A question we are often asked concerns the effects of second-hand cannabis smoke and whether being in and around weed smokers could cause a positive drugs test for cannabis for somebody that has not actually smoked the drug.
Will second-hand cannabis smoke influence the results of a urine drug test?
Most drug testing at work is based on urine drug testing. A sample of urine is provided by the donor and analysed for the presence of drugs of abuse.
The general scientific consensus until now has been that second-hand cannabis smoke will not influence the results of a urine drug test. However, cannabis as a drug has changed in recent years. Many of the newer strains of the drug are much more potent and stronger than ever before. Because of this, new studies have been commissioned to look at the issue of second-hand smoke and it’s affects on a non-cannabis user.
A urine drug test for cannabis will detect the metabolite THC which is the product of the drug that causes many of the drug’s psychoactive effects. Some newer strains of cannabis are stronger and can contain more THC than older variants of the drug.
New study into second-hand cannabis smoke
Researchers from the University School of Medicine, Baltimore put together 12 couples. Each couple consisted of a regular cannabis smoker and a non-cannabis smoker. Together they were seated in a sealed compartment for 60 minutes whilst the cannabis user smoked on a strong joint.
After the hour was over, the 12 non-smokers were asked to urinate in a cup at regular intervals and their pee was tested for the presence of THC.
The Journal of Analytical Toxicology published the results of the study in October 2014. They concluded that the urine levels of THC only passed the typical drug test cut-off of 50 nanogram per milliliter in one individual for one very brief instance. (4-6 hours after exposure).
Positive drug tests from cannabis smoke are “likely to be rare”
The authors of the report concluded that instances of positive drug tests from second-hand cannabis smoke are “likely to be rare”. This remote possibility would only occur in the first few hours after intensive exposure to second-hand smoke, such as after being in a car with a cannabis user for a number of hours.
When air was passed into the smoking chamber, making the smoke less concentrated, the levels of THC recorded in urine did not come anywhere near the threshold of 50 ng/ml required to effect a drugs test.