Proposed Caps on THC Concentration - Is There a Way to Balance Safety and Efficacy?

Posted on Behalf of  Heidi O'Neill, Alex Powell

While some states have fully legalized marijuana use, others allow only approved medical use or access to certain types of products. Recently, several states have proposed legislation to limit THC levels in these products. Over the last ten years, the mean THC concentration in cannabis samples seized by the DEA has increased from 9.75% in 2009 to 13.88% in 2019 (El Sohly et al., 2020). The consumer market has also changed. From 2014 to 2019, a shift occurred away from flower consumption towards higher potency concentrates for dabbing or vaping. Specifically, flower consumption has decreased below 50% in recent years, and concentrates have increased from 11% in 2014 to one-third of the market by 2019. (Burness, 2021).

THC Concentration Cap Legislation

As these more concentrated cannabis products increase in popularity, concerns about increased THC concentration have come to the attention of lawmakers. Policy changes in Colorado in 2016 limited the maximum THC concentration in retail edible products to 10 mg THC per serving (maximum of 100 mg per package) but did not address potency of non-edible products (CDPHE, 2020,p. 11). Recently, a number of states have introduced bills to limit THC levels in both flower and THC concentrate products (Holland, 2021). On June 24, 2021, Colorado’s Governor Polis signed HB21-1317 into law, which limits the amount of concentrated product (8 grams/day) that can be purchased in a day, with tighter restrictions for those aged 18-21 (2 grams/day). Another of this law’s provisions funds research into the mental health effects of high concentration THC use to address gaps in data (Poblete, 21).  Florida is also considering a medical marijuana THC concentration cap of 10% (HB1455) (Holland, 21). New Jersey’s medical marijuana law had a provision placing a 10% THC cap on cannabis products, but was quickly abandoned, and the law was amended (Holland, 2021). Caps have largely failed elsewhere, though Vermont limited flower at 30% THC and concentrates at 60% THC when it legalized marijuana in 2020 (Burness, 2021). Iowa’s THC cap in 2014 was 3% or less for qualifying patients, although by June, 2020, this limit was changed from a 3% THC cap to a per-patient purchase limit of 4.5 grams total THC over a 90-day period, or 50 mg a day (Holland, 2021). Within Colorado, THC levels were >15% in 92.9% of retail products sold, while THC concentrates averaged 56.6% in 2014 and 68.6% in 2017 (upper limit of 90%) (CDPHE, 2020,p. 10).  

Moving Forward- To Cap or Not To Cap

Proponents of a THC cap are mainly concerned with public health and safety, especially where access to high potency THC concentrates are available to those 18-21 years old with medical marijuana cards (Burness, 2021). In a 2020 report, the Colorado Department of Public Health & Environment (CDPHE) reported that there is “moderate” evidence that adolescents and young adults who use higher THC concentration products (>10% THC) are more likely than non-users to have mental health symptoms and disorders (CDPHE, 2020,p. 35). While some studies suggest a connection between mental health outcomes and cannabis use, comorbidities such as drug, tobacco, and alcohol use, or genetic factors, such as variations in the AKT1 or COMT genes, may also predispose cannabis users to an increased risk of developing mental health effects, and should be considered (Di Forti et al., 2012; Caspi et al., 2005). Ultimately, this report concluded that “[s]pecific to THC concentrate products, evidence is insufficient when examining the association to dependence and acute health effects” (CDPHE, 2020p. 52).

Those arguing against a THC concentration cap acknowledge that chronic pain and cancer patients needing higher doses of cannabis for pain relief would be required to increase product use to obtain that relief, which, in of itself, could increase risk. Establishing a THC potency cap has also been compared to “soft prohibition” of the cannabis industry, akin to limiting high proof alcohol sales (Burness, 2021).

Ultimately, more studies are needed to evaluate high concentration product safety and their potential links to health effects, both beneficial and detrimental. Recent movement in the U.S. Senate Caucus on International Narcotics Control proposes passage of S.253, the Cannabidiol and Marihuana Research Expansion Act, which would reduce barriers to more comprehensive research (U.S. Congress, 2021). A component of this effort is a collaboration between the National Institutes of Health (NIH) and the FDA in order to increase research into the short- and long-term effects of concentrated cannabis product use (U.S. Congress, 2021). Further research into high-concentration product safety can both provide guidance to the industry, and increase consumer confidence.

Cardno ChemRisk scientists have extensive experience evaluating health risks posed by potential metals, pesticides, and microbial contamination, using state-of-the-art risk assessment methods. As part of the cannabis initiative, our team offers a multidisciplinary approach to resolving health and safety issues related to cannabis and cannabis-derived products. For more information on Cardno ChemRisk’s capabilities, please contact Elise de Gandiaga or Dr. Heidi O’Neill.