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Background: Electronic cigarettes (EC) are tobacco-free nicotine delivery devices that aerosolize fluid containing nicotine, a humectant, flavorings, and contaminants. I previously showed that one brand of EC contains significant levels of metals in its cartomizer fluid and aerosol. These data have been used by regulatory agencies to formulate polices governing EC use. I now propose to undertake a broader in depth study on metals in EC aerosol. Objective: I hypothesize that aerosols from leading brands of EC contain metal particles and nanoparticles in concentrations that are both higher than the concentrations in conventional cigarette smoke and toxic to cells. I propose to test this hypothesis in three Specific Aims that will identify the metals in EC aerosols, determine the concentrations of each metal, establish how metal concentration is affected by different puff conditions, and determine if these metals are cytotoxic and/or genotoxic to lung cells. Research Plan: Specific Aim 1 will identify and quantify the metals in EC aerosols from 8 major brands, determine if metals in EC aerosols exist as nanoparticles (particles <100 nm in diameter), and identify the source of the metals in EC aerosols. EC aerosol samples, generated on a smoking machine, will be analyzed using advanced instrumentation that can determine which metals are present and the concentration of each. Metal nanoparticles will be identified in aerosol using a high resolution microscope and software for metal analysis to create elemental maps of nanoparticles. Pellets centrifuged from EC fluids and structural components of EC will also be analyzed to identify metals. The source of aerosol metals will be identified by correlating metals in EC components to those in aerosols. Specific Aim 2 will evaluate the effect of puff volume and puff interval on the concentration of metals in EC aerosols. To evaluate the effect of puff volume on metal concentration, three aerosol samples will be made from the 5 brands with the highest metal content in their aerosol (determined in Aim #1) using a higher air flow rate to create a larger volume puff. These data will be compared to data from Aim #1 in which aerosols were produced using a low flow rate (smaller volume). The samples will be analyzed using advanced instrumentation to determine how metal concentration is affected by puff volume. To determine if metal concentration in aerosol increases with extended EC use, the 5 brands with the highest metal concentrations (determined in Aim #1) will be used to make aerosols by collecting puffs 1-60, 61-120, and 121-180. Three aerosol samples for each interval from each brand will be analyzed to determine if metal concentrations increase during later intervals of collection. Specific Aim 3 will determine if metals in EC aerosols are cytotoxic and/or genotoxic using assays with cultured lung cells. Aerosol samples will be prepared in culture medium, and cells will be treated with varying concentrations of aerosol to establish dose response curves for cytotoxicity and genotoxicity, which will be determined using well characterized assays. To determine if the toxicity of the aerosol is due specifically to metals, a chelator will be used to remove metals from the aerosols, which will then be retested. Aerosols will also be made from propylene glycol to which metals are added, and then tested in the toxicity assays. Impact: The data produced by this study will determine: (1) how widespread metals are in EC aerosols, how metal concentrations vary among brands/models, what metal nanoparticles are in EC aerosols, and which metal structures in EC contribute metals to aerosols, (2) how different puffing conditions and extended use of EC effect metal content in aerosols the origin of metals in the EC aerosols, (3) if metals in EC aerosol produce cytotoxic and genotoxic effects on human lung cells. These data will inform EC users about products that may be dangerous to their health and contribute to a foundation of science that can be used by government agencies to establish rational regulatory policies for EC manufacture, sales, marketing, and use. |
