Study Finds Positive Drug Test from Secondhand Marijuana Smoke Unlikely

A new study finds it is unlikely that a person exposed to secondhand marijuana smoke will test positive for marijuana themselves.

While it is possible that extreme marijuana smoke exposure could produce a positive urine test, this occurrence is likely to be rare and limited to the hours immediately after exposure, according to researchers from Johns Hopkins University.

Six experienced marijuana users smoked marijuana with different concentrations of THC, the drug’s psychoactive ingredient, in a sealed chamber. Six non-smokers were seated next to the smokers. In two sessions, the participants were in a room with no ventilation, while in the third session they were in a ventilated room. The non-smokers’ urine was tested 13 times over the next 34 hours. Urine levels of THC surpassed typically detectable levels in only one participant, four to six hours after exposure. When the researchers used a more sensitive test, which is usually not used in workplace drug testing, they could detect lower THC levels, but only for 24 hours.

Non-smokers in the ventilated room did not come close to meeting the threshold for a positive drug test, Newsweek reports.

The findings are published in the Journal of Analytical Toxicology.

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    Rw derek

    March 22, 2017 at 10:50 PM

    Dear long time therapist, i have to say you are so right about people saying they quit and still are dirty, im a weed smoker been for 35 years and i had the same excuse as your patients. I was on federal parole and my parole officer laughed handcuffed me i went back to finish my sentence. So why was i hanging around knuckle heads because i was a knuckle head for telling myself i could get away with it thats a lame excuse now that im clean, i got high from being in the same room with people smoking weed, why lie?

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    November 30, 2016 at 7:43 PM

    I have been going through a few problems. Back in Nov 2015 I made the foolish mistake of smoking the synthetic weed. Stopped shortly there after after seeing warnings and friends warnings about it. In January 2016 I had been tested and it came up with THC and Cocaine. The following month had tested positive for just THC. A month later was clean. Then again a month later (have been doing tests almost once a month now) I tested positive for THC and a turpentine derivative (not sure the medical name for it sorry), then clean. Then clean again, then positive for THC. Then clean, then positive for the turpentine derivative, then clean and then again positive for THC. I have been using supplements (bought from the states and then only from Canada). I am trying to find any and all info on false positives (as I do not smoke THC and have not for quite a few years). This is causing me serious problems at work and has been for the past 11 months now. Can anyone help me or guide me in a direction please?!

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    August 18, 2015 at 9:01 PM

    I had been clean for 10 weeks, after being a heavy smoker for about 9 months. I tested positive. The weed these days are way more stronger and I think more research needs to be done!
    If ur blood and hair can be positive even after your urine is clean , why can you not test positive again after abstinence?

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    February 16, 2015 at 11:36 AM

    I tested positive for a job I was applying for which was not just a menial customer service job. No this was for my career. So they had to do all tests, just to be sure. My mother smokes this garbage “medically”. So naturally I am unfortunately exposed to it.

    I actually was denied the position which would have been $16/ hour-40 hours/week, with paid sick/ vacation days, weekends off- WITH MEDICAL, DENTAL AND VISION INSURANCE, WHICH IS AMAZING for a young person right out of school.
    I was denied because I showed positive.

    I have no reason to smoke it, I am too mature for it. Weed just makes you lazy and hungry so what’s the point? Not to mention I am trying to find a career, not a “job” my career, they WILL drug test.

    I think the stuff ought to be illegal all together.

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    long time therapist

    October 22, 2014 at 1:28 PM

    It is good to see this because we see so much baloney from patients trying to say they have been clean when we know they have been still smoking. And when someone tells me it was from the buddies smoking near them, I say to them that if you are really serious about staying clean and starting a recovery, why are you still hanging around those knuckleheads?

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