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 vapour 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 vaporisers 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 vapour, and acrolein is a powerful irritant. Emission rates ranged from tens to thousands of nanograms of toxicants per milligram of e-liquid vaporised, and they were significantly higher for a single-coil vs a double-coil vaporiser (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 ?g 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 build-up of polymerisation by-products that degraded upon heating. These findings suggest that thermal degradation by-products are formed during vapour 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 vapour is present.
Authors: Sleiman M, Logue JM, Montesinos VN, Russell ML, Litter MI, Gundel LA, Destaillats H. ;Full Source: Environmental Science & Technology. 2016 Jul 27. [Epub ahead of print] ;