With less than a month until federal legislation makes recreational cannabis legal in Canada, experts say gaps in understanding about the drug and impairment remain the biggest challenge facing employers preparing for the change.

Before Oct. 17, experts say workplaces should update substance use policies to include cannabis.

Éric Courcelles, director of strategy for World Trade Center Winnipeg, said while some of the updates may seem like common sense — "don't come to work high or drunk" — the fine points of what precisely that means and setting standards to prove it are touchy.

The centre has run an information session on cannabis in the past, and he said some employers voiced anxiety or lack of understanding about the drug and legalization.

"The [question] that we've seen the most is people wondering, 'What is considered inebriated? What is considered high?'" Courcelles said.

"Someone having a beer is not necessarily drunk. Is it a question of how many grams, is it a question of hours? How is that broadly defined?"

Workplace safety, impairment and increased use of cannabis were the main concerns identified by employers in a Conference Board of Canada report.

Allison Cowan, spokesperson for the Conference Board of Canada, said a Conference Board report earlier this year suggested Canadian employers' top concerns are workplace safety, impairment and increased use of cannabis. The report highlighted the importance of employee education following legalization.

Cowan said cannabis isn't as well-understood by science or the public as, say, alcohol. It lingers in the body longer after consumption and impairment is less predictable based on quantity.

Different strains contain different amounts of the intoxicating compound THC — medical strains, for instance, may be far less potent than recreational options. There's still some controversy around testing for the drug, including concerns about invasiveness and accuracy.

"For the most part, we have a really solid understanding of how alcohol works. With cannabis, we don't.… There's no way of saying, 'Well, here's a hard-and-fast test where we can say yes you're impaired right now or no, you're not,'" said Jamie Jurczak, a Winnipeg-based lawyer who leads sessions advising employers on workplace cannabis policies.

"That is the challenge of cannabis. That is the grey area, and that is what's posing the biggest issue for, I would say, employers who are going to have deal with this in the workplaces."

'We have to work with what we've got'

In running information sessions — which have been organized by World Trade Centre Winnipeg, Chartered Professionals in Human Resources Manitoba and other groups — Jurczak said she's seen an appetite from employers to address cannabis proactively.

Some policies don't need to be updated extensively, while others need to incorporate accommodations for medical use, she said.

Employers with concerns about workplace intoxication still have tools to assess impairment, Jurczak said.

Unlike in a criminal court, they don't need to prove intoxication beyond a reasonable doubt — they just need to assess the likelihood that cannabis impairment had a role in the person's performance, or whether somebody breached workplace policies.

That may be determined on a more individual basis or in combination with medical information and testing, she said.

"The training and the policy … is being developed in a world where we have to work with what we've got, which is those grey areas, and how do we deal with those grey areas in an effective way," she said.

"We don't have all of the answers yet, and I think those answers are going to be developed over time. But that's not to say [that] with the information that we currently have and the tools that we do have there is no way to deal with this."

The important piece is that employers are educated about myths and misconceptions around cannabis, and that they make their rules and consequences clear to employees and managers, Jurczak said.

'Iterative process'

Ron Gauthier, CEO of  Chartered Professionals in Human Resources Manitoba, said employers need to look at their specific circumstances and the impact of impairment in their workplace.

The group is running an information session on cannabis for its members next month, he said, at which Jurczak will be a presenter.

"Each organization has to look at its own situation and its own uniquenesses, and create a policy that works for them and supports their culture and their guiding principles as well," he said.

The Conference Board's Cowan said employers aren't expected to get it perfect the first time around.

"It's going to be an iterative process. Regardless of opinion, the legalization of recreational cannabis is coming and we will all have to adapt," she said.

"But I do think that employers will play a really critical role in shaping the way forward and a really critical role in education for people."