The Ongoing Myth of Potency Accuracy in Cannabis Analysis




Heating Technologies Improve Profitability for Cannabis Greenhouses


Cultivators Address New Health and Safety Issues for Plants and Workers


Cannabis Science Conference Fall 2023: Where Collaboration and Connections Grow


By Megan L'Heureux, Madeline Colli, and Erin McEvoy

Articles

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Cannabis Science and Technology October 2023 Interactive Digital Edition

Accuracy measures how far away a measurement is from its true value. In the absence of a matrix reference materials with known cannabinoid concentrations, it is impossible to obtain potency accuracy in cannabis analysis. This leads to all sorts of problems, including inter-laboratory variation, and people always assuming their laboratory is right and everyone else’s is wrong with resultant arguments. Here, we suggest some solutions to the problem.

I’m a laid-back guy—really, I am. But I get very frustrated when I see bad science threatening the health of cannabis patients and the viability of our industry. Early on in this column series I spent a lot of time railing against the lack of scientific rigor in cannabis analysis (1). I then promised you, dear reader, to shut up and see if my columns made any difference. After spending a few years writing about the basics of the use of spectroscopy and chromatography in cannabis potency analysis, I am afraid to report that I have seen little progress on the issues I have brought up previously. It appears I have been screaming into the void. Since I am a glutton for punishment, I will continue to scream into the void with this column in the hopes that someone will hear. I wrote a previous column on cannabis potency calibration problems (1-3). Those columns are the starting point and expand on some of the topics from those columns.

I have written on this topic previously (4), but as I like to say, a review never hurt anybody. The concepts of accuracy and precision are shown visually in 

Figure 1 makes clear that accuracy and precision are not the same thing. Imagine we are measuring the mass of a standard on a balance seven times. The bullseye on the target represents the known mass and the dots represent its measurements. Precision is a measure of the spread, scatter, variance, or dispersion in a set of measured values. Accuracy measures how far away you are from the true value.

The leftmost target in Figure 1 shows data that are imprecise and inaccurate. This is because there is a wide scatter in the data meaning the data are imprecise, and the data points are far away from the center of the bullseye meaning the data are inaccurate. The center target in Figure 1 shows data that is precise, but inaccurate. The data are precise because they are tightly clustered with respect to each other. However, the data are inaccurate because this cluster is far from the true value as represented by the bullseye. The data in the rightmost target in Figure 1 are what we want, data that are precise and accurate. These data are precise because the data points are tightly clustered together. These data are accurate because they are tightly clustered around the bullseye, the true value. Please note, and this is important, that to calculate accuracy we must have a known value of the quantity being measured.

Where Do We Find True Values for Cannabis Potency Analysis?

A commonly used technique used to determine potency values in cannabis samples is chromatography. Both gas and liquid chromatography have been used, however, for several reasons high performance liquid chromatography (HPLC) is used most often these days. As I have discussed in the past, my favorite HPLC potency method is that of Giese and colleagues (5).

For the sake of example, let's imagine we want to calibrate an HPLC for tetrahydrocannabinol (THC) analysis of cannabis plant material. Any number of companies, some of whom advertise in this esteemed publication, sell THC standard samples. These typically consist of a solvent with a known concentration of THC dissolved in it. They can be made, for example, by weighing out a known amount of pure THC and dissolving it in a known volume of solvent. The standard samples are then injected into the HPLC and the peak height or area (assume we are using peak area going forward) of THC’s corresponding peak is measured. 

 shows an HPLC chromatogram for a sample containing cannabinoids. Peak #5 is for THC.

Then, using the principles of calibration science (to be covered in an upcoming column series) and a series of standards of differing known concentration, a mathematical model relating HPLC peak area to THC concentration is computed. To determine the concentration of THC in an unknown sample, it is injected into the HPLC, the THC peak area is determined, then the calibration model and the measured peak area are used to predict the concentration of THC in the unknown sample.

There are number of places where this process can go wrong. Firstly, we found out the hard way soon after the legalization of cannabis and the initial sale of cannabis HPLC standards that some cannabinoids are not stable in certain solvents! So, when buying cannabinoid HPLC standards please make sure you know what solvent your cannabinoids are dissolved in, double check with the manufacturer to make sure the standards are stable, and make sure to abide by all instructions for storing your standards and what their expiration dates might be. In many cases, your standards will need to be stored in a refrigerator and may only be good for a limited amount of time once opened.

Let’s assume that we have miraculously solved all the problems with cannabinoid HPLC standards and that we have achieved a perfect separation and calibration. Is this sufficient to give us a true THC potency accuracy measurement? Afraid not. The problem is that the standard we inject into the HPLC is in idealized form, pure THC in solvent. Unfortunately, that is not the state of the actual sample being analyzed. In reality, our samples can be plant material, extracts, distillates, hashish, or final products such as tinctures or edibles. These samples are nothing like the final solution of pure cannabinoids that are injected into an HPLC. Also, all these samples require significant amounts of sample preparation, including extraction, mixing, filtering, dilution, and injection into a chromatograph. As I have discussed previously (2), based on my observations at dozens of cannabis laboratories, one of the biggest sources of variation between laboratories is the extraction process. A goal of any chromatographic extraction process should be to get all the analyte into the solution that will be injected into the chromatograph; if any analyte is left behind, we will not measure the true value of the concentration of the analyte in the sample actually being analyzed, which means this measurement will be inaccurate. An extraction method that consistently removes a given percentage of the analyte, let’s say 80%, will be precise because the results may cluster tightly around a given value, but this data will still be inaccurate because we will be 20% off from the true value. Most, if not all, published cannabis potency methods say nothing about whether they tested to see whether they got all of the analyte out or not. In other words, we have no way of validating chromatographic extraction methods in the cannabis industry!

To solve this problem we need cannabis flower, extract, distillate, and final products with known amounts of our analytes of interest such as cannabinoids and terpenes in these matrices. Only then will we have a known value of our analyte in our sample matrix and have a way of determining whether our extraction technique is correct or not. The National Institutes of Standards and Technology (NIST) call these types of standards 

Where Can One Find Cannabis Matrix Reference Materials?

In the US, true values for analytical work are typically provided by NIST, and they are perfectly capable of producing good matrix reference materials. For example, for the analysis of green tea there exists a matrix reference material of known composition that can be used to check an instrument’s calibration (7). That is, green tea plant material samples exist with known amounts of the analytes of interest for the green tea industry. These samples can be used to validate extraction methods to make sure they work correctly.

I chose green tea as an example because it is a good mimic for cannabis plant material; if NIST can put together good green tea matrix reference materials it should be able to issue good cannabis matrix reference materials such as for cannabis plant material. Except that they can’t. Because of the perversion in the way cannabis is regulated in the US, anything with more than 0.3% total THC is illegal at the federal level. It would be illegal for NIST, being a federal agency, to ship matrix reference materials with greater than 0.3% total THC in it across state lines. Hence, the lack of NIST issued cannabis matrix reference materials. This means there are no true values available for cannabis potency analysis. This is why I say that accuracy in cannabis potency measurements is a myth. It will take rationalization of cannabis regulation, and legalization at the federal level, for this problem to be solved.

You Cannot Compare Potency Measurements Between Different Instruments or Methods!

Again, accuracy is a measure of how far off you are from the true value, and in cannabis potency analysis those true values must be supplied by appropriate matrix reference materials. Currently, there are no appropriate cannabis reference materials available, for example, there are no known true values. And again, this is because we have no way of validating sample extraction methods. How then can we calculate accuracies in cannabis potency analyses? We can’t! The proof that varying methods cause variations in potency analyses of the same sample has been well documented (8).

I realize that any number of research groups and professional organizations are working on or have published cannabis potency methods, but no two of these methods are the same, and lacking appropriate matrix reference materials we have no way of knowing whether some, none, or all of these methods are accurate. I strongly encourage these groups and organizations to stop work on all their different methods, wait until there are appropriate cannabis matrix reference materials available, and then work together to promulgate a single cannabis potency method that our industry can use.

At the end of the day, the lack of appropriate cannabis matrix reference materials means that we have no way of measuring potency accuracy in the cannabis industry. This means that potency measurements made with different methods or with different instruments cannot be compared to each other. Think about that for a little bit. Measurements made by different third-party laboratories cannot be compared to each other, and even measurements made by the same laboratory using the same method but on different instruments cannot be compared to each other. This can lead to any number of problems.

As many of you know, I have done extensive research on the application of mid-infrared spectroscopy to cannabis analysis (8-14). The lack of appropriate cannabis matrix reference materials has given me no end of trouble in my attempt to gain converts to this method. Here are two stories:

I am in the process of trying to develop a spectroscopic tincture analysis method for a potential customer. We of course need standard samples with known concentrations of the analytes to be able to obtain a calibration. The accuracy of the concentration determination of the standards is probably the biggest contributor to the accuracy of predicted concentrations. So, we measured the spectra of the tincture standards, and I was provided with the “true” analyte values by the potential customer. When I asked about the accuracy of the true values I was told, “The method used to analyze these samples was certified by government agency XYZ.” I said, “That’s nice, what potency analysis method was used?” Of course, the response was chromatography. Then I asked, “What was the accuracy of the chromatographic method?” The response, “I don’t know, the method was certified by government agency XYZ.” A perfect example of circular logic. The customer then went on to criticize the accuracy of my spectroscopic method with no knowledge of whether the reference data were any good or not.

To bless any analysis by saying it was done by spectroscopy or chromatography is meaningless. We are analytical chemists, and we need numbers to provide meaning to our analyses. It is never scientifically correct to accept the results of a method on blind faith. Analytical data lacking accuracy determinations is meaningless. A set of tincture matrix reference materials would solve this problem.

Your Results Don’t Match My Laboratory!

It is a rule of thumb that a properly calibrated spectrometer will be 1.5x to 2x less accurate than the reference method used to calibrate it, which in cannabis analysis is typically chromatography. I have written extensively about the problem of inter-laboratory variation in the cannabis industry (8). A large part of this problem is the lack of proper matrix reference materials for cannabis potency analyses as discussed above, not to mention the lack of a standardized cannabis potency method. Now, science knows how to compensate for variations across methods, it’s called a crossover study. We simply run a set of standards using method 1, the same standards using method 2, and then compare the results. The problem with this approach in the cannabis potency business is that because of the lack of matrix reference materials we lack the proper standards for a crossover study! This means we cannot compare cannabis potency data across instruments or laboratories until the proper matrix reference materials appear. Why this makes me pull my hair out, is that in my work all mid-infrared spectrometers are calibrated using reference HPLC values from a state licensed, International Organization for Standardization (ISO) certified laboratory (15).

All too often I will be contacted by someone saying that their pet laboratory’s numbers using HPLC do not match those obtained by mid-infrared spectroscopy. The problem here isn’t the mid-infrared method, it is that the two chromatographic methods in question are not the same, and we have no way of knowing which one is correct because of the lack of appropriate cannabis matrix reference materials.

The solution to this problem is for the customer’s spectrometer to be calibrated using values from their preferred laboratory. Of course, customers bristle at having to do this and end up thinking there is something wrong with spectroscopy potency methods rather than understanding that the problem is lack of appropriate matrix reference materials.

What we can aspire to have here is precision and a well implemented cannabis potency method should be able to achieve this goal. Given the problems discussed in this column, we may not get a true value, but we can at least aspire to reproducibility giving us precise but inaccurate data. This will at least allow cannabis businesses to use potency analyses to run their operations. For example, if we tweak a distillation and the measured potency goes up, that increase is probably real, and the adjustment is worth keeping. Where the lack of accuracy is dangerous is in the final products we sell to cannabis patients. It is essential that we know what the exact amount of THC, cannabidiol (CBD), and other analytes are in products put into or onto a human being so we can ensure cannabis patients are getting the right dose of medicine.

If Cannabis Matrix Reference Materials Were Ever to Magically Appear

In a perfect future alternative universe where cannabis is regulated rationally and appropriate cannabis matrix reference materials are available, what would we do then? I believe a mass inter-laboratory variation study is needed. All 3rd party laboratories that want to be legally certified to provide cannabis potency measurements to the public need to be required to be involved in this study. Once these laboratories run samples with known true values and then compare their own results, they can ascertain whether their methods are good or not. Only once we have this vital information, can we take cannabis potency measurements out of the realm of mythology and into science.

The lack of appropriate cannabis potency matrix reference materials means that accuracy measurements in these analyses cannot be computed. This means we cannot compare potency measurements across instruments, methods, or laboratories. This lack of accuracy makes adaptation of new technologies for potency measurements difficult, and the resultant error in cannabis dosage measurements threatens patient health. If, and when, appropriate cannabis matrix reference materials appear, a massive round-robin study involving all laboratories that wish to provide certified potency measurements to the public needs to be performed.

Smith, B.C., Dispelling Cannabis Analysis Calibration Myths, 

Smith, B.C., How Standardized Sample Preparation Can Solve the Inter-Laboratory Variation Problem, 

Smith,B.C., Dispelling Cannabis Analysis Myths, Part I, 

Smith, B.C., Error, Accuracy, and Precision, 

Giese, M.W., Lewis, M.A., Giese, L., and Smith, K.M., 

NIST Tools for Cannabis Laboratory Quality Assurance, 

https://www.nist.gov/programs-projects/nist-tools-cannabis-laboratory-quality-assurance

Green Tea Standard Reference Material (SRM), 

https://www.nist.gov/image/greenteastandardreferencematerialsrmjpg

Smith, B.C., Lessard, P., and Pearson, R., Inter-Laboratory Variation in Cannabis Analysis: Pesticides and Potency in Distillates, 

Smith, B.C., Lewis M., and Mendez, J., Optimization of Cannabis Grows Using Fourier Transform Mid-Infrared Spectroscopy, PerkinElmer Application Note,

Smith, B.C., Quantitation of Cannabinoids in Dried Ground Hemp by Mid-Infrared Spectroscopy, 

Smith, B.C., A Proposed Representative Sampling Plan for Hemp Grows, 

Smith, B.C., Fucetola, C.A., Ehrmantraut, K., and Hagan, T., 

, PhD, is Founder, CEO, and Chief Technical Officer of Big Sur Scientific. He is the inventor of the BSS series of patented mid-infrared based cannabis analyzers. Dr. Smith has done pioneering research and published numerous peer-reviewed papers on the application of mid-infrared spectroscopy to cannabis analysis, and sits on the editorial board of Cannabis Science and Technology. He has worked as a laboratory director for a cannabis extractor, as an analytical chemist for Waters Associates and PerkinElmer, and as an analytical instrument salesperson. He has more than 30 years of experience in chemical analysis and has written three books on the subject. Dr. Smith earned his PhD on physical chemistry from Dartmouth College.
Direct correspondence to: 

Smith, B., The Ongoing Myth of Potency Accuracy in Cannabis Analysis, 

Cannabis Analysis 

It is impossible to obtain potency accuracy in cannabis analysis. Here, we suggest some solutions to the problem.

The Ongoing Myth of Potency Accuracy in Cannabis Analysis

Hydronic heating systems are the most energy-efficient way to distribute heat. Equipment like low-mass boilers and low-volume aluminum finned heat pipes reduce energy consumption by heating up 83% less water and only 20% of the mass. Strategies like root zone heating bring heat distribution close to the plants to minimize energy waste. This column describes how cultivation facility operators can use greenhouse heating technologies that reduce natural gas consumption to improve profitability.

Most of the heating, ventilation, and air conditioning (HVAC) conversation around cannabis cultivation centers on cooling. But, regardless of location, cannabis cultivation facilities need some type of heat. Energy for space heating can account for less than 5% of indoor farm annual energy use, but greenhouse natural gas usage for heating end uses can account for 70–80% of annual energy usage (1,2).

Most greenhouse heating (70–80%) demand happens at night (3). Greenhouses growing cannabis have lots of ways to achieve their target environmental conditions in every season. Most greenhouses use unit heaters (steam, hot water, oil, or gas direct-fired units), a central boiler producing steam or hot water, or a combination of these systems (4). Larger greenhouses are more likely to use boilers, while smaller greenhouses more commonly utilize unit heaters. Steam heating and infrared systems are more commonly found in older greenhouses while hot water systems are more likely to be used in newer greenhouses or new construction projects (5).

Heat can be distributed via in-floor, in-bench, on-bench, under-bench, root-zone, gutter, perimeter, or top (above plant canopy) heating systems. Top heating is popular. Unit heaters represent 60% of all heating equipment dollars spent for greenhouses (3).

Unit heaters can be vented or unvented. Condensing vented unit heaters are the most energy-efficient choice, but some growers elect to use unvented unit heaters as a source of CO

 enrichment. There are some disadvantages to this strategy, as plants cannot utilize CO

 at night, which is when the unit heater is usually running, and byproducts of combustion like ethylene are detrimental to plant growth and development (6).

Greenhouses may use boilers to serve hydronic heating systems. Like unit heaters, condensing boilers offer better efficiency ratings. Low-mass boilers maximize heat transfer with lower water volumes and offer the best efficiency of any commercially available boiler technology. The newest generation of low-mass boiler equipment can also cover larger areas. Today’s technology can cover 1.5 acres with one 2,000,000-Btu boiler, when previous generations could cover only 0.5 acres with the same capacity (7).

Facilities using boilers often distribute heat using steel pipes filled with hot water. Innovations in heat pipe technology include finned heat pipes for perimeter, under-bench, and top of canopy applications. Moving heat distribution under-bench can save 20% or more in heating costs and may increase yield and plant quality (6). Since the heat is located at plant level, space temperatures can be reduced and result in persistent energy savings. Biotherm makes finned pipes out of aluminum, which transfers heat three times faster than steel (8).

Greenhouse cultivators can improve profitability by installing high-efficiency heating systems to reduce energy costs. If next steps are unclear, reach out to experts at Energy Resources Integration, LLC (ERI) for a greenhouse heating study or other energy-related services (9).

Market Characterization of Indoor Agriculture (Non-Cannabis), 

https://www.etcc-ca.com/reports/market-characterization-indoor-agriculture-non-cannabis

Sanford, S., Reducing greenhouse energy consumption – An overview, 

https://farm-energy.extension.org/wp-content/uploads/2019/04/2.-A3907-01.pdf

Stone, P., and Youngsman, J., Gas-Fired Infrared Heating for Greenhouses, 

http://www.rg-cloud.com/RG/manuals/IRGHM_Greenhouse_Manual-lo-res.pdf

Reducing Energy Costs in California Greenhouses, 

University of California Cooperative Extension Service

https://www.canr.msu.edu/floriculture/resources/energy/assets/ReducingEnergyCostsinCalifoniaGreenhouses.pdf

Greenhouse Structures, Equipment, and Technology, 

https://www.ipgbook.com/ball-redbook-products-9781733254113.php

Sanford, S., Greenhouse Unit Heaters – Types, Placement, & Efficiency, 

https://farm-energy.extension.org/wp-content/uploads/2019/04/3.-A3907-02.pdf

Zurko, J., Not Your Grandfather’s Boiler Room, 

https://www.biothermsolutions.com/news/not-your-grandfathers-boiler-room/

Rearden, J., The Benefits of Finned Pipes, 

https://www.growertalks.com/Article/?articleid=25776

ERI Offers A Suite of Energy-related Services to Cannabis Cultivators, 

, PE, is a Senior Energy Engineer at Energy Resources Integration, LLC where she implements energy efficiency programs and provides direct consulting services. She is the former Technical Director of the Resource Innovation Institute and manager of the organization’s Technical Advisory Council. She authored RII’s Lighting, HVAC, and Facility Design & Construction Best Practices Guides for Controlled Environment Agriculture and the Lighting, HVAC, and Controls Best Practices Guides for Cannabis Cultivation. She has worked with partners like the University of Vermont to optimize commercial and industrial buildings, including greenhouses and controls systems used for academic research on hemp and other cultivars. She has a B.S. in Architectural Engineering from the University of Wyoming and an M.S. in Civil Engineering from Stanford University. She is a licensed Civil Professional Engineer in California and Vermont.

Schimelpfenig, G., Heating Technologies Improve Profitability for Cannabis Greenhouses, 

The Cultivation Classroom

How can greenhouse cultivators improve profitability by installing high-efficiency heating systems to reduce energy costs?

Heating Technologies Improve Profitability for Cannabis Greenhouses

While the legal cannabis landscape for adult use expands to include new states, most recently Maryland and Minnesota, cultivators are undergoing fine-tooth scrutiny about how they grow and process the plant, and what a more diverse consumer market expects for the safety of their cannabis. As is often the case when an emerging industry goes under the research microscope, there are some newly discovered concerns amidst the product processing developments.

There are growing controversies about how the plant is grown and processed. For example, cannabis cultivators and their crews have been experiencing occupation illnesses from processing the product—key among them are respiratory issues, asthma attacks, and even death.

At 11 p.m. on January 7, 2022, an employee who was packaging ground cannabis into pre-rolls at the Trulieve dispensary in Holyoke, Massachusetts suffered an asthma attack and later died in the hospital (1). The Occupational Safety and Health Administration (OSHA) fined the facility $35,219 (2). Trulieve closed its Nevada operations a month later; they closed their Massachusetts operations a year later (3). They still own and operate 17 cultivation and processing facilities in seven different states.

There are other worker and health regulations that may apply to the cannabis industry, as noted by the California Department of Industrial Relations Division of Occupational Safety & Health unit, including electrical hazards, flammable liquids and gases, heat illness, repetitive motion injuries, and more (4). But not all cultivators are required to follow those guidelines.

According to a blog by two Delaware lawyers (5), OSHA, who did an inspection of the Trulieve facility on January 11, was taken to task for claiming that the reason for the asthma attack that caused the death of one of their workers was due to “general cannabis dust” (GCD), which OSHA said was a hazardous chemical. But no determination of GCD as a hazardous chemical exists. Trulieve entered a voluntary agreement with OSHA to determine whether ground cannabis dust is required to be classified as a hazardous chemical, according to OSHA regulations (6). OSHA reduce their fine by half as part of the agreement (7).

This column discusses new worker health and safety issues in cannabis cultivation, causing cultivators to take a closer look at their operations, and how more science is being brought to bear on slowing the effect that a latent viroid disease is having on the grows of cultivators around the country and the world.

Understanding the Tragic Death of a Cannabis Worker

In its hazard alert letter (8) about the Holyoke tragedy, OSHA cited an article that outlined the possible health safety effects for cannabis workers (9) at a cultivation facility. The article by Dr. Coralynn Sack (10) and four other researchers at the Department of Environmental and Occupational Health Sciences, University of Washington in Seattle, reported on a study of a small indoor grow facility in Washington State which involved mostly daily cannabis users. “Regardless of the underlying route of sensitization, participants reported a high rate of work-aggravated symptoms, implying that occupational exposures to cannabis or other workplace substances may have either caused or exacerbated health complaints,” the report concluded. “A better understanding of the occupational hazards and health risks is urgently needed, particularly given the rapid expansion of cannabis cultivation.”

Dr. Sack explained to us that what stood out to her was the high prevalence of people who were reporting work-related symptoms and respiratory symptoms, and a high rate of sensitization to cannabis. “All the employers I've spoken with have been extremely engaged, wanting to ensure that the appropriate safety protocols are in place,” said Dr. Sack. “I think there needs to be involvement. I think action needs to happen now.”

She added that there's a lot of collaboration between the states right now because they recognize that this is a growing industry with the potential of a multitude of different work hazards. “We know a lot from other agricultural industries,” she said. “The same types of workplace controls will work here, especially for things that generate a lot of aerosol dust, ensuring we have good local ventilation systems, ensuring that when they have people doing those particular jobs they have appropriate respiratory protection and good education programs so that they understand what the potential risks are. All those are standard safety practices (from agricultural industries) could be applicable here.”

Dr. Sack and her research group are just starting a new major study about cannabis and worker health, where they are hoping to visit 15–20 different grow facilities and work with about 120 workers.

While research about cannabis workers handling and processing continues, there are still issues to be discovered about the plant itself—mysteries to solve—that may contribute to why it’s making people sick.

Aside from the respiratory symptoms related to inhaling cannabis dust, Dr. Sack said sensitization tests suggested that there may be something in the plant protein itself that people are becoming allergic to. “Studies predominantly out of Europe have shown that people can form antibodies to specific proteins in the cannabis plant. So there's definitely a need for us to understand what the process is, what's causing these symptoms, and try to disentangle it so that we can provide better guidance for both regulators and employers to protect workers,” said Dr. Sack.

Another mystery of the plant is how to develop new cultivars with desirable cannabinoid profiles, high productivity, pest resistance, and overall vigor, according to an editorial by researcher Rachel Backer (11,12), working with McGill University, along with four other Canadian and Italian researchers. Polyploidization—or the multiplication of a complete chromosome set of a certain species to give birth to a new species (13)—has been used successfully in hemp breeding. But it has not been attempted in cannabis. “We are a long ways from where you can confidently pick a cultivar from a reputable breeder and know what it is,” said Backer. “The science is clear that an OG Kush from one grower may be completely different from one made from another grower. And they may have two completely different names that are actually genetically identical cannabis strains. It's very unusual compared to other agricultural markets and commodities.”

Cannabis in nature is a very diverse crop, Backer explained. “This means that, as scientists, we have a lot to draw upon in terms of breeding, whether or not that's related to support production, related to flowering time, or related to chemovars or flower structure. So until we're able to produce genetically uniform seeds it just means that you're constantly sorting through which plants you may want to propagate and which ones are going to give you the best yields and the best characteristics,” said Backer.

There's this notion that came on strong in the last 10 years of plant biology about understanding how things are more than a sum of their parts, Backer stated. “I think cannabis is such a perfect example of that,” she said. “Even if you have the exact same genotype, if you vary the production conditions, you may still get a different product.”

She made the comparison to wine production, where, for example, 2018 was a great year and 2019 was not a good year—from the exact same vineyard. “I think understanding where those features are both within the genetics of the plant and also within the environmental conditions that you're using for production, and actually collecting all of that data and fully understanding it, is a 10 year project,” she said. “There are so many variables. You just need enormous amounts of data.”

One of her findings was that plant yields could be positively influenced by plant growth-promoting rhizobacteria (PGPR), which have contributed to yield increases in other cultivated crops. For example, members of 

 (15) may improve cannabis and hemp yield or quality via direct growth stimulation, improved nutrient acquisition, and biological control of pathogens.

Research has demonstrated that inoculating plants with plant-growth promoting PGPR or treating plants with microbe-to-plant signal compounds can be an effective strategy to stimulate crop growth, according to another article by Backer (16). These strategies can also improve crop tolerance for the abiotic stresses (such as drought, heat, and salinity), which are likely to become more frequent as climate change conditions continue to develop.

This discovery has resulted in multifunctional PGPR-based formulations for commercial agriculture, to minimize the use of synthetic fertilizers and agrochemicals.

There’s good bugs such as PGPR as well as the kind in the human gut (17). And there’s bad bugs such as the

fungus, one of the most common mold species found in most cannabis grow facilities, which causes localized infections, allergic responses, and fatal respiratory fungal infections. Inhaling 

) into the lungs may cause multiple diseases, which depend on the immunological status of the host in humans. These diseases include invasive pulmonary aspergillosis, aspergilloma, and different forms of hypersensitivity diseases such as allergic asthma, pneumonitis, and allergic bronchopulmonary aspergillosis, as spelled out in a study from Iranian researchers (18).

However, there are even worse bugs such as hop latent viroid (HLVd), now found in nearly all cultivations across the country which affect the plant—but not the human consumer, at least as it’s currently understood. A recent article (19) about the viroid reported on a survey conducted in 2021 by Dark Heart Nursery Research (20), in Oakland, California, involving 200,000 tissue tests, and concluded that 90% of cannabis-growing facilities in California were contaminated with HLVd.

Researchers found out that the viroid infection could significantly affect the plants’ vigor and yield. It has been estimated that it could cause losses of up to $4 billion annually for the cannabis industry, in part because HLVd-infected crops could suffer anywhere from a 50–70% loss in tetrahydrocannabinol (THC) content, considerably lowering the commercial value. Now the race is on to kill the viroid . . . or at least slow its infection growth.

One solution may be through the RNA enzyme, according to Zamir Punja, a professor of plant biotechnology at Simon Fraser University near Vancouver, British Columbia (21). “We can at least demonstrate that the RNase is not super invincible,” said Punja. “There are things out there that can destroy (the viroid) vis-a-vis the enzyme. The problem is, if we were to put this into a practical perspective, where we'll be able to identify such an enzyme, how would we get enough of it to actually use it as, for example, a cleaning agent, or as a surface disinfectant. So we're looking at microbes and other organisms that could produce similar enzymes.”

Bacteria get infected by viruses in nature, and develop mechanisms to protect themselves from these viruses, he explained. As the virus tries to enter the bacterial cell, the cell secretes enzymes to basically break down the virus. “So my first search is to see if we can find naturally occurring bacteria or microbes that are secreting the type of RNase enzyme that is needed, which is RNase III,” said Punja.

But buying the enzyme and applying it would be completely cost prohibitive, he added, costing thousands of dollars for 1 g. “Something that produces it naturally would be useful,” he said.

While HLVd is found mostly in indoor grows, where he has done the majority of his work, Punja said he is seeing more cases in outdoor grows as well. “It is found at a lower level outdoors,” he said. “Most of it, I think, originated from the seed. So there's definitely a seed transmission aspect that growers need to consider. Not just for cannabis, but also for hemp.”

Punja talked about a hemp grower who had started seed indoors, got the plants germinated, then transplanted them out in the field and spaced them out really well. “So unlike hydroponics, if growing is spaced out in an outdoor grow instead, you won't see that plant-to-plant spread of the viroid. And there's not water flowing through it, and the roots aren't touching one another. But if (the infection) did start with seed, I think you will find a certain percentage of infection in outdoor plants. You wouldn't see outdoors what we're seeing indoors, where plants are clustered together, sitting on the bench, sharing the water system or using recycled water,” he explained.

He said that bleach is still the go-to product right now, not just for the tools used to process the cannabis but for surface disinfecting. “We haven't looked at treating water. You've got all this recycling water. What do you do with that? The other thing we've looked at that's really encouraging right now is hypochlorous acid (22). There are claims that it works,” said Punja.

He doesn’t know how much parts-per-million of hypochlorous acid to add to water to treat it. Too much and it could make the water like a swimming pool that just stinks of chlorine. “You can't use it that way. There’s got to be some way we can inject hypochlorous. But not enough to kill the plant,” said Punja.

Understanding the diversity of the plant, its true origins, and its genetic makeup is an ongoing goal of researchers as they seek to develop more protocols for growing and processing this ancient plant. Safety is becoming more of a top concern.

The hop latent viroid has emerged as a real head-scratcher, gaining momentum within cultivations. Punja has discovered that there are some strains that are less susceptible to HLVd. “So I started testing a whole bunch of strains, not just to see how they respond, but to try to understand what the plant is doing to minimize the infection,” he said. “Is it not getting infected? Or is it getting infected but it's not allowing it to spread? Those are two key things. Maybe it doesn't move as fast out of the roots up into the flowers in a resistant or tolerant plant. And how do you measure that? So that's kind of what we're trying to wrap our heads around. Is it a movement thing?”

The viroid is definitely spreading once it's introduced, Punja explained. “Then it moves around in a facility. So the way to prevent that is to find these plants that are the mother plants, and if they are super infected, just get rid of them. So we did that in one facility. But then all of a sudden, sometimes, two months later, there's a huge spike in the number of plants that are infected. ‘What happened?’ Well, somebody brought in some genetics that hadn't been necessarily tested, and they put it out on the greenhouse floor, and all of a sudden, the water started spreading it. So you get these outbreaks because of either poor management or unanticipated events, because when you've got a large facility there are different people doing different things.”

But there is good news, according to Punja. “There's not a lot of variation (in the viroid) right now. And hopefully this viroid is stable, with just one strain, maybe two, unlike COVID which mutates all the time. I’m hoping we just get rid of it.”

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Tech Innovations

As the legal recreational cannabis industry expands, regulators and safety watchdogs are taking a closer look at how the industry polices itself.


Cultivators Address New Health and Safety Issues for Plants and Workers

As Rhode Island’s first cannabis conference, the Cannabis Science Conference Fall 2023 brought three days of in-depth education and discussions on the various aspects of cannabis and psychedelics, from scientific and therapeutic aspects to growing methods and new technology. Throughout each of the four tracks—analytical science, medical, cultivation, and psychedelics—the emphasis constantly shone on how continued collaboration and forming new connections are key to success in the industry. The conference provided many opportunities for this kind of networking. Below are highlights from the entire event, including links to plenty of our speaker interviews for you to dive even deeper into the material!

A group of learners gathered at Canna Boot Camp to kick off the three day event, and it was truly an immersive educational experience. The full-day, hands-on workshop kicked off with demonstrations and presentations from Agilent Technologies, Spex (an Antylia company), Medical Marijuana 411, and Zac Hildenbrand, PhD. Next, attendees were given an incredible behind-the-scenes look at the cultivation, extraction, processing, and retail aspects of a vertically integrated cannabis company, Mother Earth Wellness in Pawtucket, Rhode Island. Watch onsite 

interviews with Pete Mitchell, the Director of Manufacturing

, for insights into their laboratory; an 

interview with Director of Cultivation, Vinnie Clause

 for more on the growing process; and an 

 to hear more about operating Rhode Island’s largest dispensary.

Thank you to Mother Earth Wellness, Agilent Technologies, Spex, Medical Marijuana 411, and Dr. Hildenbrand for providing this one-of-a-kind learning experience!

Cannabis Science Conference Fall: Day One

As the keynote speaker for the first day, Dustin Sulak, DO, presented “Knowledge and Art of Combining Cannabinoids for Treatment Success,” which explored the potential beneficial and harmful effects of combining certain cannabinoids when treating patient conditions (see 

). Drawing on several published studies and his own clinical experience, Dr. Sulak explained the effects of cannabinoids such as cannabigerol (CBG), tetrahydrocannabivarin (THCV), cannabichromene (CBC), and cannabidivarin (CBDV), plus new understandings of interactions between tetrahydrocannabinol (THC) and cannabidiol (CBD). He also provided recommendations and cautions for moving forward.

Following Dr. Sulak’s presentation, the cultivation track held a general session fireside chat discussion between Adam Jacques and cultivation program chair Zacariah Hildenbrand, PhD, about cannabis genetics throughout the decades. For an in-depth look at this presentation, watch 

. Other day one highlights from the cultivation track included author Jeff Lowenfels, who explained the latest developments in his the soil food web, and microbiologist Frankie Claunch, who presented “Microbial Consultation Guidelines for Common Reservoirs of Contamination in Cultivation Facilities.”

The first day of the medical track featured many trailblazers in the field. First up, a screening of the documentary 

 by veteran and filmmaker Steve Ellmore, followed by a panel discussion of four veterans—Steve Ellmore, Ellen Brown, Stephen Mandile, and Wayne Smith— who 

delved deep into the importance of veteran access to medical cannabis

, moderated by program chair Cherissa Jackson, RN. For more on this topic, listen to our Noid Knowledge podcast episode with Ellmore. Later in the day, investigators Blake Pearson and Mikelle Bryson-Campbell co-presented “Exploring cannabinoid therapy as a safer alternative for dementia symptom management,” followed by Amanda Reiman, Chief Knowledge Officer of New Frontier Data, discussing characteristics of a large sample of medical cannabis patients—

 moderated the panel discussion “Clinical Directors – Navigating Legalization and Beyond” featuring 

, National Clinical Director Consortium, Clinical Director of Dispensaries; 

, Clinical Director with Curaleaf; and Kevin Harbison, Manager of Clinical Services and Regulatory Operations at PharmaCan. Next, Operations Research Specialist and Clinical Cannabis Pharmacist, Monica Werkheiser presented “Layered Microdosing of Cannabis for Health and Wellness,” and ending the first day of the track on a forward-thinking note, Jordan Tishler, MD, presented “Building a More Effective Medical Cannabis System.”

In the analytical track, industry leaders provided valuable insights addressing pressing concerns related to the science and testing in the industry. First, Harry Behzadi, President and CEO of AccuScience Labs, presented “Is it time to pay more attention to flavonoids in cannabis products,” followed by Sergei Leikin, Managing Director at Texas Scientific Products, and 

, Research and Development Chemist at Inorganic Ventures, co-presenting “Analysis of Cannabis Products for As, Cd, Hg, Pb by ICP-OES: Meeting the DL Challenge.” Next, Melinda Urich, Advanced Scientist at Restek, investigated six extraction methods in “Cannabinoid Extraction Efficiency for Potency Analysis: An in Depth Look of Multiple Techniques.” Laboratory Director at Method Testing Labs, Anthony Repay presented “Quality control in Cannabis microbiology; How to comply and go further than industry standard,” which was paired with a complementary presentation “The Curious Case of Cannabis: Understanding the Microbiology of Cannabis,” by Maria McIntyre, Head of Cannabis at bioMérieux who was filling in for the original speaker, Patrick Bird. After their presentations, both Repay and McIntyre held a group Q&A directly with the audience to answer their questions and comments.

In a content crossover, Dr. Hildenbrand presented “Getting the Most Out of Analytical Testing,” which was 

. Three complementary presentations ended the first day of the track: Dominika Gruszecka, Market Manager at Shimadzu Scientific Instruments presented “Cannabis Testing: Current Needs and Approaches,” followed by Scott Churchill, Vice President of Scientific Development at MCR Labs with “Pathogen Testing: Why, Where and How,” and Maria McIntyre, Head of Cannabis at bioMérieux, with “Impacts of Plant Pathogens on Yield.” All four presenters came together along with Pete Mitchell from Mother Earth Wellness to hold a group Q&A to engage with responses from the audience.

Finally, in the psychedelics track, students from the University of Miami—Owen Berke, Amrit Baral, and Brea-Necole Diggs—presented their recent discoveries in “Next Generation of Scientists Examining How to Mitigate Chronic Disease with Psychedelics,” which was moderated by psychedelics program chair, Denise Vidot, PhD. Next, Dan DeLurio, Business Development Manager, at Restek, presented findings from “Preparation and Analysis of Psychoactive Alkaloids and Their Metabolites in Multiple Matrices.” Then, scientist 

, moderated the engaging panel discussion “Barriers to and Learnings from Psychedelics Research,” featuring input and insights from 

Cannabis Science Conference Fall was held in Providence, Rhode Island from September 20-22, 2023. Here we provide highlights from this exciting event.