LANSING, Mich. – A report released this week by a Michigan state commission recommended the state not set a limit on how much THC drivers can have in their system before being deemed impaired.
The Impaired Driving Safety Commission, a six-member panel mandated by state law to research and recommend a scientifically-supported THC threshold, released its report Friday.
The Gov. Snyder-appointed board is made up of a mix of people from different backgrounds, including a representative from Michigan State Police, a medical marijuana patient, toxicologist, doctors and professors with expertise in the areas of traffic safety and cannabis use.
"Based on the total body of knowledge presently available, the Commission finds there is no scientifically supported threshold of THC bodily content that would be indicative of impaired driving," the report reads in part. "There is a poor correlation between driving impairment and the blood (plasma) levels of THC at the time of blood collection."
According to the report, THC levels in blood drop rapidly, but impairment happens more slowly and peaks after blood levels have already dropped.
Additionally, level of impairment varies based on prior usage.
"The implications of tolerance to cannabis are that lower blood THC levels in infrequent users may result in impairment that would only be experienced at higher THC levels by regular cannabis users," the report’s authors wrote. "Therefore, because there is a poor correlation between THC bodily content and driving impairment, the Commission recommends against the establishment of a threshold of THC bodily content for determining driving impairment and instead recommends the use of a roadside sobriety test(s) to determine whether a driver is impaired."
According to the commission’s report, of the 33 states that have legalized both recreational and medical marijuana, six have adopted impaired driving per se thresholds of THC bodily content in blood:
- Colorado: 5 ng/ml
- Montana: 5 ng/ml
- Nevada: 2 ng/ml
- Ohio: 2 ng/ml
- Pennsylvania: 1 ng/ml
- Washington: 5 ng/ml
Michigan voted to legalize recreational marijuana in 2018, but legislation is still in the works.