Pot ban on drivers won’t work, health experts say

published on November 8, 2016 by Mike Hager in The Globe and Mail

It would be unrealistic to bar drivers from having any trace of marijuana in their system when it becomes legal in Canada, as B.C. has suggested, because the drug can be detected long after a person is impaired, public-health experts say.

The federal government’s task force on the future of legalization has highlighted impaired driving as one of the core issues it must address before making its recommendations by the end of this month.

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Instead, Dr. Milloy said, the federal government should invest in researching how and to what degree cannabis impairs drivers. Then policy makers can create an objective limit of THC impairment, he said. The best option for testing that limit may be by swabbing someone’s saliva, which could reveal use of the substance hours – not days – beforehand, he added.

Still, he said, Washington and Colorado’s established limits of five nanograms of THC per millilitre of blood are arbitrary because different people can metabolize the drug to widely varying degrees, depending on their body type and history of using cannabis.

There are other barriers to a testing and enforcement regime. Roadside cannabis tests are still in their pilot stages, and researchers are trying to determine how, and at what level, marijuana affects drivers. The Toronto-based Centre for Addiction and Mental Health could release results as early as next month on its three-year study of how marijuana impairs one’s driving ability.