Abstract
Thousands of electronic cigarette refill fluids are commercially available. The concentrations of nicotine and the solvents, but not the flavor chemicals, are often disclosed on product labels. The purpose of this study was to identify and quantify flavor chemicals in 39 commercial refill fluids that were previously evaluated for toxicity. Twelve flavor chemicals were identified with concentrations ≥1 mg/ml: cinnamaldehyde, menthol, benzyl alcohol, vanillin, eugenol, p-anisaldehyde, ethyl cinnamate, maltol, ethyl maltol, triacetin, benzaldehyde, and menthone. Transfer of these flavor chemicals into aerosols made at 3V and 5V was efficient (mean transfer = 98%). We produced lab-made refill fluids containing authentic standards of each flavor chemical and analyzed the toxicity of their aerosols produced at 3V and 5V using a tank Box Mod device. Over 50% of the refill fluids in our sample contained high concentrations of flavor chemicals that transferred efficiently to aerosols at concentrations that produce cytotoxicity. When tested with two types of human lung cells, the aerosols made at 5V were generally more toxic than those made at 3V. These data will be valuable for consumers, physicians, public health officials, and regulatory agencies when discussing potential health concerns relating to flavor chemicals in electronic cigarette products.
Highlights
In 2014, more than 7,000 electronic cigarette (EC) refill fluid products with unique flavor names were commercially available online and from local shops, and the number of products continues to grow[1]
We : (1) identified the flavor chemicals in each product, (2) produced “lab-made” refill fluids with authentic standards of those flavor chemicals present in concentrations ≥1 mg/ml, (3) determined how much of each flavor chemical is transferred from the lab-made refill fluids into aerosols made at high and low voltages, (4) examined the cytotoxicity of these aerosols using human lung cells, and (5) identified reaction products formed due to the aerosolization process
Little is known about the flavor chemicals used in EC refill fluids and their effects on human health
Summary
In 2014, more than 7,000 electronic cigarette (EC) refill fluid products with unique flavor names were commercially available online and from local shops, and the number of products continues to grow[1]. In a study of 30 refill fluids, total flavor chemical concentrations ranged from 10–40 mg/ml[2]. Cinnamaldehyde was subsequently identified as the dominant flavor chemical in a small library of commercial cinnamon-flavored refill fluids, and its concentration was directly correlated with its cytotoxicity in the MTT assay[5]. The “creamy/buttery”-flavored refill fluids led to more cytotoxic aerosols than did fluids in other flavor classes, again suggesting that flavor chemicals are differentially important in determining cytotoxicity of EC products. We : (1) identified the flavor chemicals in each product, (2) produced “lab-made” refill fluids with authentic standards of those flavor chemicals present in concentrations ≥1 mg/ml, (3) determined how much of each flavor chemical is transferred from the lab-made refill fluids into aerosols made at high and low voltages, (4) examined the cytotoxicity of these aerosols using human lung cells, and (5) identified reaction products formed due to the aerosolization process
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