Assessing electronic cigarette emissions: linking physico-chemical properties to product brand, e-liquid flavoring additives, operational voltage and user puffing patterns

Inhal Toxicol. 2018 Feb;30(2):78-88. doi: 10.1080/08958378.2018.1450462. Epub 2018 Mar 22.


Users of electronic cigarettes (e-cigs) are exposed to particles and other gaseous pollutants. However, major knowledge gaps on the physico-chemical properties of such exposures and contradictory data in published literature prohibit health risk assessment. Here, the effects of product brand, type, e-liquid flavoring additives, operational voltage, and user puffing patterns on emissions were systematically assessed using a recently developed, versatile, e-cig exposure generation platform and state-of-the-art analytical methods. Parameters of interest in this systematic evaluation included two brands (A and B), three flavors (tobacco, menthol, and fruit), three types of e-cigs (disposable, pre-filled, and refillable tanks), two puffing protocols (4 and 2 s/puff), and four operational voltages (2.2-5.7 V). Particles were generated at a high number concentration (106-107 particles/cm3). The particle size distribution was bi-modal (∼200 nm and 1 µm). Furthermore, organic species (humectants propylene glycol and glycerin, nicotine) that were present in e-liquid and trace metals (potassium and sodium) that were present on e-cig heating coil were also released into the emission. In addition, combustion-related byproducts, such as benzene and toluene, were also detected in the range of 100-38,000 ppbv/puff. Parametric analyzes performed in this study show the importance of e-cig brand, type, flavor additives, user puffing pattern (duration and frequency), and voltage on physico-chemical properties of emissions. This observed influence is indicative of the complexity associated with the toxicological screening of emissions from e-cigs and needs to be taken into consideration.

Keywords: Electronic cigarette; exposure assessment; inhalation toxicology; particulate matter; smoking; vaping.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerosols
  • Air Pollutants / analysis*
  • Benzene / analysis
  • Electronic Nicotine Delivery Systems*
  • Flavoring Agents
  • Fruit
  • Glycols / analysis
  • Menthol
  • Metals / analysis
  • Nicotine / analysis
  • Particle Size
  • Tobacco
  • Toluene / analysis
  • Vaping*


  • Aerosols
  • Air Pollutants
  • Flavoring Agents
  • Glycols
  • Metals
  • Menthol
  • Toluene
  • Nicotine
  • Benzene