As cannabis becomes legal in other states, each state has adopted its own guidelines without assistance from federal agencies. However, many of the state guidelines are not grounded in scientific research, according the authors of the report, Microbiology Testing in Cannabis Safety.
Written by a group of experts in plant microbiology, medical microbiology and the safety testing of agricultural and food products, the report promotes the adoption of regulatory guidelines that are “rational, consistent and safe.” It also highlights the reasons why current testing is not meeting those objectives.
Current Tests for Bacteria, Mold & Yeast in Marijuana
The authors point to guidelines in Washington and Colorado as examples of states that developed cannabis testing guidelines without the benefit of regulations and scientific support by agencies like the U.S. Department of Agriculture (USDA) and Food and Drug Administration (FDA).
Washington’s guidelines were drawn from the American Herbal Products Association (AHPA) microbiology guidelines, which are used in some food industries. The bacteria, mold and yeast limits in the guidelines are based on surveys from AHPA members and thought to reflect what levels are common for dried herbal products. AHPA microbiology guidelines were never intended to be used as a testing protocol, however.
In Colorado, guidelines for cannabis microbiological testing were passed as part of the Amendment 64 legislation. Much of the guidelines pertaining to mold were drawn from contemporary literature on cannabis microbiology. This literature examined marijuana smuggled into the U.S. in the 1970’s and 1980’s, making the research irrelevant to commercially-grown, domestic cannabis.
Outside of the cannabis industry, most existing food safety protocols do not mandate the testing of end products for pathogens. Instead, most food safety protocols require the testing and certification of facilities and processes. The authors suggest that cannabis food products be treated the same, subject to facilities testing rather than end product testing.
Microbiological Marijuana Testing Rules in New Mexico
In New Mexico, medical cannabis providers must comply with microbiology standards set in the United States Pharmacopeia (USP). The USP standard is 1,000 yeast or mold colony forming units (CFUs) per gram of material. This standard has caused much controversy in the New Mexico medical cannabis community.
In a public rule-making hearing in early 2016, Kathleen O’Dea, owner and laboratory director of Scepter Labs, gave evidence that 1,000 CFUs/gram was a difficult standard for cannabis producers to meet.
Scepter conducted 5,000 microbial panels on cannabis materials over a period of 14 months, including more than 1,000 yeast and mold tests. Based on empirical data, 20% of indoor-grown and 85% of outdoor-grown marijuana has failed the 1,000/CFUs standard.
Despite not meeting the standard, there is substantial evidence that the material is still safe for consumption, according to the testimony.
Organizations like the World Health Organization, the American Products Association and the American National Standards Institute have adopted a standard of 10,000 CFUs/gram, while the Cannabis Safety Institute recommends 100,000 CFUs/gram.
SIDEBAR
The authors of Microbiology Testing in Cannabis Safety offer the following eleven guidelines for testing cannabis:
Water activity can be used as a marker for overall microbial levels.
Plant material with high water activity support microbial growth, making the completion of the drying process essential to the insurance against microbial dangers.
Fresh Cannabis will require a different set of microbiological guidelines.
Trends are emerging in which consumers are ingesting marijuana raw. This increases the small chance for microbial infection, so fresh raw cannabis for commercial purposes should be tested for Pseudomonas aeruginosa, Clostridium botulinum, and toxigenic E. coli.
Edible Cannabis products should be regulated by local health departments.
Local and state health departments should inspect facilities just like all other commercial food product facilities, rather than end products. Commercial facilities should follow modern HAACP guidelines.
Cannabis should be tested for four species of Aspergillus:
A. flavus, A. fumigatus, A. niger, and A. terreus. These are the only pathogens that pose a clear danger to cannabis users and are responsible for cases of invasive pulmonary aspergillosis.
Cannabis should be tested for total generic E. Coli.
The only indicator test recommended in the report, samples that have levels above 100 CFUs/gram should be rejected.
Cannabis should be tested for Salmonella.
Though the odds of salmonella infection from cannabis is low, it is a bacterial pathogen that poses a potential risk to smokers.
There is no need to test Cannabis for Pseudomonas
aeruginosa, Listeria, toxigenic E. Coli (e.g., H7:0157), or other
bacterial pathogens besides Salmonella. Cannabis is both dried and heated before use, so it is not a potential delivery vehicles for these organisms, or most bacterial pathogens.
There is no need to test Cannabis for “total yeast and mold”.
Total yeast and mold tests detect only a small fraction do not correlate with the presence of pathogenic species. Aspergillus is the only pathogenic mold species on cannabis, but these must be tested separately.
There is no need to test Cannabis for aflatoxins.
Seedless cannabis plants are not capable of supporting aflatoxin production, and aflatoxins would be at least partly degraded by the heat of smoking or decarboxylation.
Statistical sampling procedures must be used for microbial
testing. The authors advocate batch testing, recommending that 5g per pound be sampled from every batch of cannabis in five individual, randomly-chosen 1g increments.
Cannabis extracts and concentrates require different types
of microbial screening. The process of extracting cannabinoids with solvents like butane is likely sterilizing, as are alcohol extracts. Concentration processes that use water or mechanical force generally have low water activity, but they can have enough moisture to support fungal or bacterial growth. The authors recommend they should be screened exactly as dry cannabis flowers are screened.
