title: Conventional and electronic cigarettes (e-cigarettes) have different smoking characteristics.
abstract: BACKGROUND
  Electronic cigarettes or e-cigarettes are marketed as tobacco-free nicotine delivery devices that have received little laboratory evaluation. In this study, the smoking properties of conventional and e-cigarettes were compared by examining the vacuum required to produce smoke (conventional cigarettes) or aerosol (e-cigarettes) and the density of the smoke/aerosol over time.
  
  
  METHODS
  Vacuum was measured using a manometer coupled to a smoking machine. The density of aerosol or smoke was measured spectrophotometrically. E-cigarettes were subjected to smoke-out experiments in which vacuum and aerosol density were measured until each cartridge was exhausted.
  
  
  RESULTS
  The vacuum required to smoke conventional cigarettes varied among the eight brands tested. Lights and ultra-light brands required stronger vacuums to smoke than unfiltered and regular filtered brands. Except for one brand, higher vacuums were required to smoke e-cigarettes than conventional brands. Smoke/aerosol density was stable for conventional brands and for e-cigarettes over the first 10 puffs; however, aerosol density of e-cigarettes dropped during subsequent smoking, and higher vacuums were required to produce aerosol as the puff number increased. While conventional cigarettes were uniform in their smoking behavior within brands, vacuum and density varied within brands of e-cigarettes.
  
  
  CONCLUSIONS
  Generally, e-cigarettes required stronger vacuums (suction) to smoke than conventional brands, and the effects of this on human health could be adverse. The amount of aerosol produced by e-cigarettes decreased during smoking, which necessitated increasing puff strength to produce aerosol. The decreased efficiency of aerosol production during e-cigarette smoking makes dosing nonuniform over time and calls into question their usefulness as nicotine delivery devices.
authors.affiliation: Department of Cell Biology & Neuroscience, University of California, Riverside, CA 29521, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Trtchounian
authors.forename: Monique
authors.initials: M
authors.lastname: Williams
authors.forename: Prue
authors.initials: P
authors.lastname: Talbot
mesh_terms: D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects / Q000032:analysis* / Q000517:prevention & control; D009330:Nebulizers and Vaporizers; D009538:Nicotine / Q000009:adverse effects / Q000032:analysis*; D012906:Smoke / Q000009:adverse effects / Q000032:analysis* / Q000517:prevention & control; D012907:Smoking / Q000009:adverse effects; D016540:Smoking Cessation / Q000379:methods; D013053:Spectrophotometry; D014030:Tobacco, Smokeless / Q000009:adverse effects / Q000032:analysis*; D014618:Vacuum
chemical_list: D012906:Smoke; D009538:Nicotine