Chemical Composition of Aerosol from an E‑Cigarette: A Quantitative Comparison with Cigarette Smoke

There is interest in the relative
toxicities of emissions from
electronic cigarettes and tobacco cigarettes. Lists of cigarette smoke
priority toxicants have been developed to focus regulatory initiatives.
However, a comprehensive assessment of e-cigarette chemical emissions
including all tobacco smoke Harmful and Potentially Harmful Constituents,
and additional toxic species reportedly present in e-cigarette emissions,
is lacking. We examined 150 chemical emissions from an e-cigarette
(Vype ePen), a reference tobacco cigarette (Ky3R4F), and laboratory
air/method blanks. All measurements were conducted by a contract research
laboratory using ISO 17025 accredited methods. The data show that
it is essential to conduct laboratory air/method measurements when
measuring e-cigarette emissions, owing to the combination of low emissions
and the associated impact of laboratory background that can lead to
false-positive results and overestimates. Of the 150 measurands examined
in the e-cigarette aerosol, 104 were not detected and 21 were present
due to laboratory background. Of the 25 detected aerosol constituents,
9 were present at levels too low to be quantified and 16 were generated
in whole or in part by the e-cigarette. These comprised major e-liquid
constituents (nicotine, propylene glycol, and glycerol), recognized
impurities in Pharmacopoeia-quality nicotine, and eight thermal decomposition
products of propylene glycol or glycerol. By contrast, approximately
100 measurands were detected in mainstream cigarette smoke. Depending
on the regulatory list considered and the puffing regime used, the
emissions of toxicants identified for regulation were from 82 to >99%
lower on a per-puff basis from the e-cigarette compared with those
from Ky3R4F. Thus, the aerosol from the e-cigarette is compositionally
less complex than cigarette smoke and contains significantly lower
levels of toxicants. These data demonstrate that e-cigarettes can
be developed that offer the potential for substantially reduced exposure
to cigarette toxicants. Further studies are required to establish
whether the potential lower consumer exposure to these toxicants will
result in tangible public health benefits.