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Organic Cannabis: What Makes it Special?

Organic cannabis is easily the most sought-after product on the market today. Whether looking for high-quality flower for personal use, sale, or manufacturing purposes, organic marijuana is a tremendous commodity in this sector.

Organic Marijuana Benefits

1. Richer Microbiome in Organic Cannabis Grow Ops

Organic cannabis soil mixes offer a better microbiome. This is the community of microbes in the plants’ environment that contribute to healthy growth.

Think of organic cannabis soil mixes as ecosystems demonstrating complexity. They have plenty of fungi, bacteria, and an assortment of other microscopic organics. This, of course, includes nematode worms. You simply cannot get this complexity any other way.

This type of soil benefits the plants in several ways. It helps maintain nitrogen and retain water, prevents root diseases, and stimulates plant growth. This is why many organic cannabis cultivators choose to make their own “super-soil.”

2. Organic Cannabis is Safer for Consumption

As consumers become more knowledgeable about unsafe cultivation practices plaguing the cannabis industry, they make better choices. While it’s not too much additional effort to grow organic cannabis small-scale at home, the large-scale operations have to take on more risk.

While some cultivators are willing to invest in their crops to produce organic marijuana, others aren’t so quick to risk smaller yields. Some purists believe in letting the plants grow naturally, even though some organic cannabis cultivators prefer to use natural nutrients and pesticides.

The main difference between organic soil-grown cannabis is that the grower doesn’t use chemical fertilizers and pesticides. While these aid in plant growth and flowering, natural options are available – and safer.

Organic cannabis nutrients are actually quite cheap. In some cases, they’re free as they’re made through composting. This involves tossing organic food in a composter, then adding it to your soil.

3. Organic Marijuana is More Potent

Organic cannabis plants get everything they need to develop to their highest potential. These plants have specific and in-depth demands to optimize their growth, and if you give your plants what they need, the result is impressive.

The simplicity behind conventional cannabis nutrient systems gives plants the minimum of what they need to survive and grow. These cannabis nutrient mixes usually contain the essential macronutrients (nitrogen, phosphorous, potassium, calcium, magnesium, and sulfur) and essential micronutrients (boron, copper, zinc, iron, molybdenum, and manganese).

Organic cannabis nutrient systems bring other beneficial trace elements into the mix. While not viewed as crucial, nutrients that can contribute to plant growth but aren’t usually found in commercial fertilizers include sodium, cobalt, chlorine, and nickel.

4. Better Yields in Organic Cannabis Grows

While some commercial growers worry that organic cannabis cultivation could reduce their yield, the opposite can happen. If all conditions are optimized properly, it’s possible to increase yields one would get through a conventional grow.

However, without the right micro-environment, the yield can be significantly less than non-organically grown marijuana. But now that organic fertilizers for commercial cannabis grows are available, it’s easier. Cultivators also have a better understanding of how to use these fertilizers now.

5. More Flavorful, Aromatic Buds for Organically Grown Cannabis

The microenvironment is better when you’re organically growing cannabis. This ensures your plants are producing more of the cannabinoids that make flower more flavorful and aromatic. You’ll find higher concentrations of terpenoids, flavonoids, and other cannabinoids resulting from these grow methods.

The terpenes and terpenoids are aromatic compounds responsible for plant fragrance. Cannabis has plenty of these compounds, offering each strain notes of citrus, skunky, spicy, pine-like, sweet, diesel, or a combination of these scents.

The flavonoids found in cannabis are equally important. However, these contribute more to the experience by providing antioxidant effects that promote health and longevity.

6. Organically Grown Marijuana is Better for the Environment

The least environmentally damaging way to grow cannabis is to use natural sunlight outside. With this in mind, the most significantly problematic aspect of growing cannabis is energy consumption from growing inside. But another issue is pesticide runoff.

Organic cannabis cultivation is easier on the environment. It’s especially beneficial for the water in areas where people grow cannabis commercially.

Synthetic vs. Organic Fertilizers for Cannabis

Some growers choose to use modern, petrochemical-intensive monoculture production. This involves sterile conditions and manipulating variables to optimize cannabis production. However, this typically involves bottled nutrients that contain precise NPK values and a short pH range. In turn, this keeps everything efficient to support impressive cannabis growth.

However, growing organic marijuana takes advantage of soil microbiology. Just like in nature, cultivators can feed the roots of their plants with proper proportions naturally with the best soil mixes for cannabis. While the first time growing cannabis organically could be challenging, it’s a rewarding experience to produce cannabis flower that’s free of harmful chemicals.

Bottled fertilizers aren’t always synthetic. However, these organic fertilizers are usually watered down. Furthermore, combining all of the organic cannabis nutrients you need in a single stabilized bottle is challenging due to chemistry and plant physiology limitations.

Organic Cannabis Nutrients to Consider

To produce organic cannabis, you can make your own fertilizer. These are the essential organic cannabis macronutrients used to promote plant growth:

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)

These macronutrients can come from a variety of natural sources. For nitrogen, worm castings, crustaceous meal, bat guano, and chicken manure are all excellent. But even human urine is an option, as long as it’s diluted with a ratio of 10:1 parts water to urine. This keeps the ammonia levels low, avoiding root burn in the process.

For organic phosphorus sourcing, you can use boiled banana peels and moistened soil. Allow this concoction to ferment a little to add some P to your soil composition. You can also use bone and fish meals, rock dust, and chicken manure to source phosphorus.

Potassium is also easy to source naturally. You can use banana peel, bat guano, kelp, wood ash, compost, siliceous rocks, and fish meal to deliver K to cannabis plants.

Besides N, P, and K, you’ll also need micronutrients calcium and magnesium. These are essential during bloom, and with optimized levels, your plants use macronutrients efficiently.

Non-Smoker Exposure to Secondhand Cannabis Smoke. I. Urine Screening and Confirmation Results

Increased cannabis potency has renewed concerns that secondhand exposure to cannabis smoke can produce positive drug tests. A systematic study was conducted of smoke exposure on drug-free participants. Six experienced cannabis users smoked cannabis cigarettes (5.3% THC in Session 1 and 11.3% THC in Sessions 2 and 3) in a sealed chamber. Six non-smokers were seated with smokers in an alternating manner. Sessions 1 and 2 were conducted with no ventilation and ventilation was employed in Session 3. Non-smoking participant specimens (collected 0–34 h) were analyzed with four immunoassays at different cutoff concentrations (20, 50, 75 and 100 ng/mL) and by GC-MS (LOQ = 0.75 ng/mL). No presumptive positives occurred for non-smokers at 100 and 75 ng/mL; a single positive occurred at 50 ng/mL; and multiple positives occurred at 20 ng/mL. Maximum THCCOOH concentrations by GC-MS for non-smokers ranged from 1.3 to 57.5 ng/mL. THCCOOH concentrations generally increased with THC potency, but room ventilation substantially reduced exposure levels. These results demonstrate that extreme cannabis smoke exposure can produce positive urine tests at commonly utilized cutoff concentrations. However, positive tests are likely to be rare, limited to the hours immediately post-exposure, and occur only under environmental circumstances where exposure is obvious.

Introduction

Cannabis is the most widely produced and illicitly consumed drug globally. The number of cannabis users has been estimated to be as high as 224 million worldwide, and prevalence of use has remained stable in recent years (1). Over the last decade, indoor cultivation of cannabis has proliferated. Increased indoor growing has been mirrored by an increase in shops and Internet sites that provide information, supplies, equipment and seeds for production. The increased support system for cannabis cultivation together with availability of high-quality seeds has greatly expanded access to high-yielding and highly potent cannabis varieties (1). These plants have high levels of Δ9-tetrahydrocannabinol (THC), the primary cannabinoid responsible for psychoactive effects, and, most commonly, negligible levels of cannabidiol (CBD) and other trace cannabinoids that may have therapeutic potential and may counteract some of the effects of THC (2). Use of cannabis preparations containing high potency THC/low CBD cannabinoid ratios has been linked to a number of putative outcomes (3) including increased risk of psychosis (4) and cannabis dependence (5).

Cannabis terminology varies considerably and numerous terms are in use referring to similar or related cannabis products. The term ‘marijuana’ is generally used to refer to the Cannabis plant (leaves, stems, seeds and flowering tops); whereas, the term ‘sinsemilla’ refers to the flowering tops of unfertilized female plants with no seeds. Globally, two main products are produced from cannabis: cannabis herb and cannabis resin. Cannabis resin, also known as ‘Hashish’ is composed of the resinous parts of the flowering tops of cannabis and is mixed with some plant particles and shaped into a variety of forms, e.g., balls, sticks or slabs. ‘Hash oil’ is a liquid or semi-solid concentrated extract of cannabis plant material.

Cannabis herb is produced and consumed in almost all countries of the world, whereas cannabis resin is produced primarily in North Africa, the Near and Middle East and South-West Asia (6). More recently, there has been a proliferation of alternative cannabis preparations and routes of administration with the advent of more relaxed laws regarding cannabis use and the introduction of a commercial market in some areas. These include various forms of cannabis extracts and oils sold as ‘dab’, ‘wax’, ‘shatter’ and a multitude of cannabis-infused food products (e.g., brownies, candy, butter, granola, beverages), commonly referred to as ‘edibles’. Cannabis is often consumed for the psychoactive and physiological effects produced following use including heightened mood or euphoria, relaxation and an increase in appetite, though the use of cannabis for purported medical/health benefit has gained prominence in the past several decades.

THC is present in cannabis herb preparations as THC and as carboxylic acid precursor molecular forms (precursor acids referred to as Δ9-tetrahydrocannabinolic acid A and Δ9-tetrahydrocannabinolic acid B). The structures of THC and the related precursor acids (THCA-A and THCA-B) are shown in Figure  1 . The precursor acids present in cannabis herb should not be confused with the two key human metabolites [11-hydroxy-Δ9-tetrahydrocannabinol (11-HO-THC) and 9-carboxy-11-nor-Δ9-tetrahydrocannabinol (THCCOOH)] produced through metabolism of THC (also shown in Figure  1 ). Decarboxylation of the precursor THC acids, THCA-A and THCA-B, in cannabis herb occurs during storage, upon heating (e.g., smoking), or under alkaline conditions. The end result of decarboxylation of either acid is the formation of THC (7). Consequently, potency estimates of THC in cannabis herb products are usually expressed as total THCtot (combination of THC, and THCA-A and THCA-B).

Molecular Structures of THC, THCA-A, THCA-B, 11-HO-THC and THCCOOH.

The shift in cultivation practices over the last 30 years toward production of higher potency THC cannabis with negligible levels of CBD has raised concerns that current cannabis is ‘somehow a different drug than that consumed in previous decades’ (3). Indeed, the THC potency of confiscated cannabis in the US was 2.83% for marijuana and 7.28% for sinsemilla in 1985 (8). THC potency of federal seizures increased steadily over the ensuing years, reaching 6.73% for marijuana and 16.19% for sinsemilla in 2012, with the average potency for all cannabis types being 13.19% (9).

Given these consistent potency increases, the possible impact of higher potency cannabis on various drug-testing programs prompted renewed study and evaluation. Concerns have been expressed for decades that a non-smoker in the vicinity of cannabis smokers are exposed, in much the same way as non-smokers are exposed to tobacco smoke, to vaporized constituents of cannabis. A variety of studies have documented the extent of secondhand cannabis smoke exposure to non-smokers under varying condition such as enclosed unventilated rooms [six non-smokers exposed to 16 smoked cannabis cigarettes, 2.8% THC (10–12); a single non-smoker in close proximity to four smokers smoking 0, 0.86, 1.54 or 1.83% THC (13); four non-smokers exposed to six smokers smoking a cannabis cigarette containing 17.2 mg THC (∼1.5% THC) (14); two or three non-smokers exposed to four smokers smoking a cannabis cigarette containing 26.2 mg (∼2.6% THC) (15); and three non-smokers exposed to four cannabis cigarettes containing 27 mg THC (∼2.7% THC) (16)], non-smoker exposure to hashish smoking (17), exposure in a small, closed car in which five non-smokers were exposed to three smokers smoking 1.5% THC cannabis or two smokers smoking 1.5% THC hashish cigarettes (18) and exposure in a non-ventilated room or medium-sized station wagon to 2.5% THC or 2.8% THC cannabis cigarettes (19).

Two more recent exposure studies have been conducted with higher potency cannabis cigarettes. In one study, four non-smokers were exposed to cannabis smoke generated by four smokers who consumed a single cannabis cigarette containing either 5.4% or 10.4% THC cannabis in an unventilated eight-passenger van (20). The second study was conducted as a field experiment in a ventilated coffee shop (establishment where cannabis and hashish can be openly consumed) in the Netherlands (21). In this study, eight non-smokers remained in the shop for 3 h in the presence of numerous smokers who consumed cannabis primarily by smoking, but some individuals used hashish pipes or water pipes. The exact cannabis potency, number of cigarettes, or amount of cannabis consumed in this study is not known. As with the prior studies, the two studies involving high-potency cannabis exposure to non-smokers resulted in the detection of THC and metabolites in urine, blood and oral fluid specimens collected from non-smokers after exposure.

The goal of the current study was to extend research involving high-potency environmental cannabis smoke exposure (commonly referred to as ‘passive exposure’) to non-smokers. Specifically, the study was designed to ascertain the effects of cannabis potency and room ventilation on both pharmacokinetic and pharmacodynamic outcomes when non-smokers were exposed to concentrated cannabis smoke. Urine and other biological fluids and tissues were collected before and after smoke exposure to determine if exposure under any of these conditions would produce positive drug tests based on commonly used drug-testing standards. This report provides a detailed description of the experimental conditions employed in the study and provides complete initial screening and confirmatory data derived from urine specimens.

Experimental

Participants

Volunteer participants were recruited through newspaper advertisements, flyers posted on campus and community bulletin boards and word-of-mouth. Two types of volunteers were recruited: (i) current cannabis users (self-reported use of cannabis at least two times per week during the prior 90 days) who were not currently trying to quit; and (ii) healthy volunteers who had a history of lifetime cannabis exposure, but had not used cannabis or other illicit substances within the previous 6 months (self-report). Current cannabis users were required to test positive for cannabis (>50 ng/mL THCCOOH) and negative for recent use of other commonly used psychoactive substances (amphetamines, benzodiazepines, cocaine, MDMA, opioids, PCP and alcohol) at the screening visit and upon admission to the research unit for each experimental session. Non-smokers were required to test negative for all of the above substances at screening and at admission to experimental sessions. Only non- or minimal tobacco users were enrolled; no tobacco use was permitted during study participation.

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Eight current cannabis users participated in three experimental cannabis smoking sessions. The eight subjects (three females and five males) had an average [standard deviation (SD), range] age of 29 (6, 24–40) years, weighed an average of 75 (20, 50–108) kg and had an average body mass index of 25.6 (5.1, 20.3–34.2). These eight subjects self-identified their race/ethnicity as follows: four White, non-Hispanic, two Black or African American, one Hispanic or Latino and one as Middle Eastern (Turkish). The smokers self-reported an average of 12 (7, 2–25) years smoking cannabis. They reported an average of 28 (2, 25–30) days of cannabis use in the previous month and consumed an average of 1.5 (2, 0.4–5.2) grams of cannabis per day. The 18 non-smoker participants (nine females and nine males) had an average age of 28 (7, 20–45) years, weighed an average of 74 (12, 55–98) kg and had an average body mass index of 24.7 (3.6, 18.7–33.0). These subjects self-identified as follows: 12 White, non-Hispanic, three African American, two Hispanic or Latino and one Asian.

To the extent possible, conditions were standardized across sessions. Consequently, the six cannabis smokers who participated in Session 1 were invited to continue their participation in Sessions 2 and 3. Four smokers (2M/2F) participated in all three sessions. Two smokers (1M/1F) participated in two sessions and two (2M) participated in a single session. Each of the 18 non-smoking subjects participated in only a single session.

Written informed consent was obtained prior to study participation. The study was approved by the Johns Hopkins Medicine Institutional Review Board and conducted in accordance with the ethical standards of the Helsinki Declaration. All subjects were compensated for their participation.

Chamber construction and layout

A specially designed smoking chamber, made of plexi-glass walls with aluminum supports and measuring 10 ft. × 13 ft. (3.05 m × 3.96 m) with a 7 ft. (2.13 m) ceiling, was constructed for this experiment. It was situated in a larger room that allowed direct observation of all parts of the chamber from three sides. The door to the exposure chamber was also constructed of plexi-glass and aluminum and was fitted with magnets that ran the entire perimeter to create a seal when closed. The door remained closed during each session with two exceptions. One non-smoker smoker (Session 2) and one smoker (Session 3) were allowed a brief bathroom break that lasted ∼5 min. Consequently, the door was opened briefly for exit and entry in those sessions. A metal/plastic utility table (30 in × 6 ft.) was located in the center of the chamber and 12 metal/plastic folding chairs were situated equidistant around the table. During each exposure session, six smokers and six non-smokers were seated in alternate seating positions around the table.

All participants donned disposable paper clothing including booties over their own clothing before entering the experimental chamber for each session. Smokers also wore disposable head coverings to prevent deposition of cannabinoids on their hair during the session. Non-smokers did not wear head coverings because deposition of cannabinoids on hair during naturalistic secondhand exposure might affect hair drug test results, a secondary study outcome. All participants were supplied with goggles for use as needed for reduction of eye irritation from the smoke. During each session, participants remained in their assigned seats and played games, conversed, or engaged in other activities (e.g., listened to music, used cell phone). Smokers were allowed to drink from bottles of water (supplied at the start of the session). Non-smokers were not allowed to eat or drink during the session or after the session until after the first oral fluid specimen was collected. As a safety measure, pulse oximeter readings were collected pre-session and at 15-min intervals during each session to ensure that an adequate oxygen supply was maintained within the chamber.

Cannabis cigarettes

Cannabis for research purposes was obtained through the US federal drug supply program. Two types of Mississippi-grown cannabis with varying cannabinoid content were supplied for the study and were characterized and rolled into cigarettes by staff at Research Triangle Institute, International. The lower potency cannabis cigarettes were machine rolled and were 85 mm in length × 25 mm circumference and weighed a mean weight (SD) of 0.92 (0.06) g/cigarette; the cigarettes had an assayed mean content of cannabinoids as follows: 5.3% (0.48%) total THC; 0.01% (0.0%) CBD and 0.35% (0.04%) cannabinol (CBN). The higher potency cigarettes were hand-rolled and were 70 mm in length (24.5 mm) and had a mean weight (SD) of 1.0 (0.04) g/cigarette; the cigarettes had an assayed mean content (n = 12 for THC; n = 4 for other cannabinoids) of cannabinoids as follows: 11.3% (0.29%) total THC; 0.08% (0.12%) CBD and 0.76% (0.06%) CBN.

Experimental cannabis exposure conditions

Three experimental cannabis sessions were conducted at weekly or greater intervals. Cannabis exposure sessions lasted 1 h, during which smokers consumed cannabis ad-libitum in the presence of non-smokers inside the closed chamber. The primary goal of these sessions was to conduct a pharmacokinetic evaluation of cannabinoids in biological fluids of non-smokers following extreme exposure to secondhand cannabis smoke. Across the three experimental sessions, cannabis potency and room ventilation conditions were manipulated: Session 1 was conducted without air ventilation and cannabis cigarettes containing 5.3% THC were smoked; Session 2 was conducted without air ventilation and cannabis cigarettes containing 11.3% THC were smoked; Session 3 was conducted with active air ventilation comparable to home air-conditioning (11.2 air changes per hour) and cannabis cigarettes containing 11.3% THC were smoked. Each smoker received a pre-weighed individual supply of cannabis cigarettes at the start of each session, and residues and unused portions were collected for weighing at session end.

Experimental procedures following cannabis smoke exposure

At the end of each 1-h cannabis exposure session, participants exited the room and immediately discarded their disposable clothing and washed their hands and face with soap and water. After drying, they proceeded to a cannabis-free room (investigative area) for participation in specimen collections and behavioral and physiological assessments.

Urine, whole blood and oral fluid specimens were collected prior to each session (baseline) and at timed intervals following each session. Coincident with biological specimen collection, vital signs (heart rate, blood pressure), subjective ratings of intoxication and measures of cognitive performance were also obtained. Hair specimens were collected before and after each session from non-smokers. A single pre-study baseline hair specimen was collected from each cannabis smoker and an additional hair specimen was after Session 1 (or subsequent session for smokers who did not participate in all 3 sessions). Experimental measures were obtained every 30 min for the first 2 h, hourly during hours 2–4 and every 2 h during hours 6–8. Smokers were discharged after the 8-h post-exposure time point. Non-smokers remained in the study under supervision over-night and biological specimens and pharmacodynamic measures were obtained through the 34-h post exposure time point. Assessments and outcomes, other than urine testing results, will be reported elsewhere.

Urine collections

Baseline urine specimens were collected ∼1 h prior to each cannabis session. Following the end of each 1-h cannabis exposure period (designated zero time), participants were asked to void at 0.25, 1, 2, 3 and 4 h. Thereafter, urine specimens were pooled for each subject for the following time intervals: 4–6, 6–8, 8–10, 10–12, 12–22, 22–26, 26–30 and 30–34 h. If multiple specimens were produced by an individual during a pool period, they were combined into an individual pool. Each participant was asked to empty their bladder at the end of each pool period for inclusion in that period. No mixing of specimens between participants occurred.

Because of the logistics involved in collecting multiple types of measures from 12 participants, the exact timing of early specimen collections was somewhat variable; consequently, all specimen times should be considered as nominal values (i.e., ±10 min).

Urine specimens were collected in clean, plastic containers labeled with the participant’s identification number, date and collection time. Specimens to be pooled were transferred to a labeled plastic pooling vessel and kept refrigerated during the collection period. The volumes of each individual specimen (first 4 h) and of each pooled sample were measured and two aliquots (minimum of 30 mL each) of each were transferred to polypropylene bottles (bottles ‘A’ and ‘B’). If the specimen volume was <60 mL, the specimen was divided into aliquots of approximately equal volume. All aliquots were stored frozen (≤−20°C) and shipped frozen by overnight express to a designated laboratory for analysis.

Analytical methods

Initial analyses of urine specimens were conducted by Clinical Reference Laboratory (CRL), Lenexa, KS. Bottle A specimens were thawed and aliquots were analyzed by immunoassay and gas chromatography–mass spectrometry (GC–MS). Initial analyses of Bottle A specimens by immunoassays were conducted according to manufacturer’s procedure with the Microgenics DRI assay on a Bayer ADVAI 2,400 analyzer for cannabinoids in urine at both 20 ng/mL and 50 ng/mL cutoff concentrations. Creatinine was determined with Siemens modified Jaffe reagent. Specific gravity was determined with a Rudolph J57 refractometer. Determinations of pH were made with Axiom pH reagents (Axiom Diagnostics, Tampa, FL, USA).

THCCOOH concentrations were measured by a current, validated GC-MS method by CRL. Briefly, 40 ng/mL of internal standard (THCCOOH-d9, Cerillant Corp., Round Rock, TX) was added to 1 mL of specimen and the sample was hydrolyzed with 0.2 mL of 5N NaOH. After hydrolysis, 1.5 mL of glacial acetic acid (pH 4) was added and THCOOH was extracted with a solid phase column (3 mL J-65 cation exchange, Biochemical Diagnostics, Edgewood, NY, USA). The column was eluted with 1.5 mL of n-butyl chloride/triethylamine (80/20, v/v) and the eluate was evaporated and derivatized with bistrimethylsilyltrifluoroacetamide (BSTFA). The specimen was transferred to an injection vial and analyzed on an Agilent 5,975 GC/MS. Ions (m/z) monitored were 380 and 479 for the internal standard and 371, 473 and 488 for THCCOOH. The calibration standard (single point calibration) contained 15 ng/mL of THCCOOH and 40 ng/mL of THCCOOH-d9. Four controls (negative, 6 ng/mL, 18.5 ng/mL, pooled positive urine for hydrolysis control) were assayed with each batch. The method had a limit of detection (LOD) and limit of quantification (LOQ) for THCCOOH of 0.75 ng/mL and an upper limit of linearity (ULOL) of 600 ng/mL. Specimens with concentrations ≥ULOL were diluted to provide accurate quantitation. Criteria for acceptance of results included the following: retention times of analyte and internal standard within ±2% of the calibrator; ion ratios within ±20% of the calibrator; and positive control concentrations ±20% of established concentrations.

Following analyses of Bottle A by CRL, Bottle B specimens were thawed for additional immunoassay determinations, aliquoted, and frozen aliquots were immediately shipped to three additional laboratories. Bottle B aliquots were sent to selected laboratories with differing types of immunoassays. They were analyzed as follows (laboratory, location, immunoassay type, cutoff concentrations): CRL, Lenexa, Microgenics DRI, 20 ng/mL, 50 ng/mL; MEDTOX Laboratories, St Paul, MN, KIMS, 20 ng/mL, 50 ng/mL; MetroLab-Legacy Laboratory Services, Portland, OR, EMIT II, 20 ng/mL, 50 ng/mL; and One Source Toxicology Laboratory, Pasadena, TX, CEDIA, 20 ng/mL, 50 ng/mL, 75 ng/mL, 100 ng/mL.

Sensitivity, specificity and agreement

The sensitivity, specificity and agreement of the immunoassays for detection of cannabinoids in urine were calculated by comparison of the qualitative immunoassay response at different cutoff concentrations to the quantitative GC–MS result for THCCOOH. The confirmation cutoff concentration of ≥15 ng/mL for THCCOOH, as utilized in the Substance Abuse and Mental Health Services Administration (SAMHSA) Mandatory Guidelines for Federal Workplace Drug Testing Programs (22), was used to determine if a specimen was positive. True-positive (TP) (immunoassay response ≥ cutoff concentration and GC–MS positive), true-negative (TN) (immunoassay response < cutoff concentration and GC–MS negative), false-positive (FP) (immunoassay response ≥ cutoff concentration and GC–MS negative), and false-negative (FN) (immunoassay response < cutoff concentration and GC–MS positive) were calculated versus GC–MS at the 15 ng/mL cutoff concentration. Diagnostic sensitivity, 100 × [TP/(TP + FN)]; diagnostic specificity, 100 × [TN/(TN + FP)]; and agreement, 100 × [(TP + TN)/(TP + TN + FP + FN)] were calculated at multiple screening cutoff concentrations.

Results

Cannabis use and reported smoke effects

The total, overall amount of cannabis material smoked (determined by weighing cannabis cigarettes provided to all six smokers prior to smoking and weighing remaining cannabis cigarettes and ‘butts’ at the end of each 1-h exposure period) by session was as follows: Session 1, total of 10.3 g of 5.3% THC cannabis; Session 2, total of 14.4 g of 11.3% THC cannabis; and Session 3, total of 16.5 g of 11.3% THC cannabis. The mean (range) and median amount of cannabis consumed per smoker was as follows: Session 1, 1.7 g (1.1–2.5 g), 1.6 g; Session 2, 2.4 g (1.6–2.9 g), 2.48 g; and Session 3, 2.8 g (2.1–3.4 g), 2.9 g.

Participants were supplied with goggles to wear during sessions to keep smoke from their eyes and reduce eye irritation. In Session 1, most participants elected not to wear the goggles initially, but then experienced substantial eye irritation. As a result, some smokers reported that they stopped cannabis consumption to avoid adding more smoke to the room at a point where they would have otherwise continued to smoke. Other smokers reported stopping cannabis use during Session 1 because they felt social pressure to do so because others had stopped smoking (due to eye irritation). After Session 1, all participants (both smokers and non-smokers) utilized the goggles part-time or full-time and no longer had issues with eye irritation. The combined effect of these occurrences and possibly other factors was that total cannabis consumption in Session 1, at the lower THC potency, was less than in Sessions 2 and 3.

There was considerable smoke generation in all sessions. Session 2 smoke conditions are illustrated photographically from outside the exposure chamber in Figure  2 . The photograph was taken approximately mid-way through the 60 min session. Smoke conditions were visibly less in Session 3, during which the ventilation system was in operation to simulate typical home air-conditioning conditions based on HVAC building standards. All subjects were carefully observed throughout each session and there were no attempts by non-smokers to ‘actively’ inhale sidestream smoke. Overall, observations from outside the smoking chamber were that there was considerable accumulation of smoke during Sessions 1 and 2 (no ventilation), whereas the level of smoke during Session 3 (active ventilation) remained visible but greatly reduced in comparison to previous sessions.

Photograph from outside the exposure room approximately mid-way through Session 2 in which six cannabis smokers and six non-smokers participated in cannabis smoke studies.

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Urinalyses of non-smoker specimens

A complete tabulation of THCCOOH concentrations in urine specimens (determined by GC-MS) is shown in Table  I for the 18 non-smokers who participated in Sessions 1, 2 and 3. Average THCCOOH concentrations (n = 6) determined by GC–MS across time for the six non-smokers in each session are shown in Figure  3 . All non-smoker urine specimens tested negative for cannabinoids by GC–MS and immunoassay on the morning immediately prior to their participation in the experimental session. Following each session, THCCOOH became detectable for all non-smokers by GC-MS at LOQ (0.75 ng/mL) within 0.25 to 3 h and remained detectable in the last specimen collection pool (30–34 h) for 12 (67%) of the 18 participants. Maximum THCCOOH concentrations (Cmax) appeared in urine within 2–11 h (Tmax) following exposure (Table  II ). THCCOOH concentrations declined over the 34 h collection period, but frequently remained detectable by GC–MS. The concentrations and times of the last specimens with detectable THCCOOH (Clast, ng/mL and Tlast, hour) are shown in Table  II .

Table I

Analyses of non-smokers urine specimens following exposure to concentrated secondhand cannabis smoke

Subject # Time, h THCCOOH GC/MS, ng/mL Volume, mL Creatinine, mg/dL Specific gravity pH CRL1 DRI, Cutoff = 20 ng/mL, (Equivalent IA response = 20) Med Tox KIMS 20 Cutoff = 20 ng/mL, (Equivalent IA response = 0) MetroLab EMIT II Plus 20 Cutoff = 20 ng/mL, (Equivalent IA response = 100) One Source CEDIA 20 Cutoff = 20 ng/mL
Session 1
7 −1 NA 56.0 1.0055 6.7 −2 −151 10 NEG
7 0.25 230 64.5 1.0066 7.1 −149 15 NEG
7 1 3.8 49 187.7 1.0155 6.5 28 −36 110 NEG
7 2 7.0 50 177.8 1.0162 6.3 34 13 158 POS
7 3 2.6 190 52.6 1.0056 6.2 −3 −133 42 NEG
7 4 1.3 220 24.1 1.0028 5.9 1 −138 21 NEG
7 4–6 1.1 450 22.2 1.0027 7.0 −2 −145 24 NEG
7 6–8 2.0 380 50.4 1.0062 7.1 3 −119 37 NEG
7 8–10 3.9 195 106.3 1.0132 6.4 8 −91 50 NEG
7 10–12 2.6 455 37.2 1.0051 6.8 −139 24 NEG
7 12–22 1.9 440 82.5 1.0114 6.2 2 −112 35 NEG
7 22–26 1.3 640 50.7 1.0084 6.9 −2 −147 23 NEG
7 26–30 1.7 305 124.5 1.0155 7.1 −3 −133 30 NEG
7 30–34 1.0 670 40.1 1.0076 7.3 −3 −146 15 NEG
11 −1 NA 122.0 1.0153 6.2 −8 −167 7 NEG
11 0.25 122 64.9 1.0109 6.8 2 −113 40 NEG
11 1 3.1 69 86.5 1.0121 5.5 28 −47 102 NEG
11 2 1.8 140 53.1 1.0073 5.6 9 −94 60 NEG
11 3 1.3 170 41.2 1.0048 5.4 4 −112 33 NEG
11 4 3.8 35 151.7 1.0161 5.7 25 −36 100 NEG
11 4–6 6.8 71 142.1 1.0173 5.5 27 6 112 NEG
11 6–8 2.2 140 65.1 1.0094 6.1 7 −84 50 NEG
11 8–10 2.1 140 96.1 1.0139 6.8 5 −88 60 NEG
11 10–12 1.8 210 52.3 1.0070 5.8 1 −141 27 NEG
11 12–22 1.5 730 54.4 1.0073 7.3 −1 −142 32 NEG
11 22–26 1.0 300 86.4 1.0142 7.1 −4 −126 36 NEG
11 26–30 1.1 280 51.6 1.0093 7.3 −2 −129 42 NEG
11 30–34 1.3 180 130.6 1.0174 6.2 −2 −106 38 NEG
13 −1 0.0 NA 56.2 1.0126 7.1 −6 −163 22 NEG
13 0.25 0.8 218 19.6 1.0041 7.2 −142 18 NEG
13 1 4.0 190 46.8 1.0094 7.4 10 −110 65 NEG
13 2 13.1 54 100.7 1.0179 7.4 34 9 170 POS
13 3 15.6 36 91.1 1.0154 7.1 36 35 174 POS
13 4 14.1 48 100.6 1.0148 6.2 30 14 139 POS
13 4–6 9.6 170 90.0 1.0135 5.8 19 −63 80 NEG
13 6–8 4.7 140 52.2 1.0089 5.8 7 −113 51 NEG
13 8–10 7.0 140 115.5 1.0197 6.0 11 −56 68 NEG
13 10–12 19.3 210 142.2 1.0234 5.8 33 83 188 POS
13 12–22 3.3 480 98.9 1.0195 5.7 −1 −102 41 NEG
13 22–26 0.9 510 28.7 1.0076 6.5 −2 −153 24 NEG
13 26–30 2.8 180 87.3 1.0177 6.2 −2 −127 30 NEG
13 30–34 1.6 250 55.9 1.0110 5.4 −2 −131 27 NEG
14 −1 NA 28.9 1.0062 7.2 −3 −157 23 NEG
14 0.25 1.1 94 82.6 1.0144 7.3 −2 −139 43 NEG
14 1 1.4 155 42.0 1.0077 7.2 2 −127 42 NEG
14 2 1.6 200 31.7 1.0057 7.1 2 −140 32 NEG
14 3 2.6 140 48.0 1.0079 6.9 3 −106 37 NEG
14 4 12.2 45 119.1 1.0161 6.3 26 −25 103 NEG
14 4–6 5.2 160 98.5 1.0148 6.8 4 −83 63 NEG
14 6–8 2.9 170 70.8 1.0120 6.5 1 −110 35 NEG
14 8–10 1.5 200 46.4 1.0079 7.2 −117 38 NEG
14 10–12 1.7 220 67.2 1.0109 7.0 1 −132 30 NEG
14 12–22 1.9 830 89.1 1.0128 6.4 −2 −138 26 NEG
14 22–26 260 17.4 1.0037 7.0 −3 −152 22 NEG
14 26–30 220 75.2 1.0129 7.0 −3 −125 31 NEG
14 30–34 140 23.5 1.0060 6.9 −4 −147 17 NEG
15 −1 NA 21.9 1.0046 7.3 −3 −161 15 NEG
15 0.25 112 16.2 1.0037 7.2 −1 −167 20 NEG
15 1 136 10.0 1.0021 7.0 −1 −147 17 NEG
15 2 140 10.4 1.0020 6.6 −2 −138 13 NEG
15 3 1.0 100 14.5 1.0029 6.1 −148 23 NEG
15 4 1.7 94 30.7 1.0057 6.3 −1 −113 31 NEG
15 4–6 1.7 110 35.8 1.0069 7.0 −1 −155 38 NEG
15 6–8 130 12.8 1.0027 6.1 −2 −147 19 NEG
15 8–10 1.0 130 24.9 1.0057 7.2 −1 −143 28 NEG
15 10–12 1.9 165 44.0 1.0099 7.2 −1 −122 46 NEG
15 12–22 0.8 360 54.7 1.0085 6.0 −2 −147 30 NEG
15 22–26 0.8 280 38.1 1.0082 6.0 −2 −158 25 NEG
15 26–30 335 18.4 1.0044 7.0 −4 −142 22 NEG
15 30–34 1.3 420 49.4 1.0104 6.5 −4 −131 22 NEG
16 −1 NA 105.9 1.0108 7.4 −6 −147 26 NEG
16 0.25 1.0 98 57.1 1.0065 7.2 −1 −134 38 NEG
16 1 6.1 28 225.8 1.0197 7.4 33 −51 182 NEG
16 2 1.1 120 30.0 1.0033 7.0 1 −140 28 NEG
16 3 4.5 92 105.5 1.0102 6.4 13 −69 89 NEG
16 4 1.0 89 21.1 1.0025 6.2 −142 24 NEG
16 4–6 20.1 103 19.7 1.0028 7.0 38 −43 103 POS
16 6–8 2.8 105 77.3 1.0090 7.1 3 −124 56 NEG
16 8–10 2.9 100 141.8 1.0127 6.9 4 −103 68 NEG
16 10–12 2.1 130 122.2 1.0112 6.5 2 −78 52 NEG
16 12–22 3.5 170 171.8 1.0185 7.2 3 −86 65 NEG
16 22–26 1.2 330 50.0 1.0086 7.5 −3 −134 36 NEG
16 26–30 1.8 190 113.8 1.0160 7.4 −2 −148 53 NEG
16 30–34 120 249.4 1.0230 6.3 −1 −91 59 NEG
Session 2
8 −1 257 12.0 1.0017 6.0 1 −157 17 NEG
8 0.25 440 15.4 1.0027 6.9 2 −165 19 NEG
8 1 5.6 125 42.9 1.0063 6.2 22 −81 79 NEG
8 2 MS MS MS MS MS MS MS MS MS
8 3 10.8 190 39.7 1.0063 5.1 25 −45 93 NEG
8 4 3.1 420 10.1 1.0016 5.6 6 −148 30 NEG
8 4–6 MS MS MS MS MS MS MS MS MS
8 6–8 6.2 375 32.3 1.0053 6.6 8 −114 53 NEG
8 8–10 4.8 300 32.6 1.0062 7.2 7 −127 48 NEG
8 10–12 9.5 180 64.7 1.0127 7.1 13 −90 83 NEG
8 12–22 6.3 530 80.5 1.0117 6.0 7 −109 54 NEG
8 22–26 1.9 520 24.9 1.0054 7.3 2 −149 32 NEG
8 26–30 2.6 440 40.5 1.0067 7.3 1 −146 35 NEG
8 30–34 4.3 220 86.4 1.0129 7.2 2 −127 44 NEG
23 −1 40 262.5 1.0263 5.6 −7 −128 16 NEG
23 0.25 610 22.4 1.0029 6.2 1 −135 21 NEG
23 1 3.6 790 21.4 1.0026 6.3 8 −139 34 NEG
23 2 6.9 270 17.0 1.0021 6.1 10 −103 52 NEG
23 3 27.3 160 61.6 1.0079 5.4 40 −4 144 POS
23 4 18.8 340 42.4 1.0054 5.6 26 −43 100 NEG
23 4–6 57.5 100 168.7 1.0212 5.6 47 108 226 POS
23 6–8 36.8 90 139.1 1.0198 5.6 44 48 179 POS
23 8–10 32.7 220 162.4 1.0219 5.6 40 69 196 POS
23 10–12 17.4 270 98.3 1.0157 6.0 22 −50 98 NEG
23 12–22 25.2 510 175.6 1.0226 5.8 29 −6 108 POS
23 22–26 5.3 970 36.3 1.0062 7.3 4 −135 45 NEG
23 26–30 12.4 350 121.3 1.0178 7.1 6 −71 90 NEG
23 30–34 9.3 400 112.8 1.0179 6.4 4 −89 59 NEG
37 −1 138 42.3 1.0066 5.4 −163 22 NEG
37 0.25 395 31.0 1.0045 5.5 3 −147 35 NEG
37 1 4.7 110 34.4 1.0044 5.4 13 −99 61 NEG
37 2 17.0 60 109.3 1.0138 5.5 45 47 170 POS
37 3 23.6 40 161.2 1.0206 5.5 42 106 218 POS
37 4 46.3 40 149.7 1.0218 6.9 46 118 285 POS
37 4–6 36.9 75 157.3 1.0218 7.1 45 86 243 POS
37 6–8 24.1 130 110.1 1.0197 7.2 33 2 170 NEG
37 8–10 21.3 150 88.8 1.0194 6.8 27 −24 123 NEG
37 10–12 19.3 170 85.5 1.0198 6.9 24 −33 121 POS
37 12–22 20.4 550 99.5 1.0194 6.2 23 −48 114 NEG
37 22–26 10.4 360 55.1 1.0128 7.2 9 −87 79 NEG
37 26–30 15.6 170 108.3 1.0208 7.3 13 −74 108 NEG
37 30–34 10.3 180 103.1 1.0219 7.1 4 −91 73 NEG
38 −1 114 102.5 1.017 5.8 −5 −166 14 NEG
38 0.25 750 11.0 1.0018 6.7 1 −163 16 NEG
38 1 1.9 117 10.8 1.0016 6.3 5 −138 33 NEG
38 2 2.9 625 10.5 1.0016 6.4 5 −145 38 NEG
38 3 7.8 380 23.7 1.0039 6.0 13 −109 55 NEG
38 4 20.1 123 62.7 1.0097 5.6 32 −33 117 POS
38 4–6 19.7 220 66.1 1.0119 6.1 26 −47 105 NEG
38 6–8 8.3 475 39.2 1.0073 6.0 9 −97 62 NEG
38 8–10 8.1 670 43.8 1.0085 6.2 10 −110 49 NEG
38 10–12 4.5 390 27.8 1.0053 6.1 5 −145 39 NEG
38 12–22 4.4 1,480 40.7 1.0063 5.8 6 −141 22 NEG
38 22–26 1.2 1,860 12.7 1.0024 5.9 2 −167 20 NEG
38 26–30 2 1,120 31.1 1.0056 6.9 −153 27 NEG
38 30–34 1.8 790 34.8 1.007 7.2 −2 −165 31 NEG
40 −1 150 44.9 1.0052 6.6 −2 −136 21 NEG
40 0.25 190 66.8 1.0076 6.7 1 −132 30 NEG
40 1 1.6 162 96.6 1.0099 6.5 9 −105 61 NEG
40 2 5.5 60 128.8 1.0155 6.3 19 −66 100 NEG
40 3 3 122 58.8 1.0091 6.5 5 −106 58 NEG
40 4 2.8 165 48.5 1.0083 6.7 3 −124 44 NEG
40 4–6 500 28.0 1.0048 6.9 1 −150 36 NEG
40 6–8 3.1 710 19.5 1.0034 6.7 2 −132 28 NEG
40 8–10 1.3 350 33.2 1.0065 7.2 −1 −143 40 NEG
40 10–12 1.1 750 25.9 1.0056 7.2 −1 −137 27 NEG
40 12–22 1.5 750 63.6 1.0094 7.1 −136 35 NEG
40 22–26 3.6 480 22.8 1.0049 6.8 1 −143 32 NEG
40 26–30 1.4 405 76.9 1.0118 7.2 −2 −131 43 NEG
40 30–34 550 37.8 1.0065 7.2 −1 −143 27 NEG
41 −1 290 16.7 1.0032 5.8 −2 −135 12 NEG
41 0.25 605 18.4 1.0031 5.6 −144 18 NEG
41 1 5.8 350 22.1 1.0036 6.6 10 −103 50 NEG
41 2 20.4 240 37.0 1.0078 7.3 27 −52 121 NEG
41 3 12.2 335 21.0 1.0049 7.1 11 −100 75 NEG
41 4 29.1 115 52.1 1.0108 7.3 28 −27 138 POS
41 4–6 29.7 215 56.5 1.0108 7.2 28 −37 127 NEG
41 6–8 12 560 24.5 1.0052 7.2 8 −103 67 NEG
41 8–10 20.7 170 52.0 1.0105 7.4 19 −45 126 NEG
41 10–12 9.6 590 28.8 1.0064 7.2 7 −98 60 NEG
41 12–22 11.1 1,000 50.5 1.0082 6.5 8 −99 67 NEG
41 22–26 1,260 56.0 1.0081 7.2 −2 −150 24 NEG
41 26–30 9 350 68.5 1.0114 7.2 4 −120 68 NEG
41 30–34 3.7 920 34.1 1.0070 7.3 −1 −161 35 NEG
Session 3
25 −1 72 109.5 1.0084 5.8 1 −151 12 NEG
25 0.25 190 56.7 1.0064 5.9 2 −150 23 NEG
25 1 350 18.2 1.0029 7.0 5 −149 26 NEG
25 2 1.8 210 25.4 1.0039 7.2 4 −146 26 NEG
25 3 1.1 440 18.1 1.0026 7.1 4 −148 18 NEG
25 4 1.2 460 18.3 1.0025 7.1 4 −144 19 NEG
25 4–6 2.2 560 39.0 1.0057 7.3 3 −119 24 NEG
25 6–8 1.1 610 25.3 1.0037 7.1 2 −150 18 NEG
25 8–10 0.8 320 27.2 1.0030 6.9 4 −141 25 NEG
25 10–12 2.4 200 88.6 1.0089 6.4 4 −134 31 NEG
25 12–22 1,950 38.5 1.0041 6.7 3 −145 21 NEG
25 22–26 2,150 13.3 1.0030 7.2 3 −164 15 NEG
25 26–30 880 36.4 1.0054 7.3 −165 18 NEG
25 30–34 680 43.6 1.0079 6.7 1 −146 21 NEG
26 −1 30 168.7 1.0228 6.1 −6 −148 13 NEG
26 0.25 150 136.7 1.0196 6.1 −5 −157 19 NEG
26 1 1.7 50 146.0 1.0199 6.1 −2 −147 26 NEG
26 2 4.6 40 153.6 1.0209 6.1 1 −129 33 NEG
26 3 5.2 60 149.2 1.0208 6.2 2 −125 41 NEG
26 4 6.6 100 156.7 1.0213 6.2 3 −117 46 NEG
26 4–6 8.3 130 170.4 1.0220 6.9 5 −121 56 NEG
26 6–8 8.0 200 152.2 1.0222 7.1 2 −105 56 NEG
26 8–10 8.7 270 160.1 1.0227 7.1 2 −123 51 NEG
26 10–12 6.8 170 143.0 1.0240 7.0 −126 50 NEG
26 12–22 3.4 630 109.2 1.0178 6.5 −141 33 NEG
26 22–26 2.7 170 112.9 1.0159 7.1 −1 −139 33 NEG
26 26–30 2.5 350 96.7 1.0143 7.2 −129 32 NEG
26 30–34 2.0 550 88.6 1.0152 7.1 −146 23 NEG
27 −1 360 27.1 1.0057 6.2 2 −137 14 NEG
27 0.25 460 20.2 1.0047 7.3 3 −178 19 NEG
27 1 2.6 150 48.3 1.0091 7.2 9 −122 54 NEG
27 2 8.2 110 82.0 1.0141 7.1 17 −78 77 NEG
27 3 7.3 50 130.9 1.0183 6.1 15 −73 79 NEG
27 4 1.8 230 24.3 1.0046 6.3 5 −148 25 NEG
27 4–6 3.3 150 43.7 1.0080 6.9 4 −128 35 NEG
27 6–8 7.0 95 127.6 1.0193 7.1 8 −110 67 NEG
27 8–10 5.1 290 180.1 1.0230 5.6 4 −108 47 NEG
27 10–12 5.1 90 146.5 1.0234 6.1 4 −86 42 NEG
27 12–22 1.4 710 74.0 1.0128 5.9 1 −142 23 NEG
27 22–26 0.8 480 39.6 1.0100 7.2 −157 20 NEG
27 26–30 0.8 540 47.2 1.0100 7.4 −1 −150 29 NEG
27 30–34 550 49.0 1.0093 7.2 1 −132 24 NEG
28 −1 330 28.6 1.0107 6.9 −1 −161 16 NEG
28 0.25 315 32.3 1.0107 6.7 1 −147 24 NEG
28 1 4.3 60 64.7 1.0162 5.8 5 −111 47 NEG
28 2 5.5 95 60.7 1.0145 6.1 7 −132 43 NEG
28 3 3.5 210 23.7 1.0065 6.5 4 −140 30 NEG
28 4 2.2 270 15.3 1.0043 6.7 3 −151 27 NEG
28 4–6 9.0 80 87.8 1.0182 6.3 4 −105 50 NEG
28 6–8 3.8 290 52.0 1.0125 7.0 2 −138 34 NEG
28 8–10 1.3 330 21.8 1.0054 6.7 3 −148 21 NEG
28 10–12 2.6 170 53.9 1.0118 6.7 2 −145 32 NEG
28 12–22 2.5 340 130.8 1.0197 5.8 −1 −130 29 NEG
28 22–26 0.9 730 27.7 1.0084 7.2 2 −149 31 NEG
28 26–30 1.0 460 33.3 1.0087 7.3 1 −159 33 NEG
28 30–34 1.0 450 40.3 1.0105 7.3 −1 −151 34 NEG
29 −1 170 32.9 1.0031 6.2 −143 17 NEG
29 0.25 390 10.3 1.0016 6.8 2 −148 33 NEG
29 1 300 9.7 1.0018 7.2 2 −148 26 NEG
29 2 340 20.2 1.0034 6.5 3 −127 29 NEG
29 3 1.3 170 18.9 1.0041 7.3 4 −148 20 NEG
29 4 1.1 320 15.6 1.0032 7.3 3 −157 24 NEG
29 4–6 0.8 570 13.1 1.0025 7.3 4 −132 27 NEG
29 6–8 250 19.1 1.0033 7.2 2 −154 23 NEG
29 8–10 600 20.0 1.0032 7.4 3 −131 19 NEG
29 10–12 400 21.1 1.0040 7.4 3 −158 30 NEG
29 12–22 1.3 660 73.2 1.0086 6.9 1 −151 27 NEG
29 22–26 1,510 12.5 1.0025 7.4 3 −155 18 NEG
29 26–30 540 26.1 1.0048 7.3 3 −153 24 NEG
29 30–34 1,550 13.6 1.0031 6.8 3 −150 22 NEG
36 −1 40 164.0 1.0233 6.1 −8 −139 27 NEG
36 0.25 380 25.3 1.0045 6.7 1 −139 23 NEG
36 1 1.6 230 24.4 1.0044 6.9 4 −130 21 NEG
36 2 2.4 310 22.2 1.0042 6.6 3 −143 25 NEG
36 3 7.1 80 58.9 1.0092 6.2 6 −111 44 NEG
36 4 15.0 50 124.7 1.0174 6.9 14 −59 94 NEG
36 4–6 15.5 100 147.8 1.0209 7.4 14 −57 107 NEG
36 6–8 4.8 230 46.5 1.0102 7.4 4 −127 38 NEG
36 8–10 3.4 170 39.2 1.0089 7.4 3 −144 38 NEG
36 10–12 3.9 250 55.7 1.0112 7.2 2 −127 46 NEG
36 12–22 7.1 380 145.4 1.0198 6.7 1 −114 56 NEG
36 22–26 1.5 850 29.3 1.0077 7.4 2 −150 32 NEG
36 26–30 5.3 220 103.1 1.0168 7.4 1 −120 61 NEG
36 30–34 1.0 1,010 26.7 1.0058 7.4 2 −172 34 NEG

IA, immunoassay; NA, not applicable; MS, missing specimen; NEG, negative; POS, positive.

Table II

THCCOOH concentrations (maximum and last) and times in non-smoker’s urine specimens following secondhand exposure to concentrated cannabis smoke

Session 1st Subject 2nd Subject 3rd Subject 4th Subject 5th Subject 6th Subject Mean/ Median
Cmax, ng/mL
1 7 6.8 19.3 12.2 1.9 20.1 11.2/9.6
2 10.8 57.5 46.3 20.1 5.5 29.7 28.3/24.9
3 2.4 8.7 8.2 9 1.3 15.5 7.5/8.5
Tmax, h a
1 2 5 11 4 11 5 6.3/5.0
2 3 5 4 4 2 4 3.7/4.0
3 11 9 2 5 3 4 5.7/4.5
Clast, ng/mL
1 1 1.3 1.6 1.9 1.3 1.8 1.5/1.5
2 4.3 9.3 10.3 1.8 1.4 3.7 5.1/4
3 2.4 2 0.8 1 1.3 1 1.4/1.2
Tlast, h a
1 32 32 32 17 32 28 28.8/32
2 32 32 32 32 28 32 31.3/32
3 11 32 28 32 17 32 25.3/30

a Tmax for pooled specimens is expressed as the midpoint of the collection period.

Average THCCOOH concentrations in urine specimens collected from six non-smokers exposed to cannabis smoke (note: data are plotted at the mid-point for pooled specimens collected after 4 h).

A total of 27 specimens (3 in Session 1, 22 in Session 2 and 2 in Session 3) had THCCOOH concentrations ≥15 ng/mL (confirmatory test cutoff concentration recommended by SAMHSA) (22). These specimens were produced by two participants (#13, #16) in Session 1, four participants (#23, #37, #38, #41) in Session 2 and one participant (#36) in Session 3.

Accompanying data (volume, creatinine, specific gravity and pH) for each individual specimen or specimen pool are also included in Table  I . In addition, immunoassay data are shown for four different screening assays (DRI, KIMS, EMIT II and CEDIA) at a cutoff concentration of 20 ng/mL. Although CRL laboratory conducted equivalent immunoassays (DRI) on Bottles A and B, only the data for Bottle A are shown in Table  I . All non-smoker specimens screened negative for cannabinoids at cutoff concentrations of 100 and 75 ng/mL for all screening assays.

Screening assays for cannabinoids at a 50 ng/mL cutoff concentration produced a single presumptive positive result (0.4% positivity rate) by the Lab Corp EMITII 5B3 THC Assay for Subject # 37 (4 h post exposure, Session 2). This result was the only presumptive positive produced by immunoassay from the five laboratories; the remaining four laboratories reported the same specimen as negative. However, all five laboratories reported this specimen as positive at the 20 ng/mL cutoff concentration. The individual who produced the specimen was a 24-year-old female who weighed 98.1 kg and had a body mass index (BMI) of 29.9. As shown in Table  I , the specimen contained 46.3 ng/mL of THCCOOH (GC/MS); creatinine was 149.7 mg/dL; and the specific gravity of the specimen was 1.0218.

Multiple presumptive positive results for non-smokers occurred by immunoassay at the 20 ng/mL cutoff concentration across the three exposure sessions as shown in Table  I . The number of positives at the 20 ng/mL cutoff concentration in each session by assay (DRI, KIMS, EMIT II, CEDIA) was as follows, respectively: Session 1, 12, 6, 12, 6; Session 2, 22, 8, 22, 12; and Session 3, 0, 0, 1, 0. The first appearance of a presumptive positive (initial test) result at the 20 ng/mL cutoff concentration occurred in specimens collected within 1–4 h following exposure. Following the appearance of the first presumptive positives, individuals continued to test positive for 2–22 h.

Sensitivity and specificity of immunoassays

Immunoassay responses from the 250 non-smoker urine specimens (18 participants, 3 experimental exposure sessions; 14 specimens per subject; two missing specimens) were compared with GC–MS measures of THCCOOH concentration (Table  III ). Specimens were designated as TP, TN, FP or FN based on whether the specimen contained ≥15 ng/mL of THCCOOH by GC–MS and demonstrated an appropriate response by the immunoassay at the designated cutoff concentration. Overall, more TPs and FPs and fewer FNs were identified at the 20 ng/mL cutoff concentration than at higher concentrations. Sensitivity and agreement also increased, whereas specificity decreased, at the lower cutoff concentration. There were 27 FNs registered by four immunoassays (CEDIA, DRI, KIMS and EMIT II) and 26 FNs by the EMIT II 5B3 assay at the 50 ng/mL cutoff concentration. The mean (range) THCCOOH concentration of the 27 FNs was 24.6 (15.0–57.5) ng/mL. The corresponding mean (range) creatinine for these specimens was 102.6 (19.7–175.6) mg/dL. The major portion (n = 22, 81.5%) of the FNs were from participants in Session 2. Three (11.1%) FNs came from Session 1 and two (7.4%) came from Session 3.

Table III

Comparisons of immunoassay responses to confirmation analyses in non-smoker’s urine specimens following secondhand exposure to concentrated cannabis smoke

One Source CEDIA 100 ng/mL One Source CEDIA 75 ng/mL One Source CEDIA 50 ng/mL CRL1 DRI 50 ng/mL CRL2 DRI 50 ng/mL Med Tox KIMS 50 ng/mL MetroLab EMIT II Plus 50 ng/mL Lab Corp EMIT II 5B3 50 ng/mL
TP 1
TN 223 223 223 223 223 223 223 223
FP
FN 27 27 27 27 27 27 27 26
Total 250 250 250 250 250 250 250 250
Sensitivity 3.7
Specificity 100 100 100 100 100 100 100 100
Agreement 89.2 89.2 89.2 89.2 89.2 89.2 89.2 89.6
One Source CEDIA 20 ng/mL CRL1 DRI 20 ng/mL CRL2 DRI 20 ng/mL Med Tox KIMS 20 ng/mL MetroLab EMIT II Plus 20 ng/mL
TP 15 23 16 10 25
TN 220 212 214 219 213
FP 3 11 9 4 10
FN 12 4 11 17 2
Total 250 250 250 250 250
Sensitivity 55.6 85.2 59.3 37.0 92.6
Specificity 98.7 95.1 96.0 98.2 95.5
Agreement 94.0 94.0 92.0 91.6 95.2

TP, true positive; TN, true negative; FP, false positive; FN, false negative.

The DRI immunoassay was initially performed at 50 and 20 ng/mL cutoff concentrations upon receipt and thawing of the frozen specimens (bottle A). Additional immunoassays were performed subsequently with Bottle B. Results of these immunoassays are shown in Table  III . The first and second set of DRI analyses of bottles A and B are designated as ‘CRL1 DRI’ and ‘CRL2 DRI’, respectively. At the 50 ng/mL cutoff concentration, the results of the repeat analyses for bottle B versus bottle A were identical. At the 20 ng/mL cutoff concentration, two FPs and seven TPs for bottle A were converted to two TNs and seven FNs, respectively.

Discussion

Cannabis is widely used as a drug of abuse, but is also used for purported medical benefits by patients with various disease states such as anorexia, nausea, multiple sclerosis and neuropathic pain (23–25). The widespread prevalence and multi-purpose use of high-potency cannabis has led to renewed concerns regarding the effects of secondhand or ‘passive’ smoke exposure. This study was conducted to re-evaluate the risk of non-smokers testing positive for cannabis because of secondhand exposure to cannabis smoke under extreme conditions. The study used higher potency cannabis material, relative to earlier studies, that is more similar to strengths of THC currently encountered in cannabis in the USA. In addition, cannabis-using participants in the present study were allowed to smoke cannabis cigarettes on an ad libitum basis, simulating actual use patterns, rather than being experimentally limited, as was done in a prior study using higher potency cannabis (20). Non-smokers sat in close proximity to smokers for each 1-h exposure session. In the two unventilated sessions, smoke conditions were noticeably high and caused irritation to eyes and mucous membranes when goggles were not used. Overall study conditions were designed to produce a high-intensity, short-term cannabis smoke environment in which subjects would clearly recognize that they were undergoing cannabis smoke exposure.

The current study demonstrated that short-term extreme cannabis smoke exposure produces absorption of sufficient amounts of THC for some non-smokers to test positive in urine assays employing sensitive cutoff criteria for initial and confirmatory testing. These results are not unlike earlier cannabis smoke exposure studies (10–21), but comprehensively demonstrate the important role that initial immunoassay screening tests play in determining a presumptive positive followed by a secondary confirmatory method. Immunoassays employing a cutoff concentration of 50 ng/mL, as recommended by the SAMHSA Mandatory Guidelines for Federal Workplace Drug Testing Programs produced negative test results (99.6% negative) with the single exception for one assay (EMIT II), whereas initial tests with a 20 ng/mL cutoff concentration produced multiple positive results. This is important because some private non-regulated drug testing programs utilize lower initial screening cutoffs (e.g., 20 ng/mL), which our study shows increases the likelihood of a positive test result in non-smokers exposed to secondhand cannabis smoke. It is important to note that THCCOOH was detectable in all subjects in all exposure sessions by GC–MS at the LOQ of the confirmatory assay. A total of 27 (10.8%) of 250 non-smoker’s specimens had THCCOOH concentrations ≥15 ng/mL for confirmation analysis; 17 specimens had concentrations in excess of 20 ng/mL. One participant (#16 at 4–6 h) produced a specimen with a concentration of 20.1 ng/mL of THCCOOH in Session 1 and four participants (#’s 23, 37, 38, 41) produced a total of 16 specimens with >20 ng/mL concentrations of THCCOOH in Session 2. These specimens were excreted 2–22 h following exposure. No participants in Session 3 produced specimens >20 ng/mL of THCCOOH demonstrating the important effect that room air ventilation had upon lowering exposure and intake of THC by non-smokers.

There was considerable variation in the response across the different immunoassay tests to specimens containing ≥15 ng/mL of THCCOOH. The KIMS 20 assay produced the lowest number of TPs (n = 10) and EMIT II produced the highest number (n = 25). Following cannabis exposure, THCCOOH is excreted in urine primarily as a glucuronide conjugate along with small amounts of free metabolite (26, 27). The differences in immunoassay response to specimens containing ≥15 ng/mL of THCCOOH was likely due to differences in cross-reactivity with the glucuronide conjugate of THCCOOH. Package insert information regarding immunoassay cross-reactivity with the glucuronide conjugate at a 20 ng/mL cutoff concentration appear to be only reported for EMIT II (79%) and KIMS (44.1%).

Study limitations

Limitations of the present study include the fixed order of conditions, non-blindness to the ventilation conditions, the single session and small number of participants in each study condition and the possibility of within-session social influences among the smokers. The extent of passive cannabis smoke exposure and absorption is known to vary according to a number of factors including THC potency, amount of cannabis smoked, duration of exposure and environmental factors such as enclosure space, ventilation conditions and proximity of non-smokers to smokers. Additional considerations include assay sensitivity and specificity and administratively designated cutoff concentrations that determine whether a test is reported as positive or negative.

In the present study, non-smokers were seated alongside smokers in very close proximity. Distance of non-smokers from smokers is likely to be an important factor in determining the extent of absorption of aerosolized THC. Also, the study only evaluated the effects of an acute 1-h exposure period to high-intensity smoke conditions. Hence, the conditions of this study were designed to simulate short-term extreme exposure to cannabis smoke. Multiple exposures to cannabis smoke over longer periods and varying intensities could conceivably result in some accumulation of THC and produce different results. However, an earlier study of smoke exposure from lower potency cannabis (2.8% THC) in which subjects were exposed over six consecutive days for 1 h each day produced only suggestive evidence of accumulation or enhancement of positivity rates (12).

The current study employed chronic, daily cannabis smokers to create extreme smoke exposure conditions in the study chamber. Occasional cannabis smokers may produce greater amounts of side stream smoke as a result of fewer inhalation attempts, but it is presumed that they would combust less cannabis overall in a typical smoking session. Other methods of cannabis inhalation, e.g., ‘vaping’ devices that deliver aerosolized oil derived from cannabis, may also alter levels of exposure to non-smokers. Consequently, the current results should be interpreted as being most representative of short-term exposure to extreme, high-intensity cannabis smoke and can only be partially extrapolated to the multiple scenarios of exposure that may occur for non-smokers in other situational and environmental conditions (e.g., ventilation conditions, amount and frequency of exposure).

Conclusions

Cannabis potency and room ventilation were demonstrated to be two major factors in determining the extent of cannabis smoke exposure to non-smokers residing in close proximity to smokers. Short-term exposure to high-intensity smoke from combusted cannabis resulted in non-smoker inhalation of sufficient amounts of THC to produce positive presumptive urine tests by immunoassay with a 20 ng/mL cutoff concentration, but only a single positive occurred at higher cutoff concentrations (50 ng/mL). GC–MS analysis of presumptive positives confirmed the presence of THCCOOH at ≥15 ng/mL in some specimens. Whether test results for non-smokers would be reported as positive or negative will be highly dependent upon the sensitivity of initial and confirmatory tests and related reporting criteria. Overall, these results indicated that extreme smoke exposure can produce positive tests at lower cutoff concentrations, but not generally at the higher initial test cutoff concentration in general use by SAMHSA’s Mandatory Guidelines for Federal Workplace Drug Testing Programs.

Funding

SAMHSA provided financial support for the study. NIDA provided material support for the study (cannabis) and financial support for the participation of Dr. Herrmann ( T32-DA07209 ).

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