Audra Dieffenbach enjoyed working in the purchasing department at MaineHealth, the company that runs a dozen hospitals in the state.

So when the opportunity came this summer for the Wells woman to switch from a temporary procurement assistant to a permanent position as a buyer, she was thrilled when her managers suggested she apply.

Everything went well for Dieffenbach, until the final step – a drug test, which was mandatory because MaineHealth receives federal funding.

She was stunned when she flunked the urine test, tripped up by tiny amounts of THC, the chemical responsible for marijuana’s psychological effects, apparently present in a CBD supplement she takes to relieve pain from endometriosis. CBD, or cannabidiol, is derived from cannabis, but it typically contains little or no THC and is widely used for medicinal purposes.

Not only did she not get the permanent job, she was fired from her temporary position, as well, and is now looking for work.

“It was really shocking,” Dieffenbach said. “I just didn’t think that would happen based on me taking a supplement. I had done everything right up to that point.”

Dieffenbach’s case illustrates the murky employment waters companies and employees are trying to navigate in a world where Maine and federal laws differ markedly on marijuana. Under federal law, marijuana is a Schedule 1 drug – dangerous and with a high likelihood of abuse. Other Schedule 1 drugs include LSD and heroin.

In Maine, marijuana for both medical and recreational use is legal.

That difference creates uncertainty over employment law, throwing many hiring practices into uncharted waters. Most federal jobs, or jobs with companies that receive federal funding or operate under federal regulation, require drug tests before hiring new employees. Other companies test for certain jobs that entail high risks, such as operating heavy equipment.

But Maine law generally bars pre-employment drug testing for marijuana, except for applicants required to be tested under federal rules.

So someone applying to be a clerk in the office of a private company that doesn’t receive federal money should not undergo drug testing for marijuana. But that same person applying for a job with a federal defense contractor, like BIW or Pratt and Whitney, would. MaineHealth requires drug testing of job applicants because it receives Medicare funding.

Last week, workers at the Twin Rivers paper mill in Madawaska successfully ratified a new union contract that removes THC from its random drug testing list.

Michael L. Buescher, a lawyer with Drummond Woodsum in Portland who specializes in cannabis law, acknowledges workplace laws are unclear.

“What I can say with certainty is that there is some uncertainty,” Buescher said. “The rules and regulations right now are in flux. There’s a lot of uncertainty and it’s confusing.”

Because people can legally use cannabis products, employers in Maine must apply a “reasonable suspicion” threshold when determining if an employee is impaired on the job. Employers can take action only if they have a “reasonable suspicion” that an employee is using marijuana at work or is under the influence when on the job.

The changes were adapted in Maine law in the wake of a 2016 referendum that legalized adult-use marijuana and resulted in changes to employment law that took effect in 2018. Maine is still drafting its rules for recreational marijuana use, Buescher said, and some of the employment laws might be changed as a result.

MaineHealth declined to comment on Dieffenbach’s case specifically, but said it conducts pre-employment testing under Maine and federal guidelines. Spokesman John Porter said the company uses a 50-nanogram level for initial screening. If the results show THC levels above 50 nanograms per milliliter of urine, a second test is conducted. A person fails that test if the reading is above 15 nanograms. Dieffenbach’s second test showed 24 nanograms.

She says she was using a supplement called Amethyst Elixir, made by a Freeport company. The company’s website says its water-soluble CBD is made from hemp and contains less than 0.3 percent THC, which is the legal limit under federal law. It also posted a certificate of analysis that shows its THC content, by weight, is 0.28 percent.

Dieffenbach said she was taking about 1,000 milligrams a day, a little higher than the recommended dosage, because she had been taking the supplement for a couple of years. Other people using the supplement, she said, suggested she increase the dosage to maintain the benefits and she had also read that 1,000 mg is more effective in cases with chronic inflammation.

When the test results came back in early August, Dieffenbach said, she was classified as “non-negative”: The test showed that she had 24 nanograms of THC per milliliter of urine, above the federally prescribed limit of 15 nanograms.

Dieffenbach appealed, but to no avail. The company did not conduct a new test, she said, and not only was her promotion and permanent hire rescinded, her job as a temporary employee was terminated on Aug. 26.

She said she emailed MaineHealth before she was originally hired, in February, to tell them she was taking a CBD supplement and no one voiced any objections. Dieffenbach, who continues to take the CBD supplement to relieve the pain from the endometriosis, said she has no hard feelings toward MaineHealth, and felt that the company, her supervisors and co-workers were supportive during her time there.

But “as a temp, I was making a minimal amount and just scraping by,” she said, so she was looking forward to a permanent job at higher pay and with benefits.

CBD is very popular and used in a wide variety of products, said Matt Simon, the New England political director for the Marijuana Policy Project, a group that supports marijuana legalization efforts.

“There’s a huge unlicensed market,” Simon said, and the levels of THC vary. “It’s somewhat difficult to remove all of it.”

He said testing is problematic in that environment.

“This touches on the difficulty of regulating cannabis products,” he said. “Employers are losing out on good employees in many cases.”

Only Nevada and New York City have outright bans on pre-employment drug testing, and the District of Columbia is considering one, said Morgan Fox, a spokesman for the National Cannabis Industry Association. He said those bans allow exceptions for positions that affect public safety, transportation and law enforcement.