Approximately 150 employers from across Alberta met in Edmonton on Friday to discuss the likely impact of cannabis legalization on the workplace.

Many of the employers at the Cannabis At Work conference are already playing catchup as more and more of their employees are being prescribed medical marijuana.

"The rates [of use] are going up. The amount of conditions that medical cannabis seems to support or improve are quite broad. It does have a lot of pharmaceutical benefit," said Jason Sheehy, director of occupational health services at SureHire, a company that conducts drug tests for employers.

Alison McMahon, the CEO of Cannabis At Work, started the conference to highlight the challenges that marijuana legalization is presenting for employers. (Travis McEwan/CBC) "People do have the right to access medical cannabis and to use it, but that's in direct conflict with workplace safety, which is where this conflict and rub exist," said Alison McMahon, the CEO of Cannabis At Work.

As employers work through that, there's also the expected legalization of marijuana, which could lead to even more employees lighting up.

Just last week, Prime Minister Justin Trudeau said new marijuana legislation should be ready by the summer.

Sheehy says that as this legislation is updated, employers need to update their drug policies too.

"It's not a blanket policy that if someone has evidence of any drug in their system that they're incapable of work. That's not really the way we want to go," he said.

Jason Sheehy says Alberta employers should adjust their drug policies to prepare for increased marijuana use after legalization. (Travis Mcewan/CBC) "The policy really should be about responsible suspicion, about concern, near-miss or post-incident testing."

No test for 'active impairment'

But here's the catch: THC can remain in the body for prolonged periods, meaning an employee can't necessarily prove that they weren't impaired while working.

"We don't have a test today that measures active impairment. We can only use tests to measure recent use. It makes it more challenging for us as employers," said McMahon.

For potentially dangerous jobs, many employers have a zero-tolerance policy. McMahon says even if marijuana is legal, employers in these jobs may want to pass on pot.

"While technically you can do what you want in your personal time, if you held a safety-sensitive position and were subject to drug testing as part of that job, you could still fail a drug test and be subject to whatever disciplinary process an employer has in their policies about that."

The City of Edmonton is also being proactive in the leadup to marijuana legalization. A report will be presented to council on Tuesday outlining new bylaw changes. It is expected to include considerations around retail cannabis sales in preparation for legalization.

@Travismcewancbc

Travis.mcewan@cbc.ca