Cannabis Testing & Exposure Standards
Levels of mold & other contaminants in cannabis / marijuana

This private email discussion in 2023 is reported here to invite reader and expert comments & suggestions about the question raised by the reader.

Photo: mildew growing on a common plant leaf - one of the most common mold families found on plants, might also be found on growing cannabis.

This discussion focuses on more-harmful mold genera/species that may be found on cannabis as well as on harmful byproducts of those molds, particuarly but not limited to several species of Aspergillus.

[Click to enlarge any image]

Acceptable Limits of Aspergillus species: Aflavus, A niger, A terrus and A fumagatis on Inhaled Cannabis (Marijuana)

I found your site very helpful.  I'm wondering if you have any data / guidance based on your background on acceptable limits of aspergillus (flavus, niger, terrus and fumagatis) on an inhaled product like cannabis.  Most states have a no detect limit but I wanted to know if there is research or data to back up the limit.

Our firm is a method developer of qPCR and NGS for pathogens in the cannabis and hemp sector.  We wanted to support the regulators with additional data on why aspergillus testing is important. 

- Anonymous by private email 2023/06/23

Moderator Reply: OPINION - Aspergillus testing is important but may be dangerously insufficient

Thanks for an interesting question.

I will do some research but off-hand I don't have an allowable mold standard for cannabis.

In my opinion (based on field and lab work) is that it may be reasonable to use one or a few molds as "markers" for mold contamination on mold friendly material such as cannabis, but one wants to be very careful to avoid claiming that just because mold A is not found that a product is mold free.

I'm also concerned that the method used to detect the presence of mold or MVOCs or other harmful substances produced by mold on cannabis may be seriously deficient.

Watch out: some time ago I performed forensic analysis on imported teas for a U.S. importer/vendor who was getting mold complaints.

We identified several kinds of mold on the tea, including some species of Aspergillus.

There will almost always be multiple mold genera/species present. Focusing on just one is risky. For example, downy or powdery mildew may be common on most plant leaves and some stems.

Even at low levels the mold was causing reactions in some customers, varying by level and nature of exposure and of course individual sensitivity and vulnerability.

Watch out for what methods you're using to "identify" mold in cannabis. At https://inspectapedia.com/mold/Mold_Culture_Test_Method.php we described using culture media to grow some molds found in tea, but I warn that as much as 90% or perhaps even more of molds won't grow in any culture media whatsoever.

So if we're screening a plant material for mold by using cultures, we're 90% wrong the moment we start our test.

In my OPINION states setting a "not detected" limit for mold in cannabis for sale to the public are being smart.

There may be more than one hazard sort if cannabis is moldy:

1. exposure to inhaled harmful molds or MVOCs or other chemicals from the product while stored and handled. This is the more-straightforward concern.

2. exposure to mvocs and unknown levels of mold and mold combustion products during smoking. Before having any actual authoritative data whatsoever, my instinct says that this is a very risky situation since a user is inhaling smoke that may contain burned, partially-burned, and even un-burned mold spores and mvocs, often deeply into the lungs.

3. Let's both see what more research we can find and report back to one another.

Watch out when reading research papers however.

It may seem natural to research standards and effects regarding mold in tobacco. But while tobacco blue mold is a serious annual concern for tobacco growers in the U.S. and Canada, cured tobacco may respond to mold quite differently from cannabis. I'm doubtful that the mold friendliness of the two plants will be found to be equal.

Research & Standards for Mold in Cannabis

Note that typical testing limits for mold in cannabis set a limit of "Absent" in a "Present/Absent" type test.

• 25 Citations: Aspergillosis ASSOCIATED with CANNABIS / Cannibis Use [Image]
• AOAC, STANDARD METHOD PERFORMANCE REQUIREMENTS FOR VIABLE TOTAL YEAST AND MOLD COUNT ENUMERATION [PDF] (2021) AOAC Cannabis Analytical Science Program, AOAC, 2275 Research Blvd, Ste 300 Rockville, MD 20850 + USA, Tel: 1 (800) 379-2622 Web: aoac.org/
  Excerpt:
  AOAC Standard Method Performance RequirementsSM (SMPRs) describe the minimum 7 recommended performance characteristics to be used during the evaluation of a method.
  
  The evaluation may be an on-site verification, a single-laboratory validation, or a multi-site collaborative study.
  
  SMPRs are written and adopted by AOAC stakeholder panels composed of representatives from industry, regulatory organizations, contract laboratories, test kit manufacturers, and academic institutions.
  
  AOAC SMPRs are used by AOAC expert review panels in their evaluation of validation study data for method being considered for Performance Tested MethodsSM or AOAC Official Methods of AnalysisSM and can be used as acceptance criteria for verification at user laboratories.
• ASTM Standard Practice for Determination of Water Activity (aw) in Cannabis Flower (D8196)
• ASTM Standard Specification for Maintaining Acceptable Water Activity (aw) Range (0.55 to 0.65) for Dry Cannabis Flower (D8197)
• Benedict, Kaitlin, George R. Thompson III, and Brendan R. Jackson. CANNABIS USE AND FUNGAL INFECTIONS IN A COMMERCIALLY INSURED POPULATION, UNITED STATES, 2016 [PDF] Emerging Infectious Diseases 26, no. 6 (2020): 1308.
  Abstract:
  
  Case reports have identified invasive fungal diseases in persons who use cannabis, and fungal contamination of cannabis has been described. In a large health insurance claims database, persons who used cannabis were 3.5 (95% CI 2.6–4.8) times more likely than persons who did not use cannabis to have a fungal infection in 2016.
  
  Cannabis can contain fungal pathogens that cause serious and often fatal infections in persons with immunocompromising conditions, such as cancer, transplant, or infection with HIV (1). In these patients, some reasons for using cannabis include pain and nausea relief and appetite stimulation.
  
  The frequency of fungal infections associated with cannabis is unknown but is a growing concern as more states legalize its medicinal and recreational use.
  
  We used health insurance claims data from 2016 to evaluate the prevalence of fungal infection diagnosis codes among persons who use cannabis and persons who do not use cannabis and to compare demographic and clinical features between these 2 groups.
• CA, MEDICINAL AND ADULT-USE COMMERCIAL CANNABIS REGULATIONS CALIFORNIA CODE OF REGULATIONS TITLE 4 [PDF] California Department of Cannabis Control, Division 19. Department of Cannabis Control, retrieverd 2023/06/26 original source: cannabis.ca.gov/wp-content/uploads/sites/2/2021/10/DCC-Cannabis-Regulations-Sept.-2021.pdf
• Cannibis Testing Regulations by State - from these private providers (as of 2023/067/26)
  
  medicinalgenomics.com/resource/cannabis-microbial-testing-regulations-by-state/
  
  pathogendx.com/state-cannabis-microbial-testing-regulations/
• Freeman, Kalev, M. McHenry, W. Cats-Baril, and T. Grace. CANNABIS TESTING FOR PUBLIC SAFETY-BEST PRACTICES FOR VERMONT ANALYTICAL LABORATORIES [PDF]  PhytoScience Institute (2016).
  Excerpts:
  
  This paper provides a summary of the best practices for analytical laboratories that perform testing of Cannabis and Cannabis-derived products intended for human consumption. Specifically, we address the following questions for regulators and policy makers interested in ensuring safety as the Vermont Cannabis industry evolves: How should Cannabis products be tested for public safety? How should the testing laboratories be regulated and accredited?
  
  What will it cost to do the recommended testing? In the absence of guidance from the United States Department of Agriculture (USDA), the Food and Drug Administration (FDA), or the Environmental Protection Agency (EPA), regulatory agencies in states allowing retail sales of Cannabis and Cannabis-derived products must decide whether safety testing will be required of these products.
  
  States also must decide how to inspect and certify the laboratories that will perform the necessary analytical testing. We provide specific recommendations that can serve as a roadmap for policy makers seeking direction in the uncharted territory of Cannabis in public health and safety considerations.
  
  This information should be widely generalizable to governmental regulatory bodies and private sector interests throughout the United States who are confronted with similar challenges as those faced in Vermont.

• Hospenthal, D. R., K. J. Kwon-Chung, and J. E. Bennett. "Concentrations of airborne Aspergillus compared to the incidence of invasive aspergillosis: lack of correlation." Medical mycology 36, no. 3 (1998): 165-168.
  
  Abstract:
  Air sampling of the rooms and corridors of the oncology wards of the hospital was carried out over a 54-week period to assess the concentration of viable Aspergillus conidia. A. fumigatus and A. flavus were recovered at a mean of 1·83 cfu m-3 air sampled.
  
  Individual samplings yielded concentrations of up to 11·6 cfu m-3. Other Aspergillus spp. were recovered at a mean of 2·38 cfu m-3 (maximum 32·6 cfu m-3).
  
  Concentration was not correlated with season or hospital ward. Review of autopsy results showed an average of 6·6 cases of aspergillosis annually over a 22-year period. No seasonal variation in case incidence was found. Six cases of invasive aspergillosis were diagnosed on the three cancer wards during the air-sampling period, but no association was seen linking these cases with changes in recovery of airborne Aspergillus.
  
  A seasonal pattern was not observed in the overall incidence of aspergillosis cases nor concentrations of airborne conidia.
• Marcoux, Rita, Lauren Holmes, and F. Randy Vogenberg. "Regulatory and legislative disparities with cannabis present challenges to P&T committees and health care providers." Pharmacy and Therapeutics 44, no. 5 (2019): 290.
• McKernan, Kevin, Jessica Spangler, Yvonne Helbert, Ryan C. Lynch, Adrian Devitt-Lee, Lei Zhang, Wendell Orphe et al. "Metagenomic analysis of medicinal Cannabis samples; pathogenic bacteria, toxigenic fungi, and beneficial microbes grow in culture-based yeast and mold tests." F1000Research 5, no. 2471 (2016): 2471.
• MD MEDICAL CANNIBIS TESTING, Technical Authority (2020) Maryland Medical Cannabis Commission (MMCC), retrieved 2023/06/26, original source: mmcc.maryland.gov/Documents/2019_2020 Laboratory Testing Page Updates/MMCC_TechnicalAuthority-Final-12-15-20.pdf
  Excerpt:
  The Maryland Medical Cannabis Commission (MMCC) has developed this technical authority document to define contaminants and corresponding action limits associated with those contaminants in medical cannabis. This information is intended for use by the independent testing laboratories registered with the MMCC.
• MI, SAMPLING AND TESTING TECHNICAL GUIDANCE FOR MARIJUANA PRODUCTS [PDF] (2022) Michigan State Government, CRA, retrieved 2023/06/26, original source: michigan.gov/cra/-/media/Project/Websites/cra/bulletin/5Technical/Sampling_and_Testing-_Technical_Guidance_for_Marijuana_Products_694124_7.pdf
  
  Excerpt:
  The Cannabis Regulatory Agency (CRA) is committed to evidence-based decisionmaking when implementing technical guidance for licensed laboratories. As research into marijuana use, safety, and testing advances, this guide may be revised and updated to reflect these changes where appropriate.
  
  Upon licensing of a safety compliance facility/marihuana safety compliance facility, licensees must comply with all applicable statutes, administrative rules.
• NJ, PESONAL USE CANNABIS RULES [PDF] New Jersey state government, Chapter 30. Web: nj.gov
• NM, TESTING MEDICAL CANNABIS [PDF] New Mexico Government
• NYS, REQUIRED TESTING OF EACH LOT OF ADULT USE CANNABIS AND MEDICAL CANNIBIS PRODUCT [PDF] New York State Office of Cannabis Management, retrieved 2023/06/26, original source: https://cannabis.ny.gov/system/files/documents/2023/01/ocm-testing-limits.pdf
  Excerpt:
  
  This document lists the permitted analytes and sets testing limits for contaminants as directed in 9 New York Codes, Rules and Regulations (NYCRR) Part 130 and Cannabis Law.
  
  Testing for each contaminant is required for all final adult- use and medical cannabis product types unless expressly noted.
  
  Additional analytes may be added. These limits may be modified where it is in the best interest of public health and safety
• PA, GUIDANCE FOR QUALITY TESTING AND SAMPLING BY APPROVED LABORATORIES [PDF] (2018) Pennsylvania Department of Health, retrieved 2023/06/26, original source: .health.pa.gov/
• Seltenrich, Nate. CANNABIS CONTAMINANTS: REGULATING SOLVENTS, MICROBES, AND METALS IN LEGAL WEED [PDF] (2019): 082001. US NIH, Envrionmental Health Perspectives, EHP, retreived 2023/06.26 original source: https://ehp.niehs.nih.gov/doi/full/10.1289/EHP5785
  
  Abstract excerpt:
  
  Policing the quality and safety of cannabis products is far from straightforward.
  
  Such products come in many forms and infusions that can be inhaled or ingested, including traditional cured “flower” for smoking or vaporizing; a range of concentrates, oils, and tinctures; and all manner of foods and drinks.
  
  Further complicating the matter is the plant’s dual role as both a recreational and a medical drug used to treat a wide range of conditions.
  
  Cannabis users include not only healthy adults but also more sensitive or vulnerable members of the population, including children and patients with cancer or HIV.
• Yaghmaee, Pareastoo, PhD, TOTAL YEAST & MOLD COUNT: WHAT CULTIVATORS & BUSINESS OWNERS NEED TO KNOW [PDF] (2017), Cannabis Industry Journal, retrieved 6/26/2023, original source: cannabisindustryjournal.com/feature_article/total-yeast-mold-count-what-cultivators-business-owners-need-to-know/
  
  Excerpt: Dec 12, 2017 — 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.