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Electronic cigarettes (EC) are new tobacco products that are sold worldwide and are growing in popularity, especially among young adults. Although EC are an alternative to conventional tobacco products, their effects on human health are not well understood. EC do not burn tobacco and therefore do not produce secondhand smoke. However, users of EC do exhale large clouds of aerosol that settle on indoor surfaces and produce a chemical residue that we refer to as EC exhaled aerosol residue (ECEAR). Little is known about the chemical composition of ECEAR, how it is distributed in multiuser buildings, and how it affects human health. This project, which focuses the chemical composition and toxicity of ECEAR, directly addresses the TRDRP research priority “Environmental Exposure and Toxicology”. Nicotine and cinnamaldehyde (a widely used flavoring in EC) will be used as biomarkers of ECEAR deposition and will be studied when freshly deposited on terry cloth in both laboratory-controlled conditions and in field sites. Nicotine is an important biomarker because it can lead to addiction, it is toxic, and it can cause birth defects. Cinnamaldehyde is chosen as it is highly toxic, it is often present in high concentration in EC products, and it is used in many flavors, including popular berry and fruit flavors. We propose to test the hypotheses that: (1) ECEAR is deposited in areas where EC are used indoors and ECEAR can travel to adjacent spaces in multi-user buildings, and (2) ECEAR extracts contain chemicals that can kill cells and impair cell health and survival. To test these hypotheses, Aim #1 will identify and quantify, nicotine and cinnamaldehyde in samples of terry cloth exposed to ECEAR collected in both controlled laboratory conditions and in three field sites. Controlled laboratory conditions will allow quantitative analysis of refill fluids, EC aerosol, EC exhaled aerosol, and ECEAR, while samples from field sites will represent real world scenarios where multiple refill fluids and ECs are used. In both laboratory and field sites, terry cloth will be exposed to EC exhaled aerosols for different lengths of time and will either be studied immediately or allowed to “age” prior to analysis. In Aim # 2, ECEAR extracts will be tested to characterize their toxicity, determine which cell types are most sensitive to ECEAR, determine how ECEAR harms cells, and to identify the molecules that are affected by ECEAR. ECEAR will be deposited on pieces of terry cloth in plastic tanks by EC users exhaling aerosol in laboratory controlled conditions. EC fluids will contain propylene glycol (a solvent used in refill fluids), nicotine, and cinnamaldehyde. After various times of exposure to aerosols, residues on the terry cloth will be extracted in cell culture medium and extracts will be screened in a toxicity assay. Concentrations of ECEAR extract that produce no observable effects in treated cells will serve as a benchmark to evaluate cell health using a novel live-cell imaging assay. The most sensitive cell health endpoints will be further investigated using molecular techniques that will identify specific targets of nicotine and cinnamaldehyde. Similar analyses will be done with extracts of ECEAR from laboratory-aged terry cloth and terry cloth collected from field sites. This will be the first study on ECEAR to test, quantify, and compare nicotine and cinnamaldehyde concentrations in laboratory and field sites and to examine the cytoxicity of ECEAR using a spectrum of toxicity assays. Our data will specifically establish: (1) what concentrations of nicotine and cinnamaldehyde are present in fresh and aged ECEAR in laboratory conditions and field sites, (2) how much nicotine and cinnamaldehyde are absorbed vs exhaled by EC users, (3) the potency of nicotine and cinnamaldehyde in ECEAR, (4) the cell processes affected by exhaled ECEAR, and (5) which cell types, molecular targets and pathways are affected by ECEAR. These data will provide information on the risks associated with indoor use of EC and will contribute to the foundation of regulatory science that can inform policies for the indoor use of EC products.
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