Electronic cigarettes (E-cigarettes) generate aerosol containing metal contaminants.
Our goals were to quantify aerosol metal concentrations and to compare the effects
of power setting and device type (closed-system vs. open-system) on metal release.
Aerosol samples were collected from two closed-system devices (a cigalike and pod)
and two open-system devices (mods). Each open-system device was operated at three
different power settings to examine the effect of device power on metal release. Concentrations
of 14 metals in e-cigarette aerosol collected via droplet deposition were measured
using inductively coupled plasma mass spectroscopy. Aerosol metal concentrations were
reported as mass fractions (μg/kg) in the e-liquid. For open-system device 1 (OD1),
median arsenic (As), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel
(Ni), lead (Pb), antimony (Sb), tin (Sn), and zinc (Zn) concentrations increased 14,
54, 17, 30, 41, 96, 14, 81, 631, and 7-fold when the device power was increased from
low (20 W) to intermediate (40 W) setting. When the power was further increased from
intermediate (40 W) to high (80 W) setting, concentrations of As, Cr, Cu, Mn, Ni,
and Sb did not change significantly. For open-system device 2 (OD2), Cr and Mn concentrations
increased significantly when device power was increased from low (40 W) to intermediate
(120 W) setting, and then decreased significantly when power was further increased
from intermediate (120 W) to high (200 W) setting. Among the four devices, aerosol
metal concentrations were higher for the open-system than the closed-system devices,
except for aluminum (Al) and uranium (U). For Cr, median (interquartile range) concentrations
(μg/kg) from the open-system devices were 2.51 (1.55, 4.23) and 15.6 (7.88, 54.5)
vs. 0.39 (0.05, 0.72) and 0.41 (0.34, 0.57) for the closed-system devices. For Ni,
concentrations (μg/kg) from the open-system devices were 793 (508, 1169) and 2148
(851, 3397) vs. 1.32 (0.39, 3.35) and 11.9 (10.7, 22.7) from the closed-system devices.
Inhalation of 0% and 100% of samples from OD1, 7.4% and 88.9% from OD2 by typical
e-cigarette users would exceed chronic minimum risk levels (MRL) of Mn and Ni, respectively.
No MRL exceedance was predicted for the closed-system devices. A large fraction of
users of OD1 (100%) and OD2 (77.8%) would be exposed to Ni levels higher than those
from reference tobacco cigarette 3R4F. Our findings suggest that power setting and
device type affect metal release from devices to aerosol which would subsequently
be inhaled by users. Metal concentrations from open-system devices first increased
with device power, and then leveled off for most metals. Open-system devices generate
aerosol with higher metal concentrations than closed-system devices. These findings
inform tobacco regulatory science, policy makers and health professionals on potential
metal health risks associated with e-cigarette use, design and manufacturing.