Indoor Air Quality-Pharmacokinetic Simulation of Passive Inhalation of Marijuana Smoke and the Resultant Buildup of 11- Nor-Delta-9-Tetrahydrocannabinol-9-Carboxylic Acid in Urine

• NCJ Number: 168695
• Journal: Journal of Forensic Sciences Volume: 42 Issue: 2 Dated: (March 1997) Pages: 323-325
• Author(s): N J Giardino
• Date Published: 1997
• Length: 3 pages
• Publication Format: Article
• Publication Type: Test/Measurement
• Language: English
• Country: United States of America
• Note: DCC.

Annotation

This microcomputer simulation determined whether or not a passive marijuana smoker, who is in the source room or the rest of the house, can receive enough of a total dose to have an amount equal to or greater than the Department of Defense (DOD) legal limit of 15 ng/mL of THCA (11-nor-delta-9- tetrahydrocannabinol-9-carboxylic acid) in his/her urine.

Abstract

In military courts of law, the "good soldier" defense is often used by the defendant to explain the presence of THCA above the DOD established limit of 15 ng/mL. The defense will contend the defendant unwittingly breathed side-stream marijuana smoke, thus resulting in the presence of THCA in the defendant's urine. The purpose of the current work was to link an indoor air quality model (IAQ) with a pharmacokinetic (PK) model to predict a passive marijuana smoker's resultant concentration of the major urinary metabolite THCA. A three-compartment design was used for the residence; it consisted of the source room (30 cubic meters), the rest of the house (250 cubic meters), and the outdoors. The air-exchange rate between the source room and the rest of the house was 1.0 air-changes per hour (ACH), and between the rest of the house and outdoors, 0.5 ACH. These values are typical of a small residence. The source term was 0.24 mg/hour of THC released to the air by the person smoking the marijuana. This is equivalent to six 2.5-percent NIDA-certified marijuana cigarettes smoked over the course of 1 hour. The pharmacokinetic (PK) model was built using real-world measurements taken from the literature for a standard 70-kg male. The PK model treats the body as a single compartment in which absorption occurs through inhalation of side-stream marijuana smoke. Initial results from the model's application show that at the end of the 8-hour exposure period, the passive smoker in the source room attained a level of 4.4 ng/mL, significantly less than the 15 ng/mL set by the DOD. The passive smoker in the rest of the house measured 2.6 ng/mL in the urine. These values are comparable to experimental results reported by others. 1 table, 3 figures, and 7 references