Study: Cannabis Use During Off-Hours Not Associated with Elevated Risk of Workplace Accidents

Employees who consume cannabis during their off-hours possess no greater risk of occupational injury than do those who abstain from marijuana altogether, according to data published this week in the Canadian Journal of Public Health.

Researchers affiliated with the University of Toronto, Dalla Lana School of Public Health, assessed the relationship between cannabis use and workplace accident risk in a cohort of 2,745 Canadians.            

Consistent with prior studies, investigators reported “no difference in workplace injury risk” among those employees who consumed cannabis while away from the job versus abstainers.

By contrast, those employees who reported using cannabis during or immediately prior to work experienced a nearly two-fold increased risk of occupational injury.

Authors determined: “In this longitudinal study, we evaluated the relationship between past-year cannabis use and the risk of workplace injury, differentiating workers who used cannabis before and/or at work (workplace use) from those using outside of work only (non-workplace use). While no statistically elevated relationship existed between non-workplace use and workplace injury, workplace use was associated with an almost two-fold increase in the risk of workplace injury.”

They concluded: “Study results bring greater clarity to the question of whether cannabis use increases the risk of experiencing a workplace injury, an issue that the conflicting findings of previous studies have hampered. Findings suggest that, when thinking about the potential occupational safety impacts of a worker’s cannabis use, it is important to consider when that use is taking place. More specifically, only use in close temporal proximity to work appears to be a risk factor for workplace injuries, not use away from work.”

Conventional drug testing for cannabis identifies the presence of either THC or its primary metabolite carboxy-THC. In more habitual consumers, THC may be present in blood for several days post-abstinence. Carboxy-THC may be detectable in urine for several weeks or even months after past exposure. A positive test result for either substance cannot determine whether one has recently consumed cannabis or whether they are under its influence.

NORML has long opined against the use of pre-employment and employment drug detection tests and has instead called for greater use of performance testing technology such as DRUID and AlertMeter.

Writing in a new syndicated op-ed, NORML’s Deputy Director Paul Armentano said: “Requiring would-be hires and employees to undergo urine screens for past cannabis exposure are invasive and ineffective. They neither identify workers who may be under the influence nor contribute to a safe work environment. … Those who consume alcohol legally and responsibly while away from their jobs aren’t punished by their employers unless their work performance is adversely impacted. Those who legally consume cannabis should be held to a similar standard.”

Last month, Michigan regulators moved to abolish pre-employment marijuana screens for most public employees. Lawmakers in Nevada and Washington have recently adopted similar bans.

Additionally, the District of Columbia plus California, Connecticut, Montana, New Jersey, New York, and Rhode Island have amended their laws so that many employees are no longer terminated from their jobs solely because of a positive drug test for THC metabolites. 

The full text of the study, “Workplace and non-workplace cannabis use and the risk of workplace injury: Findings from a longitudinal study of Canadian workers,” is available online. Additional information is available from the NORML Fact Sheet, ‘Marijuana Legalization and Impact on the Workplace.’