According to a press release sent out today, ASTM International’s D37 cannabis committee has approved three new standards for environmental conditions during packaging, shipping and storing cannabis and hemp flower. The three new standards are:
Standard Specification for Environmental Conditions for Post Packaged Storage and Retail Merchandising of Cannabis/Hemp Flower (soon to be published as D8423);
Standard Specification for Environmental Conditions While In-Transit for Packaged Cannabis/Hemp Flower (soon to be published as D8432); and
Standard Specification for Environmental Conditions While Packaging Cannabis/Hemp Flower (D8450).
ASTM members will be presenting at the Cannabis Quality Conference & Expo, October 17-19 in New Jersey. Click here for more information. Jonathan DeVries, a member of ASTM, says these standards are designed for the entire cannabis supply chain, from cultivation, manufacturing and transportation all the way to the end consumers. “These standards are designed to support the safety and quality of packaged cannabis and hemp flower as it moves through the supply chain,” says DeVries. “This includes the activities following curing and drying, namely packaging, transit, and storage, until it reaches the final end user.”
Plant genetics are an important consideration for cultivators planning to grow cannabis crops. Genetics can affect how well a plant grows in a particular environment under various conditions and have a major impact on the production of cannabinoids, terpenes as well as other molecules and traits expressed by the plant.
Front Range Biosciences is a hemp and cannabis genetics platform company, leveraging proprietary next generation breeding and Clean Stock® tissue culture nursery technologies to develop new varieties for a broad range of product applications in the hemp and cannabis industries. FRB has global reach through facilities in Colorado, California and Wisconsin, and a partnership with the Center for Research in Agricultural Genomics in Barcelona, Spain. FRB is headquartered in Lafayette, Colorado.
We spoke with Jonathan Vaught, Ph.D., CEO and co-founder of Front Range Biosciences. Jonathan co-founded Front Range in 2015 after a successful career in the diagnostics and food testing industries.
Jonathan Vaught: This was a collaborative project between the BioServe group at the University of Colorado Boulder, which is a part of their aerospace engineering program. They do research on the International Space Station, and they have for quite some time. We partnered with them and another company, Space Technology Holdings, a group that’s working on applications of space travel and space research. We teamed up to send tissue culture samples to the space station and let them sit in zero gravity at the space station for about a month, and then go through the reentry process and come back to Earth. We brought them back in the lab to perform some genomic analyses and try to understand if there’s any underlying genetic changes in terms of the plants being in that environment. We wanted to know if there was anything interesting that we could learn by putting these plant stem cells and tissue cultures in an extreme environment to look for stress response, and some other possible changes that might occur to the plants by going through those conditions.
Aaron: That’s an interesting project! Are there any trends that you’re following in the industry?
Jon: We’re excited to see ongoing legalization efforts around the world. We’ve seen continued progress here in the United States. We still have a long way to go, but we’re excited to see the additional markets coming onboard and regulations moving in the right direction. Also, we’re excited to see some of the restorative justice programs that have come out.
Aaron: How did you get involved at Front Range Biosciences?
Jon: It really starts with my background and what I was doing before Front Range Biosciences. I’ve spent more than 15 years developing commercializing technologies in human diagnostics, food safety and now agriculture.
I started my career during graduate school in biotech at the University of Colorado at Boulder, where I helped develop some of the core technology for a human diagnostic startup company called Somalogic here in Colorado. I went to work for them after finishing my dissertation work and spent about six years there helping them grow that company. We ended up building the world’s largest protein biomarker discovery platform primarily serving pharmaceutical companies, hospitals and doctors, with personalized medicine and lab tests for things like early detection of chronic illness, cancer, heart disease and inflammation.
I then went to another startup company called Beacon Biotech, that was interested in food safety. There I helped develop some similar technologies for detecting food-borne illness — things like salmonella, listeria and E. coli. That was my introduction to big food and big agriculture. From there, I went to help start another company called Velocity Science that was also in the human diagnostic space.
Along the way, I started a 501(c)3 nonprofit called Mountain Flower Goat Dairy, a dairy and educational non-profit that had a community milk-share, which included summer camps and workshops for people to learn about local and sustainable agriculture. I became more and more interested in agriculture and decided to take my career in that path and that’s really what set me up to start Front Range Biosciences.
Aaron: Do you have any co-founders?
Jon: I have two other co-founders. They both played various roles over the last four years. One was another scientist, Chris Zalewski, PhD. He currently works in the R&D department and helps oversee several different parts of the company including pathology and product development. My other co-founder, Nick Hofmeister served as chief strategic officer for the last few years, and has helped raise the majority of our funding. We’ve raised over $45 million dollars, and he played a big role in that.
Aaron: What makes you different from other cannabis seed companies?
John: We’ve built the first true cannabis genetics platform. What I mean by that is we built a platform that allows us to develop and produce new plant varieties that support both the hemp and the cannabis markets. To us, it’s all cannabis. Hemp and cannabis are scientifically the same plant. They just have different regulatory environments, different products and different markets, but we stay focused on the plant. Our platform is built on several different pillars. Genetics are one of the core pieces, and by genetics I mean, everything from molecular based breeding to marker assisted breeding to large germplasm collections. We collect different varieties of germplasm, or seed, from all over the world and use those to mix and match and breed for specific traits. We also have large nursery programs. Another one of our pillars of the platform includes greenhouse nursery production — everything from flowering cannabis plants to producing cannabis seeds to cloning and producing mother plants and rooted cuttings or clones.
Then tissue culture is another part of the platform, it’s basically the laboratory version of a greenhouse nursery. It’s housed in a sterile environment and allows us to produce plants that are clean and healthy. It’s a much more effective, modern way to manage the nursery. It’s part of our clean stock program, where we start clean, stay clean, and you can finish clean. It’s really built on all of those different pieces.
We also have capabilities in analytical chemistry and pathology, that allow us to better understand what drives performance and the plants, and both different regions as well as different cannabinoid products or terpene products. All of the science and capabilities of the platform are what allow us to create new varieties faster, better, stronger.
Aaron: It sounds like you’re vertically integrated on the front-end of cannabis cultivation.
Jon: Absolutely, that’s a great way to think about it.
The last piece I’d say is that we have areas of research and development that cover the full span of multiple product lines. We think about it from an ingredient perspective. Cannabinoids and terpenes are certainly what drive a large part of the cannabis market in terms of edibles, smokable flower, vapes and extracts and the different effects and flavors that you get. We also are looking at other ingredients, like plant-based protein and hemp as a viable protein source and the ability for hemp to produce valuable fiber for textiles, as well as industrial building materials and applications.
Lastly, there are additional small molecules that we’re working on as well from a food ingredients perspective. There are all kinds of interesting compounds. Everybody talks about the cannabinoids and terpenes, but there are also things like flavonoids, and some other very interesting chemistries that we’re working on as well.
Aaron: What geographies are you currently in?
Jon: Colorado and California primarily and we have a small R&D partnership in Barcelona.
Aaron: Do you have plans for expansion beyond that?
Jon: Our current headquarters are out of Colorado, and most of our Colorado operations right now are all hemp. Our hemp business is national and international.
We work with a licensed cannabis nursery partner in California which is our primary focus for that market, but we will be expanding the cannabis genetics and nursery program into Colorado next year. From a regulated cannabis perspective, that’s the first move. Beyond that, we’re in conversations with some of the multi-state operators and cannabis brands that are emerging to talk about how to leverage our technology and our genetics platform across some of the other markets.
Aaron: How do you think about genetics in your products?
Jon: Genetics means a lot of things to different folks depending on your vantage point and where you sit in the supply chain. Our business model is based on selling plants and seeds. At the end of the day, we don’t develop oils, extracts and products specifically, but we develop the genetics behind those products.
For us, it’s not only about developing genetics that have the unique qualities or ingredients that a product company might want like CBD, or other minor cannabinoids like THCV for example, but also about making sure that those plants can be produced efficiently and effectively. The first step is to introduce the ingredient to the product. Then the second step is to make sure that growers can grow and produce the plant. That way they can stabilize their supply chain for their product line. Whether it’s for a smokable flower product, or a vape product, or an edible product, it’s really important to make sure that they can reproduce it. That’s really how we think about genetics.
Aaron: What is a smart plant? That’s something I saw on your website.
Jon: It’s really about plants that perform under specific growing regions, or growing conditions. For example, in hemp, it’s one thing to produce CBD or CBG. It’s another thing to be able to produce it efficiently in five different microclimates around the U.S. Growing hemp in Florida or Alabama down on the Gulf Coast versus growing on the Pacific Northwest coast of Washington, or Oregon are two very different growing conditions that require smart plants. Meaning they can grow and thrive in each of those conditions and still produce the intended product. Generally, the different regions don’t overlap. The genetics that you would grow in Pacific Northwest are not going to do as well as some better selected varieties for the South East.
It’s not only different outdoor growing regions, but it’s different production styles too. When you think about regulated cannabis the difference between outdoor and indoor greenhouse is mixed light production. Even with hydroponic type growing methods, there are lots of different ways to grow and produce this plant and it’s not a one size fits all. It’s really about plants that perform well, whether it’s different regions in the United States in outdoor production or different indoor greenhouses with mixed lights and production methods.
Aaron: You market CBG hemp as a product line. What made you start with CBG? Is that a pull from the market or something you guys see trending?
Jon: So I think it’s a little bit of both. We offer CBD dominant varieties and CBG dominant varieties of hemp. We also now have other cannabinoids in the pipeline that we’ll be putting out in different varieties next year. Things like CBC as well as varins, or propyl cannabinoids. Also things like CBDV, CBCV, or CBGV, which are the propylcannabinoid versions of the more familiar compounds.
There was a lot of market demand for CBG. It was a fairly easy cannabinoid to produce as a single dominant cannabinoid similar to CBD or THC. There’s a lot of up-and-coming demand for some of the other minor cannabinoids. Up until a few years ago, CBD was considered a minor cannabinoid. It wasn’t until Charlotte’s Web in the Sanjay Gupta story that it became a major cannabinoid. So I think we see some level of market pull across the category.
On the flip side of that, we have one of the world’s largest R&D teams and consolidated expertise in terms of cannabis. We see the potential for minor cannabinoids, and even terpenes and other compounds like flavonoids to have wide ranging implications in human health. Everything from wellness products, to active pharmaceutical ingredients, to recreational products. From our perspective, that’s the reason why we’re pushing these ingredients. We believe that there are a lot of good products that come out of this work and the genetics that produce these minor cannabinoids.
Aaron: Okay, great. And then last question, is there anything you’re interested in learning more about?
Jon: I think the most exciting thing for me, given my background in clinical diagnostics and human health, is to see more data around how all of these different compounds of the plant can support improved wellness, health and nutrition. I think we’ve only scratched the tip of the iceberg. This type of research and data collection takes years, even decades, especially to see outcomes over time of people using these products. I’m really excited to see more of that and also hopefully be able to make stronger conclusions about some of the benefits that can be had from this plant.
Aaron: That’s the end of the interview, thanks Jon!
There’s a better way to design HVAC for cannabis grow rooms, and it may seem a little odd at first.
Central chillers are a tried-and-true solution for projects requiring large refrigeration capacity. They’re found in college campuses, hospitals, office buildings and other big facilities.
While central chillers are a good default for most large-scale applications, they fall short in this industry. Grow rooms, with their need for tight, variable conditions and scalable, redundant infrastructure, have HVAC requirements that the central chiller model simply can’t deliver on.
Let’s unpack the shortcomings with the central chiller in this niche and explore some possible solutions.
What’s Wrong With Chillers?
Building a scalable HVAC system is essential for the cannabis industry as it continues to ramp up production in the U.S. and Canada.
Many growers are building their large facilities in phases. In Canada, this is common because growers must have two harvests before they can receive a production permit, so they build just one phase to satisfy this requirement and then build out the facility after the government’s approval.
This strategy of building out is less feasible with a central chiller.
A chiller and its supporting infrastructure are impractical to expand, which means it and the rest of the facility needs to be built to full size for day one, even though the facility will be in partial occupancy for a long time. This results in high upfront capital costs.
If the facility needs to expand later down the road, to meet market demand for example, that will be difficult because, as mentioned, it’s expensive to add capacity to a central chiller.
Additionally, the chiller creates a central point of failure for the facility. When it goes down, crops in every room are at risk of potentially devastating loss. Grow rooms are unusual because of their requirement for strict conditions and even a slight change could have big impact on the crop. Losing control due to mechanical failure could spell disaster.
One Southern Ontario cannabis grower met with some of these issues after constructing their facility, which uses a central chiller for cooling and dehumidification. The chiller was built for full size, but the results were disappointing as early as phase one of cultivation. While sensible demands in the space are being easily met, humidity levels are out of control – flowering rooms are up to 75% RH.
Humidity is one of the most important control aspects to growers. Without a handle on it, growers risk losing their entire crop either because there’s not enough and the plants dry out, or there’s too much and the plants get mold disease. This facility has fortunately not yet reported serious crop issues but is mindful of the potential impact on harvest quality.
By going unitary, capital costs scale on a linear basis.If tight control over humidity is what you need, then a chilled water system needs very careful consideration. That’s because typical chiller system designs get the coils cold enough to lower the air temperature, but not cold enough to condense water out of the air as effectively as a properly designed dehumidifier coil.
A chilled water system capable of achieving the coil temperatures needed for adequate dehumidification in a typical flower room will also require full-time reheat to ensure that air delivered to the plants isn’t shockingly cold — either stunting their growth or killing them altogether. This reheat source adds complexity, cost and inefficiency which does not serve growers well, many of whom are under pressure from both utilities and their management to minimize their energy usage.
How Do Unitary Systems Solve These Problems?
Compared to central chillers, a unitary setup is more agile.
A facility can commence with the minimum capacity it needs for start-up and then add more units in the future as required. They’re usually cheaper to install than a central system and offer several reliability and efficiency benefits as well.
The real business advantage to this approach is to open up the grower’s cash flow by spreading out their costs over time, rather than a large, immediate cost to construct the entire facility and chiller for day one. By going unitary, capital costs scale on a linear basis.
Growers can have more control over their crop by installing multiple units to provide varying conditions, room-by-room, instead of a single system that can only provide one condition.
For example, flowering rooms that each have different strains of crop may require different conditions – so they can be served by their own unit to provide variability. Or, rooms that need uniform conditions could just be served by one common unit. The flexibility that growers can enjoy with this approach is nearly unlimited.
Some growers have opted for multiple units installed for the same room, which maximizes redundancy in case one unit fails.
A cannabis facility in the Montreal area went this direction when building their HVAC system. Rather than build everything in one shot, this facility selected a unitary design that had flowering rooms served independently by a series of units, while vegetation rooms shared one. The units were sized to provide more capacity than currently required in each room, which allows the grower to add more plants and lighting in the future if they choose.
This facility expects to build more grow rooms in a future phase, so it was important to have an intelligent system that could accommodate that by being easy to add capacity to. This is accomplished by simply adding more units.Multiple, small systems also have a better return-on-investment.
The grower, after making a significant investment in this facility, was also averse to the risk of losing crop due to mechanical failure, which is why they were happy to go with a system of independent grow room control.
Multiple, small systems also have a better return-on-investment. Not only are they easier to maintain (parts are easier to switch out and downtime for maintenance is minimal) but they can actually be more efficient than a large, central system.
Some units include heat recovery, which recycles the heat created by the dehumidification process to efficiently reheat the unit’s cold discharge air and keep the space temperature consistent, without needing expensive supplementary heaters. There’s also economizer cooling, which can be used to reduce or even eliminate compressor usage during winter by running the unit on dry outside air only.
Demand for cannabis continues to increase and many growers are looking to expand their businesses by adding new facilities or augmenting existing ones. Faced with the limitations of the traditional chiller system, like the lack of flexibility, scalability and redundancy, they’re looking for an intelligent alternative and the unitary approach is earning their trust. It’s expected this option will soon become the leading one across North America.
It is that time of year where the holidays afford us an opportunity for rest, recuperation and introspection. Becoming a new father to a healthy baby girl and having the privilege to make a living as a scientist, fills me with an immeasurable sense of appreciation and indebtedness. I’ve also been extremely fortunate this year to spend significant time with world-renowned cannabis experts, such as Christian West, Adam Jacques and Elton Prince, whom have shared with me a tremendous wealth of their knowledge about cannabis cultivation and the development of unique cannabis genetics. Neither of these gentlemen have formal scientific training in plant genetics; however, through decades of experimentation, observation and implementation, they’ve very elegantly used alchemy and the principles of Mendelian genetics to push the boundaries of cannabis genetics, ultimately modulating the expression of specific cannabinoids and terpenes. Hearing of their successes (and failures) has triggered significant wonderment and curiosity with respect to what can be done beyond the genetic level to keep pushing the equilibrium in this new frontier of medicine.
Lighting conditions can greatly impact the expression of terpenes (and cannabinoids) in cannabis.Of course genetics are the foundation for the production of premium cannabis. Without the proper genetic code, one cannot expect the cannabis plant to express the target constituents of interest. However, what happens when you have an elite genetic code, the holy grail of cannabis nucleotides if you will, and yet your plant does not produce the therapeutic compounds that you want and/or that are reflective of that elite genetic code? This ‘loss in translation’ can be explained by transcriptomics, and more specifically, epigenetics. In order for the genetic code (DNA) to be expressed as a gene product (RNA), it must be transcribed, a process that is modulated by epigenetic processes like DNA methylation and histone modification. In other words, the methylation of the genetic code can dictate whether or not a particular segment of DNA is transcribed into RNA, and ultimately expressed in the plant. To put this into context, if the DNA code for the enzyme THCA synthase is epigenetically silenced, then no THCA synthase is produced, your cannabis cannot convert CBGA into THCA, and now you have hemp that is devoid of THC.So what is the best lighting technology to enhance the expression of terpenes?
With all of that being said, how do we ensure that our plants thrive under favorable epigenetic conditions? The answer is the environment; and the expression of terpenes is an ideal indicator of favorable environmental conditions. While amazing anti-inflammatories, anti-oxidants and metabolic regulators for humans, terpenes are also extremely powerful anti-microbial agents that act as a robust a line of defense for the plant against bacteria and pests. So, if the threat of microbes can induce the expression of terpenes, then what about other environmental factors? I am of the opinion that the combination of increased exposure to bacteria and natural sunlight enhances the expression of terpenes in outdoor-grown cannabis compared to indoor-grown cannabis. This is strictly my opinion based off of my own qualitative observations, but the point being is that lighting conditions can greatly impact the expression of terpenes (and cannabinoids) in cannabis.
So what is the best lighting technology to enhance the expression of terpenes? Do I use full spectrum lighting or specific frequencies? The answer to these questions is that we don’t fully know at this point. Thanks to the McCree curve we have a fundamental understanding of the various frequencies within the visible light spectrum (400-700nm) that are beneficial to plants, also known as Photosynthetically Active Radiation (PAR). However, little-to-no research has been conducted to determine the impacts that the rest of the electromagnetic spectrum (also categorized as ‘light’) may have on plants. As such, we do not know with 100% certainty what frequencies should be applied, and at what times in the growth cycle, to completely optimize terpene concentrations. This is not to disparage the lighting professionals out there that have significant expertise in this field; however, I’m calling for the execution of peer-reviewed experiments that would transcend the boundaries of company white papers and anecdotal claims. In my opinion, this lack of environmental data provides a real opportunity for the cannabis industry to initiate the required collaborations between cannabis geneticists, technology companies and environmental scientists. This is one field of research that I wish to pursue with tenacity and I also welcome other interested parties to join me in this data quest. Together we can better understand the environmental factors, such as lighting, that are acting as the molecular light switches at the interface of genetics and transcriptomics in cannabis.
Editor’s note: This article should serve as a foundation of knowledge for yeast and mold in cannabis. Beginning in January 2018, we will publish a series of articles focused entirely on yeast and mold, discussing topics such as TYMC testing, preventing yeast and mold in cultivation and treatment methods to reduce yeast and mold.
Cannabis stakeholders, including cultivators, extractors, brokers, distributors and consumers, have been active in the shadows for decades. With the legalization of recreational adult use in several states, and more on the way, safety of the distributed product is one of the main concerns for regulators and the public. Currently, Colorado1, Nevada and Canada2 require total yeast and mold count (TYMC) compliance testing to evaluate whether or not cannabis is safe for human consumption. As the cannabis industry matures, it is likely that TYMC or other stringent testing for yeast and mold will be adopted in the increasingly regulated medical and recreational markets.
The goal of this article is to provide general information on yeast and mold, and to explain why TYMC is an important indicator in determining cannabis safety.
Yeast & Mold
Yeast and mold are members of the fungi family. Fungus, widespread in nature, can be found in the air, water, soil, vegetation and in decaying matter. The types of fungus found in different geographic regions vary based upon humidity, soil and other environmental conditions. In general, fungi can grow in a wide range of pH environments and temperatures, and can survive in harsh conditions that bacteria cannot. They are not able to produce their own food like plants, and survive by breaking down material from their surroundings into nutrients. Mold cannot thrive in an environment with limited oxygen, while yeast is able to grow with or without oxygen. Most molds, if grown for a long enough period, can be detected visually, while yeast growth is usually detected by off-flavor and fermentation.
Due to their versatility, it is rare to find a place or surface that is naturally free of fungi or their spores. Damp conditions, poor air quality and darker areas are inviting environments for yeast and mold growth.
Cannabis plants are grown in both indoor and outdoor conditions. Plants grown outdoors are exposed to wider ranges and larger populations of fungal species compared to indoor plants. However, factors such as improper watering, the type of soil and fertilizer and poor air circulation can all increase the chance of mold growth in indoor environments. Moreover, secondary contamination is a prevalent risk from human handling during harvest and trimming for both indoor and outdoor-grown cannabis. If humidity and temperature levels of drying and curing rooms are not carefully controlled, the final product could also easily develop fungi or their growth by-product.
What is TYMC?
TYMC, or total yeast and mold count, is the number of colony forming units present per gram of product (CFU/g). A colony forming unit is the scientific means of counting and reporting the population of live bacteria or yeast and mold in a product. To determine the count, the cannabis sample is plated on a petri dish which is then incubated at a specific temperature for three to five days. During this time, the yeast and mold present will grow and reproduce. Each colony, which represents an individual or a group of yeast and mold, produces one spot on the petri dish. Each spot is considered one colony forming unit.
Why is TYMC Measured?
TYMC is an indicator of the overall cleanliness of the product’s life cycle: growing environment, processing conditions, material handling and storage facilities. Mold by itself is not considered “bad,” but having a high mold count, as measured by TYMC, is alarming and could be detrimental to both consumers and cultivators.
The vast majority of mold and yeast present in the environment are indeed harmless, and even useful to humans. Some fungi are used commercially in production of fermented food, industrial alcohol, biodegradation of waste material and the production of antibiotics and enzymes, such as penicillin and proteases. However, certain fungi cause food spoilage and the production of mycotoxin, a fungal growth by-product that is toxic to humans and animals. Humans absorb mycotoxins through inhalation, skin contact and ingestion. Unfortunately, mycotoxins are very stable and withstand both freezing and cooking temperatures. One way to reduce mycotoxin levels in a product is to have a low TYMC.
Yeast and mold have been found to be prevalent in cannabis in both current and previous case studies. In a 2017 UC Davis study, 20 marijuana samples obtained from Northern California dispensaries were found to contain several yeast and mold species, including Cryptococcus, Mucor, Aspergillus fumigatus, Aspergillus niger, and Aspergillus flavus.3 The same results were reported in 1983, when marijuana samples collected from 14 cannabis smokers were analyzed. All of the above mold species in the 2017 study were present in 13 out of 14 marijuana samples.4
Aspergillus species niger, flavus, and fumigatus are known for aflatoxin production, a type of dangerous mycotoxin that can be lethal.5 Once a patient smokes and/or ingests cannabis with mold, the toxins and/or spores can thrive inside the lungs and body.6, 7 There are documented fatalities and complications in immunocompromised patients smoking cannabis with mold, including patients with HIV and other autoimmune diseases, as well as the elderly.8, 9, 10, 11
For this reason, regulations exist to limit the allowable TYMC counts for purposes of protecting consumer safety. At the time of writing this article, the acceptable limit for TYMC in cannabis plant material in Colorado, Nevada and Canada is ≤10,000 CFU/g. Washington state requires a mycotoxin test.12 California is looking into testing for specific Aspergillus species as a part of their requirement. As the cannabis industry continues to grow and advance, it is likely that additional states will adopt some form of TYMC testing into their regulatory testing requirements.
Centre for Disease control and prevention. 2004 Outbreak of Aflatoxin Poisoning – Eastern and central provinces, Kenya, Jan – July 2004. Morbidity and mortality weekly report.. Sep 3, 2004: 53(34): 790-793
Cescon DW, Page AV, Richardson S, Moore MJ, Boerner S, Gold WL. 2008. Invasive pulmonary Aspergillosis associated with marijuana use in a man with colorectal cancer. Diagnosis in Oncology. 26(13): 2214-2215.
Szyper-Kravits M, Lang R, Manor Y, Lahav M. 2001 Early invasive pulmonary aspergillosis in a leukemia patient linked to aspergillus contaminated marijuana smoking. Leukemia Lymphoma 42(6): 1433 – 1437.
Verweii PE, Kerremans JJ, Voss A, F.G. Meis M. 2000. Fungal contamination of Tobacco and Marijuana. JAMA 2000 284(22): 2875.
Ruchlemer R, Amit-Kohn M, Raveh D, Hanus L. 2015. Inhaled medicinal cannabis and the immunocompromised patient. Support Care Cancer. 23(3):819-822.
McPartland JM, Pruitt PL. 1997. Medical Marijuana and its use by the immunocompromised. Alternative Therapies in Health and Medicine. 3 (3): 39-45.
Hamadeh R, Ardehali A, Locksley RM, York MK. 1983. Fatal aspergillosis associated with smoking contaminated marijuana, in a marrow transplant recipient. Chest. 94(2): 432-433.
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