The whole harm reduction and reduced exposure frameworks that the FDA and others use to assess alternative inhaled tobacco products assumes that the specific details of the aerosol that these products deliver to users has a substantial effect on risks. New research by Poonam Rao, Matt Springer, and their colleagues at UCSF raises serious questions about this framework, at least in terms of the influence of different products on blood vessel function.
As Poonam Rao nicely explained in her presentation at the 2022 UCSF Tobacco Center It’s About a Billion Lives symposium (starting at 1 hr 19 min), arteries are constantly adjusting how big they are in order to deliver the right amount of blood flow to your body. This adjustment, known as flow mediated dilation (FMD), involved arteries getting bigger (“dilating”) when there is a need for more blood flow. This ability to dilate is a major element of maintaining balance in the cardiovascular system. Compromised FMD is a predictor of heart disease.
You can measure FMD by blocking an artery briefly, then measuring how much bigger the artery gets when you release the blockage so that the blood can surge through. Less dilation — lower FMD — indicates compromised arterial function.
We have know for a long time that smoking and passive smoking compromise FMD and more recent research has shown similar effects for e-cigarettes, the heated tobacco product IQOS, and cannabis smoke and aerosol.
Now, Dr. Rao and her colleagues have published “Comparable Impairment of Vascular Endothelial Function by a Wide Range of Electronic Nicotine Delivery Devices in Nicotine and Tobacco Research that extends this comparison.
Specifically, they measure immediate changes in FMD in rats exposed to air (as a control group) a wide range of e-cigarettes with and without nicotine and different flavors, IQOS, an ultrasonic e-cigarette that did not use a coil to aerosolize the e-liquid, and Marlboro Red cigarettes. The bottom line (shown in the figure above, which is taken from their paper): Except for the air — which as expected had no effect on FMD — all the other products similarly depressed artery function (FMD).
What this means is that minor changes in how the inhaled aerosol is generated doesn’t matter. In particular, combustion is not all that important. FDA and others need to seriously rethink how they relate specific exposures to specific risks. The details may not be as important as people — including me — thought.
Here is the abstract of the paper:
Introduction: Electronic nicotine delivery systems (ENDS; i.e., vaping devices) such as e-cigarettes, heated tobacco products, and newer coil-less ultrasonic vaping devices are promoted as less harmful alternatives to combustible cigarettes. However, their cardiovascular effects are understudied. We investigated whether exposure to aerosol from a wide range of ENDS devices, including a new ultrasonic vaping device, impairs endothelial function.
Methods: We measured arterial flow-mediated dilation (FMD) in rats (n=8/group) exposed to single session of 10 cycles of pulsatile 5s exposure over 5 minutes to aerosol from e-liquids with and without nicotine generated from a USONICIG ultrasonic vaping device, previous generation e-cigarettes, 5% nicotine JUUL pods (Virginia Tobacco, Mango, Menthol), and an IQOS heated tobacco product; with Marlboro Red cigarette smoke and clean air as controls. We evaluated nicotine absorption and serum nitric oxide levels after exposure, and effects of different nicotine acidifiers on platelet aggregation.
Results: Aerosol/smoke from all conditions except air significantly impaired FMD. Serum nicotine varied widely from highest in the IQOS group to lowest in USONICIG and previous generation e-cig groups. NO levels were not affected by exposure. Exposure to JUUL and similarly acidified nicotine salt e-liquids did not affect platelet aggregation rate. Despite lack of heating coil, the USONICIG under airflow conditions heated e-liquid to ~77˚C.
Conclusions: A wide range of ENDS, including multiple types of e-cigarettes with and without nicotine, a heated tobacco product, and an ultrasonic vaping device devoid of heating coil, all impair FMD after a single vaping session comparably to combusted cigarettes.
Implications: The need to understand the cardiovascular effects of various ENDS is of timely importance, as we have seen a dramatic increase in the use of these products in recent years, along with the growing assumption among its users that these devices are relatively benign. Our conclusion that a single exposure to aerosol from a wide range of ENDS impairs endothelial function comparably to cigarettes indicates that vaping can cause similar acute vascular functional impairment to smoking and is not a harmless activity.
The full citation is: Rao P, Han DD, Tan K, Mohammadi L, Derakhshandeh R, Navabzadeh M, Goyal N, Springer ML. Comparable Impairment of Vascular Endothelial Function by a Wide Range of Electronic Nicotine Delivery Devices. Nicotine Tob Res. 2022 Jan 31:ntac019. doi: 10.1093/ntr/ntac019. Epub ahead of print. PMID: 35100430. It is available here.