Cannabis Impairment

Detection vs. Impairment: Why Objective Testing Matters

As cannabis reform continues across the U.S., employers find themselves between a rock and a hard place in their efforts to both keep their workplace safe and respect their employees’ choices outside of work.

To address workplace safety, some legislators and organizations have introduced a series of new laws and testing methods increasingly focused on identifying the signs of impairment. However, the subjectivity of these impairment tests may indicate a “positive” result when employees have not used cannabis in a timeframe that could impact their work performance.


For the better part of a decade, I spent weeks running on as little as one to three hours of sleep. The reason? Four babies in 4.5 years with a set of twins in the mix to make things a bit more challenging. All had fussy bellies, and none were sleeping well, so between the nursing and the sleep training, I survived on 30-minute naps whenever I could take them. This sleep pattern was even more challenging because I returned to work at the end of each maternity leave. Those long workdays amplified the sleep deprivation, and I will admit to more than one lunch break with no food involved – just a blissful 15-minute siesta.

So here is a question: During this time, would I be considered impaired at work? I wasn’t driving a truck or operating equipment, but I was an executive managing a large team and business function. Was I giving peak performance? I can answer the question with a definitive NO. Was my performance a direct result of being sleep deprived? Yes. But was I impaired?


Impairment is defined as ‘the act of impairing something or the state or condition of being impaired:diminishment or loss of function or ability.’1 

I do not doubt that I would have failed an impairment test during that period. But would I have failed a workplace drug test during this time? No. Apart from an occasional glass of red wine, I used no impairing substances. And when I did have that glass of wine, it was not before or during work. 

Fast forward a decade, and my world has changed dramatically. Two of my daughters are in college, and the twins are successful high school sophomores. I have sleepless nights with four teenagers, but they are thankfully few and far between these days.  

Something else has changed, too. In 2012, Colorado and Washington became the first states to legalize the adult use of recreational cannabis. Since then, 19 more states and DC have followed. A robust cannabis industry is booming nationwide, and cannabis use is more widespread than ever.2 

With increased use, the discussion around impairment seems to be in constant debate. Impairment is complex and the cause of impairment is difficult to determine. As we explore this issue, we need to ask if we are close to measuring impairment and identifying and isolating its source – not just relying on a defined per se legal limit or cognitive and behavioral abnormalities.  

My industry colleague, Faye Caldwell, founding partner at Caldwell Everson, a leading employment law firm based in Houston, Texas, spoke about this challenge earlier this year at one of the largest employee screening conferences in the country. 

“While impairment is a word tossed around a lot, it is not a defined standard. Previously, the presence of an illegal drug – even if the person hadn’t recently used it – was enough to remove a person from a position. Because most employees have increased access to legal cannabis, this approach may no longer be seen as an appropriate inquiry or the basis for a decision on employment status.”

– Faye Caldwell, Employment Attorney 

Technology is racing to the market to help employers and law enforcement identify impairment caused by cannabis. The fact is, in reality, IMPAIRMENT is not the issue.


Impairment can be the result of the combination of many factors. In the U.S., we spent several decades trying to understand alcohol impairment. Finally, in 1998, President Bill Clinton called for the promotion of a national limit over which it would be illegal to operate a motor vehicle. The nationwide legal limit is .08 – except for Utah, which reduced the legal limit to .05 in 2018.3 An illegal per se law makes it illegal in and of itself to operate a motor vehicle with a blood alcohol concentration (BAC) measured at or above the established level of .08.4 This is regardless of whether or not the driver exhibits visible signs of intoxication.5  

Barry Sample, Ph.D., a leading toxicology and workforce drug testing expert, explains why determining impairment from cannabis isn’t possible yet. 

“The main point many people fail to realize is that alcohol had decades, literally decades, of study to get to an impairment standard. Researchers examined blood, then breath, and it took an extraordinary amount of time for the scientific and legal communities to reach a consensus on a national standard and per se limits for blood alcohol levels and the relationship between blood and breath. Study data and broad consensus on its outputs are key pieces legislators have been missing as part of determining an impairment standard for cannabis.”

– Barry Sample, Ph.D., Workforce Drug Testing Expert

Returning to the scenario at the beginning of this piece, let’s consider whether I was impaired according to various workplace drug tests.

  • Breath alcohol test – No  
  • Breath, oral fluid, urine, or hair cannabis test – No  
  • Non-biological sample assessments such as virtual reality goggles that subjectively measure impairment – Most likely, yes 

It’s clear I was not impaired from cannabis use. But on the roadside, how would a law enforcement officer be able to differentiate between cannabis use and my lack of sleep? Only an objective testing method using a biological sample capable of specifically isolating recent cannabis use could provide this data.


At work, these scenarios are even more complex. Workplace performance management is a complicated undertaking intended to measure goals, objectives, and milestones by evaluating criteria such as physical agility, reliability, behavior, and compliance with company policies. However, workplace drug testing is not and has never been about impairment. Workplace drug testing is a risk mitigation tool providing an objective measurement to reinforce a policy. It is a leading performance measure that deters drug use at work.

Historically, employers have relied on biological samples such as oral fluid, urine, and hair to detect the absence (or confirm the presence) of cannabis in an employee’s system. These tests demonstrate the validity of using biological samples to provide objective data about an employee’s cannabis use. However, because of their long detection windows, they are no longer practical or enforceable in the era of cannabis legalization.

What this tells us, according to a leading substance prevention program leader, is that employers need a new biological sample type to provide objective, relevant data about recent cannabis use. This helps employers identify use that has the potential to negatively impact an employee’s workday, instead of relying on a false impairment narrative.

“Historic programs using oral fluid, urine, or hair testing only measured the presence of a substance. Those results merely indicate that a substance is detected in a person’s system, not when it was used. But many employers want to ensure that employees are fit for duty when they show up to work and stay fit for duty throughout the workday.”

– Robin Schelling, Substance Prevention Program Leader 

Testing breath for cannabis is the answer. The detection window of a cannabis breath test only extends for 2-3 hours after use.6 With the shortest cannabis detection window in the drug testing industry, a breath test gives employers a way to detect and deter marijuana use correlating to the employee’s workday. This precise detection window helps employers enforce policies that prohibit use immediately before or during work but do not penalize cannabis use outside of work as outlined in the employer’s policy.

For more than 40 years, employers have relied on workplace drug testing as a risk mitigation tool to effectively deter drug use, prevent incidents, and identify recent use in the case of an accident. Contrary to the assumption of several new laws, workplace drug testing has never been a measure of impairment – it is a tool to deter use immediately before or during work hours. Cannabis breath testing fits the intent of workplace drug testing by providing an objective measure to reinforce policies that prohibit cannabis use immediately before or during the workday.

And, perhaps equally important, to provide objective differentiation between a policy violation and a 3 a.m. feeding.  

April 20, 2023