The number of workers and job applicants who tested positive for marijuana climbed 10% last year to 2.3%, according to an analysis of 10 million urine, saliva and hair samples by Quest Diagnostics Inc., one the nation’s largest drug-testing laboratories. The Quest data, which is set to be released Thursday, found 4.4% of the analyzed samples contained traces of both legal and illegal controlled substances including pot, prescription painkillers and other drugs—the highest such rate since 2004.
Since then, the number of drug tests showing signs of cocaine, heroin, prescription sleep aids and certain opiates like morphine has fallen sharply. But the tests indicate marijuana use has steadily risen for the general U.S. workforce, including among employees in safety-sensitive jobs such as airplane pilots, nuclear power-plant operators and train conductors.
“Marijuana use is on the rise in society, so it’s not surprising that we’re starting to see that filter into the workplace,” said Barry Sample, Quest’s senior director for science and technology. Quest has been analyzing workplace drug-testing data since 1988.
Most urine and saliva tests indicate only whether pot’s psychoactive ingredient—tetrahydrocannabinol, or THC—is present but not how long ago the drug was used or whether someone is currently impaired, a distinction some employers increasingly say is important. Because THC can linger in the body for months, a positive marijuana test is sometimes interpreted as a “lifestyle” indicator, rather than confirmation of current or regular use, Dr. Sample said.
Federal employees have been prohibited from using drugs on or off duty since 1986, when President Reagan authorized drug testing for those who applied to government jobs. The Drug-Free Workplace Act of 1988 ushered in an era of widespread testing and zero-tolerance drug policies among many federal contractors and employers in sectors like trucking, aviation and energy pipeline operators.
More recently, as some lawmakers have sought to redress what advocates say are overzealous or discriminatory drug-enforcement policies, more than 30 states have adopted measures allowing most adults to use marijuana to treat medical conditions like cancer and post-traumatic stress disorder. Ten states and Washington, D.C., now permit recreational use, but workers in safety-sensitive jobs are still held to the federal ban on drug use.
The Quest data show 0.88% of safety-sensitive workers tested positive for marijuana last year, up from 0.84% in 2017. Evidence of opiate use also picked up, with more safety-sensitive workers testing positive for drugs like OxyContin and other painkillers, even as the national crackdown on excessive opioid prescriptions has led to lower rates of use in the broader U.S. workforce.
In 2018 the government expanded the number of prescription painkillers for which it required truckers and pipeline workers to be tested, which the Quest researchers said may have contributed to the increase in positive findings.
Members of Congress have introduced a number of bills to better define the rights of medical marijuana users in recent months, and some states like Maine have enacted laws specifically barring employers from discriminating against residents who use cannabis products. In March, Rep. Charlie Crist (D., Fla.) proposed a bill that would allow military veterans who use cannabis to treat PTSD or other conditions to work in federal jobs.
Cannabis is the name of the plant family that includes marijuana as well as cannabidiol, or CBD, a chemical found in a growing range of products that doesn’t contain THC and whose properties proponents say are calming but “non-psychoactive.”
As more states legalize marijuana, some employers have stopped screening for its use among job candidates, Dr. Sample said. That makes this year’s uptick in marijuana results worrying, he said, because a greater share of those drug tests were issued following workplace accidents or personnel issues. For safety-sensitive workers in 2018, 4.7% of samples sent to Quest after an accident came back positive for potentially illicit drugs, up from 3.1% the year before.
“The increases we’re seeing in post-accident positive drug tests is very concerning,” said Dr. Sample.
Some companies are seeking more precise ways of gauging whether workers’ abilities are impaired on the job. An Oakland-based startup called Hound Labs is marketing a new type of breathalyzer that can detect whether someone has smoked pot or ingested a product containing THC within the prior two to three hours.
Privately held construction firm Suffolk Construction Company hopes to be one of the first employers to test the new Hound Labs device.
“We need a more pragmatic way of dealing with the reality of drug use in the different states where we operate,” said Alex Hall, the company’s executive vice president of environmental health and safety.
Mr. Hall said Suffolk and its subcontractors currently test workers on federal worksites, but in states like California and Massachusetts, the company is shifting the focus of its substance-use policies. In the future, construction workers will be evaluated for signs of inebriation on the job, rather than tested for drug use in general, he said.
“It makes a difference if someone used marijuana at some point in the last four hours, versus the last four days,” Mr. Hall said.