Following the lead of a pioneering few, more states around the country are warming up to the idea of legalizing marijuana use for medical or recreational purposes, or both. But with legalized pot still in its infancy, it may be a while before insurers get a clear idea of its impact on society and how liability stemming from marijuana use may affect coverage issues.

In the meantime, employers in states that have legalized pot are assessing how to avoid liability by minimizing pot’s potential adverse effects on the workplace.

Kevin Glennon vice president of clinical education and quality assurance for One Call Care Management, a large provider of specialty services for the workers’ compensation industry, told an audience at the RIMS 2015 Conference on Wednesday that the circumstances present a challenge for companies that have established themselves as a “drug free workplace.

“One problem is, how do you determine the level of intoxication in someone who uses pot,” Glennon said.

THC, tetrahydrocannabinol, is the chemical contained in marijuana that produces most of its psychological effects. “It’s the component that gives you the euphoric high and alters your state of well being,” Glennon said.

So far, unlike with alcohol use, neither regulatory nor law enforcement authorities in states where pot has been legalized have set a benchmark for the amount of THC in one’s blood that constitutes intoxication.

In addition, accurately assessing a person’s marijuana use, even from a blood test, is not a slam-dunk.

Glennon explained that the THC drawn into the body through smoking or ingesting weed is stored in fatty tissues and released slowly into the bloodstream. Traces of the chemical can be found the urine of an occasional user for up to five days after consumption. But in a person who uses several times a week over a period of years, THC may remain detectable for six weeks or more, he said.

“Blood tests are just not reliable, and they can take up to three weeks to get results – there’s no breathalyzer test for marijuana,” Glennon said.

Markie Davis, risk manager for the state of Colorado, which has legalized pot for both medical and recreational purposes, said another issue that puts employers in a difficult position is conflict between state and federal laws.

Under the federal Controlled Substances Act of 1970, marijuana remains classified as a Schedule 1 substance, meaning that its cultivation and distribution are felonies. Possession of pot for personal use is a misdemeanor, but cultivating more than 100 marijuana plants carries a mandatory five-year prison sentence.

In Colorado, which legalized recreational pot through a voter initiative in 2012, the Legislature passed basic state rules governing it. A person must be at least 21 years old to buy, possess or consume, and must be a Colorado resident in order to buy up to one ounce.

Davis said that because the state has experienced a big jump in tourism stemming from legalized pot, the Legislature did not want to discourage visitors from using weed, and so decided to allow non-residents to buy up to 1/4 ounce at a time.

The state’s laws for both medical and recreational marijuana note that employers may continue to enforce their drug-free workplace policies, though Davis said most employers are limiting their random drug-testing to employees whose jobs can directly affect their own or others’ safety.

The results of the Colorado’s legalization move are clear in its budget. Taxes and fees from the marijuana business pumped $76 million into state coffers last year, stemming from $700 million spent by consumers on marijuana.

“That’s a lot of pot,” Davis said.

Pot’s revenue potential is drawing other states into the fold. Alaska, Oregon and Washington, have legalized weed for both medical and recreational use, as has Washington, D.C.

Davis said that with broad use still relatively new in Colorado, authorities have not yet amassed solid data or other information about the impact it may be having in workplaces.

“One of our biggest struggles has been with (regulating pot use in) driving,” she said. “Every year there’s a new bill to try to establish a legal limit for driving under the influence of marijuana,” but because a regular user may have higher levels of THC and be less impaired than a one-time user, the state has not been able to arrive at a fair standard, she said.

While the state lacks reliable data as to whether marijuana has increased violent crime or highway accidents, or reduced workplace safety, “I don’t think we’ve seen anything dramatic from a risk management standpoint,” Davis said.

Nevertheless, many regulators are standing firm against marijuana use. The medical use of pot is not approved in Official Disability Guidelines, or by the American College of Occupational and Environmental Medicine or any state medical treatment guidelines, and it would be denied in utilization review, even if recommended by a treating physician, Davis said.

In addition, the American Society of Addiction Medicine and the American Cancer Society remain opposed, as does the American Glaucoma Society, even though some opinions suggest that pot can reduce intraocular pressure.

Despite growing interest in legalization among states, there is simply a lack of evidence to support the use of marijuana for medicinal purposes, Davis said.

Finn is a New Orleans-based freelancer writer.