Tag Archives: air

Cannabis Manufacturing Considerations: From Raw Materials to Finished Goods

By David Vaillencourt, Kathleen May
2 Comments

Facility layout and design are important components of overall operations, both in terms of maximizing the effectiveness and efficiency of the process(es) executed in a facility, and in meeting the needs of personnel. Prior to the purchase of an existing building or investing in new construction, the activities and processes that will be conducted in a facility must be mapped out and evaluated to determine the appropriate infrastructure and flow of processes and materials. In cannabis markets where vertical integration is the required business model, multiple product and process flows must be incorporated into the design and construction. Materials of construction and critical utilities are essential considerations if there is the desire to meet Good Manufacturing Practice (GMP) compliance or to process in an ISO certified cleanroom. Regardless of what type of facility is needed or desired, applicable local, federal and international regulations and standards must be reviewed to ensure proper design, construction and operation, as well as to guarantee safety of employees.

Materials of Construction

The materials of construction for interior work surfaces, walls, floors and ceilings should be fabricated of non-porous, smooth and corrosive resistant surfaces that are easily cleanable to prevent harboring of microorganisms and damage from chemical residues. Flooring should also provide wear resistance, stain and chemical resistance for high traffic applications. ISO 22196:2011, Measurement Of Antibacterial Activity On Plastics And Other Non-Porous Surfaces22 provides a method for evaluating the antibacterial activity of antibacterial-treated plastics, and other non-porous, surfaces of products (including intermediate products). Interior and exterior (including the roof) materials of construction should meet the requirements of ASTM E108 -11, Standard Test Methods for Fire Tests of Roof Covering7, UL 790, Standard for Standard Test Methods for Fire Tests of Roof Coverings 8, the International Building Code (IBC) 9, the National Fire Protection Association (NFPA) 11, Occupational Safety and Health Administration (OSHA) and other applicable building and safety standards, particularly when the use, storage, filling, and handling of hazardous materials occurs in the facility. 

Utilities

Critical and non-critical utilities need to be considered in the initial planning phase of a facility build out. Critical utilities are the utilities that when used have the potential to impact product quality. These utilities include water systems, heating, ventilation and air conditioning (HVAC), compressed air and pure steam. Non-critical utilities may not present a direct risk to product quality, but are necessary to support the successful, compliant and safe operations of a facility. These utilities include electrical infrastructure, lighting, fire detection and suppression systems, gas detection and sewage.

  1. Water
Microbial monitoring methods can include frequent/consistent testing

Water quality, both chemical and microbial, is a fundamental and often overlooked critical parameter in the design phase of cannabis operations. Water is used to irrigate plants, for personnel handwashing, potentially as a component in compounding/formulation of finished goods and for cleaning activities. The United States Pharmacopeia (USP) Chapter 1231, Water for Pharmaceutical Purposes 2, provides extensive guidance on the design, operation, and monitoring of water systems. Water quality should be tested and monitored to ensure compliance to microbiological and chemical specifications based on the chosen water type, the intended use of the water, and the environment in which the water is used. Microbial monitoring methods are described in USP Chapter 61, Testing: Microbial Enumeration Tests 3and Chapter 62, Testing: Tests for Specified Microorganisms 4, and chemical monitoring methods are described in USP Chapter 643, Total Organic Carbon 5, and Chapter 645, Water Conductivity 6.Overall water usage must be considered during the facility design phase. In addition to utilizing water for irrigation, cleaning, product processing, and personal hygiene, water is used for heating and cooling of the HVAC system, fogging in pest control procedures and in wastewater treatment procedures  A facility’s water system must be capable of managing the amount of water required for the entire operation. Water usage and drainage must meet environmental protection standards. State and local municipalities may have water usage limits, capture and reuse requirements and regulations regarding runoff and erosion control that must also be considered as part of the water system design.

  1. Lighting

Lighting considerations for a cultivation facility are a balance between energy efficiency and what is optimal for plant growth. The preferred lighting choice has typically been High Intensity Discharge (HID) lighting, which includes metal halide (MH) and high-pressure sodium (HPS) bulbs. However, as of late, light-emitting diodes (LED) systems are gaining popularity due to increased energy saving possibilities and innovative technologies. Adequate lighting is critical for ensuring employees can effectively and safely perform their job functions. Many tasks performed on the production floor or in the laboratory require great attention to detail. Therefore, proper lighting is a significant consideration when designing a facility.

  1. HVAC
urban-gro
Proper lighting is a significant consideration when designing a facility.

Environmental factors, such as temperature, relative humidity (RH), airflow and air quality play a significant role in maintaining and controlling cannabis operations. A facility’s HVAC system has a direct impact on cultivation and manufacturing environments, and HVAC performance may make or break the success of an operation. Sensible heat ratios (SHRs) may be impacted by lighting usage and RH levels may be impacted by the water usage/irrigation schedule in a cultivation facility. Dehumidification considerations as described in the National Cannabis Industry Association (NCIA) Committee Blog: An Introduction to HVACD for Indoor Plant Environments – Why We Should Include a “D” for Dehumidification 26 are critical to support plant growth and vitality, minimize microbial proliferation in the work environment and to sustain product shelf-life/stability. All of these factors must be evaluated when commissioning an HVAC system. HVAC systems with monitoring sensors (temperature, RH and pressure) should be considered. Proper placement of sensors allows for real-time monitoring and a proactive approach to addressing excursions that could negatively impact the work environment.

  1. Compressed Air

Compressed air is another, often overlooked, critical component in cannabis operations. Compressed air may be used for a number of applications, including blowing off and drying work surfaces and bottles/containers prior to filling operations, and providing air for pneumatically controlled valves and cylinders. Common contaminants in compressed air are nonviable particles, water, oil, and viable microorganisms. Contaminants should be controlled with the use appropriate in-line filtration. Compressed air application that could impact final product quality and safety requires routine monitoring and testing. ISO 8573:2010, Compressed Air Specifications 21, separates air quality levels into classes to help differentiate air requirements based on facility type.

  1. Electrical Infrastructure

Facilities should be designed to meet the electrical demands of equipment operation, lighting, and accurate functionality of HVAC systems. Processes and procedures should be designed according to the requirements outlined in the National Electrical Code (NEC) 12, Institute of Electrical and Electronics Engineers (IEEE) 13, National Electrical Safety Code (NESC) 14, International Building Code (IBC) 9, International Energy Conservation Code (IECC) 15 and any other relevant standards dictated by the Authority Having Jurisdiction (AHJ).

  1. Fire Detection and Suppression

“Facilities should be designed so that they can be easily expanded or adjusted to meet changing production and market needs.”Proper fire detection and suppression systems should be installed and maintained per the guidelines of the National Fire Protection Association (NFPA) 11, International Building Code (IBC) 9, International Fire Code (IFC) 10, and any other relevant standards dictated by the Authority Having Jurisdiction (AHJ). Facilities should provide standard symbols to communicate fire safety, emergency and associated hazards information as defined in NFPA 170, Standard for Fire Safety and Emergency Symbols 27.

  1. Gas detection

Processes that utilize flammable gasses and solvents should have a continuous gas detection system as required per the IBC, Chapter 39, Section 3905 9. The gas detection should not be greater than 25 percent of the lower explosive limit/lower flammability limit (LEL/LFL) of the materials. Gas detection systems should be listed and labeled in accordance with UL 864, Standard for Control Units and Accessories for Fire Alarm Systems 16 and/or UL 2017, Standard for General-Purpose Signaling Devices and Systems 17 and UL 2075, Standard for Gas and Vapor Detectors and Sensors 18.

Product and Process Flow

Product and process flow considerations include flow of materials as well as personnel. The classic product and process flow of a facility is unidirectional where raw materials enter on one end and finished goods exit at the other. This design minimizes the risk of commingling unapproved and approved raw materials, components and finished goods. Facility space utilization is optimized by providing a more streamlined, efficient and effective process from batch production to final product release with minimal risk of errors. Additionally, efficient flow reduces safety risks to employees and an overall financial risk to the organization as a result of costly injuries. A continuous flow of raw materials and components ensures that supplies are available when needed and they are assessable with no obstructions that could present a potential safety hazard to employees. Proper training and education of personnel on general safety principles, defined work practices, equipment and controls can help reduce workplace accidents involving the moving, handling, and storing of materials. 

Facilities Management

Facilities management includes the processes and procedures required for the overall maintenance and security of a cannabis operation. Facilities management considerations during the design phase include pest control, preventative maintenance of critical utilities, and security.

Damage from whiteflies, thrips and powdery mildew could be prevented with an appropriate PCP

A Pest Control Program (PCP) ensures that pest and vermin control is carried out to eliminate health risks from pests and vermin, and to maintain the standards of hygiene necessary for the operation. Shipping and receiving areas are common entryways for pests. The type of dock and dock lever used could be a welcome mat or a blockade for rodents, birds, insects, and other vermin. Standard Operating Procedures (SOPs) should define the procedure and responsibility for PCP planning, implementation and monitoring.

Routine preventative maintenance (PM) on critical utilities should be conducted to maintain optimal performance and prevent microbial and/or particulate ingress into the work environment. Scheduled PMs may include filter replacement, leak and velocity testing, cleaning and sanitization, adjustment of airflow, the inspection of the air intake, fans, bearings and belts and the calibration of monitoring sensors.

In most medical cannabis markets, an established Security Program is a requirement as part of the licensing process. ASTM International standards: D8205 Guide for Video Surveillance System 23, D8217 Guide for Access Control System[24], and D8218 Guide for Intrusion Detection System (IDS) 25 provide guidance on how to set up a suitable facility security system and program. Facilities should be equipped with security cameras. The number and location of the security cameras should be based on the size, design and layout of the facility. Additional cameras may be required for larger facilities to ensure all “blind spots” are addressed. The facility security system should be monitored by an alarm system with 24/7 tracking. Retention of surveillance data should be defined in an SOP per the AHJ. Motion detectors, if utilized, should be linked to the alarm system, automatic lighting, and automatic notification reporting. The roof area should be monitored by motion sensors to prevent cut-and-drop intrusion. Daily and annual checks should be conducted on the alarm system to ensure proper operation. Physical barriers such as fencing, locked gates, secure doors, window protection, automatic access systems should be used to prevent unauthorized access to the facility. Security barriers must comply with local security, fire safety and zoning regulations. High security locks should be installed on all doors and gates. Facility access should be controlled via Radio Frequency Identification (RFID) access cards, biometric entry systems, keys, locks or codes. All areas where cannabis raw material or cannabis-derived products are processed or stored should be controlled, locked and access restricted to authorized personnel. These areas should be properly designated “Restricted Area – Authorized Personnel Only”.

Future Expansion

The thought of expansion in the beginning stages of facility design is probably the last thing on the mind of the business owner(s) as they are trying to get the operation up and running, but it is likely the first thing on the mind of investors, if they happen to be involved in the business venture. Facilities should be designed so that they can be easily expanded or adjusted to meet changing production and market needs. Thought must be given to how critical systems and product and process flows may be impacted if future expansion is anticipated. The goal should be to minimize down time while maximizing space and production output. Therefore, proper up-front planning regarding future growth is imperative for the operation to be successful and maintain productivity while navigating through those changes.


References:

  1. United States Environmental Protection Agency (EPA) Safe Drinking Water Act (SDWA).
  2. United States Pharmacopeia (USP) Chapter <1231>, Water for Pharmaceutical Purposes.
  3. United States Pharmacopeia (USP) Chapter <61>, Testing: Microbial Enumeration Tests.
  4. United States Pharmacopeia (USP) Chapter <62>, Testing: Tests for Specified Microorganisms.
  5. United States Pharmacopeia (USP) Chapter <643>, Total Organic Carbon.
  6. United States Pharmacopeia (USP) Chapter <645>, Water Conductivity.
  7. ASTM E108 -11, Standard Test Methods for Fire Tests of Roof Coverings.
  8. UL 790, Standard for Standard Test Methods for Fire Tests of Roof Coverings.
  9. International Building Code (IBC).
  10. International Fire Code (IFC).
  11. National Fire Protection Association (NFPA).
  12. National Electrical Code (NEC).
  13. Institute of Electrical and Electronics Engineers (IEEE).
  14. National Electrical Safety Code (NESC).
  15. International Energy Conservation Code (IECC).
  16. UL 864, Standard for Control Units and Accessories for Fire Alarm Systems.
  17. UL 2017, Standard for General-Purpose Signaling Devices and Systems.
  18. UL 2075, Standard for Gas and Vapor Detectors and Sensors.
  19. International Society for Pharmaceutical Engineers (ISPE) Good Practice Guide.
  20. International Society for Pharmaceutical Engineers (ISPE) Guide Water and Steam Systems.
  21. ISO 8573:2010, Compressed Air Specifications.
  22. ISO 22196:2011, Measurement Of Antibacterial Activity On Plastics And Other Non-Porous Surfaces.
  23. D8205 Guide for Video Surveillance System.
  24. D8217 Guide for Access Control Syst
  25. D8218 Guide for Intrusion Detection System (IDS).
  26. National Cannabis Industry Association (NCIA): Committee Blog: An Introduction to HVACD for Indoor Plant Environments – Why We Should Include a “D” for Dehumidification.
  27. NFPA 170, Standard for Fire Safety and Emergency Symbols.

The Power of Prevention: Pathogen Monitoring in Cannabis Cultivation and Processing Facilities

By Nathan Libbey
2 Comments

As the cannabis market matures and the value chain becomes modernized, it’s important to address product safety in a comprehensive way. In other areas of manufacturing, Hazard Analysis & Critical Control Points (HACCP) has been the standard for reducing hazards both for employees and for the products themselves. A Critical Control Point (CCP) is any spot from conception to consumption where a loss of control can potentially result in risk (Unnevehr, 1996). In the food realm, HACCP has been used to drive quality enhancements since the 1980s (Cichy, 1982).

In a nutshell, HACCP seeks to help identify where a problem may enter a product or environment and how that problem may be addressed before it escalates. In cannabis, these hazards include many of the same problems that food products have: specifically molds, yeasts, and pathogenic bacteria (Listeria, E. coli, etc.). While the current industry standard is to test products at the end stage for these contaminants, this late-stage pass/fail regimen leads to huge lots of destroyed product and a risk for consumer distrust (Yamashiro, 2019). HACCP, therefore, should be applied at every stage of the production process.

Pathogen Environmental Monitoring (PEM) is a tool that can be used to identify CCPs in a cannabis cultivation or processing facility. The main goal of a PEM program is to find a contaminant before it reaches a surface that touches the product or the product itself. PEM is conducted using a pre-moistened swab or a sponge to collect a sample from the cannabis environment. The swab can then be sent to a lab for microbial testing. Keys to an effective PEM are:

1. Start with a broad stroke – When the FDA comes to a facility suspected of producing pathogen-laced food products, they conduct what is known as a Swab-a-thon. A Swab-a-thon is a top to bottom collection of samples, usually totaling 100 or more. Similarly, preemptively swabbing should be the first step in any PEM—swab everything to see what exists as a baseline.

2. Map your scene – identify on a map of your facility the following:

  • Cannabis contact surfaces (CCS) (belts, clippers, tables, etc)
  • Non-cannabis contact surfaces (Non-CCS) (floors, lighting, drains, etc)
  • Flow of air and people (where do air and people enter and where do they go?

Identifying the above zones will help deepen your understanding of where contaminants may come into contact with cannabis and how they may migrate from a Non-CCS to a CCS. 

3. Plan and execute:

  • Based on the results of mapping, and Swab-a-thon, identify where and when you will be collecting samples on a consistent and repeatable basis. Emphasis should be placed on areas that are deemed a risk based on 1) and 2). Samples should be collected at random in all zones to ensure comprehensive screening.

4. Remediate and modify:

  • If you get a positive result during PEM, don’t panic—pathogens are ubiquitous.
  • Remediate any trouble spots with deep cleaning, remediation devices or other protocols.
  • Re-test areas that were positive for pathogens to ensure remediation is successful.
  • Revisit and modify the plan at least once a year and each time a new piece of equipment is added or production flow is otherwise changed.

The steps above are a good starting point for a grower or processor to begin a PEM. Remember that this is not a one-size-fits-all approach to safety; each facility has its own unique set of hazards and control points.

Comprehensive guides for PEM can be found at the links below, many of the concepts can be applied to cannabis production.


https://affifoodsafety.org/lcp/advanced-search/

http://www.centerforproducesafety.org/amass/documents/document/263/Listeria%20Guidance%20UFPA%202013.pdf

Cichy, R. (1982). HACCP as a quality assurance tool in a commissary food-service system. International Journal of Hospitality Management, 1(2), 103-106.

Unnevehr, L., & Jensen, H. (1996). HACCP as a Regulatory Innovation to Improve Food Safety in the Meat Industry. American Journal of Agricultural Economics, 78(3), 764-769.

Yamashiro, C, & Baca, Y. (2019).  Prevent high-value cannabis crop loss with innovative environmental monitoring tool.

Fungal Monitoring: An Upstream Approach to Testing Requirements

By Bernie Lorenz, PhD
1 Comment

Mold is ubiquitous in nature and can be found everywhere.1 Cannabis growers know this all too well – the cannabis plant, by nature, is an extremely mold-susceptible crop, and growers battle it constantly.

Of course, managing mold doesn’t mean eradicating mold entirely – that’s impossible. Instead, cultivation professionals must work to minimize the amount of mold to the point where plants can thrive, and finished products are safe for consumption.

Let’s begin with that end in mind – a healthy plant, grown, cured and packaged for sale. In a growing number of states, there’s a hurdle to clear before the product can be sold to consumers – state-mandated testing.

So how do you ensure that the product clears the testing process within guidelines for mold? And what tools can be employed in biological warfare?

Mold: At Home in Cannabis Plants

It helps to first understand how the cannabis plant becomes an optimal environment.

The cannabis flower was designed to capture pollen floating in the air or brought by a pollinating insect.

Photo credit: Steep Hill- a petri dish of mold growth from tested cannabis

Once a mold spore has landed in a flower, the spore will begin to grow. The flower will continue to grow as well, and eventually, encapsulate the mold. Once the mold is growing in the middle of the flower, there is no way to get rid of it without damaging the flower.

A Name with Many Varieties

The types of spores found in or around a plant can make or break whether mold will end with bad product.

Aspergillus for example, is a mold that can produce mycotoxins, which are toxic to humans2. For this reason, California has mandatory testing3for certain aspergillus molds.

Another example, Basidiospores, are found outside, in the air. These are spores released from mushrooms and have no adverse effects on cannabis or a cannabis cultivation facility.

Fungi like powdery mildew and botrytis (PM and Bud Rot) typically release spores in the air before they are physically noticed on plants. Mold spores like these can survive from one harvest to the next – they can be suspended in the air for hours and be viable for years.

How Mold Travels

Different types of spores – the reproductive parts of mold – get released from different types of mold. Similar to plants and animals, mold reproduces when resources are deemed sufficient.

The opposite is also true that if the mold is under enough stress, such as a depleting nutrient source, it can be forced into reproduction to save itself.4

In the end, mold spores are released naturally into the air for many reasons, including physical manipulation of a plant, which, of course, is an unavoidable task in a cultivation facility.5

Trimming Areas: A Grow’s Highest Risk for Mold

Because of the almost-constant physical manipulation of plants that happen inside its walls, a grow’s trimming areas typically have the highest spore counts. Even the cleanest of plants will release spores during trimming.

Best practices include quality control protocols while trimming

These rooms also have the highest risk for cross contamination, since frequently, growers dry flower in the same room as they trim. Plus, because trimming can be labor intensive, with a large number of people entering and leaving the space regularly, spores are brought in and pushed out and into another space.

The Battle Against Mold

The prevalence and ubiquitous nature of mold in a cannabis facility means that the fight against it must be smart, and it must be thorough.

By incorporating an upstream approach to facility biosecurity, cultivators can protect themselves against testing failures and profit losses.

Biosecurity must be all encompassing, including everything from standard operating procedures and proper environmental controls, to fresh air exchange and surface sanitation/disinfection.

One of the most effective tactics in an upstream biosecurity effort is fungal monitoring.

Ways to Monitor Mold

Determining the load or amount of mold that is in a facility is and always will be common practice. This occurs in a few ways.

Post-harvest testing is in place to ensure the safety of consumers, but during the growing process, is typically done using “scouting reports.” A scouting report is a human report: when personnel physically inspect all or a portion of the crop. A human report, unfortunately, can lead to human error, and this often doesn’t give a robust view of the facility mold picture.

Another tool is agar plates. These petri dishes can be opened and set in areas suspected to have mold. Air moves past the plate and the mold spores that are viable land on the dishes. However, this process is time intensive, and still doesn’t give a complete picture.

Alternatively, growers can use spore traps to monitor for mold.

Spore traps draw a known volume of air through a cassette.The inside of the cassette is designed to force the air toward a sticky surface, which is capable of capturing spores and other materials. The cassette is sent to a laboratory for analysis, where they will physically count and identify what was captured using a microscope.

Spore trap results can show the entire picture of a facility’s mold concerns. This tool is also fast, able to be read on your own or sent to a third party for quick and unbiased review. The information yielded is a useful indicator for mold load and which types are prevalent in the facility.

Spore Trap Results: A Story Told

What’s going on inside of a facility has a direct correlation to what’s happening outside, since facility air comes infromthe outside. Thus, spore traps are most effective when you compare a trap inside with one set outside.

When comparing the two, you can see what the plants are doing, view propagating mold, and understand which of the spore types are only found inside.

Similar to its use in homes and businesses for human health purposes, monitoring can indicate the location of mold growth in a particular area within a facility.

These counts can be used to determine the efficacy of cleaning and disinfecting a space, or to find water leaks or areas that are consistently wet (mold will grow quickly and produce spores in these areas).

Using Spore Traps to See Seasonality Changes, Learn CCPs

Utilizing spore traps for regular, facility-wide mold monitoring is advantageous for many reasons.

One example: Traps can help determine critical control points (CCP) for mold.

What does this look like? If the spore count is two times higher than usual, mitigating action needs to take place. Integrated Pest Management (IPM) strategies like cleaning and disinfecting the space, or spraying a fungicide, are needed to bring the spore count down to its baseline.

For example, most facilities will see a spike in spore counts during the times of initial flower production/formation (weeks two to three of the flower cycle).

Seasonal trends can be determined, as well, since summer heat and rain will increase the mold load while winter cold may minimize it.

Using Fungal Monitoring in an IPM Strategy

Fungal monitoring – especially using a spore trap – is a critical upstream step in a successful IPM strategy. But it’s not the only step. In fact, there are five:

  • Identify/Monitor… Using a spore trap.
  • Evaluate…Spore trap results will indicate if an action is needed. Elevated spore counts will be the action threshold, but it can also depend on the type of spores found.
  • Prevention…Avoiding mold on plants using quality disinfection protocols as often as possible.
  • Action…What will be done to remedy the presence of mold? Examples include adding disinfection protocols, applying a fungicide, increasing air exchanges, and adding a HEPA filter.
  • Monitor…Constant monitoring is key. More eyes monitoring is better, and will help find Critical Control Points.

Each step must be followed to succeed in the battle against mold.

Of course, in the battle, there may be losses. If you experience a failed mandatory product testing result, use the data from the failure to fix your facility and improve for the future.

The data can be used to determine efficacy of standard operating procedures, action thresholds, and other appropriate actions. Plus, you can add a spore trap analysis for pre- and post- disinfection protocols, showing whether the space was really cleaned and disinfected after application. This will also tell you whether your products are working.

Leveraging all of the tools available will ensure a safe, clean cannabis product for consumers.


References

  1. ASTM D8219-2019: Standard Guide for Cleaning and Disinfection at a Cannabis Cultivation Center (B. Lorenz): http://www.astm.org/cgi-bin/resolver.cgi?D8219-19
  2. Mycotoxin, Aspergillus: https://www.who.int/news-room/fact-sheets/detail/mycotoxins
  3. State of California Cannabis Regulations: https://cannabis.ca.gov/cannabis-regulations/
  4. Asexual Sporulation in Aspergillus nidulans (Thomas H. Adams,* Jenny K. Wieser, and Jae-Hyuk Yu):  https://pdfs.semanticscholar.org/7eb1/05e73d77ef251f44a2ae91d0595e85c3445e.pdf?_ga=2.38699363.1960083875.1568395121-721294556.1562683339
  5. ASTM standard “Assessment of fungal growth in buildings” Miller, J. D., et al., “Air Sampling Results in Relation to Extent of Fungal Colonization of Building Materials in Some Water Damaged Buildings,” Indoor Air, Vol 10, 2000, pp. 146–151.
  6. Zefon Air O Cell Cassettes: https://www.zefon.com/iaq-sampling-cassettes
Soapbox

California Banned Ozone Generator “Air Purifiers”

By Jeff Scheir
2 Comments

California was the first state to step up to defend consumers from false marketing claims that ozone generators are safe, effective air purifiers. In reality, ozone is a lung irritant, especially harmful to allergy and asthma sufferers. In 2009, California became the first state in the nation to ban ozone generators. The Air Resources Board of the California Environmental Protection Agency states:

Not all air-cleaning devices are appropriate for use — some can be harmful to human health. The ARB recommends that ozone generators, air cleaners that intentionally produce ozone, not be used in the home or anywhere else humans are present. Ozone is a gas that can cause health problems, including respiratory tract irritation and breathing difficulty.

The regulation took effect in 2009 along with a ban on the sale of air purifiers that emit more than 0.05 parts per million of ozone. The ARB says that anything beyond this is enough to harm human health; however, some experts say that there is no safe level of ozone.

The National Institute for Occupational Safety and Health recommends an exposure limit to ozone of 0.1 ppm and considers levels of 5 ppm or higher “immediately dangerous to life or health.”

If you’re shopping for an air purifier, it’s best to avoid ozone generators, especially if you have a respiratory condition. Ozone generators, and ionic air cleaners that emit ozone, can cause asthma attacks in humans while doing little to nothing to clean the air.

O3 is a free radical, an oxidizer; when it meets any organic molecule floating around it bonds to it and destroys it. In a grow room, organic molecules include the essential oils in cannabis which produce the fragrance. When using ozone within your grow room, too much will not only all but eliminate the smell of your flowers but with prolonged exposure, it begins to actually degrade the cell walls of trichomes and destroy the structure of the glands.

Despite the claims of some manufacturers, ozone does not have an anti-microbial effect in air unless levels far exceed the maximums of the regulation and is therefore harmful humans.

Keeping the grow room clean of mold and bacteria is important, but ozone is not the technology you want to employ to satisfy this goal. Looking into a combination of UVC and Filtration will better meet the goal while keeping both your plants and staff healthy.

Keeping Your Environment Clean: Preventative Measures Against Contamination

By Jeff Scheir
2 Comments

For years we have heard about and sometimes experienced, white powdery mildew when growing cannabis. It is a problem we can see, and we have numerous ways to combat it. But now more and more states are introducing regulatory testing on our harvests and they are looking for harmful substances like Escherichia coli., Aspergillis Fumigatus, Aspergillis terreus, …  just to name a few. Mycotoxins, mold and bacteria can render a harvest unusable and even unsellable- and you can’t see these problems with the naked eye. How much would it cost you to have to throw away an entire crop?

You bring in equipment to control the humidity. You treat the soil and create just the right amount of light to grow a superior product. You secure and protect the growing, harvesting, drying and production areas of your facility. You do everything you can to secure a superior yield… but do you?

Many of the organisms that can hurt our harvest are being multiplied, concentrated and introduced to the plants by the very equipment we use to control the growing environment. This happens inherently in HVAC equipment.

Your air conditioning equipment cools the air circulating around your harvest in a process that pulls moisture from the air and creates a perfect breeding ground in the wet cooling coil for growth of many of the organisms that can destroy your yield. As these organisms multiply and concentrate in the HVAC system, they then spew out into the very environment you are trying to protect at concentrated levels far greater than outside air. In effect, you are inoculating the very plants you need to keep safe from these toxins if you want to sell your product.

The cannabis industry is starting to take a page from the healthcare and food safety industries who have discovered the best way to mitigate these dangers is the installation of a proper UVC solution inside their air conditioning equipment.

Why? How does UVC help? What is UVC?

What is Ultraviolet?

Ultraviolet (UV) light is one form of electromagnetic energy produced naturally by the sun. UV is a spectrum of light just below the visible light and it is split into four distinct spectral areas – Vacuum UV or UVV (100 to 200 nm), UVC (200 to 280 nm), UVB (280 to 315 nm) and UVA (315 to 400 nm). UVA & UVB have been used in the industry to help promote growth of cannabis.

What is UVC (Ultraviolet C)?

The entire UV spectrum can kill or inactivate many microorganism species, preventing them from replicating. UVC energy at 253.7 nanometers provides the most germicidal effect. The application of UVC energy to inactivate microorganisms is also known as Germicidal Irradiation or UVGI.

UVC exposure inactivates microbial organisms such as mold, bacteria and viruses by altering the structure and the molecular bonds of their DNA (deoxyribonucleic acid). DNA is a “blue print” these organisms use to develop, function and reproduce. By destroying the organism’s ability to reproduce, it becomes harmless since it cannot colonize. After UVC exposure, the organism dies off leaving no offspring, and the population of the microorganism diminishes rapidly.

Ultraviolet germicidal lamps provide a much more powerful and concentrated effect of ultraviolet energy than can be found naturally. Germicidal UV provides a highly effective method of destroying microorganisms.

To better understand how Steril-Aire UVC works, it is important to understand the recommended design. Directed at a cooling coil and drain pan, UVC energy destroys surface biofilm, a gluey matrix of microorganisms that grows in the presence of moisture. Biofilm is prevalent in HVAC systems and leads to a host of indoor air quality (IAQ) and HVAC operational problems. UVC also destroys airborne viruses and bacteria that circulate through an HVAC system and feed out onto the crop. HVAC cooling coils are the largest reservoir and amplification device for microorganisms in any facility.

For the most effective microbial control, UV germicidal Emitters are installed on the supply side of the system, downstream from the cooling coil and above the drain pan. This location provides more effective biofilm and microbial control than in-duct UVC installations. By irradiating the contaminants at the source – the cooling coils and drain pans – UVC delivers simultaneous cleaning of surface microorganisms as well as destruction of airborne microorganisms and mycotoxins. Steril-Aire patented this installation configuration in 1998.

The recirculating air in HVAC systems create redundancy in exposing microorganisms and mycotoxins to UVC, ensuring multiple passes so the light energy is effective against large quantities of airborne mycotoxins and cleaning the air your plants live by.

Where are these mycotoxins coming from?

Aspergillus favors environments with ample oxygen and moisture. Most pre-harvest strategies to prevent these mycotoxins involve chemical treatment and are therefore not ideal for the cannabis industry.

Despite the lack of cannabis protocols and guidelines for reducing mycotoxin contamination, there are some basic practices that can be utilized from other agricultural groups that will help avoid the production of aflatoxins and ochratoxins.

When guidelines are applied correctly to the cannabis industry, the threat of aflatoxin and ochratoxin contamination can be significantly reduced. The place to start is a clean air environment.

Design to win

The design of indoor grow rooms for cannabis is critical to the control of airborne fungal spores and although most existing greenhouses allow for the ingress of fungal spores, experience has shown that they can be retrofitted with air filters, fans, and UVC systems to make them relatively free of these spores. Proper designs have shown clearly that:

  1. Prevention via air and surface disinfection using germicidal UVC is much better than chemical spot treatment on the surface of plants
  2. High levels of air changes per hour enhance UVC system performance in reducing airborne spores
  3. Cooling coil inner surfaces are a hidden reservoir of spores, a fertile breeding ground and constitute an ecosystem for a wide variety of molds. Continuous UVC surface decontamination of all coils should be the first system to be installed in greenhouses to reduce mildew outbreaks.

UVC can virtually eliminate airborne contaminants

Steril-Aire graphic 4

Steril-Aire was the first and is the market leader in using UVC light to eliminate mold and spores to ensure your product will not be ruined or test positive.

  1. Mold and spores grow in your air handler and are present in air entering your HVAC system.
  2. Steril-Aire UVC system installs quickly and easily in your existing system.
  3. The Steril-Aire UVC system destroys up to 99.999% of mold/spores.
  4. Plants are less likely to be affected by mold…with a low cost and no down time solution.

It’s time to protect your harvest before it gets sick. It’s time to be confident your yield will not test positive for the contaminants that will render it unusable. It’s time to win the testing battle. It’s time for a proper UVC solution to be incorporated throughout your facilities.

Why the Central Chiller Isn’t So Central to Grow Room HVAC

By Geoff Brown
6 Comments

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.

solsticegrowop_feb
Indoor cultivator facilities use high powered lights that give off heat, requiring an efficient air cooling system.

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.

Talltrees
One of the flowering rooms in an indoor set up (Image: Tall Trees LED Company)

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.

HACCP

Implementing a HACCP Plan to Address Audit Concerns in the Infused Market

By Daniel Erickson
1 Comment
HACCP

The increasing appeal and public acceptance of medical and recreational cannabis has increased the focus on the possible food safety hazards of cannabis-infused products. Foodborne illnesses from edible consumption have become more commonplace, causing auditors to focus on the various stages of the supply chain to ensure that companies are identifying and mitigating risks throughout their operations. Hazard Analysis and Critical Control Points (HACCP) plans developed and monitored within a cannabis ERP software solution play an essential role in reducing common hazards in a market currently lacking federal regulation.

What are cannabis-infused products?

Cannabis infusions come in a variety of forms including edibles (food and beverages), tinctures (drops applied in the mouth), sprays (applied under the tongue), powders (dissolved into liquids) and inhalers. Manufacturing of these products resembles farm-to-fork manufacturing processes common in the food and beverage industry, in which best practices for compliance with food safety regulations have been established. Anticipated regulations in the seed-to-sale marketplace and consumer expectations are driving cannabis infused product manufacturers to adopt safety initiatives to address audit concerns.

What are auditors targeting in the cannabis space?

The cannabis auditing landscape encompasses several areas of focus to ensure companies have standard operating procedures (SOP’s) in place. These areas include:

  • Regulatory compliance – meeting state and local jurisdictional requirements
  • Storage and product release – identifying, storing and securing products properly
  • Seed-to-sale traceability –  lot numbers and plant identifiers
  • Product development – including risk analysis and release
  • Accurate labeling –  allergen statements and potency
  • Product sampling – pathogenic indicator and heavy metal testing
  • Water and air quality –  accounting for residual solvents, yeasts and mold
  • Pest control – pesticides and contamination

In addition, auditors commonly access the reliability of suppliers, quality of ingredients, sanitary handling of materials, cleanliness of facilities, product testing and cross-contamination concerns in the food and beverage industry, making these also important in cannabis manufacturers’ safety plans.

How a HACCP plan can help

HACCPWhether you are cultivating, harvesting, extracting or infusing cannabis into edible products, it is important to engage in proactive measures in hazard management, which include a HACCP plan developed by a company’s safety team. A HACCP plan provides effective procedures that protect consumers from hazards inherent in the production and distribution of cannabis-infused products – including biological, chemical and physical dangers. With the lack of federal regulation in the marketplace, it is recommended that companies adopt these best practices to reduce the severity and likelihood of compromised food safety.

Automating processes and documenting critical control points within an ERP solution prevents hazards before food safety is compromised. Parameters determined within the ERP system are utilized for identification of potential hazards before further contamination can occur. Applying best practices historically used by food and beverage manufacturers provides an enhanced level of food safety protocols to ensure quality, consistency and safety of consumables.

Hazards of cannabis products by life-cycle and production stage

Since the identification of hazards is the first step in HACCP plan development, it is important to identify potential issues at each stage. For cannabis-infused products, these include cultivation, harvesting, extraction and edibles production. Auditors expect detailed documentation of HACCP steps taken to mitigate hazards through the entire seed-to-sale process, taking into account transactions of cannabis co-products and finished goods at any stage.

Cultivation– In this stage, pesticides, pest contamination and heavy metals are of concern and should be adequately addressed. Listeria, E. coli, Salmonella and other bacteria can also be introduced during the grow cycle requiring that pathogenic indicator testing be conducted to ensure a bacteria-free environment.

Harvesting– Yeast and mold (aflatoxins) are possible during the drying and curing processes. Due to the fact that a minimal amount of moisture is optimal for prevention, testing for water activity is essential during harvesting.

Extraction – Residual solvents such as butane and ethanol are hazards to be addressed during extraction, as they are byproducts of the process and can be harmful. Each state has different allowable limits and effective testing is a necessity to prevent consumer exposure to dangerous chemical residues.

Edibles– Hazards in cannabis-infused manufacturing are similar to other food and beverage products and should be treated as such. A risk assessment should be completed for every ingredient (i.e. flour, eggs, etc.), with inherent hazards or allergens identified and a plan for addressing approved supplier lists, obtaining quality ingredients, sanitary handling of materials and cross-contamination.

GMPFollowing and documenting the HACCP plan through all of the stages is essential, including a sampling testing plan that represents the beginning, middle and end of each cannabis infused product. As the last and most important step before products are introduced to the market, finished goods testing is conducted to ensure goods are safe for consumption. All information is recorded efficiently within a streamlined ERP solution that provides real-time data to stakeholders across the organization.

Besides hazards that are specific to each stage in the manufacturing of cannabis-infused products, there are recurring common procedures throughout the seed-to-sale process that can be addressed using current Good Manufacturing Practices (cGMP’s).  cGMPs provide preventative measures for clean work environments, training, establishing SOPs, detecting product deviations and maintaining reliable testing. Ensuring that employees are knowledgeable of potential hazards throughout the stages is essential.Lacking, inadequate or undocumented training in these areas are red flags for auditors who subscribe to the philosophy of “if it isn’t documented, it didn’t happen.” Training, re-training (if necessary) and documented information contained within cannabis ERP ensures that companies are audit-ready. 

Labeling

The importance of proper labeling in the cannabis space cannot be understated as it is a key issue related to product inconsistency in the marketplace. Similar to the food and beverage industry, accurate package labeling, including ingredient and allergen statements, should reflect the product’s contents. Adequate labeling to identify cannabis products and detailed dosing information is essential as unintentional ingestion is a reportable foodborne illness. Integrating an ERP solution with quality control checks and following best practices ensures product labeling remains compliant and transparent in the marketplace.

Due to the inherent hazards of cannabis-infused products, it’s necessary for savvy cannabis companies to employ the proper tools to keep their products and consumers safe. Utilizing an ERP solution that effectively manages HACCP plans meets auditing requirements and helps to keep cannabis operations one step ahead of the competition.

Total Yeast & Mold Count: What Cultivators & Business Owners Need to Know

By Parastoo Yaghmaee, PhD
2 Comments

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

Photo credit: Steep Hill- a petri dish of mold growth from tested cannabis

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. 

Aspergillus species niger
Photo: Carlos de Paz, Flickr

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.

Aspergillus flavus on culture.
Photo: Iqbal Osman, Flickr

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.

References:

  1. https://www.colorado.gov/pacific/sites/default/files/Complete%20Retail%20Marijuana%20Rules%20as%20of%20April%2014%202017.pdf
  2. http://laws-lois.justice.gc.ca/eng/acts/f-27/
  3. https://www.ucdmc.ucdavis.edu/publish/news/newsroom/11791
  4. Kagen SL, Kurup VP, Sohnle PG, Fink JN. 1983. Marijuana smoking and fungal sensitization. Journal of Allergy & Clinical Immunology. 71(4): 389-393.
  5. 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
  6. 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.
  7. 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.
  8. Verweii PE, Kerremans JJ, Voss A, F.G. Meis M. 2000. Fungal contamination of Tobacco and Marijuana. JAMA 2000 284(22): 2875.
  9. Ruchlemer R, Amit-Kohn M, Raveh D, Hanus L. 2015. Inhaled medicinal cannabis and the immunocompromised patient. Support Care Cancer. 23(3):819-822.
  10. McPartland JM, Pruitt PL. 1997. Medical Marijuana and its use by the immunocompromised. Alternative Therapies in Health and Medicine. 3 (3): 39-45.
  11. 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.
  12. http://apps.leg.wa.gov/wac/default.aspx?cite=314-55-102