The prevalence of the use of e-cigarettes is increasing. E-cigarettes are marketed as an alternative to smoking tobacco that only produces harmless water vapor, with no adverse impact on indoor air quality. However, published literature seems to show that e-cigarettes are not harmless. (1) Photo 1 shows an e-cigarette user exhaling a dense visible aerosol into the surrounding air. This visible aerosol consists of condensed submicron liquid droplets, which contain many chemicals including some that are carcinogenic, such as formaldehyde, metals (cadmium, lead, nickel), and nitrosamines.
Figure 1 is a schematic of typical e-cigarette components. E-cigarettes contain a liquid, typically propylene glycol and/or glycerol, that include varying amounts of nicotine (e.g., 0 to 36 mg/mL) as well as flavorants. A wicking material is used to transport the liquid by capillary action from a reservoir to the heater. When the user draws on the e-cigarette, a sensor detects the draw and a microprocessor activates the heater, which vaporizes the fluid to produce a saturated vapor at an elevated temperature (i.e., > 350[degrees]C [662[degrees]F] in the center of the heating [unit.sup.2]). Propylene glycol, glycerol, and nicotine are liquids with relatively high boiling points: propylene glycol (188[degrees]C [370[degrees]F]), glycerol (290[degrees]C [554[degrees]F]), and nicotine (247[degrees]C [477[degrees]F]). Consequently, the vaporized fluid immediately condenses upon leaving the heating element, forming an aerosol of submicron spherical liquid droplets with the visible appearance of smoke or fog.
While the word vapor is used to describe what e-cigarettes produce, and vaping is a term used to describe the process of inhaling from an e-cigarette, the emissions out of the mouthpiece are not actually a vapor, which is a gas, but rather they are primarily an aerosol. This aerosol consists of submicron particles of the condensed vapor of glycols containing the nicotine and flavorants. So users are not vaping, but rather they are aerosolizing.
What are the chemical emissions from e-cigarettes?
We searched through the published literature for information on the chemical emissions from e-cigarettes. We then used these chemical emissions to calculate the direct exposure to users and the indirect (passive) exposure to non-users, with usage and exposure assumptions selected to produce worst-case exposure scenarios. For both the direct and indirect exposures, we calculated the hazard quotients as the ratio of the calculated exposures to both cancer and non-cancer health exposure guidelines. Hazard quotients in excess of 1.0 indicate a health risk.
The paper by Goniewicz et. al. (3) contained the largest study of chemical emissions from e-cigarettes and forms the primary basis for our analyses. In this paper the chemical emissions of 11 chemicals, including carbonyl compounds, volatile organic...
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