Cannabis E-Cigarette Composition and Voltage Significantly Affect Toxicity, Study Finds
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While the e-cigarette or vaping associated acute lung injury (EVALI) outbreak in 2019 was relatively brief, lasting only around eight months before the CDC stopped its case reporting, EVALI did leave a lasting impact on drug research. Suddenly, all eyes were on the vape market. And this increased attention began to raise questions about the safety of vaping.
From the testing of products and biological samples it was quickly determined that the use of the diluent thickener vitamin E acetate (VEA) was strongly associated with EVALI cases in illicit market cannabis vape products and nicotine e-cigarettes. However, the actual pathogenesis of the EVALI disease is still unclear, as is scientists’ understanding of the properties of e-cigarette vapor.
Now, a new study from environmental health and nanotechnology experts at Harvard University has found that the operational voltage of vape equipment and the chemical composition of e-liquids can greatly affect the physicochemical properties of vape aerosols, as well as their toxicity and inflammatory effects on the body.
Operating voltage and e-liquid composition can significantly affect risk
The researchers previously developed a novel e-cig-exposure generation system (E-cig-EGS) platform, which was used here to vape e-cigarette cartridges into an environmental chamber under a precisely controlled puffing pattern and at a customizable operating voltage.
The e-liquids inside the vape cartridges were prepared by the researchers to mimic the composition of common cannabis and nicotine vape products. Three e-liquids representing cannabis vape products were made using delta-8 THC, varying concentrations of VEA (0%, 27%, 54% VEA), and a mixture of common terpenes. Delta-8 THC was used instead of delta-9 THC due to federal restrictions, the researchers explained, though they also noted that many of the products tested during the EVALI outbreak contained higher than normal ratios of delta-8 THC to delta-9 THC.
Three preparations of nicotine-based e-cigarettes were prepared, containing either 2% nicotine, 5% nicotine, or 5% nicotine with 2% menthol. A seventh e-liquid of 100 percent VEA was also tested.
The researchers bubbled the aerosol and gasses collected in the environmental chamber through standard cell culture medium, to infuse the media with the emissions. Human lung epithelial cells and human peripheral blood monocytes were then cultured on this media and used to study the effects of these emissions on the body. These specific cell lines were chosen as both represent the first line of defense in the airways against toxicants and particulate matter, and so are often involved in acute lung injury and EVALI cases.
Overall, the researchers saw minimal differences between the delta-8 THC and nicotine e-liquids and could not determine any strong correlation between any specific aerosol generated by the delta-8 THC/VEA vapes and the development of EVALI.
However, they did find significant differences between tests done using VEA alone and the more representative mixture. Specifically, compared to VEA alone, the nicotine-based e-liquids and the delta-8 THC/54 percent VEA e-liquid were significantly more potent at manipulating the proinflammatory cytokines and inducing cytotoxicity in the cell lines tested.
Particles generated by vaping penetrate deep into the lungs
In addition to testing the effects of these aerosols on human cell lines, the researchers also monitored the e-cigarette emissions in real-time within the environmental chamber. Using a variety of equipment, including a scanning mobility particle sizer spectrometer, aerodynamic particle sizer spectrometer, indoor air quality monitor, and a photoionization detector sensor, the researchers were able to examine the particulate matter (PM) and gaseous byproducts released in the aerosolized e-cigarette emissions.
“As evident from the real-time aerosol number-size distribution and time-integrated PM mass-size distribution [results], nearly all of the particles generated by vaping are in the fine particle size (<2.5 mm),” the researchers wrote. “Which means they are deposited in the deeper bronchoalveolar regions of the respiratory tract, where they could affect a range of adverse pulmonary outcomes depending on their chemical composition.”
They also found that the total particulate number concentrations (tPNC), concentration of total gaseous volatile organic compounds (tVOCs), and the concentration of CO2 emitted were very sensitive to e-liquid composition, though these changes did not appear to follow any universal trend. However, it was clear that the synthesized e-liquids performed differently to VEA alone. Raising the operational voltage from 3.7 V to 5 V was also seen to affect these metrics significantly. For example, higher voltages tended to raise the peak concentration of VOCs emitted.
Based on the results of this study, the researchers say that it is essential for future studies on e-liquids to avoid exclusively focusing on the toxicity and effects of individual diluents or additives. Instead, looking at these compounds of interest within a more complete e-liquid mixture is more likely to accurately reflect the physicochemical properties and bioactivity of real-world vape products.
VEA and EVALI
The first recorded cases of EVALI were reported in the summer of 2019 and reached a peak by that September. As of February 2020, when the CDC halted its regular case reporting, a total of 2,807 hospitalizations and 68 deaths had been recorded that were associated with EVALI.
Initially, all THC vape products were implicated in the outbreak as a great number of the cases reported tended to involve cannabis vape product users. However, further testing revealed the presence of VEA in the lungs of EVALI patients, which was traced back to illicit market vapes specifically.
“Vitamin E acetate is very heavily used in the illegal vaping market; 20, 30, 60 percent of a cartridge could be vitamin E acetate,” Dr Swetha Kaul, the chief scientific officer at Cannalysis, told Analytical Cannabis back in 2019. “Vitamin E acetate is extremely viscous and it’s cheaply available, so it makes a perfect cutting agent. So if you’re working on the illegal side and you want to fill more cartridges, it’s easier if you can cut it with something.”
Retrospective analysis of state cannabis laws backs up this illicit market distinction. A 2020 study found that states with a recreational cannabis market had significantly lower EVALI case rates than those with no legal access to cannabis or where only medical cannabis was available. Another recent study found that states that fell into the highest quintile of EVALI cases tended to enforce blanket cannabis prohibition or have a strict medical cannabis program with no provisions for home cultivation.