Breath Testing for Cannabis Impairment: Does It Work?

As the legalization of cannabis continues to spread across the United States, concerns about cannabis-impaired driving have grown. This has led to the search for reliable methods to detect recent cannabis use, similar to the breathalyzer tests used for alcohol. However, current studies indicate that breath testing for cannabis impairment is not as accurate or reliable as previously thought. This article explores the challenges and limitations of breath testing for cannabis impairment and discusses potential solutions for ensuring road safety.

The Need for Accurate Cannabis Impairment Testing

Challenges in Measuring Cannabis Impairment

Unlike alcohol, where a specific blood alcohol concentration (BAC) level is associated with impairment, there is no agreed-upon threshold for cannabis impairment. The psychoactive compound in cannabis, delta-9-tetrahydrocannabinol (THC), affects individuals differently, making it challenging to establish a standardized level of impairment. Furthermore, THC can remain in the body for days or even weeks after last use, making it difficult to determine if a driver is currently impaired or if they used cannabis in the past.

The Science Behind Breath Testing for Cannabis

How Breath Testing Works

Breath testing for cannabis impairment is based on the idea that THC and other cannabis compounds can be detected in breath samples. By measuring the concentration of THC in a person's breath, it is theorized that one can determine if they have recently used cannabis and are potentially impaired.

Current Breath Testing Devices and Techniques

Several breath testing devices are in development to detect cannabis impairment, with some companies claiming to have created accurate and reliable devices. However, these claims are met with skepticism, as no cannabis breath testing device has seen widespread adoption or proven to be consistently accurate.

Limitations and Challenges of Breath Testing for Cannabis

Inconsistency in THC Levels Detected

A recent study conducted by researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder found that THC levels in breath samples were too inconsistent to determine recent cannabis use. The study involved 18 participants who smoked marijuana with a THC concentration of approximately 25%. Breath and blood samples were collected before and after marijuana use, and THC levels in breath samples showed no clear correlation with recent use.

Difficulty in Establishing a Standard for Impairment

As mentioned earlier, there is no agreed-upon threshold for cannabis impairment. This makes it challenging to establish a standardized level of THC concentration in breath samples that would indicate impairment. Additionally, factors such as individual tolerance, method of consumption, and THC potency can affect the level of impairment experienced by users.

Lack of Reproducible Results

The inconsistency in THC levels in breath samples highlights the lack of reproducible results in breath testing for cannabis. In the NIST study, only eight of the 14 participants who provided breath samples before and after smoking marijuana showed an anticipated increase in THC levels. The remaining participants' results were inconsistent, with three post-use breath samples showing no THC detected and the rest showing similar or lower levels than baseline samples.

Reliability Issues in Field Testing

The NIST study was conducted in a controlled laboratory setting, not in the field. This raises questions about the reliability and accuracy of breath testing devices for cannabis impairment in real-world situations. With many variables at play in roadside testing, the consistency and accuracy of breath testing devices must be rigorously evaluated before widespread implementation.

Blood Testing as an Alternative to Breath Testing

Greater Reliability in Measuring THC Levels

In the same NIST study, blood measurements of THC concentrations in plasma were found to be a more reliable indicator of recent cannabis use. Blood testing may provide a more accurate and consistent method for detecting cannabis impairment compared to breath testing.

Challenges with Blood Testing

Despite its greater reliability, blood testing for cannabis impairment has its own set of challenges. Blood testing is more invasive than breath testing, requires more time and expertise to administer, and results may take longer to process. Additionally, as mentioned earlier, THC can remain in the body for extended periods, making it difficult to determine if a driver is currently impaired or if they used cannabis in the past.

Future Directions in Cannabis Impairment Detection

Further Research and Development

Given the limitations and challenges of breath testing for cannabis impairment, further research and development are needed to improve the accuracy and reliability of these devices. This includes studying different methods of cannabis consumption, such as vaping and edibles, and evaluating different breath sampling devices.

Understanding the Underlying Science

A better understanding of how THC and other cannabis compounds enter the breath and are carried in breath samples is essential for improving breath testing devices. This knowledge could help distinguish between recent cannabis use and past use, leading to more accurate impairment detection.

Developing Accurate Tests for Impairment

Rather than relying solely on THC concentrations in breath or blood samples, it may be more effective to develop tests that measure actual impairment. This could involve assessing cognitive and motor function, similar to field sobriety tests used for alcohol impairment.

Conclusion

Breath testing for cannabis impairment is a promising concept, but current research indicates that it is not a reliable indicator of recent marijuana use. Further research and development are needed to improve the accuracy and consistency of breath testing devices and to better understand the underlying science of how THC and other cannabis compounds are carried in breath samples. In the meantime, alternative methods for detecting cannabis impairment, such as blood testing and assessing cognitive and motor function, should be considered to ensure road safety.