Refining THC Exposure Estimation for Cannabis Vaping Using Inhalation Duration

Madelyn Eason
University of Florida

Co-authors: Madelyn Eason¹, Donald Porchia¹, Juan Perez¹, Robert Cook¹, Yan Wang¹, Catalina Lopez-Quintero¹, Karina Villalba^2
1University of Florida, ²University of Central Florida

Background: Quantifying tetrahydrocannabinol (THC) exposure from cannabis vaping is challenging because self-reported use is often recorded as frequency, episodes, and hits rather than directly measured product consumption. Universal grams-per-hit-ratio (GPHR) approaches provide a practical literature-based exposure estimator but do not distinguish shorter from longer inhalations.

Objectives: This study estimated vaping-related THC exposure using a universal GPHR estimator and a novel duration-informed adaptation.

Methods: We analyzed data from the Medical Marijuana and Me (M³) Study of Florida adults using medical cannabis. The analytic sample included 618 current cannabis vapers with complete data on vaping frequency, daily vaping episodes, hits per episode, and inhalation duration. The universal estimator used the published vaping/concentrate GPHR of 0.012 g/hit. The duration-informed estimator assigned GPHRs of 0.004, 0.012, and 0.020 g/hit for short (1–2 seconds), medium (3–5 seconds), and long (≥6 seconds) inhalations, respectively. The short-inhalation value was selected as a conservative adaptation consistent with consumer-facing estimates of oil delivered per vape puff, and the medium category retained the published universal GPHR. THC exposure was calculated assuming 80% THC concentration and a vaping method-of-administration efficiency constant (MAEC) of 0.5. Estimates were summarized per episode, vaping use day, and calendar day and compared by CUDIT-R risk group, age, and sex.

Results: Using the universal estimator, mean THC exposure was 16.4 mg per vaping episode, 64.7 mg per vaping use day (amount vaped divided by days used in past four weeks), and 49.7 mg per calendar day (amount vaped divided by 28 days). Corresponding estimates using the duration-informed estimator were 16.8 mg, 70.9 mg, and 55.0 mg. The duration-informed estimator produced modestly higher mean exposure with a mean difference of 6.2 mg per-use-day. The two estimators were strongly correlated, indicating that the universal estimator largely preserved relative ranking. Long-duration users had the highest estimated exposure, averaging 186.3 mg per vaping use day. Exposure estimates were higher among younger participants and those with hazardous CUDIT-R risk. Sex differences were small and not statistically significant.

Conclusions: Cannabis vaping THC exposure can be operationalized using self-reported frequency, episodes, hits, and inhalation duration. In this conservative MAEC-adjusted analysis, the duration-informed estimator produced only modestly higher overall estimates, but identified substantially higher exposure among long-duration inhalers. These findings support incorporating inhalation-duration information as a refinement to GPHR-based exposure estimation in observational studies of cannabis vaping.