With adult recreational sales of marijuana soon to begin in Ohio, detecting and punishing people driving under the influence of marijuana remains difficult.
While alcohol-related DUI offenses have a long-accepted standard of measuring sobriety—blood alcohol content—measuring whether someone is impaired by marijuana consumption is more murky.
Ohio’s current standard relies on whether THC or its metabolites are present in urine and blood, but some advocates and lawmakers believe the tests can’t discern whether someone is currently under the influence of THC or simply used it within the past few days.
When can you buy recreational marijuana in Ohio
As of Friday, 15 marijuana cultivators and 15 processors received certificates of operation from the state to produce recreational weed. Dispensaries must undergo a similar process before anyone can purchase, but some estimate sales will open for adults 21 and over as early as September.
Rates for cannabis-only DUIs are difficult to find. In a 2018 federal survey on substance abuse, 12 million (4.7%) Americans reported driving under the influence of marijuana in the past 12 months, and 2.3 million (0.9%) reported driving under the influence of other drugs.
There’s some evidence to suggest that loosening marijuana laws could lead to more marijuana DUIs; the National Highway Traffic Safety Administration found that the number of weekend nighttime drivers testing positive for THC increased by 48% from 2007 to 2013-2014, a period in which several states legalized recreational marijuana use.
No music, no celebratory signs:What Ohio forbids for the start of recreational weed sales
What Ohio says about driving under the influence of marijuana
Under Ohio’s current law, someone is deemed intoxicated if their blood has 10 nanograms of THC per milliliter (ng/ml) or if their urine contains more than 2 ng/ml.
Someone could also face DUI charges if their blood contains 50 ng/ml of THC metabolites, or if their urine contains more than 35 ng/ml of THC metabolites, which are created as the body processes marijuana. Only less than 15 ng/ml are allowed in the urine or 5 ng/ml in the blood if the person also has alcohol or other drugs in their system.
Breathalyzers for weed have not gained the same widespread use as alcohol breathalyzers, which measure ethanol in the breath to accurately detect blood alcohol content. Researchers at Colorado University say their research in attempting to develop one found that THC levels in frequent cannabis users’ breath returned to normal just an hour after use, shorter than the effects of marijuana typically last.
One company, California-based Hound Labs, says it has successfully developed a marijuana breathalyzer. The company markets the devices for use in workplace screenings, saying other tests could detect marijuana use days after the fact and unfairly target employees who legally use off the clock.
But Hound Labs stresses that its breathalyzer detects recent cannabis use, not whether someone is currently impaired.
What are the other challenges of measuring marijuana use?
The challenges of measuring marijuana impairment have attracted the attention of Ohio lawmakers.
A bill in the Ohio Senate would require marijuana intoxication to be measured by actual THC in the blood or urine, not metabolites. Since the compounds are already metabolized, they don’t produce a high, supporters of the bill say.
Senator Nathan Manning, R-North Ridgeville, sponsored the bill, which is currently in the Senate Judiciary Committee. Manning introduced a similar measure in the previous General Assembly, but the bill was unsuccessful.
“We really want to get a good law in place where people are being punished if they are impaired, but they’re not being unfairly punished just because they have a certain amount of the drug in their system,” Manning told the Dispatch in a January interview.
Manning’s bill would define marijuana intoxication as over 25 ng/mg of THC in the person’s blood or 5 ng/mg in the urine.
