Testing cannabis and cannabis derived products for microbiological contamination should be a straightforward conversation for testing labs and producers. However, a patchwork of regulations and a wide variety of perspectives on what we should, or should not, be looking for has left much of the cannabis industry searching for reliable answers.
Organizations like the AOAC are taking the first crack at creating standardization in the field but there is still a long way to go. In this conversation, we would like to discuss the general requirements that almost all states share and where we see the industry headed as jurisdictions start to conform to the recommendations of national organizations like AOAC.
We sat down with Anna Klavins and Jessa Youngblood, two cannabis testing experts at Hardy Diagnostics, to get their thoughts on microbiology testing in the current state of the cannabis industry.
Q: What are the biggest challenges facing cannabis testing labs when it comes to microbiology?
Anna Klavins & Jessa Youngblood:For microbiology testing, it comes down to a lack of standardization and approved methods for cannabis. In the US, cannabis regulation is written on a state-by-state level. As a result, the rules that govern every aspect of bringing these materials to market is as unique and varied as the jurisdiction writing them. When we are speaking specifically about microbiology, the question always comes back to yeast and mold testing. For some, the challenge will often be centered on the four main Aspergillus species of concern – A. terreus, A. niger, A. fumigatus, and A. flavus. For others, it will be the challenges of total count testing with yeast, mold, and bacteria. These issues become even more troublesome by the lack of recognized standard methodology. Typically, we expect the FDA, USP, or some other agency to provide the guidelines for industry – the rules that define what is safe for consumption. Without federal guidance, however, we are often in a situation where labs are required to figure out how to perform these tests on their own. This becomes a very real hurdle for many programs.
Q: Why is it important to use two different technologies to achieve confirmation?
Klavins & Youngblood: The push for this approach was borne out of the discussions happening within the industry. Scientists and specialists from across disciplines started getting together and creating groups to start to hash out problems which had arisen due to a lack of standardization. In regards to cannabis testing, implementing a single method for obtaining microbiology results could be unreliable. When clients compared results across labs, the inconsistencies became even more problematic and began to erode trust in the industry. As groups discussed the best way to prove the efficacy of their testing protocol, it quickly became apparent that relying on a single testing method was going to be inadequate. When labs use two different technologies for microbiology testing, they are able to eliminate the likelihood of false positives or false negatives, whichever the case may be. In essence, the cannabis testing laboratories would be best off looking into algorithms of detecting organisms of interest. This is the type of laboratory testing modeled in other industries and these models are starting make their way into the cannabis testing space. This approach is common in many food and pharma applications and makes sense for the fledgling cannabis market as well.
About Anna Klavins
Anna Klavins earned a Molecular and Cellular Biology B.S. degree from Cal Poly San Luis Obispo while playing for the Cal Poly Division I NCAA women’s tennis team. Since joining Hardy Diagnostics in mid-2016, she has gained experience in FDA submissions [510(k)] for class II microbiology in vitro devices. She has worked on 15 projects which led to a microbiology device becoming FDA cleared. She has recently begun participating in the AOAC Performance Tested Methods program.
About Jessa Youngblood
Jessa Youngblood is the Food, Beverage and Cannabis Market Coordinator for Hardy Diagnostics. A specialist in the field of cannabis microbiology for regulatory compliance, she is seated with the AOAC CASP committee working on standard methods for microbiological testing in cannabis and hemp. She also sits on the NCIA Scientific Advisory Council as well as the ASTM Cannabis Council.
I think that we need to start changing the terminology around the hazards associated with cannabis from food safety hazards to product safety hazards. These hazards have not only been associated with harmful effects for those that ingest cannabis infused products, but also for those that consume the cannabis products in other ways such as inhalation (vaping or smoking). So, when we refer to these hazards as food safety hazards, the immediate thought is edibles, which misleads cultivators, manufacturers and consumers to have a false sense of security around the safety of products that are consumed in other ways.
There are several product safety hazards that have been associated with cannabis. These hazards can become a public health problem if not controlled as they could harm the consumer, regardless of the method of consumption.
Let’s take a look at the different types of hazards associated cannabis:
Biological Hazards refer to those microorganisms that can cause illness to the consumer of a product that contain them. They are not visible to the naked eye and are very dangerous when their metabolic by-products (toxins) are ingested or their spores are inhaled. The symptoms for illnesses caused by these microorganisms will vary. Consumers may experience gastrointestinal discomfort (vomiting, diarrhea), headaches, fever and other symptoms. The ingestion of these pathogens, allergens or their by-products may lead to death, if the illness is not treated on time or if the consumer of the product is immunocompromised. In addition, the inhalation of mold spores when smoking cannabis products, can lead to lung disease and death. Some of the biological hazards associated with cannabis are: Salmonella sp., E. coli, Clostridium botulinum, Aspergillus sp. and Penicillium sp.
Chemical Hazards refer to those chemicals that can be present in the plant or finished product due to human applications (pesticides), operational processes (extraction solvents and cleaning chemicals), soil properties (heavy metals), environmental contamination (radiological chemicals) or as a result of occurring naturally (mycotoxins and allergens). Consuming high concentrations of cleaning chemicals in a product can lead to a wide range of symptoms from mild rash, burning sensation in the oral-respiratory system, gastrointestinal discomfort or death. In addition, long term exposure to chemicals such as pesticides, heavy metals, radiological contaminants and mycotoxins may lead to the development of cancers.
Physical Hazards refer to those foreign materials that may be present in the plant or finished product. Foreign materials such as rocks, plastics or metals can cause harm to the consumer by chipping teeth or laceration of the mouth membranes (lips, inner cheeks, tong, esophagus, etc.) In the worst-case scenario, physical hazards may lead to choking, which can cause death due to asphyxiation.
These hazards can be prevented, eliminated or reduced to an acceptable level when foundational programs (Good Agricultural/Cultivation Practices, Good Manufacturing Practices, Allergen Management Program, Pest Control, etc.) are combined with a Food [Product] Safety Plan. These lead to a Food [Product] Safety Management System that is designed to keep consumers safe, regardless of the method of consumption.
Cannabis legalization has taken the United States by storm, with 33 states approved for medicinal cannabis use — 11 of which are also approved for recreational use for adults aged 21 and over. With new patients and consumers entering the market every day, it’s more important than ever for cannabis cultivators to establish more effective methods for mold and fungal prevention in their crops and to ensure consumer confidence in their brands.
Today, many cultivators address the risk of mold and fungus growth by testing crops for contaminants at the end stage of production. While this helps to catch some infected product before it reaches the market, this method is largely ineffective for mold and fungal prevention during the cultivation process. In fact, recent studies have shown an 80% failure rate in mold and fungal testing in Denver cannabis dispensaries. By relying on late-stage, pass/fail testing, cannabis entrepreneurs also expose themselves to increased risk of lost crops and profits.
However, emerging sensor technologies exist that can test plants during the grow process, significantly reducing the risks associated with cannabis cultivation while increasing the bottom line for commercial grow operations. By leveraging data from these monitoring sensors along with environmental automation systems that are integrated with data analytics platforms, cannabis professionals can take a proactive approach to achieve the ideal environmental conditions for their crops and prevent against mold and fungal infestation.
Common Causes for Bud Rot in Indoor Growing Systems
Botrytis cinerea — commonly known as “bud rot” — is a pathogenic fungi species that creates a gray mold infection in cannabis plants. An air-borne contaminant, it is among the most prevalent diseases affecting marijuana crops today and can lead to significant damages, particularly when left untreated during post-harvest storage. Bud rot is one of the most difficult challenges cannabis entrepreneurs face: Once plants have been affected, only 2% can be expected to recover. This is because Botrytis cinerea can use multiple methods for attacking host plants, including using the plant’s natural defenses against it to continue infestation.
While difficult to contain, bud rot is very easy to spot. Plants affected with the fungus will begin yellowing, experience impaired growth, and develop gray fungus around its buds. Overall crop yield will be significantly reduced, leading to decreased profit for cannabis cultivators. The biggest contributing factors to a Botrytis cinerea infestation are as follows:
Humidity: Indoor grow facilities that maintain humidity levels in excess of 45% are breeding grounds for mold and fungus. These environments can become perfect conditions for mold and fungal growth.
Temperature: Bud rot typically thrives in environments where temperatures fall between 65- and 75-degrees Fahrenheit, which is why greenhouses and grow rooms are often the victim of such infestations.
Ventilation: Poor airflow is another contributing factor to Botrytis cinerea Without proper ventilation, excess moisture buildup will eventually result in mold and mildew growth.
Strain: Some marijuana strains are better equipped to fend off bud rot infection. In particular, sativa plants have a higher resistance to mold development than their C. indica and C. ruderalis cousins.
Controlling mold and fungal growth in commercial grow facilities is a top priority for cannabis cultivators. Not only detrimental to their profitability and crop yield, infected plants can pose serious health risks to consumers, especially for immunocompromised patients. Consuming cannabis products that have been compromised by bud rot or other mold and fungal infections can cause a wide range of medical concerns, including pneumonitis, bronchitis, and other pulmonary diseases. As a result, growers are required to dispose of all infected plants without the possibility to sell.
Bud rot isn’t the only culprit responsible for cannabis plant destruction. Powdery mildew, Fusarium, sooty molds, and Pythium all contribute to the challenges faced by cannabis professionals. In fact, a recent study conducted by Steep Hill Labs and University of California, Davis – Medical Center found that in 20 randomly-selected samples submitted for testing, all samples showed detectable levels of microbial contamination7. Many of these samples also contained significant pathogenic microorganism contamination. Without proper detection and prevention methods in place, these pesky plant-killers will only continue to terrorize the cannabis cultivation industry.
The Current Cannabis Cultivation Landscape
The data is clear: Current practices for cannabis cultivation are insufficient for preventing against mold and fungal growth. Sterilization and pass/fail testing do not identify the root cause of harmful infestations in plants, therefore leaving cannabis professionals in the dark about how to better optimize their grow conditions for improved crop reliability and safety. In order to prevent against damages incurred from mold and fungal infestation, marijuana growers must be more diligent in their grow condition monitoring practices.
Many cannabis professionals rely on manual monitoring to identify environmental changes within their indoor grow facilities. While it’s important to collect data on your operation’s essential systems, doing so without the right tools can be time-consuming and ineffective. Manual monitoring often relies on past data and does not illustrate the relationship between different systems and their impact on environmental changes. The goal is to assemble data from all the grow systems and create correlations on actual bio-environmental conditions during the grow process to compare to yield results. This is only available when an information management platform is synthesizing data from all the systems within the grow facility and presenting meaningful information to the growers, facility operators and owners.
Especially as the cannabis industry is expected to grow exponentially in coming years, growers need more robust tools for tracking and manipulating environmental changes within their indoor growing systems.
Leveraging Building Automation Systems & Data Analytics in Cannabis Cultivation
A powerful approach to prevent environmental conditions that are known to lead to mold and fungus growth exists in leveraging the data produced from your grow facility’s various automation systems. Most commercial cultivation facilities have multiple stand-alone and proprietary systems to control their indoor environment, making it difficult to not only collect all of this valuable data, but also to achieve the level of grow condition monitoring necessary for mold and fungal prevention.
With some data analytics platforms, such as GrowFit Analytics, data is collected across disparate systems that don’t normally communicate with one another, providing access to the key insights necessary for achieving environmental perfection with your cannabis crops. A viable solution collects vital grow facility system data and relevant bio-environmental monitoring data, and delivers this information in one, centralized software interface. The software then will apply analytic algorithms to develop key performance indicators (KPIs) while working to detect system anomalies, faults, and environmental fluctuations. The right analytics solution should also be customizable, allowing you to track the KPIs that are most important to your unique facility, and to achieve the vision of your chief grower. Ultimately, the software should serve up actionable insights that empower facility management and growers.
Collecting reliable data from different grow facility systems and environmental sensors can be a complex process and the information collected illustrates more than just what’s working right and what isn’t. By implementing an advanced data analytics solution, cannabis cultivation professionals can now be empowered to track minute details about their indoor grow facility, providing a safer, healthier environment for their crops and avoiding those environmental conditions that lead to mold and fungus altogether.
An ideal data analytics platform won’t simply collect data to be analyzed at a later date, and simple trending of sensor data is not enough. Information — especially in a commercial grow facility — is time-sensitive, which is why growers should select a system that offers real-time analytics capabilities. Some platforms offering real-time analytics utilize cloud computing, allowing for easy access from anywhere while also providing enhanced security to protect sensitive facility data. The most robust data analytics platforms provide detailed historical data for your entire crop’s lifecycle that provide a “digital recipe” to replicate successful crops, and fine-tune the process for continuous improvement.
Data analytics tools can also impact the bottom line by lowering operational costs. GrowFit Analytics, for example, was born out of a software solution designed to lower energy costs for large complex buildings like commercial grow facilities.
The data and insights provided can help identify opportunities for greater energy efficiency, which can lead to significant utility savings. Grow facilities operate 24 hours/day, with energy expenses representing one of the largest operational costs. With data analytics tools at their disposal, facility managers are armed with the information they need to improve system efficiency, increase energy savings, and improve profitability.
Eliminating Mold & Fungus from the Future of Cannabis Cultivation
By focusing on grow condition monitoring using data analytics tools, cannabis professionals can effectively eliminate the risk of mold and fungus growth in their crops. Leading data analytics tools make tracking environmental changes simple and easy to manage, allowing cannabis professionals to take a proactive approach to mold and fungus prevention. As we look to the future of the cannabis cultivation industry, it’s paramount for professionals to explore the technological advancements available that can help them address their business’ most pressing challenges.
In 1887, Julius Petri invented a couple of glass dishes, designed to grow bacteria in a reproducible, consistent environment. The Petri dish, as it came to be known, birthed the scientific practice of agar cultures, allowing scientists to study bacteria and viruses. The field of microbiology was able to flourish with this handy new tool. The Petri dish, along with advancements in our understanding of microbiology, later developed into the modern field of microbial testing, allowing scientists to understand and measure microbial colonies to detect harmful pathogens in our food and water, like E. coli and Salmonella, for example.
The global food supply chain moves much faster today than it did in the late 19th century. According to Milan Patel, CEO of PathogenDx, this calls for something a little quicker. “Traditional microbial testing is tedious and lengthy,” says Patel. “We need 21st century pathogen detection solutions.”
Milan Patel first joined the parent company of PathogenDx back in 2012, when they were more focused on clinical diagnostics. “The company was predominantly built on grant funding [a $12 million grant from the National Institute of Health] and focused on a niche market that was very specialized and small in terms of market size and opportunity,” says Patel. “I realized that the technology had a much greater opportunity in a larger market.”
He thought that other markets could benefit from that technology greatly, so the parent company licensed the technology and that is how PathogenDx was formed. Him and his team wanted to bring the product to market without having to obtain FDA regulatory approval, so they looked to the cannabis market. “What we realized was we were solving a ‘massive’ bottleneck issue where the microbial test was the ‘longest test’ out of all the tests required in that industry, taking 3-6 days,” says Patel. “We ultimately realized that this challenge was endemic in every market – food, agriculture, water, etc. – and that the world was using a 140-year-old solution in the form of petri dish testing for microbial organisms to address challenges of industries and markets demanding faster turnaround of results, better accuracy, and lower cost- and that is the technology PathogenDx has invented and developed.”
While originally a spinoff technology designed for clinical diagnostics, they deployed the technology in cannabis testing labs early on. The purpose was to simplify the process of testing in an easy approach, with an ultra-low cost and higher throughput. Their technology delivers microbial results in less than 6 hours compared to 24-36 hours for next best option.
Out of all the tests performed in a licensed cannabis testing laboratory, microbial tests are the longest, sometimes taking up to a few days. “Other tests in the laboratory can usually be done in 2-4 hours, so growers would never get their microbial testing results on time,” says Patel. “We developed this technology that gets results in 6 hours. The FDA has never seen something like this. It is a very disruptive technology.”
When it comes to microbial contamination, timing is everything. “By the time Petri dish results are in, the supply chain is already in motion and products are moving downstream to distributors and retailers,” Patel says. “With a 6-hour turnaround time, we can identify where exactly in the supply chain contaminant is occurring and spreading.”
The technology is easy to use for a lab technician, which allows for a standard process on one platform that is accurate, consistent and reproduceable. The technology can deliver results with essentially just 12 steps:
Take 1 gram of cannabis flower or non-flower sample. Or take environmental swab
Drop sample in solution. Swab should already be in solution
Transfer 1ml of solution into 1.5ml tube
Conduct two 3-minute centrifugation steps to separate leaf material, free-floating DNA and create a small pellet with live cells
Conduct cell lysis by adding digestion buffer to sample on heat blocks for 1 hour
Conduct Loci enhancement PCR of sample for 1 hour
Conduct Labelling PCR which essentially attaches a fluorescent tag on the analyte DNA for 1 hour
Pipette into the Multiplex microarray well where hybridization of sample to probes for 30 minutes
Conduct wash cycle for 15 minutes
Dry and image the slide in imager
The imager will create a TIFF file where software will analyze and deliver results and a report
Their DetectX product can test for a number of pathogens in parallel in the same sample at the same time down to 1 colony forming unit (CFU) per gram. For bacteria, the bacterial kit can detect E. coli, E. coli/Shigella spp., Salmonella enterica, Listeria and Staph aureus, Stec 1 and Stec 2 E.coli. For yeast and mold, the fungal kit can test for Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus.
Their QuantX is the world’s first and only multiplex quantification microarray product that can quantify the microbial contamination load for key organisms such as total aerobic bacteria, total yeast & mold, bile tolerant gram negative, total coliform and total Enterobacteriaceae over a dynamic range from 100 CFU/mL up to 1,000,000 CFU/mL.
Not all of the PathogenDx technology is designed for just microbial testing of cannabis or food products. Their EnviroX technology is designed to help growers, processors or producers across any industry identify areas of microbial contamination, being used as a tool for quality assurance and hazard analysis. They conducted industry-wide surveys of the pathogens that are creating problems for cultivators and came up with a list of more than 50 bacterial and fungal pathogens that the EnviroX assay can test for to help growers identify contamination hotspots in their facilities.
Using the EnviroX assay, growers can swab surfaces like vents, fans, racks, workbenches and other potential areas of contamination where plants come in contact. This helps growers identify potential areas of contamination and remediate those locations. Patel says the tool could help growers employ more efficient standard operating procedures with sanitation and sterilization, reducing the facility’s incidence of pathogens winding up on crops, as well as reduction in use of pesticides and fungicides on the product.
Deploying this technology in the cannabis industry allowed Milan Patel and the PathogenDx team to bring something new to the world of microbial testing. Their products are now in more than 90 laboratories throughout the country. The success of this technology provides another shining example of how the cannabis market produces innovative and disruptive ideas that have a major impact on the world, far beyond cannabis itself.
Microbial contamination on cannabis products represents one of the most significant threats to cannabis consumers, particularly immunocompromised patients who are at risk of developing harmful and potentially fatal infections.
As a result, regulatory bodies in the United States and Canada mandate testing cannabis products for certain microbes. The two most popular methods for microbial safety testing in the cannabis industry are culture-based testing and quantitative polymerase chain reaction (qPCR).
When considering patient safety, labs should choose a method that provides an accurate account of what is living on the sample and can specifically target the most harmful microbes, regardless of the matrix.
1. The Method’s Results Must Accurately Reflect the Microbial Population on the Sample
The main objective of any microbial safety test is to give the operator an indication of the microbial population present on the sample.
Culture-based methods measure contamination by observing how many organisms grow in a given medium. However, not all microbial organisms grow at the same rate. In some cases, certain organisms will out-compete others and as a result, the population in a post-culture environment is radically different than what was on the original sample.
One study analyzed fifteen medicinal cannabis samples using two commercially available culture-based methods. To enumerate and differentiate bacteria and fungi present before and after growth on culture-based media, all samples were further subjected to next-generation sequencing (NGS) and metagenomic analyses (MA). Figure 1 illustrates MA data collected directly from plant material before and after culture on 3M petrifilm and culture-based platforms.
The results demonstrate substantial shifts in bacterial and fungal growth after culturing on the 3M petrifilm and culture-based platforms. Thus, the final composition of microbes after culturing is markedly different from the starting sample. Most concerning is the frequent identification of bacterial species in systems designed for the exclusive quantification of yeast and mold, as quantified by elevated total aerobic count (TAC) Cq values after culture in the total yeast and mold (TYM) medium. The presence of bacterial colonies on TYM growth plates or cartridges may falsely increase the rejection rate of cannabis samples for fungal contamination. These observations call into question the specificity claims of these platforms.
The Live Dead Problem
One of the common objections to using qPCR for microbial safety testing is the fact that the method does not distinguish between live and dead DNA. PCR primers and probes will amplify any DNA in the sample that matches the target sequence, regardless of viability. Critics claim that this can lead to false positives because DNA from non-viable organisms can inflate results. This is often called the Live-Dead problem. However, scientists have developed multiple solutions to this problem. Most recently, Medicinal Genomics developed the Grim Reefer Free DNA Removal Kit, which eliminates free DNA contained in a sample by simply adding an enzyme and buffer and incubating for 10 minutes. The enzyme is instantaneously inactivated when lysis buffer is added, which prevents the Grim Reefer Enzyme from eliminating DNA when the viable cells are lysed (see Figure 2).
2. Method Must Be Able to Detect Specific Harmful Species
Conversely, qPCR assays, such as the PathoSEEK, are designed to target DNA sequences that are unique to pathogenic Aspergillus species, and they can be run using standard qPCR instruments such as the Agilent AriaMx. The primers are so specific that a single DNA base difference in the sequence can determine whether binding occurs. This specificity reduces the frequency of false positives in pathogen detection, a frequent problem with culture-based cannabis testing methods.
Additionally, Medicinal Genomics has developed a multiplex assay that can detect the four pathogenic species of Aspergillus (A. flavus, A. fumigatus, A. niger, and A. terreus) in a single reaction.
3. The Method Must Work on Multiple Matrices
Marijuana infused products (MIPs) are a very diverse class of matrices that behave very differently than cannabis flowers. Gummy bears, chocolates, oils and tinctures all present different challenges to culture-based techniques as the sugars and carbohydrates can radically alter the carbon sources available for growth. To assess the impact of MIPs on colony-forming units per gram of sample (CFU/g) enumeration, The Medicinal Genomics team spiked a known amount of live E. coli into three different environments: tryptic soy broth (TSB), hemp oil and hard candy. The team then homogenized the samples, pipetted amounts from each onto 3M™ Petrifilm E. coli / Coliform Count (EC) Plates, and incubated for 96 hours. The team also placed TSB without any E. coli onto a petrifilm to serve as a control. Figures 3 and 4 show the results in 24-hour intervals.
This implies the MIPs are interfering with the reporter assay on the films or that the MIPs are antiseptic in nature.
Many MIPs use citric acid as a flavoring ingredient which may interfere with 3M reporter chemistry. In contrast, the qPCR signal from the Agilent AriaMx was constant, implying there is microbial contamination present on the films, but the colony formation or reporting is inhibited.
This is not an issue with DNA-based methods, so long as the DNA extraction method has been validated on these matrices. For example, the SenSATIVAx DNA extraction method is efficient in different matrices, DNA was spiked into various MIPs as shown in Table 1, and at different numbers of DNA copies into chocolate (Table 2). The SenSATIVAx DNA extraction kit successfully captures the varying levels of DNA, and the PathoSEEK detection assay can successfully detect that range of DNA. Table 3 demonstrates that SenSATIVAx DNA extraction can successfully lyse the cells of the microbes that may be present on cannabis for a variety of organisms spiked onto cannabis flower samples.
Consumers are largely unaware that most commercial cannabis grown today undergoes some form of decontamination to treat the industry’s growing problem of mold, yeast and other microbial pathogens. As more cannabis brands fail regulatory testing for contaminants, businesses are increasingly turning to radiation, ozone gas, hydrogen peroxide or other damaging remediation methods to ensure compliance and avoid product recalls. It has made cannabis cultivation and extraction more challenging and more expensive than ever, not to mention inflaming the industry’s ongoing supply problem.
The problem is only going to get worse as states like Nevada and California are beginning to implement more regulations including even tougher microbial contamination limits. The technological and economic burdens are becoming too much for some cultivators, driving some of them out of business. It’s also putting an even greater strain on them to meet product demand.
It’s critical that the industry establishes new product standards to reassure consumers that the cannabis products they buy are safe. But it is even more critical that the industry look beyond traditional agricultural remediation methods to solve the microbial problems.
Mold and other microbial pathogens are found everywhere in the environment, including the air, food and water that people consume. While there is no consensus yet on the health consequences of consuming these contaminants through cannabis, risks are certainly emerging. According to a 2015 study by the Cannabis Safety Institutei, molds are generally harmless in the environment, but some may present a health threat when inhaled, particularly to immunocompromised individuals. Mycotoxins resulting from molds such as Aspergillus can cause illnesses such as allergic bronchopulmonary aspergillosis. Even when killed with treatment, the dead pathogens could trigger allergies or asthma.
There is an abundance of pathogens that can affect cannabis cultivation, but the most common types are Botrytis (bud rot, sometimes called gray mold) and Powdery Mildew. They are also among the most devastating blights to cannabis crops. Numerous chemical controls are available to help prevent or stem an outbreak, ranging from fungicides and horticultural oils to bicarbonates and biological controls. While these controls may save an otherwise doomed crop, they introduce their own potential health risks through the overexposure and consumption of chemical residues.
The issue is further compounded by the fact that the states in which cannabis is legal can’t agree on which microbial pathogens to test for, nor how to test. Colorado, for instance, requires only three pathogen tests (for salmonella, E. coli, and mycotoxins from mold), while Massachusetts has exceedingly strict testing regulations for clean products. Massachusetts-based testing lab, ProVerde Laboratories, reports that approximately 30% of the cannabis flowers it tests have some kind of mold or yeast contamination.
If a cannabis product fails required microbial testing and can’t be remedied in a compliant way, the grower will inevitably experience a severe – and potentially crippling – financial hit to a lost crop. Willow Industries, a microbial remediation company, says that cannabis microbial contamination is projected to be a $3 billion problem by 2020ii.
Remediation Falls Short
With the financial stakes so high, the cannabis industry has taken cues from the food industry and adopted a variety of ways to remediate cannabis harvests contaminated with pathogens. Ketch DeGabrielle of Qloris Consulting spent two years studying cannabis microbial remediation methods and summarized their pros and consiii.
He found that some common sterilization approaches like autoclaves, steam and dry heat are impractical for cannabis due the decarboxylation and harsh damage they inflict on the product. Some growers spray or immerse cannabis flowers in hydrogen peroxide, but the resulting moisture can actually cause more spores to germinate, while the chemical reduces the terpene content in the flowers.
The more favored, technologically advanced remediation approaches include ozone or similar gas treatment, which is relatively inexpensive and treats the entire plant. However, it’s difficult to gas products on a large scale, and gas results in terpene loss. Microwaves can kill pathogens effectively through cellular rupture, but can burn the product. Ionizing radiation kills microbial life by destroying their DNA, but the process can create carcinogenic chemical compounds and harmful free radicals. Radio frequency (which DeGabrielle considers the best method) effectively kills yeast and mold by oscillating the water in them, but it can result in moisture and terpene loss.
The bottom line: no remediation method is perfect. Prevention of microbial contamination is a better approach. But all three conventional approaches to cannabis cultivation – outdoors, greenhouses and indoor grow operations – make it extremely difficult to control contamination. Mold spores can easily gain a foothold both indoors and out through air, water, food and human contact, quickly spreading into an epidemic.
The industry needs to establish new quality standards for product purity and employ new growing practices to meet them. Advanced technologies can help create near perfect growing ecosystems and microclimates for growing cannabis free of mold contamination. Internet of Things sensors combined with AI-driven robotics and automation can dramatically reduce human intervention in the growing process, along with human-induced contamination. Natural sunlight supplemented with new lighting technologies that provide near full-light and UV spectrum can stimulate robust growth more resistant to disease. Computational fluid dynamic models can help growers achieve optimal temperature, humidity, velocity, filtration and sanitation of air flow. And tissue culture micropropagation of plant stock can eliminate virus and pathogen threats, to name just a few of the latest innovations.
Growing legal cannabis today is a risky business that can cost growers millions of dollars if pathogens contaminate a crop. Remediation methods to remove microbial contamination may work to varying degrees, but they introduce another set of problems that can impact consumer health and comprise product quality.
Earlier this month, Colorado cannabis producer Herbal Wellness LLC recalled dozens of batches of cannabis due to positive yeast and mold tests. The Colorado Department of Public Health and Environment (CDPHE) issued a health and safety advisory following the news of microbial contamination.
The Colorado Department of Revenue then identified batches of both medical and recreational cannabis produced by Herbal Wellness that were not even tested for microbial contaminants, which is a requirement for licensed producers in the state. Just a few days later, the Denver Department of Public Health & Environment (DDPHE) issued a bulletin announcing their plans to conduct random tests at dozens of dispensaries.
“In the coming weeks, the Denver Department of Public Health & Environment (DDPHE) will be conducting an assessment in approximately 25 retail marijuana stores to evaluate contaminants in products on store shelves,” reads the bulletin. “DDPHE has worked with epidemiological partners at Denver Public Heath to create the assessment methodology. Participating stores will be randomly identified for inclusion in the assessment.”
“Current METRC inventory lists for each store will be used to randomly identify samples of flower, trim/shake, and pre-rolls. Each sample will be tested for pesticides and total yeast and mold by a state- and ISO-certified marijuana testing facility. Results of their respective testing will be shared with each facility and will also be shared broadly within a write-up of results.”
Across the country, there is a patchwork of regulatory requirements that vary from state to state. Regulations focus on limiting microbial impurities (such as mold) present in cannabis in order for consumers to receive a safe product. When cultivators in Colorado and Nevada submit their cannabis product to laboratories for testing, they are striving to meet total yeast and mold count (TYMC) requirements.In a nascent industry, it is prudent for state regulators to reference specific testing methodologies so that an industry standard can be established.
TYMC refers to the number of colony forming units present per gram (CFU/g) of cannabis material tested. CFU is a method of quantifying and reporting the amount of live yeast or mold present in the cannabis material being tested. This number is determined by plating the sample, which involves spreading the sample evenly in a container like a petri dish, followed by an incubation period, which provides the ideal conditions for yeast and mold to grow and multiply. If the yeast and mold cells are efficiently distributed on a plate, it is assumed that each live cell will give rise to a single colony. Each colony produces a visible spot on the plate and this represents a single CFU. Counting the numbers of CFU gives an accurate estimate on the number of viable cells in the sample.
The plate count methodology for TYMC is standardized and widely accepted in a variety of industries including the food, cosmetic and pharmaceutical industries. The FDA has published guidelines that specify limits on total yeast and mold counts ranging from 10 to 100,000 CFU/g. In cannabis testing, a TYMC count of 10,000 is commonly used. TYMC is also approved by the AOAC for testing a variety of products, such as food and cosmetics, for yeast and mold. It is a fairly easy technique to perform requiring minimal training, and the overall cost tends to be relatively low. It can be utilized to differentiate between dead and live cells, since only viable living cells produce colonies.
There is a 24 to 48-hour incubation period associated with TYMC and this impedes speed of testing. Depending on the microbial levels in a sample, additional dilution of a cannabis sample being tested may be required in order to count the cells accurately. TYMC is not species-specific, allowing this method to cover a broad range of yeast and molds, including those that are not considered harmful. Studies conducted on cannabis products have identified several harmful species of yeast and mold, including Cryptococcus, Mucor, Aspergillus, Penicillium and Botrytis Cinerea. Non-pathogenic molds have also been shown to be a source of allergic hypersensitivity reactions.The ability of TYMC to detect only viable living cells from such a broad range of yeast and mold species may be considered an advantage in the newly emerging cannabis industry.
After California voted to legalize recreational marijuana, state regulatory agencies began exploring different cannabis testing methods to implement in order to ensure clean cannabis for the large influx of consumers.
Unlike Colorado, California is considering a different route and the recently released emergency regulations require testing for specific species of Aspergillus mold (A. fumigatus, A. flavus, A. niger and A. terreus). While Aspergillus can also be cultured and plated, it is difficult to differentiate morphological characteristics of each species on a plate and the risk of misidentification is high. Therefore, positive identification would require the use of DNA-based methods such as polymerase chain reaction testing, also known as PCR. PCR is a molecular biology technique that can detect species-specific strains of mold that are considered harmful through the amplification and analysis of DNA sequences present in cannabis. The standard PCR testing method can be divided into four steps:
The double stranded DNA in the cannabis sample is denatured by heat. This refers to splitting the double strand into single strands.
Primers, which are short single-stranded DNA sequences, are added to align with the corresponding section of the DNA. These primers can be directly or indirectly labeled with fluorescence.
DNA polymerase is introduced to extend the sequence, which results in two copies of the original double stranded DNA. DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA.
Once the double stranded DNA is created, the intensity of the resulting fluorescence signal can uncover the presence of specific species of harmful Aspergillus mold, such as fumigatus.
These steps can be repeated several times to amplify a very small amount of DNA in a sample. The primers will only bind to the corresponding sequence of DNA that matches that primer and this allows PCR to be very specific.
PCR is a very sensitive and selective method with many applications. However, the instrumentation utilized can be very expensive, which would increase the overall cost of a compliance test. The high sensitivity of the method for the target DNA means that there are possibilities for a false positive. This has implications in the cannabis industry where samples that test positive for yeast and mold may need to go through a remediation process to kill the microbial impurities. These remediated samples may still fail a PCR-based microbial test due to the presence of the DNA. Another issue with the high selectivity of this method is that other species of potentially harmful yeast and mold would not even be detected. PCR is a technique that requires skill and training to perform and this, in turn, adds to the high overall cost of the test.
Both TYMC and PCR have associated advantages and disadvantages and it is important to take into account the cost, speed, selectivity, and sensitivity of each method. The differences between the two methodologies would lead to a large disparity in testing standards amongst labs in different states. In a nascent industry, it is prudent for state regulators to reference specific testing methodologies so that an industry standard can be established.
As the operations manager at Los Sueños Farms, the largest outdoor cannabis farm in the country, I was tasked with the challenge of finding a yeast and mold remediation treatment method that would ensure safe and healthy cannabis for all of our customers while complying with stringent regulations.
While outdoor cannabis is not inherently moldy, outdoor farms are vulnerable to changing weather conditions. Wind transports spores, which can cause mold. Each spore is a colony forming unit if plated at a lab, even if not germinated in the final product. In other words, perfectly good cannabis can easily fail microbial testing with the presence of benign spores.
If all of those landed on cannabis it would be enough to cause over 450 pounds of cannabis to fail testing, even if those spores remained ungerminated.
It should also be known that almost every food item purchased in a store goes through some type of remediation method to be considered safe for sale. Cannabis is finally becoming a legitimized industry and we will see regulations that make cannabis production look more like food production each year.
Regulations in Colorado (as well as Nevada and Canada) require cannabis to have a total yeast and mold count (TYMC) of ≤ 10,000 colony forming units per gram. We needed a TYMC treatment method that was safe, reliable, efficient and suitable for a large-scale operation. Our main problem was the presence of fungal spores, not living, growing mold.
Below is a short list of the pros and cons of each treatment method I compiled after two years of research:
Autoclave: This is the same technology used to sterilize tattoo needles and medical equipment. Autoclave uses heat and pressure to kill living things. While extremely effective, readily available and fiscally reasonable, this method is time-consuming and cannot treat large batches. It also utilizes moisture, which increases mold risk. The final product may experience decarboxylation and a change in color, taste and smell.
Dry Heat: Placing cannabis in dry heat is a very inexpensive method that is effective at reducing mold and yeast. However, it totally ruins product unless you plan to extract it.
Gamma Ray Radiation: By applying gamma ray radiation, microbial growth is reduced in plants without affecting potency. This is a very effective, fast and scalable method that doesn’t cause terpene loss or decarboxylation. However, it uses ionizing radiation that can create new chemical compounds not present before, some of which can be cancer-causing. The Department of Homeland Security will never allow U.S. cannabis farmers to use this method, as it relies on a radioactive isotope to create the gamma rays.
Gas Treatment: (Ozone, Propylene Oxide, Ethylene Oxide, Sulfur Dioxide) Treatment with gas is inexpensive, readily available and treats the entire product. Gas treatment is time consuming and must be handled carefully, as all of these gases are toxic to humans. Ozone is challenging to scale while PPO, EO and SO2 are very scalable. Gases require special facilities to apply and it’s important to note that gases such as PPO and EO are carcinogenic. These methods introduce chemicals to cannabis and can affect the end product by reducing terpenes, aroma and flavor.
Hydrogen Peroxide: Spraying cannabis plants with a hydrogen peroxide mixture can reduce yeast and mold. However, moisture is increased, which can cause otherwise benign spores to germinate. This method only treats the surface level of the plant and is not an effective remediation treatment. It also causes extreme oxidation, burning the cannabis and removing terpenes.
Microwave: This method is readily available for small-scale use and is non-chemical based and non-ionizing. However, it causes uneven heating, burning product, which is damaging to terpenes and greatly reduces quality. This method can also result in a loss of moisture. Microwave treatment is difficult to scale and is not optimal for large cultivators.
Radio Frequency: This method is organic, non-toxic, non-ionizing and non-chemical based. It is also scalable and effective; treatment time is very fast and it treats the entire product at once. There is no decarboxylation or potency loss with radio frequency treatment. Minimal moisture loss and terpene loss may result. This method has been proven by a decade of use in the food industry and will probably become the standard in large-scale treatment facilities.
Steam Treatment: Water vapor treatment is effective in other industries, scalable, organic and readily available. This method wets cannabis, introducing further mold risk, and only treats the product surface. It also uses heat, which can cause decarboxylation, and takes a long time to implement. This is not an effective method to reduce TYMC in cannabis, even though it works very well for other agricultural products
Extraction: Using supercritical gas such as butane, heptane, carbon dioxide or hexane in the cannabis extraction process is the only method of remediation approved by the Colorado Marijuana Enforcement Division and is guaranteed to kill almost everything. It’s also readily available and easy to access. However, this time-consuming method will change your final product into a concentrate instead of flower and usually constitutes a high profit loss.
UV Light: This is an inexpensive and readily available method that is limited in efficacy. UV light is only effective on certain organisms and does not work well for killing mold spores. It also only kills what the light is touching, unless ozone is captured from photolysis of oxygen near the UV lamp. It is time consuming and very difficult to scale.
After exhaustively testing and researching all treatment methods, we settled on radio frequency treatment as the best option. APEX, a radio frequency treatment machine created by Ziel, allowed us to treat 100 pounds of cannabis in an hour – a critical factor when harvesting 36,000 plants during the October harvest.
Controlling your grow environment doesn’t start when you germinate your first seeds, it starts before you build your grow. There are steps you can take that will have a significant impact on mold growth and contamination, and these will vary based on the grow environment you choose.
Below is a roadmap to where each grow environment stands in terms of mold and contamination risk, and simple steps you can take to mitigate these factors.
The benefits of an outdoor grow are significant – using natural sunlight to grow plants is both inexpensive and environmentally sound. However, it allows the least amount of control and makes plants susceptible to weather conditions and outdoor contaminants including dust, wind, rain and insects. Depending on humidity and precipitation levels, mold can be a big issue as well.
When selecting an outdoor area for a cannabis farm, there are two important factors to consider: location and neighboring farmland. Geographical environments and sub-climates vary and once you have purchased land, you are committed, so be sure to consider these factors prior to purchase.
While arid desert climates have abundant sunlight and long growing seasons, flat, dry lands are subject to dust-storms, flash floods and exceedingly high winds that can damage crops. Conversely, more protected areas often have high humidity and rainfall late in the season, which can create huge issues with bud rot and mold. Neighboring farms also have an impact on your grow, so be sure to find out what they cultivate, what they spray, their harvest schedule and how they run their operation. Large farming equipment kicks up a lot of contaminant-laden dust and can damage crops by displacing insects to your farm if they harvest before you. Pesticide drift is also a major issue as even tiny amounts from a neighbor’s farm can cause your crops to fail testing, depending on what state you are in.
With outdoor grow environments always at the mercy of Mother Nature, any cultivator is wise to control contamination potential on the ground. Cover soil and protect your crop by planting cover crops and laying plastic mulch on as much ground as reasonable. In many cases it makes sense to irrigate uncultivated parts of your farm just to keep dust down.
Greenhouses are the future of cannabis cultivation. They allow growers to capture the full spectrum and power of the sun while lessening environmental impact and operating expenses, while still being able to precisely control the environment to grow great cannabis. With recent advancements in greenhouse technology such as automated control systems, positive pressure, geothermal heating or cooling and LED supplemental lighting, greenhouses are the future. However, older or economy greenhouses that take in unfiltered air from outside still have a medium amount of mold and contamination risk.
Before building your greenhouse, study the area while taking into account climate, weather conditions and sun exposure. Excessively windy areas can blow in contaminants, and extremely hot climates make cooling the greenhouse interior a challenging and costly endeavor.
There are several simple operational tactics to reduce contaminants in a greenhouse. Add a thrip screen to keep insects out, thoroughly clean pad walls with an oxidizing agent after each cycle, and keep plants at least 10 feet from pad walls. Plan to flip the entire greenhouse at once so that you can clean the greenhouse top to bottom before your next crop. A continuous harvest in your greenhouse allows contaminants to jump from one plant to the next and reduces the ability to control your environment and eliminate problems at the end of a cycle. Lastly, open shade curtains slowly in the morning. This prevents temperature inversion and condensation, which can cause water drops to fall from the ceiling and transfer contaminants onto plants below.
An indoor environment offers ultimate control to any grow operation. Cultivators can grow high-quality cannabis with the smallest potential for yeast and mold growth. Unfortunately, indoor environments are extremely expensive, inefficient and environmentally costly.
With indoor grow environments, keeping mold and contaminants at bay comes down to following a regimented plan that keeps all grow aspects clean and in order. To keep your grow environment clean, change HVAC filters multiple times a month. It’s also important to install HEPA filters and UV lights in HVAC systems to further reduce contamination threats. Clearly mark air returns if they are near the ground and keep those areas free of clutter. They are the lungs of your grow. Also, stop using brooms in the grow space. They stir up a lot of contaminants that have settled to the floor. Instead, use HEPA filter backpack vacuums or install a central vacuum system. Set up a “dirty room” for anything messy on a separate HVAC system, and be sure to thoroughly clean pots after every harvest cycle.
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