An employee has a beer or two with colleagues at a local bar after the work shift is over. Another heads home for a glass of wine with dinner. The next day, there is no alcohol impairment in the worker, and that's why an employer would not have a problem with either of these scenarios. But even in states where cannabis has been legalized, drug testing continues to search for signs of marijuana use that in no way necessarily reflects worker impairment.

THC, the active ingredient in cannabis, can linger in the body and show up in the screening process for up to 30 days after the immediate impairment of the user. Traditional THC screening cannot differentiate between actual impairment and presence due to past use of cannabis. Equating presence to impairment groups all individuals — those who use marijuana on a daily basis, for medical or recreational purposes, and those who sporadically do it — in the same category.

Backers of legalization say that is unfair and the world of work needs to adapt to changing societal norms regarding cannabis.

"There are some states, like California, where employers are completely allowed to sanction based on a drug test, even medical marijuana patients," said Tamar Todd, vice-chair of the California Cannabis Advisory Committee and lecturer on marijuana law and policy at Berkeley Law. "An employer can basically refuse to hire you or discipline you for a positive THC in your blood even if you're a lawful medical marijuana patient using lawfully under state law. And the legislature has not changed that law yet."

Employers view alcohol consumption off-duty differently from cannabis consumption, and it reflects on how they interpret drug test results and impairment, said Michelle Lee Flores, a Los Angeles-based partner with law firm Akerman.

"We get off work after a tough day, we have a glass of wine, and then go to sleep. If the next morning we were drug-tested at work, it would not show a positive level of alcohol in our system because we have honed those testings so that we can focus on the actual impairment," said Lee Flores.

Positive results for marijuana are on the rise leading more job candidates to fail drug screens.

The number of positives for drugs in the workforce has reached a 14-year high of 4.4%, according to an annual analysis conducted by Quest Diagnostics, one of the nation's largest clinical laboratory testing companies. The rates of drug use are now more than 25% higher than the 30-year low of 3.5 percent recorded between 2010 and 2012.

The Quest data shows the rate of marijuana positivity in test results increased in nearly all workforce categories. Since legalization began in 2014, positive marijuana test results increased 17% in the general workforce. Among the federally mandated, safety-sensitive workforce category, marijuana positivity grew nearly 5% year over year, and is up nearly 24% since 2014 (0.71%).

"Our analysis shows that marijuana is not only present in our workforce, but use continues to increase," said Barry Sample, senior director of science and technology at Quest Diagnostics, in the study release.

Marijuana is the outlier in test positives as drug test results for opiates and cocaine decline, according to Quest's study. Among the general workforce, opiates (mostly codeine and morphine) declined nearly 21% year over year, which was the largest drop in three years and positive test results are down nearly 37% since the peak in 2015. Positivity for oxycodones (oxycodone and/or oxymorphone) declined more than 29% between 2017 and 2018 and are down more than 46% since the five-year high in 2014.

Alaska (1.6%) is the only state among those that have had legalized marijuana where positivity rates for the drug are not above the national average, which is 2.3% of test results, according to an analysis of Quest by state. Maine (5%), Oregon (4.3%) and Nevada (4%) have the highest rates of marijuana positivity among these states.

"As marijuana policy changes, and employers consider strategies to protect their employees, customers and general public, employers should weigh the risks that drug use, including marijuana, poses to their business," Quest said in its annual survey release.