Total THC and the USDA Rule- A Data Driven Analysis
Editor’s note: This article is a modified version of a comment to the USDA written by Marion Snyder, PhD, Chief Scientific Officer of Clearwater Biotech. In this article, Dr. Snyder distills her analysis of hemp testing during the 2018 and 2019 growing seasons. Based on her data, Dr. Snyder finds that requiring “Total THC” concentrations not to exceed 0.3%, rather than just limiting ∆9-THC, severely limits the hemp strains a farmer can grow. Alarmingly, she concludes that farmers in states that have not legalized marijuana will not be able to grow strains of hemp for CBD because the “Total THC” in hemp CBD strains by nature exceeds the 0.3% threshold at maturity. -Rod Kight
The USDA’s October 29, 2019 issuance of the Final Interim Rule (Rule) regarding hemp requires pre-harvest testing to take into account total tetrahydrocannabinol (THC) (Total THC) to determine compliance. (Click here for a discussion of Total THC. -Editor) In this analysis, we argue that such a regulation does not take into account the natural THC content of hemp and is not good public policy. In short, the 0.3% Total THC limit set forth in the Rule will do great harm to the hemp industry.
TYPES OF THC
There are various forms of THC. The two most common are delta-9 (∆9) THC and THCA. (The “A” is for acid.) ∆9-THC is commonly referred to simply as THC and is the cannabinoid known for its psychoactive effects. THCA is a non-psychoactive cannabinoid found in higher concentrations in cannabis plants. The Agricultural Improvement Act of 2018 (2018 Farm Act) distinguishes hemp from marijuana by limiting its ∆9-THC concentrations. Hemp is defined as cannabis sativa with ∆9-THC concentrations less than or equal to 0.3% on a dry weight basis.
THC TESTING METHODS
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). 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 and THCA along with CBD and many other cannabinoids in the sample. On the other hand, GC subjects the sample to high heat, which converts the acid cannabinoids in the plant to the neutral form (eg, THCA converts to ∆9-THC and CBDA converts to CBD) so the ∆9-THC and CBD content reported in the plant is overestimated. (Click here for a full discussion of analytical testing methods. -Editor)
TESTING METHODS VS. HEMP VIABILITY
Figure 1, below, shows the distribution of ∆9-THC percentages detected in hemp flower samples sent to an ISO accredited laboratory using HPLC-UV detection methodology. This data shows that 97.4% (370 out of 380) samples fell at or below the 0.3% limit for ∆9-THC and would be considered compliant based on the original interpretation of the 2018 Farm Bill.
The USDA’s October 29, 2019 issuance of the Rule regarding hemp requires pre-harvest testing to take into account Total THC for compliance rather than just ∆9-THC. 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 the THCA levels in a hemp sample. If the sum of these two figures exceeds 0.3% it is unlawful.
Figure 2, below, shows the Total CBD (%) versus Total THC (%) in 380 hemp flower samples sent to an ISO accredited lab during the 2018 and 2019 growing seasons. This data shows that virtually all strains tested over the hemp growing season yield the same ratio of Total CBD to Total THC (21.7 to 1), such that Total CBD is approximately 20 times that of Total THC. In other words, as the hemp flower matures and the CBD increases, the total THC also increases, both predictably and consistently (0.1% increase in Total THC for every 2% increase in Total CBD) across the more than 50 strains tested. Using the 0.3% threshold for Total THC would dramatically limit the number of “legal” hemp plants. Specifically, only the more immature flower with lower CBD content would qualify as lawful (230/380). Requiring total THC concentrations to remain less than 0.3%, rather than just limiting ∆9-THC, severely limits the hemp strains a farmer can grow. Limiting the strains a farmer can grow places an undue and unnecessary burden on an already difficult activity.
THE TOTAL THC STANDARD WILL ELIMINATE CBD STRAINS
Perhaps our most important finding is that farmers in states that have not legalized marijuana will not be able to grow strains of hemp for CBD because the total THC in hemp CBD strains by nature exceeds the 0.3% threshold at maturity.
In order to ensure Total THC does not increase to more than 0.3%, farmers will need to carry the burden of more frequent testing. They must also harvest their crop less than half-way through the flowering season in the majority of cases.
Figure 1. Histogram showing Δ9-THC testing results for 380 hemp samples sent to an ISO accredited lab over 2018 and 2019 growing seasons. These HPLC-UV testing results show that 97.4% (370/380 samples) were below the 0.3% threshold for legal hemp.
Figure 2. Total CBD (%) versus Total THC (%) for 380 consecutive hemp samples sent to an ISO accredited lab during the 2018 and 2019 growing seasons. HPLC-UV was used to measure Total THC = Δ9-THC + 0.877*THCA and Total CBD = CBD + 0.877*CBDA.
December 3, 2019
This is a guest post by Marion Snyder, PhD. Dr. Snyder taught at Harvard University School of Medicine. She also led the development of the first clinical toxicology laboratory employing definitive LC-MS/MS testing at the renowned Brigham and Women’s Hospital in Boston, MA. She oversaw technical operations of the Greenville (SC) Health System clinical laboratories and, most recently, served as President of a well-recognized national reference laboratory.
Rod Kight is a hemp 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.
6 comments on “Total THC and the USDA Rule- A Data Driven Analysis”Add yours →
This process will put tremendous strains on the cbd industry. Many of our most popular strains will be eliminated by this process!
Thanks for your comment. I agree!
These are the first datasets we’ve seen on the relationship between THC and CBD. This blog is an exceptional source of current info for those with interests in the hemp sector.
The data also reflects the challenge in breeding CBD and THC in opposite directions. This supports the assumption that 30:1 CBD to THC is about the max with current breeding. The entire ruleset around THC will force the US into a Canadian/European model of utilizing industrial type strains with 4-8% CBD.
This will skew the industry. States that have legalized marijuana will have an unfair competitive advantage in the hemp industry. They will be able to grow CBD to full term. There will be no reason for anyone to purchase hemp from any state operating under the USDA rules simply because CBD content of their hemp will likely be below 10%. As we have seen this year, most processors will not purchase CBD under 10%
Rod, what are your thoughts about high CBG strains? Maybe smaller family-owned farms could make a switch to growing hemp for CBG, instead of trying to push the limits of current high-CBD strains beyond 6-8% total CBD; and risk their crop testing “hot”. To get around the total THC requirement, farmers could harvest their plants earlier in the budding phase and sell it for CBG extraction. I see CBG as the next big cannabinoid. I have used CBG in conjunction with CBD and find the effects, in terms of mood boosting and pain relief, to be better than using CBD alone.
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