Zero-tolerance policies towards employee cannabis use have been instituted by 40 per cent of Canadian employers surveyed for a recent Conference Board of Canada report.

The survey didn't explicitly define "zero-tolerance," meaning the term could have been open to respondents' interpretations, said Conference Board senior researcher Monica Haberl. But the think-tank's report defined zero-tolerance workplace cannabis policies as those that "(forbid) employees to have any cannabis in their systems." 

Those zero-tolerance policies were more common in safety-sensitive workplaces like transportation and warehousing, as well as the construction, manufacturing, and natural resources industries, the Conference Board found.

According to Alison McMahon, CEO of Cannabis at Work, in practice, workplace drug testing for cannabis isn't truly "zero-tolerance," but typically measures levels of cannabis-derived chemical compounds in a worker's urine or saliva against a "cutoff limit."

"For most organizations that don't have any safety-sensitive operations, or where their employees are not safety-sensitive, it's really just not legally justifiable for those organizations to put in that effort, or to really regulate cannabis use during those off-work hours," Haberl said.

Like roadside drug testing for cannabis, workplace marijuana testing is complicated by the fact that traces of cannabis can be detected in a user's body long after the impairing effects have worn off, especially among regular users.

"It's not processed in the human body in the same way that alcohol is... So as a result I think employers tend to want to err on the side of caution in this case, for obvious reasons, to essentially ensure the safety of the employees and of their clients or customers," said Haberl.

Human resources expert Alison McMahon is CEO of Alberta-based cannabis industry training, recruiting and HR consulting firm Cannabis at Work. In practice, she said, workplace drug testing for cannabis isn't truly "zero-tolerance," but typically measures levels of cannabis-derived chemical compounds in a worker's urine or saliva against a "cutoff limit."

Even though the chemical cutoff limits for cannabis testing aren't perfect from a scientific perspective, McMahon said, they at least establish some kind of boundary for safety-sensitive workplaces. But for workplaces without safety concerns, she said, "there isn't going to be the same justification to implement a drug-testing program."

"And so, in that case, if you don't have a method to actually test people for drugs or alcohol, then it makes it very challenging to implement a zero-tolerance policy." 

Employers generally don't have the legal right to control what employees do in their off-work hours as long as those activities don't conflict with workplace policies, McMahon explained.

But some Canadian employers, including airlines and police forces, have instituted bans on workers using cannabis on their own time. RCMP officers in certain positions, for example, can't use non-medical cannabis within 28 days before a duty shift.

"Science shows that cannabis can intoxicate beyond initial consumption and that there are no established safe limits or data on how it affects performance," the federal police force's website says.

Alison McMahon takes a different view of the assumption that any trace of cannabis in a worker's system could be tantamount to intoxication.

"We're lacking the science to give us a definitive answer on that, and so we're all in this middle ground," she said.

"What it comes down to is, employers are doing their best to maintain the safety of their workplaces, which should be their priority. But individuals are also looking out for their own personal interests, and it's not the first time, I guess, in workplaces where this rub between safety and privacy has been a challenge, and I expect it will continue to be."

The Conference Board of Canada surveyed 163 Canadian employers of various sizes and typesabout their cannabis policies between November 2018 and January 2019. The surveyed sample is not statistically representative of Canadian employers as a whole.