THC levels in stoned driving bill based on broad research

By Sen. Steve King

Although some people have objected to the levels of THC — the chemical component of marijuana that makes you high — allowed in the blood under the recently passed bill to regulate driving under the influence of marijuana, here is why the five nanogram per se level is essential to ensuring public safety:

✔ The five nanogram per se level for Delta 9 THC in whole blood equals the highest legal level for intoxication in the country and the world.

✔ THC has been shown to impair cognition, psychomotor function and actual driving performance and therefore crash risk, based on a 2009 study.

✔ Significant driver impairment occurs with one nanogram per millileter of Delta 9 THC in blood, and crash risk increases significantly at 2 to 5 ng/ml, according to another study released in 2009.

✔ Delta 9 THC in whole blood is indicative of extremely recent marijuana intake because, once ingested or smoked, Delta 9 THC rapidly metabolizes in the body. This occurs in two to three hours. As a result, 98 percent of users will be below 1 ng/ml in four to six hours after intake.

✔ Chronic users (such as those individuals who use medical marijuana) regularly measure at one to three ng/ml, well below the five nanogram limit. Their levels will decrease to this base range in two to three hours after intake.

Fourteen states already have DUI per se levels for marijuana. The per se levels in these states are all lower than five nanograms and are more restrictive.

Furthermore, drivers impaired by marijuana use are the second most substantial danger on Colorado roads after those impaired by alcohol.

✔ In 2009 there were 8,625 DUI tests performed in the state. Of these, 934 drivers tested positive for THC, and 222 of them were above five ng/ml. The following year, 1,376 of the 10,431 drivers for whom DUI tests were conducted tested positive for THC, and 523 of these drivers were above five ng/ml. In 2011 there were 10,393 DUI tests conducted in the state, with 1,435 of these drivers testing positive for THC and 574 of them above five ng/ml.

✔ In fatalities involving Colorado drivers with a positive drug test, 55 percent of those drivers test positive for cannabis, according to the Colorado Department of Transportation’s “Heat is On” Campaign 2011.

✔ A growing percentage of teenagers do not see marijuana use as a distraction while driving and almost one in five (19 percent) say they have driven shortly after using marijuana. By comparison, 13 percent say they have driven under the influence of alcohol, USA Today reported last year.

The USA Today report also cited a study by Students against Destructive Decisions establishing a “dangerous trend” toward acceptance of marijuana among teens. Additionally, the same newspaper article also reported that, for the fourth straight year in 2011, daily use of marijuana was at a 30-year peak among high school seniors.

This bill passed by the Colorado Legislature this year, for which I was the Senate sponsor, will provide a strong deterrent to impaired driving under the influence of marijuana similar to the deterrent effect of the 0.08 blood-alcohol level in alcohol-related DUI cases.

This bill follows the precedent of Colorado’s current DUI alcohol standard by using science to set reasonable standards on substances that impair the ability to drive. It does not change law enforcement procedures in any way. It merely allows a jury a permissive inference of guilt if five ng/ml of Delta 9 THC is present within two hours of driving.

This bill demonstrates the state’s recognition of the potentially dangerous consequences of driving while impaired by marijuana and puts drivers on notice that Colorado considers this offense just as dangerous as driving under the influence of alcohol.

This legislation is first and foremost a traffic safety bill and focused on keeping dangerously impaired drivers off the road. It will save lives, protect our communities and still allow for the responsible and legal use of medical marijuana. 

Sen. Steve King represents Mesa County in the Colorado Legislature. He has been working on bills to set a quantifiable standard for driving under the influence of marijuana for the past three years.


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So, there were two studies in 2009, but you couldn’t bother to cite them? How can anybody know how valid the studies actually are if they can’t access them? Oh I get it, you are a politician so I should just believe you because you said so…

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