Evaluation of Metal Emissions in Electronic Cigarettes
Electronic cigarettes (EC) are tobacco-free nicotine delivery devices comprised of metal components that aerosolize fluid containing nicotine, a humectant, flavorings, and contaminants. The purpose of this project was to determine the concentration of elements, including metals, in the aerosol of cartomizer style electronic cigarettes (EC), disposable EC, electronic hookahs (EH), and tank style EC, how these concentrations change when puffing parameters are varied, and the source of the elements present in the aerosol. The metal analysis in fluids and aerosols was done using inductively coupled optical emission spectroscopy (ICP OES) and elemental analysis of atomizers was completed using scanning electron microscopy (SEM) coupled with and energy dispersive spectroscopy. There was considerable variation in performance of EC both across and within brands. Most EC tested required higher air flow rates to produce aerosol than conventional cigarettes require to produce smoke. The total concentrations of elements/metals present in EC aerosols varied by brand and style. For the disposable EC and electronic hookahs, the results were similar with each containing various metals in their aerosol. The total concentration of elements in the aerosol collected with a cold trap varied by brand and EC model (cartomizer EC - 487 to 5,861µg/L, disposable EC - 997 to 2.296 µg/L, tank-style - 617 to 4,382 µg/L), with silicon being the dominant element in the aerosol. These concentrations did change slightly, when more puffs were collected over time, when voltage was increased, and puff volume increased. The most common metals in the aerosol of all units were chromium, nickel, copper, zinc, silicon, tin, and lead, which originated from the wires, wicks, joints, and air tubes within the atomizing unit. There were design differences between different EC models, such as shifting from solder joints to brass clamps or welds, which reduced the concentration of metals in the aerosol. The main conclusions from this study are that metals were present in EC aerosols, and metals usually originated from the components of the atomizer unit.