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Can You Fail a Drug Test from Secondhand Marijuana Smoke?

man and woman laughing together while a woman blowing off a smoke from her mouth

Given that cannabis is still federally illegal, many individuals might worry about failing an employment drug test by merely being in the vicinity of cannabis. Never fear: it’s improbable – though not impossible – to fail a drug test after being exposed to secondhand marijuana smoke.

Read on to learn everything you need to know about being exposed to secondhand smoke and why it’s unlikely to give a positive result in a drug test.

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What Drug Tests Can Detect

Before employment, drug tests are often used to determine whether a potential hire uses or abuses illicit substances or prescription medication. Employers may also use it to test individuals returning to work after a prolonged absence.

Job offers or placement are usually contingent upon the applicant’s ability to pass a drug test, which puts an understandable amount of pressure on the test-taker. Drug tests typically screen for the following but can test for others if needed:

  • Cocaine
  • Methamphetamines
  • Opiates
  • Phencyclidine
  • THC and THC metabolites

It makes sense that those exposed to secondhand cannabis smoke would be concerned about failing a drug test and the risk of losing their employment. Secondhand exposure to marijuana, particularly in an unventilated room or vehicle, can sometimes make people feel intoxicated with minor coordination or memory problems.

However, research has shown that while some THC gets into the blood of nonsmoking individuals, the amount is well below what would cause a drug test to fail. A study found that individuals who didn’t smoke cannabis and spent at least three hours in a well-ventilated space didn’t test positive for THC on a standard drug test.

The most common type of drug test is a urine test. Other types of drug tests, like the hair follicle test, are more sensitive and have a longer detection window (90 days as opposed to 30 days). However, as hair follicle drug tests are more expensive and their sensitivity can rarely pick up on recent accidental exposure, it is generally not carried out in the workplace.

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Other Effects of Secondhand Marijuana Smoke

There are other side effects of secondhand marijuana smoke besides potential intoxication or the rare failed drug test.

Plentiful research documents the health risks of secondhand exposure to cigarette smoke, raising questions about whether cannabis smoke carries the same risks. So far, little research has examined the question, but we have a few animal studies from which to draw.

A 2016 study found that rats exposed to one minute of secondhand cannabis smoke experienced impacted flow-mediated dilation (how arteries change in size with increased blood flow) of the femoral artery as much as tobacco smoke, with effects lasting up to three times longer. These effects occurred regardless of how much THC was in the smoke.

While we lack human studies, the toxins, tar levels, and other unknown growing materials in cannabis products raise concerns about exposing vulnerable populations–such as children or those with asthma–to secondhand smoke. Pets can also become intoxicated via secondhand smoke, which can be dangerous in higher amounts.

Poorly crafted products, like flower cultivated with pesticides or heavy metals, also produce carcinogens upon combustion that can damage health.

The Bottom Line: A Contact High Probably Won’t Make You Fail a Drug Test

If you’re in a well-ventilated room or outside, it’s highly unlikely you’ll fail an upcoming drug test. While it’s possible that extreme exposure could produce a positive urine sample, it’s infrequent and not likely to occur after a few hours following exposure. You may feel some effects of intoxication at the moment. Still, unless you consume THC yourself, the levels of cannabinoids in your system won’t register on anything but the most sensitive of drug tests.

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