The concentrations of elements/metals, nicotine, flavor chemicals and acids were com-pared in the e-liquids of unused and used first-generation electronic cigarettes (ECs) that were stored for 5-10 years. Metal analysis was done using inductively coupled plasma optical emission spectroscopy; nicotine and flavor chemical analysis were measured using gas chromatography/mass spectroscopy. Of 22 elements analyzed, 10 (aluminum, chromium, copper, iron, lead, nickel, selenium, silicon, tin, zinc)

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... often in the e-liquids. Five elements had the highest average concentrations: copper (1,161.6 mg/L), zinc (295.8 mg/L), tin (287.6 mg/L), nickel (71.1 mg/L), and lead (50.3 mg/L). Nicotine concentrations were always lower than label concentrations. Of 181 flavor chemicals analyzed, 11 were measured in at least one sample, with hydroxyacetone being present in all samples. In used products, some flavor chemicals appeared to be byproducts of heating. E-liquids with the highest concentrations of acids and lowest pHs also had the highest concentrations of elements/metals. Metal concentrations in e-liquids increased after use in some products, and some metal concentrations, such as nickel, were high enough to be a health concern. Leachates from discarded ECs could contribute toxic metals/chemicals to the environment sup-porting the need for better regulation of atomizer design, composition, and disposal.