What is “Total THC” and Does It Matter?
I’m frequently asked whether or not a certain hemp strain is “compliant” (ie, lawful). Typically, this occurs when a client sends me a certificate of analysis (COA) showing values for the concentration levels of various cannabinoids, including tetrahydrocannabinol (THC), in the hemp strain at issue. The client always wants to know if the THC levels are ok.
According to the Agricultural Improvement Act of 2018 (2018 Farm Bill) lawful hemp is distinguished from unlawful marijuana by virtue of its delta-9 (∆9) THC concentrations. Hemp is defined as cannabis sativa L with ∆9 THC concentrations that do not exceed three tenths of one percent (0.3%) on a dry weight basis. For this reason, when I receive a client’s COA I immediately look at the ∆9 THC values. If they do not exceed 0.3%, then I tell my client the hemp is compliant. It usually takes five or ten seconds. That’s when my client says, “Are you sure?”
I should note that my clients understand how to read a COA, and they always know when the ∆9 THC concentrations in their COA exceed 0.3%. In fact, I have never been asked whether a hemp strain is compliant in circumstances where the ∆9 THC exceeded 0.3%. So, what gives? Why do so many of my clients call me to ask about whether their hemp is compliant when they know that its ∆9 THC levels do not exceed 0.3%? And why do they say, “Are you sure?” when I say that their hemp is lawful? The answer has to do with tetrahydrocannabinolic acid (THCA) and what has become known as the “Total THC” argument.
In this article I will describe what is meant by “Total THC”, discuss why it has become an issue, lay out the arguments that support it, and conclude by arguing that the concept of “Total THC” is misplaced and not supported by the plain language of the 2018 Farm Bill. As a postlude I will explain why adopting the Total THC position is bad public policy, regardless of its legality.
[Editor’s note: The USDA’s October 29, 2019 issuance of the Final Interim Rule regarding hemp requires pre-harvest testing to take into account “total THC” for compliance. While this article argues that such a regulation was neither mandated by the statute nor good public policy, keep in mind that the USDA’s regulations are currently the law. -October 29, 2019]
There are various forms of THC. The two most common are ∆9 THC and THCA. (The “A” stands for “acid”.) ∆9 THC is the “neutral” form of THC. As most people know, it is the cannabinoid known for its psychoactive effects: it gets you high. ∆9 THC is commonly referred to simply as “THC”. (Although it’s a bit more cumbersome, I will use the full term “∆9 THC” in this article for clarity.)
THCA is a non-psychoactive cannabinoid commonly found in cannabis plants, including both marijuana and hemp. It is the acidic form of THC. According to the 2018 Farm Bill, neither its presence nor its concentration in a particular hemp plant is relevant to a determination of the plant’s legal status. Although this should be the end of the issue, it is actually the beginning. But, before delving into the arguments used to support the total THC position, it is important to understand some basic issues regarding decarboxylation and cannabis testing.
There are several methods for testing the ∆9 THC concentrations in a hemp sample. The two most common are gas chromatography (GC) and high-performance liquid chromatography (HPLC). (Note: You can read a more in-depth discussion of these testing methods here.)
When a hemp sample is analyzed using HPLC, one of the most common and reliable testing methods for botanicals, the cannabinoids remain unchanged and an accurate reading of their concentrations is obtained. In other words, an HPLC test of a hemp sample will reveal exactly the amount of ∆9 THC, along with any other cannabinoids, terpenes, and other phytonutrients, in the sample.
When THCA is heated it undergoes a chemical process through which it loses a carboxyl ring and transforms into a different molecule. This process is called decarboxylation. The molecule that THCA transforms into when it is decarboxylated is ∆9 THC, the molecule that determines the legal status of a hemp plant. As opposed to HPLC, the GC testing method heats up a sample in order to separate out its constituent parts to measure them. The heat it produces is sufficient to decarboxylate THCA in a hemp sample. In other words, the GC testing method creates the very molecule that it is measuring. This is loosely akin to a radar gun that speeds up the car it is clocking or a thermometer that heats up the water it is measuring.
By any reasonable view, GC is an improper test for measuring ∆9 THC levels in a hemp sample. By creating ∆9 THC, the GC method significantly increases the likelihood that the sample it measures will test “hot” (ie, that ∆9 THC concentrations will exceed 0.3%), resulting in the hemp crop from which the sample was taken being deemed non-compliant.
The obvious defect in the GC method for testing hemp, particularly when HPLC testing is available, begs the question of why GC should even be considered as an option. Surprisingly, GC appears to be used more often than HPLC for hemp testing. This is largely due to a misplaced belief that hemp should be tested for its “total available” or “total potential” THC concentrations. This position is flawed for several reasons. However, before explaining why it is flawed, it is important to understand what is meant by “total THC” and the arguments that are used to support it.
“Total THC” refers to the legal argument that in order for a particular cannabis sample to meet the definition of “hemp” set forth in the 2018 Farm Bill both the ∆9 THC and the THCA concentrations must be taken into consideration. Specifically, in order to determine whether a specific hemp sample is legally compliant the ∆9 THC levels in a hemp sample must be added to 87.7% of the THCA levels in a hemp sample. (Note: The short reason for this is that ∆9 THC is only 87.7% of the molecular weight of THCA. I’ll explain it in more detail, below.) If the sum of these two figures does not exceed 0.3% then the hemp sample is lawful. If it exceeds 0.3% it is unlawful.
For example, if a hemp sample has ∆9 THC concentrations of 0.10% and THCA concentrations of 0.20%, then the “total THC” is 0.10% + (0.20% x 87.70%) = 0.28%. Under the Total THC view, this sample is compliant. However, a sample with the same ∆9 THC concentrations of 0.10% and THCA concentrations of 0.30% is not compliant because it has “total THC” concentrations of 0.10% + (0.30% x 87.70%) = 0.36%. In this second example, neither the ∆9 THC nor the THCA levels exceed 0.3%; however, added together they exceed (slightly) the legal limit of 0.3%. Therefore, the sample is unlawful “hot” hemp.
The Arguments in Support of Total THC
There are several arguments in support of the Total THC position. I will describe them here and then respond in seriatim (in serial order), below. I should note that in coming to understand these arguments over the past several months, which I have attempted to present in as compelling a manner as possible, I spoke with a number of very smart, impassioned people. Although these arguments, if generally accepted, would do great harm to the hemp industry, no one with whom I spoke had bad faith or any apparent ill motive towards the hemp industry. In fact, most are participants in it. To me, this is concerning. If the very people whose livelihoods would be negatively impacted by widespread adoption of these arguments are seduced by them, they are very powerful tools in the hands of those who would use them to subvert the industry or twist it to their benefit.
The first argument in support of the “total THC” position is scientific. Under this argument, THCA is composed of ∆9 THC. Specifically, it is composed of 87.7% ∆9 THC. Another way of thinking about it is that THCA “contains” ∆9 THC in concentrations up to 87.7%. Therefore, in order to obtain an accurate reading of the ∆9 THC levels in a hemp sample the ∆9 that is part of the THCA must be counted in addition to the ∆9 THC that is not bound up in THCA molecules. The reason THCA must be counted is because the 2018 Farm Bill definition of “hemp” is the cannabis plant and “any part” of it, “including…. acids… with a ∆9 tetrahydrocannabinol concentration of not more than 0.3 percent”. Since one of the plant’s acids (ie, THCA) is composed of 87.7% ∆9 THC, it must be included in the equation.
The second argument is based on one of the particular uses of hemp, namely, inhaling it. This is done by smoking or vaping the hemp, both of which heat it. According to this argument, THCA represents “available” or “potential” ∆9 THC. If a hemp sample is decarboxylated by heating it (as when smoking or vaping), then up to 87.7% of the THCA is chemically converted to ∆9 THC. Congress intended to limit ∆9 THC to 0.3% by setting that as the legal limit. In order to do this, some ways of using hemp, such as smoking or vaping, must be taken into consideration. The only way to ensure that ∆9 THC levels do not exceed 0.3% for all users is to factor in the ∆9 THC levels that are “contained” within the THCA molecule. Therefore, the potential ∆9 THC in a sample must be taken into consideration by either using the equation I discussed above, or by using the GC testing method since it heats up and decarboxylates the sample.
The third argument in support of the “total THC” position is statutory. Specifically, this argument points to the language used in the 2018 Farm Bill that requires a state choosing to regulate hemp to submit a plan for approval by the Secretary of the USDA that includes, among other things, “a procedure for testing, using post-decarboxylation or other similarly reliable methods, ∆9 tetrahydrocannabinol concentration levels of hemp produced in the State or territory of the Indian tribe[.]” The argument is that the statute requires a state to use a “post decarboxylation” method  or a “similarly reliable” method that takes total THC into consideration. (“It’s right there in the statute” is a common phrase I hear.)
The Total THC Arguments Are Flawed
Despite how compelling the above arguments may appear to be, they are all flawed and cannot withstand careful analysis.
First, the so-called “scientific argument” is anything but scientific. Asserting that THCA “contains” or is “composed of” ∆9 THC is to misunderstand basic chemistry. THCA is a separate and distinct molecule from ∆9 THC. It does not “contain” ∆9 THC any more than wood “contains” ash or a caterpillar “contains” a butterfly. Certainly, burned wood can transform into ash (and other compounds) and a caterpillar can transform into a butterfly; however, arguing that wood “contains” ash and caterpillars “contain” butterflies is to enter into the realm of teleological philosophy, not science. The same is true for THCA and ∆9 THC. The fact is that decarboxylation, a chemical process, renders a THCA molecule into a ∆9 THC molecule by changing it: a carboxyl group is removed and carbon dioxide is released. In other words, ∆9 THC is not Han Solo trapped in carbonite by Jabba the Hutt, waiting to be released by his Rebel friends. A better analogy is Harrison Ford himself, who was transformed by Hollywood into Han Solo, an entirely different (though perhaps similar) person with different attributes.
Additionally, it is not even entirely accurate to say that THCA decarboxylates into 87.7% ∆9 THC. The most accurate statement is that ∆9 THC is 87.7% of the molecular weight of THCA. The decarboxylation process is not particularly efficient. In the best of conditions, only 75% of THCA can be converted into ∆9 THC. Usually, the percentage is much less. For this reason, and according to Leafly, “There is no official industry standard for calculating the total THC of a cannabis product and different producers and testing facilities calculate it in different ways.” So, even if the scientific argument for the total THC position was valid, simply using an equation that added 87.7% of the THCA concentrations to the ∆9 THC concentrations is inaccurate and greatly inflates the actual “total THC” (or total potential THC) in a hemp plant.
This leads to the second argument, which is that some hemp is inhaled by smoking or vaping and so the total “potential” (or total “available”) THC should be taken into consideration. The fact is that smoking and vaping hemp are both highly inefficient ways of decarboxylating THCA. Up to 70% of the “available THC” is lost in the process of smoking hemp due to pyrolysis (thermal decomposition) and side-stream smoke. Although vaporizing is more efficient, up to 50% of the “available THC” is lost. Thus, neither the mathematical method (using 87.7% as a multiple) nor an efficient decarboxylation testing method (such as GC) accurately capture the actual ∆9 THC that a hemp smoker or vaper receives. Both methods greatly inflate the amount. And, of course, this doesn’t take into consideration the fact that smoking or vaping hemp remain relatively novel. Most hemp is processed into oils or industrial products and is not decarboxylated. Why should hemp biomass that is destined to become CBD oil be subjected to decarboxylation testing for compliance when it will never be decarboxylated?
Finally, the third argument, which posits that measuring “total THC” is mandated by the statute, is flawed by reference to the plain language of the statute itself, which contemplates testing for ∆9 THC concentrations using a post-decarboxylation method or another similarly reliable method. In other words, the statute contemplates that a state will have two options for testing ∆9 THC levels in a hemp strain: (1) a “post decarboxylation” method, or (2) a non-post decarboxylation method, provided that it is a “similarly reliable” method for testing ∆9 THC. Setting aside the fact that “post decarboxylation” is not actually a testing method (see footnote 1, below), HPLC is a highly reliable and scientifically approved method of testing for ∆9 THC. It is, in fact, the most reliable method.
So, rather than supporting the argument that the statute requires a “post decarboxylation” method (presumably, GC), the plain language of the statute actually supports the opposite conclusion: that a state plan to regulate hemp can employ either a post-decarboxylation or a non-post decarboxylation method, provided that the latter is reliable. For reasons I assert below, it is vitally important for the USDA and the states to support farmers by adopting HPLC for compliance testing, a highly reliable method that is authorized by the statute.
The fact is that the argument for total THC by reference to the statute fails by the statute itself, which does not use the terms “total available” or “total potential” THC. Rather, the 2018 Farm Bill uses the term “delta-9 THC”. It would have been easy enough for Congress to use these terms (or even simply “THC”) rather than “delta-9” had they intended for THCA be a factor in determining the legal status of a hemp plant. Yet, they did not use these terms. Consequently, the concentrations of THCA in a hemp plant are irrelevant to its legal status.
Adopting Total THC is Bad Policy
Aside from legal considerations, the reason that this issue is important is because widespread adoption of the total THC position would be harmful to the hemp industry. In particular, it would harm hemp farmers. Requiring total THC concentrations to remain within 0.3%, rather than just limiting ∆9 THC, severely limits the hemp strains a farmer can grow. Growing hemp for cannabidiol (CBD) is difficult enough. Limiting the strains a farmer can grow places an undue and unnecessary burden on an already difficult activity.
Moreover, as states are beginning to submit their proposed regulatory plans under the 2018 Farm Bill to the USDA, the ones that take the total THC position, and in particular that require GC testing for compliance, place their farmers in a worse economic position than farmers in states who do not take this position and do not require GC compliance testing.
As a simple example, consider farmers in the fictional state of Xtucky, which requires hemp to be tested using GC and thus takes the total THC position. These farmers will compete in the market against farmers in the fictional state of Zarolina, that does compliance testing using HPLC and does not take THCA levels into consideration. The Xtucky farmers are constrained by the hemp strains they can use, while the farmers in Zarolina are not. Consequently, the Zarolina farmers will have a competitive edge in the market with more varieties to sell. They will also more easily find strains and phenotypes that work in their particular environments. And, of course, the Xtucky farmers will soon be competing with farmers in the international market, including farmers whose countries do not take the total THC view. There is no compelling reason to hamper hemp farmers in this way, particularly when the legal arguments used to support this position are flawed.
We all know the old saying that, “the Devil is in the details.” This is a good phrase to keep in mind as hemp regulations begin to emerge. A legal position that seems self-evident or even seductive may be anything but when analyzed under the proverbial microscope. Of the emerging positions, “total THC” is particularly fraught with Devils. Don’t be tempted.
 It is important to note that there is actually no such thing as a “post decarboxylation” testing method. Presumably, Congress intended to refer to GC but did so without receiving sufficient scientific input, thus resulting in a nonsensical term appearing in the statute. This nonsensical term has already caused considerable confusion.
May 10, 2019
Rod Kight is an attorney who represents lawful cannabis businesses. He speaks at cannabis conferences across the country, drafts and presents cannabis legislation to foreign governments, is regularly quoted on cannabis matters in the media, and maintains the Kight on Cannabis legal blog, where he discusses legal issues affecting the cannabis industry. You can contact him here.