It might be called the cannabis conundrum. As more states have legalized or are moving toward legalizing both medical and recreational cannabis, companies across the country are weighing how to accurately determine whether employees are impaired by cannabis in the workplace.

The issue seems pretty straightforward except for a major problem: There is not currently an effective method of real-time quantitative testing of cannabis impairment.

Medical marijuana is currently legal in 33 states and in Washington D.C. Recreational marijuana is allowed in 10 states and at least 10 more are considering legalizing it in 2019 with more expected to follow in 2020.