Local News

More Impaired Drivers Testing Positive for Marijuana

Feb 27, 2014

In a report compiled by Dr. Fiona Couper, State Toxicologist,  an analysis of impaired driving cases received at the Washington State Toxicology Laboratory the following increases occurred between 2012 and 2013 in THC levels of suspected impaired drivers:


  • 33.87% increase in driving cases confirming positive for THC (delta-9 THC)
  • 39.86% increase in driving cases confirming positive for carboxy-THC (metabolite of THC, indicates marijuana use)
  • 18% increase in driving cases at or above the per se 5 ng/mL level


Delta-9 THC indicates the presence of the active THC drug.  Carboxy-THC measures the metabolite of THC and is indicative of past use of marijuana, in which the THC has been metabolized.  The third number above indicates the number of driving cases where the driver was impaired above the legal limit of 5 ng/mL.

These numbers are significant,  because recreational marijuana use was not legal until December 2012, giving us some really good baseline, or pre-legalization numbers, and an entire year of data post-legalization.

Andi Ervin, Program Director for the Okanogan County Community Coalition says it's not a surprise, that we have more drivers on the road actively impaired by marijuana.  Ervin said, "The Okanogan County Community Coalition will continue to work with local law enforcement to enforce underage use – and our State’s driving laws to keep our community as safe as possible."

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