Standard breathalyzers, designed to detect alcohol, cannot identify cannabis. These devices are not equipped to detect tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis. With increasing cannabis legalization and focus on impaired driving, law enforcement and researchers are actively exploring new detection methods.
How Alcohol Breathalyzers Work
Alcohol breathalyzers operate on the principle that consumed alcohol transfers from the bloodstream into the lungs. A portion of the alcohol is then exhaled as a vapor. Breathalyzers measure this vapor’s concentration, which directly correlates to an individual’s blood alcohol content (BAC).
These devices commonly employ technologies like fuel cells or infrared spectroscopy. Fuel cell breathalyzers use a chemical reaction with platinum electrodes to generate an electrical current proportional to the alcohol present. Infrared breathalyzers measure the absorption of infrared light by alcohol molecules in the breath sample. Alcohol’s consistent presence in breath relative to blood makes these measurements reliable for determining impairment.
Why Cannabis is Different to Detect
The body processes alcohol and cannabis (THC) differently, explaining why traditional breathalyzers cannot detect cannabis. THC is a fat-soluble compound, meaning it readily binds to fat molecules in the body. Unlike alcohol, which is water-soluble and primarily metabolized by the liver before being easily exhaled, THC is largely metabolized by the liver and stored in fatty tissues.
While trace amounts of THC or its metabolites might be present in exhaled breath, these quantities do not reliably correlate with recent use or levels of impairment in the same way BAC does for alcohol. THC does not circulate freely in the bloodstream for extended periods in a predictable manner, nor does it pass into the lungs in consistent, measurable quantities. This complex metabolism and distribution in the body make it challenging to establish a direct link between breath THC levels and an individual’s level of impairment.
Current Cannabis Detection Methods
Law enforcement and other authorities use alternative methods to detect cannabis and assess impairment. Blood tests are considered most accurate for identifying recent cannabis use and impairment, as they directly measure THC concentrations in the bloodstream. However, THC levels in blood can peak quickly and then drop, making the timing of the test critical for assessing recent impairment.
Urine tests have a longer detection window, identifying cannabis metabolites for days to weeks after use, depending on frequency and dosage. These tests indicate cannabis presence but do not necessarily correlate with current impairment. Oral fluid or saliva tests also detect recent cannabis use, typically within a few hours to a few days, and can be administered roadside. Drug Recognition Experts (DREs), specially trained officers, assess impairment based on observed behavior, physiological signs, and performance on field sobriety tests.
Developing Cannabis Breath Technologies
Significant research and development efforts are underway to create effective cannabis breathalyzers. The main hurdles include the extremely low concentrations of THC found in exhaled breath compared to alcohol, which is exhaled in much higher quantities. Another challenge involves distinguishing between active THC, which indicates recent use and potential impairment, and inactive metabolites or residual THC that may linger in the breath long after the psychoactive effects have worn off.
Some prototypes utilize advanced technologies, such as nanotechnology sensors with carbon nanotubes, designed to detect THC at very low levels. Researchers are also exploring approaches like administering two breath tests within a specific time interval to observe changes in THC levels, which might indicate recent consumption. While these devices show promise, they are not yet widely available or legally validated for roadside impairment testing like alcohol breathalyzers.