Metal Concentrations in e-Cigarette Liquid and Aerosol Samples: The Contribution of Metallic Coils

BACKGROUND: Electronic cigarettes (e-cigarettes) generate an aerosol by heating a solution (e-liquid) with a metallic coil. Whether metals are transferred from the coil to the aerosol is unknown. OBJECTIVE: Our goal was to investigate the transfer of metals from the heating coil to the e-liquid in the e-cigarette tank and the generated aerosol. METHODS: We sampled 56 e-cigarette devices from daily e-cigarette users and obtained samples from the refilling dispenser, aerosol, and remaining e-liquid in the tank. Aerosol liquid was collected via deposition of aerosol droplets in a series of conical pipette tips. Metals were reported as mass fractions ([Formula: see text]) in liquids and converted to mass concentrations ([Formula: see text]) for aerosols. RESULTS: Median metal concentrations ([Formula: see text]) were higher in samples from the aerosol and tank vs. the dispenser (all [Formula: see text]): 16.3 and 31.2 vs. 10.9 for Al; 8.38 and 55.4 vs. [Formula: see text] for Cr; 68.4 and 233 vs. 2.03 for Ni; 14.8 and 40.2 vs. 0.476 for Pb; and 515 and 426 vs. 13.1 for Zn. Mn, Fe, Cu, Sb, and Sn were detectable in most samples. Cd was detected in 0.0, 30.4, and 55.1% of the dispenser, aerosol, and tank samples respectively. Arsenic was detected in 10.7% of dispenser samples (median [Formula: see text]) and these concentrations were similar in aerosol and tank samples. Aerosol mass concentrations ([Formula: see text]) for the detected metals spanned several orders of magnitude and exceeded current health-based limits in close to 50% or more of the samples for Cr, Mn, Ni, and Pb. CONCLUSIONS: Our findings indicate that e-cigarettes are a potential source of exposure to toxic metals (Cr, Ni, and Pb), and to metals that are toxic when inhaled (Mn and Zn). Markedly higher concentrations in the aerosol and tank samples versus the dispenser demonstrate that coil contact induced e-liquid contamination. https://doi.org/10.1289/EHP2175