Why is THC in breath the best proxy for recent marijuana use and peak impairment?

Why Breath Is Best?

Since 2014, Hound Labs has been working with leading scientists to measure THC in breath. The company’s goal is to extend the boundaries of clinical research by improving our understanding of how recent marijuana use relates to measurement of THC in breath.

 

The Hound Labs team has collected substantial data on THC in breath from human subjects who smoke marijuana. The research findings presented here are the results of years of tests in the lab, in the field, and on location. In addition, we reference research by other groups that have published studies relating to marijuana impairment over the past few decades.

FINDING #1

THC stays in breath for 2-3 hours
after smoking.

Scientists at Hound Labs and Triple Ring Technologies used the Hound® marijuana breathalyzer to collect over 400 samples from both frequent and infrequent smokers and then analyzed them using mass spectrometry. They found that participants had high levels of THC in their breath immediately after smoking, but the level of THC in breath samples dropped to near zero after 2-3 hours.

THC Breath Levels After Smoking Marijuana

breath-science-graph-nogrid-roboto
The average level of THC in breath decreases rapidly over 2-3 hours to near zero.

Source: Hound Labs

FINDING #2

Peak impairment lasts 2-3 hours after smoking.

Over the past few decades, multiple research groups have conducted studies on marijuana impairment. They have identified a peak window of impairment that lasts 2-3 hours after smoking, which is the same time period that THC is measurable in breath.

 

  • “Performance impairment is most significant for at least 1-2 hours following marijuana use, and lasts up to approximately 3 hours." 
    Drugs on Human Performance Fact Sheet, NHTSA, April 2014.

 

  • “A waiting period of about 3 hours after smoking a medium to strong social dose (15-20 mg) will be sufficient to reduce a driver’s impairment to that comparable to a BAC of less than 0.03%.”  
    Developing science-based per se limits for driving under the influence of cannabis (DUIC). Findings and recommendations by an expert panel, Nova-Institut, Hurth, DE, 2006.

FINDING #3

Users with THC in their breath are within the peak impairment window.

Regardless of the amount of marijuana smoked, the window for detection of THC in breath is consistent. And that window is the same as the peak window of impairment as determined by multiple research groups. Unlike alcohol, which causes someone with a higher level to be “more drunk,” someone with a higher level of THC in breath is not necessarily “more stoned.” The key is whether THC is present, because its presence indicates recent use and thus likely impairment.

Related Topics

With ongoing legalization of marijuana, understanding marijuana impairment is a priority for many. The Hound Labs research team continues to conduct important studies regarding THC in breath and how it correlates with impairment. To learn more about research conducted by Hound Labs and other research teams, please browse this section.

Environment

Environment

Although a number of independent researchers have studied the detection of THC in breath, none have studied the possible variation between indoor and outdoor smoking environments on THC breath levels. Hound Labs is the first to examine the impact of environment on THC levels in breath.

 

Environment plays a critical role in THC levels in breath — with peak levels for indoor marijuana smokers as much as 100 times higher than those for outdoor smokers. However, regardless of where marijuana was smoked, THC was no longer detected in breath after 2-3 hours. Just as important, although THC breath levels significantly differed based on whether the person smoked indoors or outdoors, observed impairment did not.

 

The significance of this finding is that the time element of how long THC stays in breath (which was found to be 2-3 hours in both indoor and outdoor environments) was the best indicator of peak impairment, more so than the actual level of THC in breath.

Implications for Second-Hand Smoke

Individuals exposed to incidental, second-hand smoke may have THC in their breath for a very brief time, but it disappears after a person is no longer exposed to the smoke. Stepping outdoors or into a well-ventilated area for about 15 minutes before taking a breathalyzer test will eliminate potential false-positive test results. This 15-minute waiting period is similar to the protocol established by alcohol breathalyzer manufacturers to avoid a high breath BAC (Blood Alcohol Content) reading that isn’t reflective of actual BAC content. Hound Labs continues to do research involving second-hand smoke and will share results of its studies.

THC Levels in Breath Vary Based on Environment

environment graph 800
Average THC levels in breath for indoor and outdoor environments. Levels outdoors are significantly lower immediately after smoking. However, levels for both environments fall to near zero within 3 hours.

Source: Hound Labs. Research results first presented at the Society for Academic Emergency Medicine (SAEM) Western Regional Meeting in February 2018.

Frequent Smokers

Frequent vs. Infrequent Smokers

Frequent smokers do not have significant amounts of THC in their breath after a few hours but do have a relatively constant low level of THC elsewhere in their bodies, including their oral fluid, blood, and urine. Unless they have used marijuana within the past few hours, frequent users are not generally considered to be impaired even though they have low levels of THC in their body fluids. We don't yet completely understand the reasons for this discrepancy.

 

Both occasional and frequent smokers are similar in that they have virtually no THC in their breath within a few hours after smoking. Baseline breath measurements of THC in chronic marijuana smokers is only 0-3 picograms per liter of breath (pg/L). Note: The Hound breathalyzer is calibrated such that it will only trigger a positive test result above this baseline.

 

The significance of this finding is that chronic smokers who occasionally have extremely low levels of THC in their breath will not test positive when tested by the Hound breathalyzer unless they have smoked within the last 2-3 hours.

Sources:
Karschner, EL et al. “ Extended Plasma Cannabinoid Excretion in Chronic Frequent Cannabis Smokers During Sustained Abstinence and Correlation with Psychomotor Performance,”

Drug Testing and Analysis, 8(7), July 2016.

Musshoff, F. And B. Madea, "Review of Biologic Matrices (Urine, Blood, Hair) as Indicators of Recent or Ongoing Cannabis Use,”

 Therapeutic Drug Monitoring, 28(2), April 2006.

Recommended Reading

Dosage

Dosage

The degree of impairment and duration of significant impairment are both somewhat dose-dependent. However, large doses do not extend the time of impairment longer than 3 hours. Low doses of cannabis are likely to produce low levels of impairment and/or a short period of significant impairment. High doses are likely to produce higher levels of impairment, but not a longer period of significant impairment.

 

The Hound Labs team included subjects who smoked a wide range of cannabis doses and observed varying degrees of significant impairment in the first few hours of smoking. Regardless of the dosage amount, however, we observed that THC returned to baseline levels within 2-3 hours after smoking. This confirms that just as impairment does not last longer for large doses, THC in breath does not last longer for large doses either. It also confirms that the presence of THC in breath – whether less than 2-3 hours after a low dose or up to 3 hours after a large dose – correlates with when an individual is impaired from smoking marijuana.

Sources:

Ramaekers, JG et al. "High-Potency Marijuana Impairs Executive Function and Inhibitory Motor Control,”

Neuropsychopharmacology, 31, 2006.

Logan, B. “Chapter 12: Marijuana and Driving Impairment,”

Marijuana and the Cannabinoids, Mahmoud A. ElSohly ed., Springer Verlag, 2007.

F. Grotenhermen, G. Leson, G. Berghaus, O. H. Drummer, H.-P. Krüger, M. Longo, H. Moskowitz, B. Perrine, J. G. Ramaekers, A. Smiley and R. Tunbridge, "Developing limits for driving under cannabis,"

Addiction, vol. 102, no. 12, pp. 1910-1917, 2007.

Heustis MA, "Cannabis (Marijuana) — Effects on Human Behavior and Performance,”

Forensic Science Review, 14(15), 2002.

Recommended Reading

Edibles

Edibles

After consuming edibles, THC passes slowly through the gut and must pass through the liver before reaching the brain. As a result, THC is not present in breath until about 1 hour after ingestion, and peak levels of THC are much lower than with smoking but THC is elevated for a longer period of time.

 

The Hound Labs research involving human subjects who consume edible marijuana confirms that THC cannot be measured in breath as immediately as THC resulting from smoked marijuana. It also confirms that THC in breath from edibles has a longer duration and a lower peak than THC levels after smoking. These findings correlate with research from third parties that shows significant driving impairment lasting approximately 1-6 hours after ingesting cannabis. We plan to publish our edibles research in 2H 2018.

Goodwin, RS et al. "D9-Tetrahydrocannabinol, 11-Hydroxy- D9-Tetrahydrocannabinol and 11-Nor-9-Carboxy- D9-Tetrahydrocannabinol in Human Plasma After Controlled Oral Administration of Cannabinoids,”

Therapeutic Drug Monitoring, 28(4), 2006.

Karschner, EL, WD Darwin, RS Goodwin, S Wright, and MA Heustis, "Plasma Cannabinoid Pharmacokinetics following Controlled Oral 9-Tetrahydrocannabinol and Oromucosal Cannabis Extract Administration,”

Clinical Chemistry, 57(1), 2011.

Menetrey, A. et al. "Assessment of Driving Capability Through the Use of Clinical and Psychomotor Tests in Relation to Blood Cannabinoids Levels Following Oral Administration of 20 mg Dronabinol or of a Cannabis Decoction Made with 20 or 60 mg Ag-THC,"

Journal of Analytical Toxicology, vol. 29, no. July/August, pp. 327-338, 2005.

Quotes

  • "The impairment [for edibles] was especially noticed during the time period ranging from 1.0 to 5.5 h[ours] post ingestion.”

    A. Menetrey, et al., Journal of Analytical Toxicology, vol. 29, 2005.

  • “The effects of oral cannabis occur later than do those of smoking and typically peak 2–3 hours after ingestion.”

    Developing science-based per se limits for driving under the influence of cannabis (DUIC). Findings and recommendations by an expert panel, Nova-Institut, Hurth, DE, 2006.

Environment

Environment

Although a number of independent researchers have studied the detection of THC in breath, none have studied the possible variation between indoor and outdoor smoking environments on THC breath levels. Hound Labs is the first to examine the impact of environment on THC levels in breath.

 

Environment plays a critical role in THC levels in breath — with peak levels for indoor marijuana smokers as much as 100 times higher than those for outdoor smokers. However, regardless of where marijuana was smoked, THC was no longer detected in breath after 2-3 hours. Just as important, although THC breath levels significantly differed based on whether the person smoked indoors or outdoors, observed impairment did not.

 

The significance of this finding is that the time element of how long THC stays in breath (which was found to be 2-3 hours in both indoor and outdoor environments) was the best indicator of peak impairment, more so than the actual level of THC in breath.

Implications for Second-Hand Smoke

Individuals exposed to incidental, second-hand smoke may have THC in their breath for a very brief time, but it disappears after a person is no longer exposed to the smoke. Stepping outdoors or into a well-ventilated area for about 15 minutes before taking a breathalyzer test will eliminate potential false-positive test results. This 15-minute waiting period is similar to the protocol established by alcohol breathalyzer manufacturers to avoid a high breath BAC (Blood Alcohol Content) reading that isn’t reflective of actual BAC content. Hound Labs continues to do research involving second-hand smoke and will share results of its studies.

THC Levels in Breath Vary Based on Environment

environment graph 800
Average THC levels in breath for indoor and outdoor environments. Levels outdoors are significantly lower immediately after smoking. However, levels for both environments fall to near zero within 3 hours.

Source: Hound Labs. Research results first presented at the Society for Academic Emergency Medicine (SAEM) Western Regional Meeting in February 2018.

Frequent Smokers

Frequent vs. Infrequent Smokers

Frequent smokers do not have significant amounts of THC in their breath after a few hours but do have a relatively constant low level of THC elsewhere in their bodies, including their oral fluid, blood, and urine. Unless they have used marijuana within the past few hours, frequent users are not generally considered to be impaired even though they have low levels of THC in their body fluids. We don't yet completely understand the reasons for this discrepancy.

 

Both occasional and frequent smokers are similar in that they have virtually no THC in their breath within a few hours after smoking. Baseline breath measurements of THC in chronic marijuana smokers is only 0-3 picograms per liter of breath (pg/L). Note: The Hound breathalyzer is calibrated such that it will only trigger a positive test result above this baseline.

 

The significance of this finding is that chronic smokers who occasionally have extremely low levels of THC in their breath will not test positive when tested by the Hound breathalyzer unless they have smoked within the last 2-3 hours.

Sources:
Karschner, EL et al. “ Extended Plasma Cannabinoid Excretion in Chronic Frequent Cannabis Smokers During Sustained Abstinence and Correlation with Psychomotor Performance,”

Drug Testing and Analysis, 8(7), July 2016.

Musshoff, F. And B. Madea, "Review of Biologic Matrices (Urine, Blood, Hair) as Indicators of Recent or Ongoing Cannabis Use,”

 Therapeutic Drug Monitoring, 28(2), April 2006.

Recommended Reading

Dosage

Dosage

The degree of impairment and duration of significant impairment are both somewhat dose-dependent. However, large doses do not extend the time of impairment longer than 3 hours. Low doses of cannabis are likely to produce low levels of impairment and/or a short period of significant impairment. High doses are likely to produce higher levels of impairment, but not a longer period of significant impairment.

 

The Hound Labs team included subjects who smoked a wide range of cannabis doses and observed varying degrees of significant impairment in the first few hours of smoking. Regardless of the dosage amount, however, we observed that THC returned to baseline levels within 2-3 hours after smoking. This confirms that just as impairment does not last longer for large doses, THC in breath does not last longer for large doses either. It also confirms that the presence of THC in breath – whether less than 2-3 hours after a low dose or up to 3 hours after a large dose – correlates with when an individual is impaired from smoking marijuana.

Sources:

Ramaekers, JG et al. "High-Potency Marijuana Impairs Executive Function and Inhibitory Motor Control,”

Neuropsychopharmacology, 31, 2006.

Logan, B. “Chapter 12: Marijuana and Driving Impairment,”

Marijuana and the Cannabinoids, Mahmoud A. ElSohly ed., Springer Verlag, 2007.

F. Grotenhermen, G. Leson, G. Berghaus, O. H. Drummer, H.-P. Krüger, M. Longo, H. Moskowitz, B. Perrine, J. G. Ramaekers, A. Smiley and R. Tunbridge, "Developing limits for driving under cannabis,"

Addiction, vol. 102, no. 12, pp. 1910-1917, 2007.

Heustis MA, "Cannabis (Marijuana) — Effects on Human Behavior and Performance,”

Forensic Science Review, 14(15), 2002.

Recommended Reading

Edibles

Edibles

After consuming edibles, THC passes slowly through the gut and must pass through the liver before reaching the brain. As a result, THC is not present in breath until about 1 hour after ingestion, and peak levels of THC are much lower than with smoking but THC is elevated for a longer period of time.

 

The Hound Labs research involving human subjects who consume edible marijuana confirms that THC cannot be measured in breath as immediately as THC resulting from smoked marijuana. It also confirms that THC in breath from edibles has a longer duration and a lower peak than THC levels after smoking. These findings correlate with research from third parties that shows significant driving impairment lasting approximately 1-6 hours after ingesting cannabis. We plan to publish our edibles research in 2H 2018.

Goodwin, RS et al. "D9-Tetrahydrocannabinol, 11-Hydroxy- D9-Tetrahydrocannabinol and 11-Nor-9-Carboxy- D9-Tetrahydrocannabinol in Human Plasma After Controlled Oral Administration of Cannabinoids,”

Therapeutic Drug Monitoring, 28(4), 2006.

Karschner, EL, WD Darwin, RS Goodwin, S Wright, and MA Heustis, "Plasma Cannabinoid Pharmacokinetics following Controlled Oral 9-Tetrahydrocannabinol and Oromucosal Cannabis Extract Administration,”

Clinical Chemistry, 57(1), 2011.

Menetrey, A. et al. "Assessment of Driving Capability Through the Use of Clinical and Psychomotor Tests in Relation to Blood Cannabinoids Levels Following Oral Administration of 20 mg Dronabinol or of a Cannabis Decoction Made with 20 or 60 mg Ag-THC,"

Journal of Analytical Toxicology, vol. 29, no. July/August, pp. 327-338, 2005.

Quotes

  • "The impairment [for edibles] was especially noticed during the time period ranging from 1.0 to 5.5 h[ours] post ingestion.”

    A. Menetrey, et al., Journal of Analytical Toxicology, vol. 29, 2005.

  • “The effects of oral cannabis occur later than do those of smoking and typically peak 2–3 hours after ingestion.”

    Developing science-based per se limits for driving under the influence of cannabis (DUIC). Findings and recommendations by an expert panel, Nova-Institut, Hurth, DE, 2006.