Article by Mike Hager, 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.
It’s an issue that several provinces have also raised as a major concern. Most recently, British Columbia’s Solicitor-General, Mike Morris, told the B.C. Liberal Party’s convention on the weekend that he favours such a zero-tolerance policy when it comes to drivers and cannabis. Mr. Morris noted that Australia has implemented such a policy.
But M.J. Milloy, an infectious-disease epidemiologist who is studying the therapeutic effects of marijuana at the B.C. Centre for Excellence in HIV/AIDS, said enforcing a zero-tolerance approach would be problematic because roadside testing could capture traces of tetrahydrocannabinol (THC), the psychoactive compound in cannabis, long after the driver feels any sort of high.
“THC sticks around for a long time,” he said, adding that blood tests can reveal traces of the compound two weeks after marijuana is consumed.
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.