Vaping Cannabinoid Acetates Leads to Ketene Formation

Tetrahydrocannabinol (THC) acetates are semi-synthetic psychoactive cannabinoids. ∆8-THC, an unregulated isomer of ∆9-THC, has become increasingly available, particularly in states where ∆9-THC is illegal. However, there is scant research concerning these cannabinoid acetates, and therefore, the health risks of ingesting these compounds are not understood.

These cannabinoid acetates possess a phenyl acetate substructure that can convert to ketene under when heated. Ketene is a highly reactive poisonous gas that is lethal at just 5 ppm. ∆8-THC acetate is a relatively new product online and in vape shops. It has a similar substructure to vitamin E acetate, which has been shown to form ketene during vaping by Doctor Robert Strongin’s research lab. [1] A recent study out of the Strongin lab investigated the potential for ketene formation from vaping ∆8-THC acetate. [2] Ketene was consistently observed in vaped condensates from ∆8-THC acetate.

 

The Experiments

A commercial formulation containing ∆8-THC acetate was purchased from Hydro-Hemp in a pre-packaged vape cartridge. Analysis of the commercial sample was performed using gas chromatography coupled with mass spectrometry operated in electron impact ionization mode. The sample contained equal amounts of Δ8-THC acetate and Δ8-THC, in addition to terpenes.

 

Dabbing Experiments

An electronic nail (“e-nail”) was used in the dabbing experiments. The e-nail temperature was set to 378°C to be consistent with prior dabbing studies that the Strongin lab has conducted, and based on a survey of social media. A ketene trapping agent was also included.

 

Vaping Experiments

The researchers employed a LUXE S mod kit for the vaping experiments. The vaping trials were run at 10 W. The pre-packaged vape cartridge containing ∆8-THC acetate was vaped into tubing attached to an impinger containing the ketene trapping agent. A Smoking Machine was subsequently attached to the impinger and used as a source of vacuum.

The researchers detected ketene formation from different cannabinoid acetates in both the dabbing and vaping experiments. When one dabs, the amount of vapor inhaled can approach full lung capacity. The National Institute of Occupational Safety and Health has set a 5.0 ppm threshold for ketene exposure equating to 8.6 mg per cubic meter. For a 0.005 m³ lung volume, the NIOSH threshold is 0.043 mg of ketene. Dabbing the ∆8-THC acetate sample produced 0.022 mg of ketene. The study authors report that “the actual levels of ketene from commercial products will typically be lower than what we have determined herein since other ingredients will likely also be present in the starting products.”

Even if ketene levels produced from commercial products are lower, Strongin’s team pointed to concerns of chronic exposure, since toxicological data is deficient, and what data there is on acute exposure to ketene is old and incomplete.

The vaping experiment showed that ketene formed when the pen was operated at a manufacturer’s recommended power level. The study authors pointed to variables like elevated temperature settings, catalysis, viscosity, airflow, device quality, and user behavior as potentially intensifying ketene formation.

This study shows that vaping conditions can produce ketene at lower temperature settings than previously studied. All four acetates, including three purified acetates and one commercial formulation, consistently showed ketene emissions whether via dabbing or vaping.

 

References

[1] Strongin RM. Toxic ketene gas forms on vaping vitamin E acetate prompting interest in its possible role in the EVALI outbreak. Proc Natl Acad Sci USA. 2020;117(14):7553-7554. [journal impact factor = 12.78; times cited = 6]

 

[2] Munger KR, Jensen RP, Strongin RM. Vaping cannabinoid acetates leads to ketene formation. Chem Res Toxicol. 2022;35(7):1202-1205. [journal impact factor = 3.973; times cited = 0]