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Why Test for Recent Marijuana Use?

By Jenny Lynn

Apr 23, 2021

In the era of cannabis legalization, it is important to understand “When” someone used marijuana, not just “If.”

Marijuana only causes impairment for a few hours after smoking. But, traces of THC (the substance that causes impairment) can stay in the body in varying amounts for many days or even weeks after a person last used. Although THC does not cause impairment for days or weeks after use, past use can still trigger a positive drug test. 

So, for an employer who wants to keep their workplace safe, the most relevant questions are “When did this person use marijuana?” quickly followed by “And how do I test for that?” 
 
Most conventional methods of testing for marijuana – oral fluid, blood, urine, and hair – are good at determining “if“ marijuana was used in the last days, weeks, or months. However, these tests cannot determine “when” that marijuana was used. Did the person use recently in the parking lot before going into work and therefore may be putting themselves, their colleagues, and their employer at risk due to impairment? Or was it used legally and responsibly last month at a concert and has no bearing on an employee’s safety or performance?
 
In an era of increasing legalization and growing acceptance of marijuana use, adults who live in places where they have legal access to cannabis should be able to use responsibly during their personal time if they choose. Many employers agree with this sentiment – they want to treat employees fairly. However, employers still have a responsibility to keep their workplaces safe, so dropping marijuana from their drug testing programs is not the answer.   

We have had the opportunity to talk with many  employers over the years and here are comments from a couple of those conversations: 

“I don’t care what they do on a Friday or Saturday night, but I do care about whether they’re impaired before they operate safety-sensitive equipment.”    ~  Wholesaler   

“I imagine 20-30% of the workforce likely has THC in their system. I am fine with it as long as it’s from last weekend and not from smoking in the car at lunch.”  ~ Manufacturer  

The windows of detection for THC in oral fluid, urine, and hair extend for days, weeks and months after impairment subsides, which makes them less useful now that marijuana is legal. Many employers are no longer just concerned with “if” someone used marijuana – they also need to know “when” it was used. They also understand that testing breath is the better way to determine “when” someone used marijuana. A marijuana breathalyzer that identifies THC in breath where it only remains for a few hours after smoking is the best indicator of very recent marijuana use – within the window of time when a person is most likely to be impaired.
 
The HOUND® MARIJUANA BREATHALYZER is an objective indicator of whether an employee used marijuana recently. The Hound® solution provides employers with the information they really need now that many employees can legally use marijuana. The results from breath samples collected by the HOUND MARIJUANA BREATHALYZER will be negative for employees who used cannabis days, weeks, or months before the test, allowing employers to focus on the “when” – positive results from recent use within hours of the breath test. Focusing on recent use will allow employers to maintain safety while balancing fairness.