Does Second Hand Marijuana Smoke Affect a Drug Test?

CandiceDF Asked :

My company is running routine drug tests for employees who work on the factory floor with heavy machinery and I am worried that mine may be affected by second hand marijuana smoke. I do not use any drug, not even nicotine, but I have been to parties where the air is thick with smoke. And some of it is marijuana smoke I guess. I was wondering if this will show up in a drug test?


This question was posted under the Marijuana THC Drug Test – Urine, Blood, Hair, Saliva, Sweat article.

Any response by the Health Hype team does not constitute a medical consultation and the advice should be viewed purely as a guide. Always consult with your doctor before making any changes to your current treatment program. The information provided in this article is not an authoritative resource on the subject matter and solely intends to guide the reader based on the questions asked and information provided.


Dr. Chris Answered :

Passive smoking or second hand smoke means that the person who is not smoking will still have trace amounts of the active drug ingredients and metabolites in their system. This could be detectable on a drug test, like a blood test, but in most cases marijuana testing involves a urine sample. It is highly unlikely that the average marijuana urine test will be able to pick up these trace amounts of the active ingredient THC and its metabolites.

However, it is not impossible as newer tests are becoming more sensitive. It is also possible that if you have the test within a few hours to a day after being exposed to marijuana, it may test positive but once again this is unlikely by traditional testing methods these days.

Every drug screening test has cut-off concentrations where it will not test positive for amounts lower than these cut-off amounts. For marijuana urine tests, the cut-off concentration is usually about 50ng/ml. Most passive smokers will not inhale or absorb enough THC for the metabolites to register at these levels in a urine test. But it also depends on what type of environment you were in during exposure to marijuana smoke and over how long you were exposed.

If you have not smoked any marijuana and if for any reason your test does return a positive result, you could make an appeal and have a blood test or follow-up urine tests. In most cases, the result of a single urine test on the first screening will not be considered as conclusive for the presence of the active ingredient and metabolites and confirmatory testing will usually be done. However, this may vary in terms of individual organizations and their policy about drug use. There is also the possibility that you company may not be testing for marijuana specifically. Refer to Does Marijuana Affect Other Blood Tests?

It is important to note that you should be limiting your exposure to marijuana smoke because it has many harmful effects which you are prone to as a passive smoker.