Abstract
Electronic nicotine delivery systems (ENDS), by virtue of their highly engineered construction (plastics, glass, e-liquids), may contain a number of emerging chemicals of concern (ECCs), including phthalates, phenolic compounds, and flame retardants. Current knowledge regarding the safety of ENDS may underestimate the health risks from ECCs. In this study, we examined the types and levels of those three groups of chemicals in the components and parts of ENDS devices, including refill liquids, tanks/cartridges, atomizers, drip tips/mouthpieces, and sealing materials. Our results suggest that phthalates were the most prevalent chemicals in all tested samples, followed by parabens and organophosphate flame retardants (OPFRs). Particularly, all measured chemicals had significantly higher detection rates in cartridges/tanks, drip tips/mouthpieces, and sealing materials in contrast to e-liquids and coil samples. Among all those three types of ENDS components, phthalates generally had the highest concentrations (0.279-3790 ng/unit) in the drip tip/mouthpiece samples, followed by the sealing materials (0.380-508.8 ng/unit) and the empty tank/cartridge samples (up to 761.7 ng/unit). For parabens, highest concentrations were observed in drip tip/mouthpiece samples (1.152-130.1 ng/unit), followed by sealing materials (0.220-30.08 ng/unit) and the tank/cartridge samples (1.794-34.24 ng/unit). For OPFRs, tris(1,3-dichloro-2-propyl) phosphate had the highest concentrations (39.40-774.1 ng/unit) in all component samples. High concentrations (20.25-260.4 ng/unit) were also observed for several OPFRs in sealing materials and drip tip/mouthpiece samples. These findings will contribute to addressing the information gaps pertinent to the presence of ECCs in ENDS and will warrant further studies for understanding the potential negative health effects and to what extent those chemicals may cause potential negative health effects when using the ENDS. The findings will also contribute to developing evidence-based standards for the regulatory control of the types and levels of ECCs in ENDS products.