Book:Past, Present, and Future of Cannabis Laboratory Testing and Regulation in the United States/Laboratory testing of cannabis/Analytical aspects of cannabis

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With a sense of history and a better understanding of the regulations and standards affecting cannabis testing and use, this chapter can finally dig into the specifics of the current and future state of laboratory testing of cannabis and related products in the U.S. According to a 2022 Facts & Factors report, the cannabis testing market is expected to grow yearly at a compound annual growth rate (CAGR) of 11.2% until at least 2028, and have an estimated revenue of around $2.9 billion by 2028.[1] With demand for testing growing and the utility of testing becoming increasingly accepted, it helps to look at the analytical aspects of cannabis and the methods and guidelines used, as well as the equipment and software typical to cannabis testing labs.

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3.1 Analytical aspects of cannabis

3.1.1 Cannabinoids

Somewhere between 104 and upwards of more than 140 of the over 750 constituents of Cannabis sativa have been identified as cannabinoids[2][3][4], active chemical compounds that act in a similar way to compounds our body naturally produces, and new cannabinoids continue to be identified during cannabis research.[4][5] Many of our body's cells have cannabinoid receptors capable of modulating neurotransmitter release in the brain and other areas.[6] The plant's cannabinoids vary, with each bonding to specific receptors in our body, providing differing effects. From a theoretical and medical standpoint, crafting a strain of cannabis that has specific cannabinoids that can aid with a particular malady, while also carefully reproducing the grow conditions to consistently make that strain in the future, is a desirable but difficult goal to achieve.[7] However, even as new strains are developed, identifying an existing strain effectively has its own set of challenges, as Mudge et al. point out: "the total [tetrahydrocannabinol] and [cannabidiol] content is not sufficient to distinguish strains [though] a combination of targeted and untargeted chemometric approaches can be used to predict cannabinoid composition and to better understand the impact of informal breeding program and selection on the phytochemical diversity of cannabis."[4]

Lab testing of cannabinoids is done primarily as a measure of psychoactive "potency," though cannabinoids have many other potential therapeutic uses. Current laboratory testing looks at only a handful of cannabinoids; more research and development of analytical techniques that can quickly and accurately detect and separate the rest is required.[8] Some of the major cannabinoids tested for include[4][9][10][11]:

  • THC (∆9-Tetrahydrocannabinol): This is the most commonly known cannabinoid found in cannabis, notable for its strong psychoactive effects and ability to aid with pain, sleep, and appetite issues. Included is its analogue ∆8-Tetrahydrocannabinol (which shows notably less strong psychoactive effects than ∆9[12]) and its homologue THCV (Tetrahydrocannabivarin), which tends to appear in trace amounts and has a more pronounced psychoactive effect, but for a shorter duration. THCV shows promise in fighting anxiety, tremors from neurological disorders, appetite issues, and special cases of bone loss. Also notable is ∆9-THCA (∆9-Tetrahydrocannabinolic acid), a non-psychoactive biosynthetic precursor to THC.
  • CBC (Cannabichromene): This non-psychoactive cannabinoid is found in trace amounts; however, it tends to be markedly more effective at treating anxiety and stress than CBD (see next). It's also notable for its anti-inflammatory properties and potential use for bone deficiencies.
  • CBD (Cannabidiol): CBD is a non-psychoactive component of cannabis, typically accounting for up to 35 to 40 percent of cannabis extracts. It acts as a counter-balance to THC, regulating its psychoactivity. It's been researched as a treatment for anxiety, sleep loss, inflammation, stress, pain, and epilepsy, among other afflictions. Included is its homologue CBDV (Cannabidivarin), which is also non-psychoactive and demonstrates promise as a treatment for epileptic seizures. Also notable is CBDA (cannabidiolic acid), a non-psychoactive biosynthetic precursor to CBD.
  • CBG (Cannabigerol): This cannabinoid is also non-psychoactive but only appears in trace amounts of cannabis. It has potential as a sleep aid, anti-bacterial, and cell growth stimulant. Also notable is CBGA (cannabigerolic acid), a non-psychoactive biosynthetic precursor to CBG.
  • CBN (Cannabinol): CBN is mildly psychoactive at best and appears only in trace amounts in Cannabis sativa and Cannabis indica. It occurs largely as a metabolite of THC and tends to have one of the strongest sedative effects among cannabinoids. It shows promise as a treatment for insomnia, glaucoma, and certain types of pain.

3.1.2 Terpenes

Mandated lab testing of terpenes—volatile organic compounds that distinctly affect cannabis aroma and taste—is done primarily as a way to ensure proper labeling of cannabis and related products, including extracts and concentrates, so buyers have confidence in what they are purchasing.[13][14][15] However, additional lab research goes into terpenes as they also show potentially useful pharmacological properties[13][15][16], and they demonstrate synergies (referred to at times as the "entourage effect") with cannabinoids, requiring further research.[17][16][15][18] Testing for specific terpenes (discussed later) has histoically been less of a standardized practice[13], though it's rapidly improving.[19] Commonly tested terpenes by third-party testing labs include[15][14][16][17][19][11][20]:

3.1.3 Contaminates

Generally speaking, a contaminant is an unwanted substance that may show up in the final product, be it recreational marijuana or a pharmaceutical company's therapeutic tincture. The following are examples of contaminants that laboratories may test for in cannabis products.

Pesticides: Pesticides represent an oft-discussed aspect not only of growing cannabis but also performing analytical testing on it. One of the core issues, again, is the fact that on the federal level marijuana is illegal. Because it's illegal, government agencies such as the Environmental Protection Agency (EPA) have historically failed to develop standards or guidelines for what's safe when it comes to residual pesticides in cannabis, let alone how to best test for them.[21][22] Additionally, researchers have faced their fair share of difficulties obtaining product to test over the years. The end result is we're only now barely understanding how inhalation of pesticide-coated marijuana smoke affects long-term health[21][22][19], and standard methods for pesticide application and testing have been slow to develop.[17][23] With numerous pesticide products and little oversight on what growers apply to their plants, combined with the technical difficulty of testing for pesticides in the lab, pesticides remain one of the most difficult contaminants to test for.[17][23] That said, several classes of of pesticides are commonly applied during cannabis cultivation and can be tested for by labs[19][10][8][24]:

  • avermectins: function as an insecticide that is useful against mites, which are a common problem for cultivators
  • carbamates: function as an insecticide, similar to organophosphates, but with decreased dermal toxicity and higher degradation
  • heterocyclics: function as a broad set of compounds with many industrial uses, including as pesticides
  • organochlorides: function as a broadly useful chemical in applications such as plastics, cleaning agents, insulators, and pesticides
  • organophosphates: function as the base of many insecticides and herbicides, valued for its easy organic bonding
  • pyrethroids: function as the base of most household insecticides and exhibits insect repellent properties

Solvents: In 2003, Canadian Rick Simpson published a recipe of sorts for preparing cannabis extract via the use of solvents such as naphtha or petroleum ether. Claiming the resulting oil helped cure his skin cancer, others hoping for a cure tried it, and the solvent method of preparation grew in popularity. Dubious healing claims aside, the solvent extraction method remains viable today, though it has evolved over the years to include less harmful solvents such as supercritical carbon dioxide, which has low toxicity, low environmental impact, and beneficial extraction properties.[17][25][26] However, chemical solvents are still used, and if not evaporated out properly, the remaining solvents can be particularly harmful to sick patients using the extract. As for what solvents should be tested for, it gets a bit trickier, though Chapter 467 of United States Pharmacopeia and The National Formulary, the Oregon Health Authority's December 2015 technical report on contaminant testing of cannabis, and the Massachusetts Department of Public Health's response to public comments on cannabis testing provide helpful guidance. Listed solvents include benzene, butane, cumene, dimethoxyethane, ethanol, hexane, pentane and propane, among others.[19][8][10][17][24][27][28]

Heavy metals: 2013 research on contaminant testing on the behalf of Washington State provides insights into heavy metals and why they're looked for in cannabis testing. That research, as well as other more recent sources, tell us[19][8][10][17][29]:

  • Heavy metals contribute to several health problems, including those of a neurological nature.
  • Cannabis can "hyperaccumulate metals from contaminated soils."
  • Research parallels can be found in tobacco research and how the FDA regulates heavy metal content in foods.
  • The most prominently tested heavy metals include arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), and nickel (Ni).

Mycotoxins and microorganisms: "The ideal conditions for cannabis growth are also ideal for the growth of potentially harmful bacteria and fungi, including yeast and molds," say Shimadzu's Scott Kuzdzal and William Lipps, "therefore microbial contamination poses health risks to consumers and immunocompromised individuals."[9] In truth, these concerns have already borne out. In fact, the University of California, Davis reported in February 2017 one of its patients had contracted an incurable fungal infection from inhaling aerosolized marijuana. They later tested 20 marijuana samples from Northern California dispensaries—using specialized techniques—and found a wide variety of potentially hazardous microorganisms.[30]

The degree to which such contaminants commonly appear in grown and stored cannabis material and to which microbiological contaminants should be tested is not clear, however. As mentioned previously, the U.S. EPA has historically had little in the way of significant guidance on cannabis testing, including microbiological contaminants.[31] Like heavy metal testing, parallels are drawn from microbial testing guidelines and standards relating to tobacco and food, where they exist.[31] As warm, moist environments are conducive to microorganism growth, maintaining stable moisture levels during cultivation and storage is essential. Regularly measuring water activity—how moist something is—is particularly useful as a front-line preventative tool to better ensure microbial growth is limited.[24] Regardless, testing of some kind is still required by many U.S. states, including for organisms such as[19][9][10][17][24][30][31][32][33]:


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