Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals

Abstract

Use of electronic cigarettes has grown exponentially over the past few years, raising concerns about harmful emissions. This study quantified potentially toxic compounds in the vapor and identified key parameters affecting emissions. Six principal constituents in three different refill "e-liquids" were propylene glycol (PG), glycerin, nicotine, ethanol, acetol, and propylene oxide. The latter, with mass concentrations of 0.4-0.6%, is a possible carcinogen and respiratory irritant. Aerosols generated with vaporizers contained up to 31 compounds, including nicotine, nicotyrine, formaldehyde, acetaldehyde, glycidol, acrolein, acetol, and diacetyl. Glycidol is a probable carcinogen not previously identified in the vapor, and acrolein is a powerful irritant. Emission rates ranged from tens to thousands of nanograms of toxicants per milligram of e-liquid vaporized, and they were significantly higher for a single-coil vs a double-coil vaporizer (by up to an order of magnitude for aldehydes). By increasing the voltage applied to a single-coil device from 3.3 to 4.8 V, the mass of e-liquid consumed doubled from 3.7 to 7.5 mg puff(-1) and the total aldehyde emission rates tripled from 53 to 165 μg puff(-1), with acrolein rates growing by a factor of 10. Aldehyde emissions increased by more than 60% after the device was reused several times, likely due to the buildup of polymerization byproducts that degraded upon heating. These findings suggest that thermal degradation byproducts are formed during vapor generation. Glycidol and acrolein were primarily produced by glycerin degradation. Acetol and 2-propen-1-ol were produced mostly from PG, while other compounds (e.g., formaldehyde) originated from both. Because emissions originate from reaction of the most common e-liquid constituents (solvents), harmful emissions are expected to be ubiquitous when e-cigarette vapor is present.

Environmental pollution and emission factors of electronic cigarettes, heat-not-burn tobacco products, and conventional cigarettes

“…Emission factors (ng/h) of selected metals and trace elements during iQOS, EC, and CC consumption. The data corresponding to EC and CC are adopted from Saffari et al (2014 in a number of previous studies (Jensen et al 2015;Gillman et al 2016;Sleiman et al 2016).…”

Electronic cigarettes—A review of the physiological health effects

“…Some of the toxicants found in EC vapour are likely formed as by-products during thermal degradation, especially with high-powered devices (Sleiman et al 2016). For example, Blair et al (2015) discovered detectable levels of acetaldehyde (suspected carcinogen), acrolein (inflammatory agent), and acetone (central nervous system depressant) in EC aerosols, though in lower amounts than in CCs.…”

“…For instance, Farsalinos et al (2015b) detected formaldehyde, acetaldehyde, acetone, and acrolein in EC aerosols; Flora et al (2016) detected formaldehyde but no acetaldehyde or acrolein in EC aerosols; and Goniewicz et al (2015) detected formaldehyde, acetaldehyde, acrolein, and o-methylbenzaldehyde in EC aerosols. Sleiman et al (2016) identified two other potential carcinogens in EC vapour: propylene oxide and glycidol. Other articles showed similar results, with increasing levels of toxicants when higher-powered devices were used (Laugesen 2008;McAuley et al 2012;Goniewicz et al 2014b;Hutzler et al 2014;Kosmider et al 2014;Tayyarah and Long 2014;Geiss et al 2015;Herrington and Myers 2015; Zucchet and Schmaltz 'Connell et al 2015;El-Hellani et al 2016;Jo and Kim 2016;Leigh et al 2016;Sleiman et al 2016;Talih et al 2016).…”

“…Sleiman et al (2016) identified two other potential carcinogens in EC vapour: propylene oxide and glycidol. Other articles showed similar results, with increasing levels of toxicants when higher-powered devices were used (Laugesen 2008;McAuley et al 2012;Goniewicz et al 2014b;Hutzler et al 2014;Kosmider et al 2014;Tayyarah and Long 2014;Geiss et al 2015;Herrington and Myers 2015; Zucchet and Schmaltz 'Connell et al 2015;El-Hellani et al 2016;Jo and Kim 2016;Leigh et al 2016;Sleiman et al 2016;Talih et al 2016). The amount and types of these degradation products vary substantially in different studies, making generalizations about the health effects of ECs difficult.…”

E-cigarettes: promise or threat?

“…31 Propylene glycol when heated may produce propylene oxide, a class 2B carcinogen. 32 Tobacco-specific nitrosamines are highly carcinogenic, but the low levels found in most ENDS products are unlikely to pose a substantial risk. 33 Certain ENDS emissions can impact the viability of established cultured cell lines, however, to a lesser degree than cigarette smoke.…”