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Breathalyzer for marijuana faces many hurdles

In 2012, Washington passed Initiative 502, which legalized the recreational use of marijuana by persons over the age of 21. One of the difficulties with recreational use of marijuana, however, is that the drug can impair a person's ability to safely operate an automobile. Even proponents of the legal use of cannabis acknowledge that the drug can cause almost the equivalent of drunk driving, and they concede the need for a portable roadside device that will reliably test for the concentration of marijuana in a person's body. So far, efforts to invent such a device have met many obstacles.

The intoxicating component in marijuana is the substance THC, which is chemically very different from alcohol. Alcohol dissolves in water and spreads evenly throughout the body. Thus, an analysis of a person's breath can reliably determine the concentration of alcohol in a driver's bloodstream. THC, however, dissolves in the body's stores of fat and releases slowly into the body. THC may persist in the body over several days after a person has smoked marijuana, and still render a false-positive test.

A second difficulty is that people respond differently to the effects of THC. A regular user may build up so much THC in their body that it is present several weeks after the last consumption of marijuana, again yielding a false-positive. A number of companies are developing products to meet the growing demand for roadside test devices. Some preliminary designs are for breathalyzers, and others are based on ignition interlock technology.

Meanwhile, state legislatures are considering bills that would define the intoxication level of THC. Colorado's legislature passed a law saying that a person with five nanograms of THC in their blood can be prosecuted for intoxicated driving. Washington state is nowhere near reaching a consensus on these issues, but regular users of marijuana should pay attention.

Source: CFN Media Group, "Dangerous Opinions Spur Need for Cannabis Breathalyzer -- CFN Media," Frank Lane, Nov. 9, 2017