Proponents of workplace drug testing policies for pot have long alleged that random testing improves workplace safety. But do they? A newly published case-control study published online ahead of print in the Journal of Addictive Diseases says "no."
 
The study, authored by the Medical Director of St. Mary’s Occupational Medicine Clinic in Evansville, Indiana assessed whether there exists a statistical association between marijuana use, as defined by the identification of the inert carboxy THC metabolite in urine, and an elevated risk of work-related accidents. The author compared the prevalence of marijuana-positive tests among employees involved in workplace accidents to a random sampling of employees not involved in workplace mishaps. Drug tests were analyzed and compared from employees who worked in variety of industries located throughout Indiana, Kentucky, Missouri, Ohio and Pennsylvania.
 
The study determined that marijuana-positive test results were not correlated with any greater frequency of workplace accidents.
 
“This study fell short of finding an association between marijuana use and involvement of workplace accidents.” The author added, although “this study cannot be taken as definitive evidence of absence of an association between marijuana and work related accidents, … the findings are compelling.”
 
The findings were also predictable. A 2010 review of 20 years of published literature pertaining to cannabis, drug testing, and workplace performance similarly concluded, “[I]t is not clear that heavy cannabis users represent a meaningful job safety risk unless using before work or on the job; urine tests have poor validity and low sensitivity to detect employees who represent a safety risk; … [and] urinalysis has not been shown to have a meaningful impact on job injury/accident rates.”
 
This is largely because standard workplace drug tests are urine tests. Conventional urinalysis -- even when the results are confirmed -- only detects the presence of inert drug metabolites, non-psychoactive by-products that linger in the body’s blood and urine well after a substance’s mood-altering effects have subsided. That is why the US Department of Justice acknowledges: “A positive test result, even when confirmed, only indicates that a particular substance is present in the test subject’s body tissue. It does not indicate abuse or addiction; recency, frequency, or amount of use; or impairment.”
 
A positive test result for carboxy THC, marijuana’s primary metabolite, provides little if any substantive information to employers. That is because carboxy THC, unlike most other drug metabolites, is fat-soluble and may remain detectable in urine for days, weeks or, in some rare cases, months after a person has ceased using cannabis. Most other common drug metabolites are water soluble and therefore undetectable some 24 hours or so after ingestion.
 
In short, a positive test result for carboxy THC does not provide any definitive information regarding an employee’s frequency of cannabis use, when he or she last consumed it, or whether he or she may have been under its influence at the time the drug screening was administered. Further, such tests discriminate against pot consumers -- who are more likely to be detected by the nature of test itself, yet pose no demonstrable workplace safety risk compared to non-tokers. As more states move forward with amending marijuana laws, employers should follow suit by, at a minimum, revisiting their existing workplace drug testing policies for pot or, preferably, repealing them altogether.