Elsevier

Drug and Alcohol Dependence

Volume 151, 1 June 2015, Pages 194-202
Drug and Alcohol Dependence

Full length article
Non-smoker exposure to secondhand cannabis smoke II: Effect of room ventilation on the physiological, subjective, and behavioral/cognitive effects

https://doi.org/10.1016/j.drugalcdep.2015.03.019Get rights and content

Highlights

  • Exposure to secondhand cannabis smoke results in absorption of cannabinoids.

  • Secondhand exposure can produce mild subjective and behavioral/cognitive effects.

  • Room ventilation ameliorates the effects of secondhand cannabis smoke exposure.

Abstract

Introduction

Cannabis is the most widely used illicit drug. Many individuals are incidentally exposed to secondhand cannabis smoke, but little is known about the effects of this exposure. This report examines the physiological, subjective, and behavioral/cognitive effects of secondhand cannabis exposure, and the influence of room ventilation on these effects.

Methods

Non-cannabis-using individuals were exposed to secondhand cannabis smoke from six individuals smoking cannabis (11.3% THC) ad libitum in a specially constructed chamber for 1 h. Chamber ventilation was experimentally manipulated so that participants were exposed under unventilated conditions or with ventilation at a rate of 11 air exchanges/h. Physiological, subjective and behavioral/cognitive measures of cannabis exposure assessed after exposure sessions were compared to baseline measures.

Results

Exposure to secondhand cannabis smoke under unventilated conditions produced detectable cannabinoid levels in blood and urine, minor increases in heart rate, mild to moderate self-reported sedative drug effects, and impaired performance on the digit symbol substitution task (DSST). One urine specimen tested positive at using a 50 ng/ml cut-off and several specimens were positive at 20 ng/ml. Exposure under ventilated conditions resulted in much lower blood cannabinoid levels, and did not produce sedative drug effects, impairments in performance, or positive urine screen results.

Conclusions

Room ventilation has a pronounced effect on exposure to secondhand cannabis smoke. Under extreme, unventilated conditions, secondhand cannabis smoke exposure can produce detectable levels of THC in blood and urine, minor physiological and subjective drug effects, and minor impairment on a task requiring psychomotor ability and working memory.

Introduction

Cannabis is the most widely used illicit drug globally (World Health Organization, 2014). The most popular route of administration is smoking, which often occurs indoors, in automobiles, or in other areas where ventilation is limited or variable. Δ9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis, is present in both mainstream smoke (inhaled by the user) and sidestream smoke (dispersed into environment; Cone et al., 1987, Fehr and Kalant, 1972, Matthias et al., 1997). Metabolism of THC yields the psychoactive metabolite, 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), which is present in blood after active or passive exposure to cannabis smoke (Huestis et al., 1992, Moore et al., 2011). THC and 11-OH-THC have similar behavioral effects, but 11-OH-THC levels peak later than THC levels after cannabis exposure (Hollister and Gillespie, 1975, Huestis et al., 1992, Järbe et al., 1994, Kosersky et al., 1974, Lemberger et al., 1973). Metabolism of 11-OH-THC yields 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH). THC-COOH is non-psychoactive, but its long half-life (∼140 h) makes it a common biomarker in urine testing for cannabis use.

Many individuals are passively exposed to secondhand cannabis smoke given the current prevalence and patterns of cannabis use, however, there has been little controlled research examining the consequences of secondhand exposure. Most research on secondhand cannabis smoke exposure has focused on detection of cannabinoids (e.g., THC, 11-OH-THC, THC-COOH) in various biological matrices. Cone and Johnson (1986) exposed five healthy men to passive smoke from either 4 or 16 cannabis cigarettes (2.8% THC) in a small, enclosed room for 1 h each day on six consecutive days. This secondhand smoke exposure reliably produced detectable levels of cannabinoids in urine and plasma, which varied in an orderly relation to dose (i.e., cannabinoid levels were higher after exposure to smoke from 16 cannabis cigarettes vs. 4 cigarettes). Similar results were obtained from studies using comparable designs (i.e., secondhand cannabis smoke exposure in small closed rooms or motor vehicles; Law et al., 1984, Mason et al., 1983, Mørland et al., 1985, Perez-Reyes et al., 1983).

At least four limitations impede interpretation of these studies with regard to current real-world secondhand cannabis smoke exposure scenarios. First, exposure in these studies always occurred under the “extreme” conditions (i.e., in small spaces without ventilation). Because secondhand cannabis exposure in the real world occurs under conditions with different degrees of air ventilation (e.g., in rooms with air conditioning or open windows, or outdoors), research examining the effects of ventilation on exposure levels is needed. Second, the average potency of “street” cannabis has increased more than 3-fold in the time since these studies were conducted (sinsemilla cannabis seized from 2002 to 2008 by federal and state law enforcement agencies in the U.S. averaged 11.1% to 11.9% THC; Mehmedic et al., 2010). To our knowledge, only one controlled study has examined passive exposure to higher potency cannabis (10.4% THC) that more closely resembles street cannabis available today (Niedbala et al., 2005). A more thorough examination of secondhand exposure using higher potency cannabis is needed to better model passive exposure to today's cannabis and its potential effects on drug test results. Third, only one study has reported both physiological and subjective effects of secondhand cannabis exposure (Cone and Johnson, 1986). Cone and Johnson (1986) reported that secondhand cannabis exposure had no systematic effects on heart rate or blood pressure, and that participant's ratings of subjective drug effects increased significantly after exposure to smoke from 16 cannabis cigarettes relative to placebo ratings. These effects were most pronounced during the first hour after exposure, and resolved within 3 h. Fourth, no prior studies have evaluated the effects of secondhand cannabis smoke exposure on behavioral/cognitive performance. Expanded research on the effects of secondhand cannabis smoke exposure in the areas outlined above is timely and warranted.

The present study was conducted to examine the influence of variations in cannabis potency (5.3% THC vs. 11.3% THC) and in room ventilation (unventilated vs. standard residential ventilation) on the effects of secondhand cannabis smoke exposure. The primary objective of the study was to characterize the pharmacokinetic profile of cannabinoids in various biological matrices following secondhand smoke exposure in order to inform federal workplace drug testing standards. A detailed report of the urine cannabinoid concentrations has been previously published (Cone et al., 2015). Here, we report the outcomes of pharmacodynamic assessments, cannabinoid concentrations in whole blood, and provide a brief summary of the urine results. Data analysis was restricted to comparisons of the ventilated vs. unventilated sessions with the same potency of cannabis (11.3% THC) because over 40% more 11.3% THC cannabis was consumed than 5.3% THC cannabis (14.4 g total vs. 10.2 g total) in comparable (unventilated) study sessions. The different levels of cannabis consumption between these 2 conditions preclude our ability to validly compare the effects of cannabis potency on study outcomes, particularly pharmacodynamic measures. This study is, to our knowledge, the first to demonstrate the effect of room ventilation on secondhand cannabis smoke exposure and is among the few secondhand cannabis smoke studies to examine pharmacodynamic outcomes or utilize cannabis with a potency that is representative of current “street” cannabis.

Section snippets

Recruitment

Frequent cannabis users and cannabis nonusers were recruited from the greater Baltimore, MD area via media advertising and word-of-mouth communication. Interested participants completed a screening session to determine eligibility. Participants provided written informed consent during the screening session. The Institutional Review Board at Johns Hopkins University School of Medicine approved this study.

Smokers

Cannabis users were eligible to participate as smokers if they: (1) were 18–45 years old,

Participants

Table 1 shows demographics of the nineteen participants (7 smokers and 12 nonsmokers) who completed the high potency (11.3% THC) unventilated and ventilated sessions of the study. Seven smokers were included in analyses because one of the original six participants who completed the unventilated session withdrew from the study and was replaced. There were no significant differences between these groups on any of the variables examined.

Exposure session conditions

Smokers consumed a considerable amount of cannabis in both

Discussion

This report describes the first study of which we are aware to examine the influence of room ventilation on secondhand exposure to cannabis smoke, and the first study to examine the effects of secondhand cannabis smoke exposure on behavioral/cognitive performance. Exposure to secondhand cannabis smoke in an unventilated chamber the size of a small room produced minor increases in heart rate, mild to moderate subjective drug effects, and minor, but detectible, levels of performance impairment on

Role of funding source

Funding for this project was provided by SAMHSA. Additional resources were provided by: (1) the Johns Hopkins Clinical Research Unit, which is funded by Grant UL1TR001079 UL1 RR025005 from the National Center for Research Resources (NCRR), a component of the NIH, and NIH Roadmap for Medical Research, (2) NIDA training grant T32-DA07209, which supported Dr. Herrmann, and (3) The NIDA Drug Supply Program for providing cannabis.

Contributors

Authors Edward Cone, John Mitchell, George Bigelow, Charles LoDico, Ron Flegel, and Ryan Vandrey designed the study and developed the protocol. Evan Herrmann, Edward Cone, and Ryan Vandrey managed literature searches and summaries of previous work. Evan Herrmann and Ryan Vandrey undertook the statistical analysis. Evan Herrmann, Edward Cone, John Mitchell, George Bigelow, Charles LoDico, Ron Flegel, and Ryan Vandrey wrote the final draft of the manuscript. All authors contributed to and have

Conflict of interest

All authors declare that they have no conflicts of interest.

Acknowledgements

The authors thank Jeannie M. Leoutsakos for statistical support, the outstanding support of the research, nursing, and pharmacy staff of the Johns Hopkins Behavioral Pharmacology Research Unit (BPRU), the Johns Hopkins Bayview Facilities group, Johns Hopkins Bayview Clinical Research Unit, Support staff at RTI International, and the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA). Without the coordinated effort of all these people, this study would not have been possible.

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