As more states move to legalize marijuana, employers are starting to rethink pre-employment screenings for drugs.

Urine tests, the most common among employers, do little to prove whether an employee is a habitual marijuana user — and links between positive drug tests and employee performance are weak.

Some experts believe testing for marijuana intoxication should stay in place, particularly in industries that operate heavy machinery, though they agree the type of testing must evolve.

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With the increased legalization of marijuana, many businesses and politicians are reconsidering workplace drug testing. Though drug testing likely won't disappear forever, experts predict the scope of testing will decrease — and they say the type of testing should change.

Earlier this month, a report by clinical laboratory Quest Diagnostics found the number of US workers and job applicants testing positive for drugs hit a 14-year high, with marijuana positivity leading the way. Around the same time, New York City approved a bill that would prohibit forcing job candidates to take marijuana screening tests, and Citigroup told Business Insider reporter Jeremy Berke it may reevaluate its policy to screen applicants for marijuana.

Read more: Marijuana use is on the rise among US workers as more states legalize the drug

New York state is considering becoming the 11th state to legalize recreational marijuana. The state is already among the 33 that legalized the use of medicinal marijuana.

With the expected expansion to legalize marijuana within the country, the use of employee drug screening is already falling out of fashion among businesses. While current screening for drugs may be flawed and costly, drug screening in the workplace will almost certainly not go away completely, experts say.

Are workplace drug screening tests effective?

Experts agree urine drug testing does little to prove intoxication at the workplace, and the link between pre-employment drug testing and better employee performance is weak.

Workplace drug testing became commonplace in the 1980s during Ronald Reagan's "War on Drugs," when the president signed an executive order that mandated federal employers refrain from using drugs. The policy led to drug testing for employee candidates, and the development of a huge industry that facilitates drug pre-screening, according to Michael Frone, author of "Alcohol and Illicit Drug Use in the Workforce and Workplace."

In his research, Frone finds little proof that drug tests reduce future substance use. In fact, he says testing deters employees from applying to companies that have a pre-screening policy in place.

Likewise, Mark Kleiman, a professor of public policy at New York University, reported that studies measuring pre-employment drug testing's impact on projected employee performance are either out-of-date or use small sample sizes. "Whether the predictive value of a positive test result is the same when applicants have incentives to actively avoid testing positive isn't obvious," Kleiman wrote to Vox.

Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws, told Business Insider that drug screening won't indicate whether a job candidate is an active user, and that urine tests do not indicate marijuana intoxication in current employees. THC, the chemical responsible for marijuana's psychoactive effects, may remain in the body for days or even weeks after a person used cannabis — meaning a positive test for cannabis does not indicate current intoxication, nor the frequency of use.

Pre-screening for drugs may also be an unnecessary cost for employers: Drug tests can cost $30 to $50 each, according to Bloomberg.

Jeremy Kidd, associate professor of law at Mercer University, studied the economics of drug testing in the workplace if employers had full autonomy. Kidd said employers now have incentives to pull back marijuana testing with increased legalization, since the drug prompted pre-employment screening in the first place. He theorized that decreasing pre-employment screening may lead to hiring better employees.

"What you ideally want as an employer is the largest pool possible to choose from," Kidd told Business Insider. "The larger the pool, the better chance you have to select the best employee."

The need for testing in safety-sensitive workplaces

There are some industries where workplace drug testing will likely remain. In New York, the proposed legislation will not ban certain professions from drug testing, including federal contract positions, and safety and security sensitive jobs.

Transportation, construction and manufacturing industries all saw at least 20% increases in marijuana positivity rates from 2015 to 2017, according to Quest Diagnostics, and workers in federal safety-sensitive jobs increased marijuana positivity since 2014. The positivity for post-accident urine testing increased a whopping 81% from 2014 to 2018.

"Increases in post-accident positivity among safety-sensitive workers should serve as a warning to employers that employee drug use may increase the risk of workforce accidents or injuries," said Kimberly Samano, PhD, scientific director at Quest Diagnostics, in a press release.

The decrease in drug screening could pose a more complex problem for industries that operate heavy machinery: with more employees testing positive for marijuana, how do you maintain a drug-free workplace while still attracting the best talent?

Michigan, where manufacturing jobs employ nearly 14% of the state, voted to fully legalize marijuana in 2018. The legalization raises questions to drug testing, as Detroit-based Ford Motor Company and Fiat Chrysler will continue to urine-test applicants, and will disqualify candidates if tests come out positive, the Detroit Free Press reports.

While manufacturing industries want to appeal to the largest pool of applicants possible, companies maintain that intoxication on the job is dangerous, according to Delaney McKinley, director of government affairs at the Michigan Manufacturing Association. "There are so many advances and changes in the auto industry; we're moving from traditional gas engines toward electrification and autonomous vehicles," McKinley said in an interview. "We're in more desperate need of new talent than ever. Michigan is absolutely in a tight situation here."

Another reason, Kidd says, that drug screening would not go away is to prevent liability of an employer in court in the case of an employee accident. The difference in federal and state laws regarding marijuana also incentivize employers that operate in multiple states to keep drug-screening tests, Andrew Singer, chair of employment law practice at a New York City-based law firm told Business Insider.

Armentano says he does not argue for getting rid of drug testing completely, but says urine testing does not provide conclusive evidence of current intoxication. Instead, he says it "discriminates" against casual marijuana users in legal states.

Armentano advocates for performance testing: you measure a baseline level of performance for subjects, and if you suspect they are under the influence, you measure potentially intoxicated employee performance with the baseline. There are already companies that specialize in performance testing and technology as a potential alternative to urine testing.

"There's a greater awareness that individuals who use marijuana off the job do not present a safety risk to employers," Armentano said. "[Urine testing] punishes for behavior outside the workplace. It seems to be a holdover from a very different time in America, where marijuana use was not legally regulated."