Breathalyzer Test for Marijuana Soon Available

The U.S. Office of National Control Policy has put drugged driving on its list of priorities and a breathalyzer test for marijuana may soon be on its way. Marijuana is considered one of the drugs that can negatively impact a person's driving as its use affects motor skills, judgment and perception, all of which are necessary to safely operate a vehicle.

Annually, about 1.5 million drivers are arrested for driving under the influence of alcohol (DUI). However, the U.S. Centers for Disease Control and Prevention (CDC) reports that 18 percent of fatal car accidents are attributed to drugs other than alcohol, including marijuana.

How It Works

The marijuana breathalyzer test will follow the same concept as the traditional alcohol breathalyzer test by detecting the substance in exhaled breath at the scene. In this case, delta-9-tetrahydrocannabinol (THC) is the main psychoactive chemical in marijuana and the main target to detect in the test.

The Pros and Cons

Pros to the marijuana breathalyzer test:

  • Screen drivers for marijuana use on-the-spot, at the side of the road
  • A Swedish study found the marijuana breathalyzer detects use in 87 percent of cases, which is the the same level of accuracy achieved through blood and urine testing

Cons to the marijuana breathalyzer test:

  • There is a short detection window of 30 minutes to two hours after drug use
  • Marijuana does not metabolize as predictably in the body as alcohol
  • 25 percent of chronic stoners can test positive after one week or more of abstinence, depending upon their body fat content--so a sober user may fail a breathalyzer test and be arrested for DUI, even though they haven't been using
  • Drug detection time does not always coincide with impairment time, which may lead to innocent drivers being convicted of DUI

Testing the Effectiveness

The efficacy of marijuana breathalyzers remains in question. The pertinent statistics include:

  • 91 percent of users tested positive one hour after using; 64 percent after 1 ½ hours
  • One confirmed user never had detectable THC
  • One chronic user still showed positive results four hours later

To make a thorough assessment of the effectiveness of drug breathalyzer testing, the science of how drugs enter the breath and how long drugs stay in the breath still needs further study and evaluation.

The driving impairment window is longer than the 30 minutes to 2 hour breath detection window of time. This makes authorities question the validity of breathalyzer testing.

Recent Findings About DUI

The American Journal of Public Health recently reported:

  • More teens are driving high
  • Those who use marijuana within three hours of driving are twice as likely to cause a serious motor vehicle accident as those who did not use marijuana

The National Institute on Drug Abuse (NIDA) developed a breath test that detects marijuana use within the previous 30 minutes to 2 hours, depending upon frequency of use. Studies done to test this method were conducted on chronic or >4 times/week users and occasional users.

Clinical Chemistry reports that 90 percent of users in these studies tested positive within one hour of getting high.Only everyday stoners tested positive after four hours. Ninety percent of occasional users tested positive one hour after smoking but none of these subjects tested positive after 1½ hours.

The Swedish study recommends the breathalyzer test be used at the scene as a preliminary test, and that the results be confirmed later with a blood test.

Interestingly, roadside saliva testing for cannabis has been done in Europe and Australia and detects the drug for up to 48 hours. This finding also raises a concern about whether or not detection actually coincides with impairment.

Current Laws for Marijuana-Related DUIs

Some states, especially those that have legalized recreational use of the drug, have marijuana blood limits:

  • Colorado and Washington: 5 nanograms per milliliter of blood is considered under the influence
  • Other states such as Arizona and Oklahoma have a zero tolerance law
  • New York has an effect-based law, which means that the driver must be visibly impaired while driving (no blood test)

THC-blood tests are the most popular choice in states with laws regulating marijuana use while driving.

Though more research must be done before finalizing the breathalyzer test, no one should ever get behind the wheel if there is any level of impairment.


Nancy Burgess is a graduate of Laboure College in Boston, MA, where she earned an Associate of Science degree in Nursing. She is a registered nurse with experience with direct patient care and nursing management. Nancy has worked in an acute care hospital setting and in an independent school environment.