Share story

VOTERS have declared that it is time to rethink our marijuana policies. It’s also time to rethink the practice of drug testing for pot.

The enactment of Initiative 502, which legalized recreational marijuana use in Washington state, is an ideal opportunity for employers to re-examine their drug-testing policies regarding employees’ off the job cannabis use. Those who consume alcohol legally and responsibly while off the job do not suffer sanctions from their employers unless their work performance is adversely affected. Employers should treat those Washingtonians who consume cannabis legally while away from the workplace similarly.

Programs that mandate the random testing of employees’ urine for alleged traces of drug residue are invasive and ineffective. They neither identify workers’ who may be impaired nor do they contribute to a safe work environment.

Immunoassay testing, the standard technology utilized in workplace urinalysis, relies on the use of antibodies (proteins that will react to a particular substance or a group of very similar substances) to document whether a specific reaction occurs. Therefore, a positive result on an immunoassay test presumes that a certain quantity of a particular substance may be present in the sample, but it does not actually identify the presence of the substance itself.

Why is this distinction significant? It’s significant because the consumption of many non-illicit drug products, from certain types of bagels to baby shampoos, may also trigger similar reactions on the immunoassay test. These incidences are known as false positives. That is why experts recommend that a more specific chemical test, known as chromatography, be performed in order to confirm any preliminary analytical test results. However, because this test is far more expensive than immunoassay testing, many private employers elect to skip this process altogether.

But even this latter test possesses serious limitations. In particular, conventional urinalysis — even when 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 U.S. 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 cannabis 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 the influence of the substance at the time the drug screening was administered.

Aside from the procedure’s practical limitations, there are larger philosophical questions raised by random workplace drug testing. Studies indicate that employees who engage in cannabis use in their off hours are little different from their peers. Their workplace performance seldom differs from their co-workers, many of whom consume alcohol, and they do not pose an increased safety risk.

Writing in the journal Addiction, investigators at the University of Victoria in British Columbia reviewed 20 years of published literature pertaining to the efficacy of workplace drug testing, with a special emphasis on marijuana. “[I]t is not clear that heavy cannabis users represent a meaningful job safety risk unless using before work or on the job,” they concluded. “Urinalysis testing is not recommended as a diagnostic tool to identify employees who represent a job safety risk from cannabis use.”

So why are Washington employers still engaging in it?

Paul Armentano is deputy director for the National Organization for the Reform of Marijuana Laws and co-author of “Marijuana Is Safer: So Why Are We Driving People to Drink?”