This blog has been examining the ramifications of Initiative-502, a referendum that was passed by Washington voters earlier this month. The measure decriminalized possession of less than one ounce of marijuana and opened the door for state-licensed shops to sell pot.
The new statute also established a baseline level of impairment above which drivers could be charged with DUI. That level is five nanograms of active THC (the psychoactive component of marijuana) per milliliter of blood. But will the establishment of this baseline accomplish the statute’s goal of reducing the number of marijuana-impaired drivers on the state’s roads?
Some speculate that the 5 nanogram level is equivalent to a .05 blood alcohol content, which is below the .08 alcohol baseline which establishes driving while intoxicated. But the National Institute on Drug Abuse reports that studies on the potency of marijuana vary widely (in large part because the drug remains illegal and is therefore less likely to be studied).
One federal study determined that after a person smokes a one-gram joint, his or her THC level would fall below the 5 nanogram threshold within hours. However, that research project used government-provided marijuana, which pot advocates say is about one-fourth of the potency of the drug sold at medical-marijuana dispensaries in the Seattle area. And there’s this disturbing finding: in heavy users (like medical marijuana patients), active THC can linger in the bloodstream for a much longer period.
One study discovered active THC in the system of a person six days after abstaining from the drug; that individual reportedly smoked 10 “large joints” on a daily basis. (Carboxy-THC, which is a different form of the compound that often gets stored in pot users’ fat cells for up to 30 days, is not used as a basis of impairment under the new law.) One thing’s for sure: the science behind marijuana usage is evolving, and it’s unclear how it will affect DUI prosecutions for marijuana in Washington in the near future.