Multi-parameter investigation of factors controlling carbonyl emissions from electronic cigarettes - Title: Multi-parameter investigation of factors controlling carbonyl emissions from electronic cigarettes
Abstract
Electronic cigarette (e-cigarette) popularity skyrocketed in recent years, especially among teens and young
adults. E-cigarette use is also growing among the older population. This trend is troubling as e-cigarette
aerosols contain varying levels of nicotine and other chemicals known to increase the risk of numerous
adverse health effects. Carbonyl compounds, such as formaldehyde, a known human carcinogen, are the most
prominent among hazardous and potentially hazardous constituents (HPHCs) found in e-cigarette aerosols.
Numerous factors were reported to influence carbonyl production by e-cigarettes: e-cigarette type, power, coil
material, e-cigarette liquid (e-liquid) composition, and puff topography (puff duration and puff flow rate).
Differences in sampling methodology and testing protocols, as well as a limited number of parameters
investigated in individual studies could have contributed to the current controversy regarding carbonyl levels in
e-cigarette aerosols or the role individual factors play in their production. This study aims to resolve the
outstanding questions regarding e-cigarette carbonyl emissions by performing a comprehensive multi-variable
testing of the most popular devices representative of the main e-cigarette types under a wide range of use
patterns. Based on the available literature data and our preliminary data, we hypothesize that (1) accurate
and reproducible carbonyl measurements can be achieved only if both particle and gas phases are
quantitatively collected; (2) flavoring compounds have a strong influence on carbonyl production, which
depends on their chemical class, concentration and interaction with e-cigarette coil; (3) e-cigarette carbonyl
emissions are a complex function of several variables that need to be investigated simultaneously. Three
Specific Aims are proposed to test these hypotheses. Aim 1 will test the main carbonyl collection methods
using a NIST-traceable formaldehyde standard and e-cigarette aerosols containing different amounts of liquid
particulates; the best performing method will be selected for the consequent tests. Aim 2 will investigate
interactions of the main flavoring compound classes with e-cigarette fresh and aged coils at different
temperatures and e-liquid formulations. Aim 3 will investigate how different combinations of power, puff
topography, and e-liquid viscosity affect carbonyl emissions of the main e-cigarette construction types. The
main innovation in the project is an experimentally-efficient systematic investigation of the effect of various
factors and their combinations on e-cigarette emissions, which is lacking in the current literature. The potential
impact will include (1) a recommendation on the best sampling methodology for carbonyls in e-cigarette
aerosols and (2) identification of e-cigarette and e-liquid characteristics and use parameters that are the main
controlling factors for carbonyl emissions by e-cigarettes. Such information is critically needed to advise the
public on potential health risks of different devices and configurations, establishing standardized testing
protocols, and informing policymakers on regulating certain e-cigarette designs and/or e-liquid constituents.
