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Aerosol Constituents

An e-cigarette, when operating correctly, should simply transfer the components of the e-liquid formulation into the aerosol for inhalation.

However, any impurities present may also be transferred, and other substances can be formed if the device is not operating correctly, for example if the heating coil gets too hot and causes thermal degradation of the e-liquid constituents or components of the e-cigarette, or there are reactions between constituents and/or degradation products. Some of the potential impurities and degradation/reaction products are toxic.

The characteristics of the aerosol depend mainly on the power applied to the heating coil, the physical characteristics of the formulation (viscosity, wettability and so on) and the specific heat capacity of the formulation. In addition, the pressure drop, airflow rate and aerosol density, may vary between and within devices[1][2].

Nicotine and other alkaloids

In an investigation of numerous cartridges and refills[3], formulations were tested in sixteen devices with a smoking simulator using puffing parameters derived from user puffing profiles. This delivered nicotine yields of 0.3±0.2mg – 8.7±1.0mg (from 150 puffs) and 0.5±0.1mg – 15.4±2.1mg (from 300 puffs).

A further study[4] investigated the yields generated from 10 puffs of an e-cigarette under two puffing regimes and three durations. The findings suggested that moving from ISO to intense puffing parameters (puff volume, duration and frequency) shows around 50% increase in particulate matter (PM) and nicotine yields – much less than the approximate threefold increase seen with conventional cigarettes; but that there were significant differences between different devices in terms of sensitivity to puff duration.

Recent analysis has shown that the other alkaloids and degradation products can be present at between 0 and 4.4% of the nicotine content, but for most of the samples tested were present at 1-2% of the nicotine[5].

Other constituents

Recent analyses have reported the presence of carbonyl compounds (formaldehyde, acetaldehyde, acrolein, and o-methylbenzaldehyde), volatile organic compounds (toluene and p-, m-xylene), tobacco-specific nitrosamines (NNN and NNK) and certain heavy metals (cadmium, nickel, lead) in the aerosols produced by a range of e-cigarettes, but at levels 9-450 times lower than the typical levels in cigarette tobacco smoke[6].


  1. Williams, M. and Talbot, P. 2011. Variability among Electronic Cigarettes in the pressure drop, airflow rate and aerosol production Opens new window. Nicotine & Tobacco Research, 13(12): 1276-1283
  2. Trtchounian, A., Williams, M. and Talbot, P. 2010. Conventional and Electronic cigarettes (e-cigarettes) have different smoking characteristics Opens new window. Nicotine & Tobacco Research, 12(9): 905-912.
  3. Goniewicz et al 2013. Nicotine levels in electronic cigarettes Opens new window. Nicotine & Tobacco Research, 15: 158-66.
  4. Taylor, M. 2012. Effect of puff duration and volume on the yields of e-cigarettes Opens new window. CORESTA Congress, Sapporo, 2012, Smoke Science/Product Technology Groups.
  5. Etter, J.F., Zäther, E. and Svensson, S. 2013. Analysis of refill liquids for electronic cigarettes Opens new window. Addiction, 108(9): 1671-1679. 
  6. Goniewicz, M. et al 2013. Levels of selected carcinogens and toxicants in vapour from electronic cigarettes Opens new window. Tobacco Control.
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