Abstract
Flavors in electronic cigarette (ECIG) liquids may increase ECIG aerosol toxicity via intact distillation or chemical transformation. For this report, we performed a meta-analysis of the literature to categorize the compounds found in flavored ECIG liquids into a few chemical classes and to predict their possible chemical transformations upon ECIG liquid aerosolization. This analysis allowed us to propose specific correlations between flavoring chemicals and aerosol toxicants. A literature search was conducted in November 2019 using PubMed. Keywords included terms related to ECIGs and flavors. Studies were included if they reported chemical ingredients of flavored liquids and clearly stated the commercial names of these liquids. The obtained data were visualized on a network diagram to show the common chemical compounds identified in flavored ECIG liquids and categorize them into different chemical classes. The systematic literature review included a total of 11 articles. Analysis of the data reported gave a total of 189 flavored liquids and 173 distinct chemical compounds that were categorized into 22 chemical classes according to their functional groups. The subsequent prediction of chemical transformations of these functional groups highlighted the possible correlation of flavor compounds to aerosol toxicants.
Highlights
The aryl class comprises chemical compounds like benzyl alcohol, benzaldehyde, cinnamaldehyde, and other related chemical compounds that can undergo oxidation to carboxylic acids followed by decarboxylation to give benzene, toluene, ethylbenzene, xylene (BTEX), and styrene.[43]
This report highlights the importance of categorizing flavor ingredients into a few chemical classes and correlating their chemical reactivity with the toxicant formation in the aerosols
This work can be used to construct a conceptual framework that may help in enhancing knowledge on how flavor compounds in electronic cigarette (ECIG) liquids contribute to toxicant emissions in ECIG aerosols
Summary
The contribution of flavors to aerosol toxicity was recognized several years ago.[11] This contribution can be due to toxic ingredients initially present in the flavored liquid, or toxicants formed when the parent liquid is heated and vaporized.[12−14] Some reports in the literature have found that flavors are a dominant source of toxic aldehyde emissions.[15,16] Others found that flavors affect the emission of radicals and reactive oxygen species (ROS).[17,18] Only a limited number of studies noted a direct correlation between
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