Carbon monoxide concentration in mainstream E-cigarette emissions measured with diode laser spectroscopy

Correspondence to Dr Dabrina D Dutcher, Chemical Engineering and Chemistry, Bucknell University, Lewisburg, PA 17837, USA; [email protected]

Introduction

The use of electronic cigarettes (e-cigarettes) has been steadily increasing^1–3 and in youth has reached epidemic levels.⁴ These devices, which can be used to deliver nicotine among other chemical species to the pulmonary system,⁵ have been promoted as safer alternatives to traditional tobacco cigarettes.⁶ However, the physicochemical properties of the mainstream effluent from these devices are still not well characterised, in part due to the newness of these devices and their rapid design evolution.^7–9

The e-liquid that is aerosolised is composed of various ratios of vegetable glycerin, propylene glycol, assorted flavouring agents and varying amounts of nicotine.¹⁰ Most e-cigarettes aerosolise the e-liquid by resistively heating a metal or ceramic filament to which e-liquid is wicked. Some e-cigarettes allow the user to customise the power of the resistive heating in addition to controlling the length of the puff and flavour of the e-fluid.¹¹

Traditional tobacco-based cigarettes deliver a range of chemical species with known deleterious health effects including 1,3-butadiene, acrolein, cyanide, arsenic, cresols, metals, N-nitrosamines, polycyclic aromatic hydrocarbons (PAHs) and carbon monoxide among others.^12–14 E-cigarette effluent, though not yet as thoroughly characterised, has been shown to contain formaldehyde, other aldehydes and ketones, other carbonyl compounds, reactive oxygen species and choloropropanols, volatile PAHs and aluminium.^15–21 The production of some of these compounds has been found to be related to both the power of the device and flavouring of the e-fluid used.

Carbon monoxide is usually produced from incomplete combustion or the oxidation of organic materials.²² The heat produced during the resistive heating—aerosolisation process in e-cigarettes has the potential to oxidise organic materials into carbon monoxide (CO) and carbon dioxide. When experimenting with different components of e-cigarettes, El-Hellani et al ²³ found that CO was one of the products in e-cigarette effluent. El-Hellani et al ²³ also found that CO and other small hydrocarbons emission rates were affected by the material of the coil, the coil geometry using home-made coils and e-fluid. Exposures to both high and low concentrations of CO have different but serious health effects.^24–26 Although less is known about short-term or moderate carbon monoxide...