A Beginners Guide to Microbial Testing in Cannabis

Posted on May 27, 2021

Microbiological testing in cannabis is regulated as part of the Cannabis Act along with various contaminants of concern such as heavy metals, pesticides, or residual solvents. Microorganisms present a multi-level concern through the potential to both impede the therapeutic effect of a product, while also posing a health risk.

Due to its therapeutic properties, cannabis is often consumed by patients with compromised immune systems who are at particular risk of adverse health effects,  highlighting the critical nature of quality microbial testing.  Of course, the mode of administration must be considered as the risk of exposure will vary depending on whether the product is smoked or digested for example.

The standards for microbiology testing in Canada typically draw the methods and limits from either the United States Pharmacopoeia (USP) or European Pharmacopeia (EP). In general, these guidance documents have been prepared for products other than cannabis, such as herbal remedies and pharmaceuticals.

Ultimately, methods optimized for the cannabis matrix will be needed as the plant material presents challenges not found with the intended products under each monograph (EP or USP). In these pharmacopoeia you will find recommended limits depending on the mode of administration of the product for Total Aerobic Microbial Count (TAMC), Total Yeast and Mold Count (TYMC), Bile-Tolerant Gram-Negative (BTGN), E. Coli and Salmonella.

What Type of Microorganisms Can Be Found in Cannabis?

A brief overview of what labs (like us!) test for in cannabis products.

  • Total Yeast and Mold
    Mold is the most common type of microbial growth on Cannabis. Mold and yeasts have the potential to produce toxic metabolites called mycotoxins. Those with weakened immune systems are particularly susceptible to exposure to spores through inhalation.
  • Total Aerobic Microbial Count
    TAMC is an indication of the overall populations of microorganisms in a sample and can provide a general sense of cleanliness of production.
  • Bile Tolerant Gram Negative
    These are bacteria that can survive in the human stomach and show growth on Violet Red Bile Glucose Agar. Some examples include Enterobacteriaceae, Pseudomonads and Aeromonas.
  • E.Coli
    This is a member of the Enterobacteriaceae family. In general E. Coli are mostly harmless and lead to gastrointestinal issues but should be considered more serious in immunocompromised individuals. More serious effects such as with Shiga toxin producing E. Coli can be life threatening.
  • Salmonella
    A group of bacteria than can cause gastrointestinal illness and fever call salmonellosis. A 1981 outbreak of salmonellosis in the US was attributed to cannabis contamination.

Are There Cannabis Regulations Within Canada?

In October 2018, Canada’s Cannabis Act became the official legal framework for cannabis production and sale in the country.   The Cannabis Regulations under this Act outline the rules and standards of the Act.

With the legalization of cannabis edible products and concentrates in 2019,  the Cannabis Regulations were amended to identify regulatory limits based on the route of exposure ( inhalation, oral, and dermal application.)   The two categories of compounds affected by this amendment were heavy metals and microbiological parameters, as the toxicity of both rely heavily on the route of administration.

The testing specifications are found in subsection 93(3) of the Cannabis Regulation, and require that license holders use reference standards from a publication under Schedule B of the Food and Drugs Act to determine the most suitable guidelines for their product.  The standards selected must be appropriate for the intended use as well as any reasonably foreseeable use of the cannabis product.

What Are the Cannabis Standards Within Canada?

Schedule B of the Food and Drug Act lists 8 different standards from which to choose an appropriate limit.  The most common guidelines in our experience are the USP and EP.  However, tracking down the appropriate limits can present a challenge as these references are not cannabis specific.

Health Canada has specifically indicated the use of oral microbial limits for herbal medicines for smoked or dried cannabis (see EP 5.1.8 as an example.)  A summary of those limits can be found in the table below. When looking at other routes of exposure, EP 5.1.4 and USP 1111, both of which provide limits for microbiological quality of non-sterile pharmaceuticals, are valuable resources to consider when looking at other routes of exposure.

Health Canada has acknowledged that the industry is seeking additional guidance on contaminant tolerance limits and testing requirements and is prepared to develop additional guidance.

Table 1.  EP 5.1.8 B Acceptance Criteria for herbal medicinal products containing extracts.

Please note: 105 = 200000 and 104 = 20000.  Trust us, we have triple checked.

What Can Be Done to Prevent Cannabis Contamination?

In some cases, the environment best suited for growing cannabis also provides optimal conditions for microbial growth.  Any steps that can be taken to mitigate this risk will therefore be key to successful production.

One valuable resource for risk mitigation practices is a guidance document released by Health Canada focused on good production practices: The Good Production Practices Guide for Cannabis.  This document details areas of focus such as storage, facility design, and water supply.

There are several areas within these guidelines where CARO can help with verification of good production practices through testing. For example, swabbing of surfaces for the presence of microorganisms can help rule out contact transfer as a source of contamination.

Additionally, Section 5.2.7 of the guidance addresses potable water, and specifies that any water that may come into contact with any cannabis product must be deemed potable (we have water testing packages that do just that!)

Another area that has started to gather more attention is the role of moisture and water activity in the promotion of microbial growth. Water activity plays an important role in the preservation of food and control of microbial growth. Through our experience in the food industry CARO can offer water activity testing according to an approved method developed by the Government of Canada Health Products and Food Branch.

CARO has been a trusted testing lab for over 30 years and has been at the forefront of Cannabis testing in Canada since 2018.  Our team of charismatic scientists are happy to share what they know – if you have any questions on microbial testing, water testing, or anything else related to cannabis testing, please do get in touch.


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