, non-smokers also felt the psychoactive effects of the substance after passive exposure. This means that a person could get "high" from ingesting secondhand marijuana smoke. However, the level of intoxication is weaker for non-smokers than for smokers.

Implications of the Study

According to the researchers, although the studies they reviewed examined the effects of marijuana in simulated environments, the findings may be generalizable to real-world settings.

In 2017, recreational marijuana use became legal in Nevada. And while the law allows the substance only to be consumed in certain areas, individuals who do not wish to smoke it might be exposed to it passively. For example, if an individual is hanging out at the house of someone who "lights up" in front of them, breathing in the smoke could get them high, and THC could be detected in their system long after they’ve left their friend's house.

Let's say this person is scheduled for a pre-employment drug test; the results will come back positive for marijuana. Nevada has a law banning employers from screening out candidates who fail marijuana drug tests, but that doesn't apply to all positions.

Nevada's law does not apply to:

  • Firefighters
  • EMTs
  • Drivers
  • Positions in which the safety of others could be adversely affected because of marijuana use

If a candidate fails a pre-employment drug screening, they can take a second test at their own expense. The employer must accept the most recent results.

Have you been charged with a drug crime in Las Vegas? Call the Law Office of David R. Fischer at  or contact us online to get started on your defense.