While marijuana is legal for medical use in 33 states and the District of Columbia, the federal status of cannabis hasn’t changed. The Drug Enforcement Agency still classifies it as a Schedule 1 drug, or one that has “no currently accepted medical use and a high potential for abuse.” Any use of cannabis is prohibited by anyone subject to the 1988 Drug-Free Workplace Act (DFWA) and by laws regulating those in safety-sensitive positions (such as transportation and commercial nuclear power). Companies required to comply with the DFWA must establish drug-free workplace policies—specifically, they must prohibit the use of controlled substances in the workplace. Companies with safety-sensitive jobs need to follow similar requirements. But how can we reconcile the legality of cannabis in many states with the need to comply with drug-free workplace policies?

MARIJUANA AND IMPAIRMENT Marijuana impairs cognitive function. According to the World Health Organization, cannabis affects memory, decision-making, response speed, accuracy, and motor coordination. It can impair performance for as long as 24 hours after smoking a moderate dose.

The most common effect of marijuana is psychoactive. Smoking or vaping produces effects within minutes. Ingesting it can delay the effects several hours. This psychoactive effect results from a release of dopamine, providing a euphoric feeling. According to the government of Canada, marijuana can heighten the senses, distort the sense of time, impair motor skills, and lower inhibitions, which might lead to risky behavior. Some people can experience anxiety, hallucinations, or paranoid feelings, particularly with high doses, although that appears to be rare.  Studies have found that cannabis users who drive while intoxicated have much higher risks of motor vehicle accidents. Frequent marijuana users showed less impairment than infrequent users at the same dose. The greatest impairment was seen twenty to forty minutes after smoking. No impairment was observed 2.5 hours after smoking 18 milligrams (reportedly one joint) or less of tetrahydrocannabinol (THC, the active ingredient in marijuana), according to research published in The American Journal on Addictions. When marijuana is smoked, THC levels in the blood peak rapidly, then fall rapidly. Measuring a driver’s impairment immediately after a crash is difficult: if a sample is delayed an hour, blood THC levels will have dropped significantly. Levels of the metabolite carboxy-THC may be high, but because of that substance’s lipophilicity, it does not correlate well with THC’s effects. Long-term use of cannabis is correlated with reduced cognitive performance, particularly when use starts at a young age. But as explained in a report from the World Health Organization, cause and effect hasn’t been clear: does cannabis cause poorer cognitive performance, or are young people with poor cognitive performance likely to become habitual cannabis users? Other long-term effects from smoking marijuana include chronic bronchitis, chronic obstructive pulmonary disease, cardiovascular disease, and possibly cancer. But these are similar to the effects seen in tobacco smokers, and drug-free workplaces do not screen for tobacco use. 

According to the DFWA, any U.S. employer that receives federal contracts worth over $100,000 or federal grants of any amount must develop and implement a drug-free workplace policy. Some federal agencies, including the Nuclear Regulatory Commission, as well as the departments of transportation and defense, require employers of workers in safety-sensitive jobs to have drug-free policies. Some private businesses that aren’t required to follow the law’s requirements may nevertheless choose to do so. The DFWA doesn’t mandate drug testing, although testing is part of the model plan for compliance published by the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA), part of the Department of Health and Human Services (DHHS). In contrast, drug testing is mandatory under laws that address safety-sensitive jobs. In workplaces regulated under DFWA, employers are required to have a formal drug-free workplace policy that clearly prohibits the manufacture, distribution, and use of drugs in the workplace. This policy must also include language detailing the consequences of violations. If employers have a testing program, it must comply with mandatory guidelines developed by DHHS and regulated by SAMHSA. But testing won’t catch all drug use. The most common type of screening, immunoassay-based drug screening, may miss synthetic opioids such as fentanyl or oxycodone, according to research published in the journal American Family Physician.  MARIJUANA TESTING According to the Department of Transportation’s regulation on Controlled Substances and Alcohol Use and Testing (49 Code of Federal Regulations 382.101), the purpose of testing for marijuana is “to help prevent accidents and injuries resulting from the misuse of alcohol or use of controlled substances.” We don’t want impaired workers trying to do jobs that require skill and attention.  According to the National Safety Council, employees with substance use disorders miss nearly 50 percent more days of work than their peers; are less likely to stay on the job, leading to more job turnover; and are less productive. Testing seems like a logical way to prevent having impaired workers. But testing for marijuana presents several problems. Employees legally prescribed marijuana for medical conditions could be at risk of losing their jobs if they take those prescriptions. Marijuana is legal in many places, but tests that are positive could result in lost jobs or missed job opportunities. The testing method for marijuana will miss drugs with similar effects (such as synthetic marijuana) but could result in positive tests for users of cannabidiol (CBD). See Table 1 for examples of workers whose potential impairment appears to be inconsistent with the likely results of drug testing.

If an employee tests positive for marijuana, the employer isn’t immediately informed. Instead, under DOT regulations and SAHMSA’s mandatory guidelines, the results are reviewed by a Medical Review Officer (MRO), a licensed physician responsible for evaluating drug testing results. Workers who test positive are contacted by the MRO and queried about the result. Positive results that are a consequence of a legitimate prescription for anything other than marijuana are reported as negative. Employees who test positive but don’t have a prescription can opt to have the specimen tested at another approved laboratory to confirm the results of the initial testing. If the MRO validates the test result as positive, the outcomes for the worker range from immediate termination to an opportunity for education, rehabilitation, and ultimately a return to work. In the U.S., a medical prescription for marijuana is not accepted as a negative test. Neither DOT nor the mandatory guidelines allow any medically prescribed use of marijuana. That blanket prohibition against medical marijuana leaves many employers with conflicting obligations. The 1990 Americans with Disabilities Act prohibits discrimination on the grounds of disability. Because cannabis is illegal under federal law, federal courts have ruled that the ADA provides no protection even for prescribed use. But some state laws specifically forbid any discrimination for medical marijuana use. For example, in Barbuto v. Advantage Sales and Marketing, LLC, the Supreme Court of Massachusetts allowed an employee to sue for disability discrimination when she was fired for a positive marijuana test. If the company has a policy of firing or refusing to hire because of positive drug tests, but the positive test results from medically prescribed marijuana, the worker might prevail in a lawsuit. Even the most lenient state laws don’t require employers to allow employees to use marijuana at work or to work under the influence of marijuana. 

THE EMPLOYER’S DUTY Drug testing was instituted because impaired workers are dangerous workers. With many drugs, a clear correlation exists between drug levels measured in the body and impairment. That correlation isn’t present with marijuana. Employers need to look for alternatives: refusing to tolerate impaired performance, training supervisors on how to recognize and handle perceived impairment, and developing clear policies that communicate to their workers that impaired performance, for whatever reason, cannot be tolerated in the workplace. The policies need to be clear, communicated, and not punitive.  Measuring impairment also presents difficulties. According to a 2017 report from the National Highway Traffic Safety Administration, peak impairment occurs 90 minutes after smoking marijuana. By that time, THC levels in blood and saliva have dropped over 80 percent from peak. Tests of a worker for THC levels in blood, saliva, or urine could very well be negative even when the worker is obviously impaired. For marijuana, impairment tests would need to be based solely on the ability to perform certain tasks. If the tasks aren’t correlated specifically with marijuana’s effects, there is a risk of considering people “guilty” not because of marijuana, but because of some other factor. Consider an employee under an incredible amount of stress. Would it be fair for an employer to discipline him because of the stress-caused impairment? The use of illegal drugs is not protected under the Americans with Disabilities Act, but disabilities are protected. Could using a test of impairment as a test of employment put employers in legal jeopardy? Blood and saliva testing would detect THC instead of the metabolite and would reflect very recent use of marijuana, but positive tests don’t necessarily indicate impairment.  The Canadian Centre for Occupational Health and Safety (CCOHS) has developed a strategy for addressing workplace impairment from marijuana. CCOHS notes that impairment can result from fatigue, life stresses, prescription drugs, and so on. CCOHS makes it clear that Canadian employers have a duty to provide a safe work environment, as well as a duty to accommodate employees with diagnosed medical conditions or disabilities. Employers in the U.S. should embrace this duty, too.    LAMONT BYRD is director of Safety and Health for the International Brotherhood of Teamsters. CARL W. HEINLEIN, ARM, CIT, CPEA, CRIS, CSHM, CSP, FAIHA, OHST, STSC, is senior safety consultant at the American Contractors Insurance Group. JANET L. KEYES, CIH, FAIHA, is a founder and principal of CHESS, a safety and health consulting firm. JASON MCINNIS is the Canadian Director of OH&S for the Boilermakers International union. DIANE RADNOFF, P.Eng., M.Eng., CIH, is senior occupational hygienist with Alberta Ministry of Labour and Immigration. SCOTT SCHNEIDER, CIH, FAIHA, recently retired as director of Occupational Safety and Health for the Laborers’ Health and Safety Fund of North America. The authors are members of a project team for the AIHA Construction Committee. Send feedback to The Synergist.