The discrepancy between state and federal views on the use of medical or recreational marijuana has presented a significant challenge for employers, especially those that have operations in multiple states. While the possession, distribution or manufacture of marijuana remains illegal under federal law, reversal of state prohibitions began with California’s Compassionate Use Act of 1996. Twenty states plus the District of Columbia currently have medical marijuana laws, and many other states are in the process of evaluating whether to permit marijuana use for medical treatment. Colorado and Washington are the two most recent states to approve the recreational use of marijuana.  

It is relatively clear-cut that employees who undergo federal drug testing programs (e.g., from the Department of Transportation) are prohibited from using any Schedule I drug, including cannabis, even if under the recommendation of a physician. Some employers—especially those that aren’t covered under federal drug testing programs—may ignore issues surrounding
state-approved recreational use if they do not have operations in states where marijuana is permitted. However, if their employees visit states that permit use by nonresidents, they could encounter an issue within the company’s drug testing program.

In the construction industry, the major concern is that an employee under the influence of marijuana is at risk of injuring himself or others in the workplace or on a jobsite. Marijuana use also carries the risks of increased absenteeism and decreased productivity.

Virtually all states permit employers to prohibit both using and being under the influence of marijuana while at work. Many states are silent on marijuana use outside the workplace and its impact on workplace drug testing, but some states specifically disallow an employer from attempting to prohibit marijuana use by employees outside the workplace. There is currently insufficient information to understand the relationship between off-shift marijuana use and workplace safety and productivity.

For some substances such as alcohol, the degree of impairment is assumed based on predetermined blood levels; however, for marijuana, it is extremely difficult to establish a relationship between a person’s THC blood or plasma concentration and performance-impairing effects. Yet, some states are evaluating impairment based on blood levels of marijuana. Correlating impairment with urine levels is entirely unreliable. The physiologic effects of marijuana on neurocognitive performance may range from several hours to beyond 28 days of subsequent abstinence based on route of delivery (smoked or ingested), the active component in the substance used, the concentration of the active ingredient and the amount used. 

Employers may need to consider whether they are required to provide an accommodation to an employee whose medical condition led to the medical marijuana recommendation. Part of the assessment of whether this accommodation is reasonable might be to evaluate whether the use of marijuana would constitute a safety concern. This would allow medical marijuana to fall under the employer’s safety policy rather than its drug and alcohol policy. The use of medical marijuana should only be
one component of the company’s safety policy; as a whole, the policy should state that the use of any medication that impacts safety will be reviewed and potentially prohibited.

Employers still have the right to prohibit employees from being under the influence of marijuana while at work regardless of the justification for using the drug. It comes down to how a company defines “under the influence” in its policy.

Because of the many issues that can affect a drug testing program, it is essential for all employers to clearly state—to both existing employees and job applicants—how they handle medical and legalized recreational marijuana in non-regulated situations. Because the legal landscape surrounding medical marijuana is almost constantly changing, it is essential to review federal and state law, as well as relevant case law, prior to forming a policy. Additionally, existing policies should be reviewed on a regular basis to assure consistent legal compliance.

Dr. Natalie P. Hartenbaum is chief medical review officer at FirstLab and OccuMedix, Inc., as well as serves on the faculty of the University of Pennsylvania and is the medical director of the Federal Reserve Bank of Philadelphia. For more information, visit

Achieving a Drug-Free Workplace
Interested in learning how to create a workplace free from substance abuse? Visit and pledge to become a partner in the Construction Coalition for a Drug- and Alcohol-Free Workplace. Online resources include state-by-state drug testing laws, a model substance abuse policy, various substance abuse testing methods, and fact sheets on the effects, symptoms and detection of alcohol, amphetamines, cocaine, marijuana, PCP and narcotics.

CNA Insurance also has an informative webinar on the impact of the nation’s prescription opioid epidemic on the construction industry. The presentation covers risk factors and solutions that construction firms can utilize to achieve a drug-free workplace. To view the archived webinar, visit the Academy for Construction Ethics, Compliance & Best Practices (under the Education  Training menu) on