Comparing the cancer potencies of emissions from vapourised nicotine products including e-cigarettes with those of tobacco smoke

Introduction:
This text is a research paper by William E. Stephens that compares the cancer potencies of various nicotine-delivering aerosols, including tobacco smoke, e-cigarette vapors, and a prototype heat-not-burn (hnB) device. The paper aims to derive a procedure for overcoming the problem of incompatible emissions data sets, reduce the information on carcinogenic risk represented by multiple individual compounds to a single latent variable (potency), and calculate cancer potencies from published emissions data. The paper also compares various nicotine product risks by factoring in exposure estimates.

Key Points:

* The study modelled the cancer potencies of various nicotine-delivering aerosols using published chemical analyses of emissions and their associated inhalation unit risks.
* The cancer potencies were compared using a conversion procedure for expressing smoke and e-cigarette vapors in common units.
* Lifetime cancer risks were calculated from potencies using daily consumption estimates.
* The aerosols form a spectrum of cancer potencies spanning five orders of magnitude from uncontaminated air to tobacco smoke.
* E-cigarette emissions span most of this range with the preponderance of products having potencies<1% of tobacco smoke and falling within two orders of magnitude of a medicinal nicotine inhaler.
* a small minority of e-cigarette samples have much higher potencies, which tend to be associated with high levels of carbonyls generated when excessive power is delivered to the atomizer coil.
* Samples of a prototype hnB device have lower cancer potencies than tobacco smoke by at least one order of magnitude, but higher potencies than most e-cigarettes.
* Mean lifetime risks decline in the sequence: combustible cigarettes > hnB > e-cigarettes (normal power) ≥ nicotine inhaler.

Main Message:
The main message of the study is that e-cigarette emissions generally have much less carcinogenic potency than tobacco smoke. however, there are circumstances in which the cancer risks of e-cigarette emissions can escalate, sometimes substantially. These circumstances are usually avoidable when the causes are known, which highlights the need for increased user awareness and personal involvement in reducing risk. The study also suggests that hnB devices have lower cancer potencies than tobacco smoke but higher potencies than most e-cigarettes, while the mean lifetime risks decline in the sequence: combustible cigarettes > hnB > e-cigarettes (normal power) ≥ nicotine inhaler. Overall, the study provides important insights into the relative harm caused by inhaling the aerosol emissions of various nicotine-delivering products, which can inform public health policies and regulations.

Stephens, William E. “Comparing the Cancer Potencies of Emissions from Vapourised Nicotine Products Including E-Cigarettes with Those of Tobacco Smoke.” Tobacco Control 27, no. 1 (January 2018): 10–17. https://doi.org/10.1136/tobaccocontrol-2017-053808.