(Unsplash)

Low levels of THC in marijuana don’t increase car crashes: B.C. study

It’s possible the impact of cannabis may increase if legalization means more people drive after using it

Smoking marijuana containing low levels of the drug’s main psychoactive ingredient does not increase most drivers’ risk of a crash even though Canada’s impaired-drug laws would penalize them, says the lead investigator of a study that analyzed THC amounts in the blood samples of more than 3,000 people who were injured behind the wheel.

Dr. Jeffrey Brubacher, associate professor in the department of emergency medicine at the University of British Columbia, said the findings apply to THC levels of less than five nanograms per millilitre of blood.

Changes to the Criminal Code when marijuana was legalized last fall set the legal blood drug concentration limits for THC so drivers with two to five nanograms in their system face a maximum $1,000 fine.

Brubacher, a toxicologist who is also an emergency room physician at Vancouver General Hospital, said blood samples taken between 2010 and 2016 at seven trauma centres as part of clinical care were used for a broad spectrum of analysis measuring THC, other recreational drugs, such as cocaine, heroin and amphetamines, as well as sedating medication.

READ MORE: 60% of British Columbians favour cannabis testing at work

The findings, published recently in the journal Addiction, show alcohol is the biggest factor in impaired-driving crashes, followed by recreational drugs, such as cocaine, heroin and amphetamines, which increased crash risk by 82 per cent. Other drugs including sleeping pills and antidepressants hiked the risk by 45 per cent.

“The complicated factor is people who use it (marijuana) medically or recreationally every day, they will have small levels in that two to five (nanogram) range,” Brubacher said. “They can have those levels days after they last use because it accumulates in the fat.

“The upside of having the low (legal) limits is that they set a very clear message: If you’re going to smoke pot, don’t drive.”

READ MORE: Impairment measurements unclear for cannabis and driving

It’s possible the impact of cannabis may increase if legalization means more people drive after using cannabis, says the study, which also included the universities of Victoria and Toronto, Dalhousie University in Halifax and the Centre for Addiction and Mental Health.

“It is also important to caution that the risk associated with cannabis may be higher in young drivers, who have a high crash risk at baseline, or in inexperienced cannabis users, who may be less able to compensate for cannabis-induced impairment,” it says.

Brubacher said how long the drug lasts in someone’s system depends on the dose, the form in which it is taken and what it was mixed with, making clear guidelines difficult when compared with alcohol.

“With co-use of alcohol and cannabis all bets are off when you do that. If you use the two together you’re going to be impaired and your risk is going to go up,” said Brubacher, adding impaired drivers tend to get into worse crashes that result in more serious injuries and sometimes death.

Chief Const. Mike Serr of the Abbotsford Police Department, who is co-chair of the drug advisory committee for the Canadian Association of Chiefs of Police, said more studies are needed to provide a clear idea of how much cannabis affects people’s ability to drive.

“If someone has smoked a joint and they’re clearly able to communicate and operate a vehicle then typically that is not going to come across our radar,” he said.

Police are waiting for a roadside device that would go beyond testing for the presence of marijuana in a driver’s saliva to providing a precise amount, Serr said.

Camille Bains, The Canadian Press

Like us on Facebook and follow us on Twitter.

Just Posted

All Nations Driving Academy gets $360K boost from province

Terrace-based driving school bridges gap in services for remote northwest B.C. communities

Skeena Watershed reopened for recreational pink and coho

Four sections and tributaries remain closed

Skeena-Bulkley Valley candidates react to finding Trudeau broke ethics law

The election campaign is heating up before the writ has even dropped

Burns Lake golfers to help end world hunger

Burns Lake residents will bring together charity and golf at the Grip… Continue reading

Houston area ski club proposes new community forest

Morice Mountain has ‘huge untapped potential’

QUIZ: How much do you remember about Woodstock?

Weekend music festival in Bethel, New York, was held 50 years ago

Advocates ‘internationalize’ the fight to free Raif Badawi from Saudi prison

Raif Badawi was arrested on June 17, 2012, and was later sentenced to 1,000 lashes and 10 years in jail for his online criticism of Saudi clerics

RCMP, search crews hunt for 4-year-old boy missing near Mackenzie

George went missing early Saturday afternoon

Canadian entrepreneurs turning beer byproduct into bread, cookies and profits

Some breweries turn to entrepreneurs looking to turn spent grain into treats for people and their pets

Canada ‘disappointed’ terror suspect’s British citizenship revoked

Jack Letts, who was dubbed “Jihadi Jack” by the U.K. media, has been detained in a Kurdish prison for about two years

Chrystia Freeland condemns violence in Hong Kong, backs right to peaceful assembly

There have been months of protests in the semi-autonomous region

B.C. VIEWS: Log exports and my other errors so far in 2019

Plastic bags, legislature overspending turn out differently

‘It’s just the freedom:’ Paralyzed Broncos player pursuing life on the water

The former Humboldt Broncos goaltender, who started in the net when he was nine, was paralyzed last year

Most Read