Electronic cigarettes: an evaluation of exposure to chemicals and fine particulate matter (PM)

Abstract

The "electronic (e-)cigarette" generates intense scientific debate about its use. Its popularity is increasing worldwide as a method to reduce/quit smoking, and to smoke indoors when restrictions on smoking tobacco are present. WHO recommends caution, until its effectiveness in helping smokers is clarified, and the possible harm evaluated. The aim of this study was to assess the content of the aromatic liquid mixture and its vapour and the Particulate Matter (PM) emissions of an Italian brand of e-cigarette and to compare its PM emissions with a conventional cigarette. Propylene glycol (66%) and glycerine (24%) were main components in the liquid, while the flavouring substances were less than 0.1%. The same substances were detected in the vapour in similar proportions. Fine and ultrafine PM emissions were higher for the conventional versus the e-cigarette (e.g.: PM10=922 vs 52 microg/m3; PM1=80 vs 14 microg/m3). The e-cigarette seems to give some advantages when used instead of the conventional cigarette, but studies are still scanty: it could help smokers to cope with some of the rituals associated with smoking gestures and to reduce or eliminate tobacco consumption avoiding passive smoking. However, the e-cigarette causes exposure to different chemicals compared with conventional cigarettes and thus there is a need for risk evaluation for both e-cigarettes and passive steam exposure in smokers and non smokers.

Full text

279
Qualitative evaluation of exposure to an Italian electronic cigarette
* Department of Chemistry, University of Perugia, Italy
** Center for Smoking Cessation, ASL Monza e Brianza, Italy
*** Faculty of Medicine and Psychology, Sapienza University of Rome, Italy
**** Department of Public Health and Infectious Diseases, Sapienza University of Rome, Italy
Ann Ig 2012; 24: 279-288
Electronic cigarettes: an evaluation of exposure to che-
micals and fine particulate matter (PM)
R.M. Pellegrino*, B. Tinghino**, G. Mangiaracina***, A. Marani****,
M. Vitali****, C. Protano****, J.F. Osborn****, M.S. Cattaruzza****
Key words: Electronic cigarette emissions, flavouring mixture, fine particulate matter, PM
Parole chiave: Emissioni sigaretta elettronica, miscela aromatizzante, particolato fine, PM
Riassunto
La sigaretta elettronica: una valutazione dei componenti chimici e del particolato sottile (PM)
L’uso della sigaretta elettronica sta generando un importante dibattito scientifico. La sua popolarità sta
crescendo in tutto il mondo come metodo per ridurre o smettere di fumare e per fumare nei luoghi chiusi
dove è vietato. L’OMS tuttavia raccomanda cautela fino a quando non sia stata chiarita la sua reale efficacia
come aiuto ai fumatori e non sia stato valutato l’eventuale possibile danno associato al suo utilizzo.
L’obiettivo di questo studio è stato quello di analizzare, per una marca italiana di sigaretta elettronica, il
contenuto liquido della miscela aromatica, il suo vapore e le emissioni di Particolato Sottile (PM) confron-
tandole con quelle di una sigaretta convenzionale.
Il propilene glicole (66%) e la glicerina (24%) sono risultati i principali componenti del liquido, mentre
le sostanze aromatiche ammontavano a meno dello 0,1%. Le medesime sostanze, all’incirca nelle stesse
proporzioni, sono state ritrovate nel vapore emesso.
Le emissioni fini ed ultrafini di PM sono risultate notevolmente più alte per la sigaretta convenzionale
rispetto a quella elettronica (rispettivamente PM10: 922 e 52 µg/m3; PM1: 80 e 14 µg/m3).
La sigaretta elettronica sembra dare alcuni vantaggi quando è usata al posto della sigaretta convenzionale,
anche se gli studi sono ancora scarsi: potrebbe aiutare i fumatori a gestire la ritualità e a ridurre o a smettere
di fumare, evitando l’esposizione al fumo passivo. Tuttavia determina anche l’esposizione a sostanze chimiche
diverse rispetto alla sigaretta convenzionale e quindi si rende necessaria un’accurata valutazione dei rischi
potenzialmente connessi con il suo uso e con l’esposizione di fumatori e non fumatori al suo vapore.
Introduction and obiectives
Recently, an electric device called
an “electronic cigarette”, “e-cigarette”
or “e-cig” has become more commonly
used by smokers to replace conventional
cigarettes.
The e-cigarette is an integrated electric
device, shaped like a cigarette, consist-
ing of a stainless steel shell, a lithium
ion battery assembly, a smart chip with
program controlled circuits, an atomiza-
tion chamber and a removable cartridge.
Flavouring is housed in the removable

280 R.M. Pellegrino et al.
cartridge, which contains propylene
glycol and other products obtained from
an extraction of tobacco flavours. Some
e-cigarettes even contain nicotine in the
removable cartridge together with flavour.
Some companies add other flavours to
the mixture such as: mint, strawberry,
orange etc (18). These products may be
very attractive to minors who may be
drawn to the technology, flavouring and
accessibility (41).
The popularity of the e-cigarette
among smokers has increased worldwide,
as a method to reduce or quit smoking,
to smoke in an indoor environment when
smoking restrictions are present, or to
“feign a smoking experience” reducing
health risks (10, 19). Besides, now-a-days
the e-cigarette is an “online leader” in
popularity among smoking alternatives,
such as snus (a moisturized tobacco pow-
der used as an alternative to chewing to-
bacco), nicotine replacement therapy, and
other medications (4). Even in the South
Korean market, the e-cigarette, described
as the “healthy cigarette”, was advertised
as an incredible and effective and healthy
smoking cessation device (25).
On the other hand, in September 2008
the World Health Organization (WHO)
decided that e-cigarettes cannot be con-
sidered as a way to stop smoking, because
there were not enough studies demostrat-
ing its effectiveness in reducing and
replacing the consumption of nicotine.
Besides, WHO recommended caution
in its use, until its effectiveness in help-
ing smokers is clarified and the possible
harm of some substances is evaluated (34,
42). After the WHO recommendations,
the topic “e-cigarette” has generated
significant scientific debate about the
promises and perils of the device (17 30,
39). Nevertheless, even now there is little
research on e-cigarette safety, while some
data on plasma nicotine, carbon monoxide
concentration, heart rate and subjective
effects have been evaluated (38). In the
first reports, e-cigarettes seem to allevi-
ate craving and to be well tolerated, at
least in short-term clinical observations
(6, 11, 27, 32), but evaluation of the tox-
icity of the different electronic devices,
the long-term safety, and the smoking
cessation efficacy is needed (14, 15). In
particular, the first priority of studies in
this field should be the characterization
of the safety profile (14, 15).
The US Food and Drug Administration
(FDA) analyzed results of a two widely
commercialized electronic cigarette prod-
ucts, suggesting that these devices may
include some of the same toxic or carci-
nogenic compounds as the conventional
cigarette. Moreover, some e-cigarettes
contain ethylene glycol, a toxic chemical
(18, 23).
The aim of the present study was to
contribute to the knowledge on toxicity of
e-cigarettes during a smoking simulation
of an Italian brand by:
- a quali-quantitative determination
of the aromatic mixture and the vapour
content;
- the evaluation of particulate matter
emission according to their size (Total
Suspended Particulate - TSP, and particles
with size ≤ 10, 7, 2.5 and 1 µm - PM10, 7,
2.5, 1 fractions, respectively).
Materials and methods
Analytical determinations were per-
formed on two types of an Italian brand
(e-cigarette Aria™ - Auripen, Italy) of
e-cigarettes: one with nicotine (Nic) and
one without nicotine (W Nic). The study
was performed in three phases.
1. In the first phase, the aromatic liq-
uid of the e-cigarette was analysed. The
cartridge had a cylindrical shape (diam-
eter 9 mm; length 40 mm) and contained

281
Qualitative evaluation of exposure to an Italian electronic cigarette
about 0.5 grams of liquid. Analyses were
performed using Agilent 5975-6890
gas-chromatography/mass-spectrometry
(GC/MS) by injecting undiluted liquid
in split mode (500:1). Chromatographic
column was a JW 5-MS (0.2 µm thick-
ness, 0.25 mm ID, 30 m Length) used
in programmed mode (45°C for 3 min,
next increment of 10°C/min to 320°C
for 2 min) with Helium as carrier gas at
constant flow of 1.1 mL/min. Qualitative
data were obtained by comparison of 70
eV electronic impact mass spectra of each
compound with database library (Wiley
and NIST). Quantitative data expressed
by weight/weight (% w/w) were obtained
by internal normalization method: the
area of the total ion current (TIC) signal
of each chromatographic peak was mul-
tiplied by the respective response factor,
that was previously determined for each
compound by analysing various synthetic
mixtures gravimetrically prepared.
2. In the second phase, the chemical
composition of the vapour was analysed.
The e-cigarette was applied to a device
that simulated 16 aspirations, each lasting
for 3 seconds with a flow rate of 0.166 L/
sec and with intervals between one aspira-
tion and the other of 8 seconds. Exhaled
steam produced by the e-cigarette was
collected into an Supelco ORBO™ 100
HBR on Carbotrap™ B. The analytes
were eluted from the adsorbent with 5
mL of carbon disulphide and collected
in a 10 mL glass tube. The solution was
dried to 100 µL with a gentle stream of
nitrogen gas, placing the bottom of the
tube in a water/ice bath. Finally, 1 µL of
the obtained solution was injected into
GC/MS apparatus under the same condi-
tions described in phase 1.
3. In the third phase, the indoor emis-
sion of particulate matter by the e-ciga-
rette (Nic) was measured and compared
with that of a traditional cigarette brand
(nicotine = 0.8 mg/cigarette; tar = 10 mg/
cigarette), using a device that produced
4 aspirations per minute, for 3 minutes
overall. Measurements were performed
with a portable laser operated aerosol
mass analyser (Aerocet 531, Metone
Instruments Inc, USA) in an air volume
of 11 m3.
The measurements were taken before
lighting the cigarette (T0), 1.5 minutes
after lighting (T1 = half smoking simula-
tion time) and after 3 minutes (T2 = end
of smoking simulation).
There was a wash-out period of 30
minutes with air exchange between the
measurements for the e-cigarette and
the conventional cigarette. This allowed
the air to return to basal indoor values,
as measured by the mass analyser. The
ambient temperature and humidity were
19.5°C and 60% respectively.
Results
The results of GC/MS analyses of
the aromatic mixtures (Nic and W Nic)
are shown in Table 1. The content of
the aromatic mixtures of Nic and W Nic
e-cigarettes are very similar: propylene
glycol was the main component found in
liquid of both e-cigarettes (66.001 and
66.115 %w/w for Nic e-cigarettes and
for W Nic e-cigarettes, respectively).
Propylene glycol together with glycerine
represented more of 90% of the total in-
gredients, while the other substances were
less than 0.1% of the total. L-nicotine was
present only in the device with nicotine
(0.250 %w/w).
The substances in the e-cigarettes’
steam found by GC/MS analysis are
reported in Table 2. A total of 11 and 10
chemicals were found at detectable levels,
respectively in the analyzed steam of Nic
and W Nic e-cigarettes (L-nicotine was

282 R.M. Pellegrino et al.
Table 1 - Composition of the e-cigarette’s aromatic mixture and their percentages expressed as %weight/weight
(%w/w)
Substance CASaNic
(% w/w)b
W Nic
(%w/w)c
1,2-propanediol (propylene glycol) 57-55-6 66.001 66.115
1,2,3-propanetriol (glycerin) 56-81-5 24.056 24.200
L-nicotine 54-11-5 0.250 < 0.001
Flavouring agents:
methyl pyrazine 109-08-0 0.028 0.024
2,3-dimethyl pyrazine 5910-89-4 0.012 0.012
5-methyl-2-furaldehyde 620-02-0 0.011 0.010
1-hydroxy-2-propanone 116-09-6 0.011 0.008
β-damascon 23726-91-2 0.010 0.010
2,5-dimethyl pyrazine 123-32-0 0.010 0.010
3-hydroxy-2-methyl-4-pyranone (maltol) 118-71-8 0.004 0.002
2,3,5,6-tetramethyl pyrazine 1124-11-4 0.001 0.002
TOTAL - 90.394d90.393d
a CAS: Chemical Abstracts Service (Registry number of each product)
b Nic: e-cigarette with nicotine
c W Nic: e-cigarette without nicotine
d Remaining % w/w of aromatic mixtures (9.606% and 9.607%) is presumably due to the water content.
Table 2 - Composition of the steam from e-cigarettes expressed as mg/m3
Name CASaNicb
mg/m3
W Nicc
mg/m3
1,2-propanediol (propylene glicol) 57-55-6 1660 1650
1, 2, 3-propanetriol (glycerin) 56-81-5 610 580
L-nicotine 54-11-5 6.21 < 0.01
methyl pyrazine 109-08-0 0.54 0.54
2,3-dimethyl pyrazine 5910-89-4 0.29 0.30
5-methyl-2-furaldehyde 620-02-0 0.27 0.27
1-hydroxy-2-propanone 116-09-6 0.26 0.26
β-damascon 23726-91-2 0.25 0.25
2,5-dimethyl pyrazine 123-32-0 0.24 0.24
3-hydroxy-2-methyl-4-pyranone (maltol) 118-71-8 0.06 0.06
2,3,5,6-tetramethyl pyrazine 1124-11-4 0.03 0.02
a CAS: Chemical Abstracts Service (Registry number of each product)
b Nic: e-cigarette with nicotine
c W Nic: e-cigarette without nicotine

283
Qualitative evaluation of exposure to an Italian electronic cigarette
found only in Nic e-cigarettes). Even in
this case, the major component of the
steam of both e-cigarettes is propylene
glycol (1660 mg/m3 for Nic and 1650 mg/
m3 for W Nic e-cigarettes, respectively),
followed by glycerine (610 and 580 mg/
m3 for Nic and W Nic e-cigarettes, respec-
tively). The other analytes recovered in
the steam, detected in trace levels, were
the same as compared to those found in
the aromatic mixture.
The maximum temperature of the
steam vapour exiting the device was
43°C.
Fine and ultrafine PM emissions meas-
ured for the electronic and conventional
cigarettes are reported in Table 3.
PM emissions measured after smoking
simulation with the electronic and the
conventional cigarettes were higher than
those detected before the experiment in
both cases. However, comparison of PM
levels produced by the electronic and con-
ventional cigarettes shows a much greater
increase (up to hundreds of times) of each
PM fraction for conventional cigarette.
At the end of the experiments (after
3 minutes from the lighting of the con-
ventional cigarette and e-cigarettes),
PM emissions produced by conventional
cigarette in the indoor air were several
times higher than PM emissions produced
by e-cigarette. Overall, total suspended
particulate matter emissions derived from
a conventional cigarette were 15 times
higher than those derived from an e-cig-
arette. For each of the different fractions
of PM, (PM1, 2.5, 7, 10), there was an higher
density (ranging from 6 to 21 times) for
conventional compared to e-cigarette.
Discussion
Much research is being done on strat-
egies that may help smokers to quit,
either using drugs or control strategies
to manage craving and behaviour (3, 5,
7, 20, 40). The use of e-cigarettes should
be seen in this way, that is, as a tool to
reduce the damage caused by real tobacco
smoke. However, well-conducted clinical
trials showing the effectiveness of these
devices for treating tobacco addiction
are lacking.
“The first priority is to characterize
the safety profile of these products, in-
cluding in long-term users. If these pro-
ducts are demonstrated to be safe, their
efficacy as smoking cessation aids should
then be tested in appropriately designed
trials. Until these studies are conducted,
continued marketing constitutes an un-
controlled experiment and the primary
outcome measure, poorly assessed, is user
health.” (14).
Table 3 - Particulate matter emissions (PM) according to their size (Total Suspended Particulate matter - TSP, and
particle with size lower than 10, 7, 2.5 and 1 µm - PM10, 7, 2.5, 1) at basal time (T0), after 1.5 min (T1) and after 3 min
(T2) of use of the e-cigarette and conventional cigarette
e-cigarette Conventional cigarette Density ratio
conventional/e-cigarettes
T0 T1 T2 T0 T1 T2 T2
PM1 µg/m31 0 14 0 42 80 6
PM2.5 µg/m32 3 43 3 281 901 21
PM7 µg/m34 8 50 5 291 919 18
PM10 µg/m36 10 52 7 293 922 18
TSP µg/m313 17 63 16 305 933 15

284 R.M. Pellegrino et al.
Some data are available about the
ingredients of different e-cigarettes (8),
but it must be considered that there are
different types of commercially available
formulations of e-cigarettes; thus, toxi-
cological aspects related to these devices
may differ widely.
The e-cigarettes analysed in this study
are produced by a single Italian manu-
facturer.
The major constituent of both the
aromatic mixture (liquid) and vapour was
propylene glycol, as shown in previous
studies on different e-cigarettes (2, 9, 12,
13, 35, 37). Propylene glycol is a clear,
colourless, odourless and tasteless liquid
at room temperature; it may exist in air in
vapour form, and it is widely used as an
antifreeze and de-icing solution for cars,
airplanes and boats, as a solvent in the
paint and plastics industries, as a chemical
to generate artificial smoke for theatrical
productions, as an additive for several
drugs, cosmetics or food products, as a
solvent for food colours and flavours (1).
In the e-cigarette, it is used to simu-
late the appearance of standard cigarette
smoke (23).
The FDA classified propylene glycol
as “generally recognized as safe”, that is
acceptable for use in flavorings, drugs,
food, and cosmetics.
The toxicological profile of propylene
glycol, traced by the Agency for Toxic
Substances & Disease Registry (1), states
that inhalation of its vapours presents
no significant hazard in ordinary appli-
cations, but limited human experience
indicate that its mists may be irritating
for some individuals.
Propylene glycol is not classified
as hazardous under the EC Regulation
1272/2008 (16) (which replaces Directive
67/548/EEC for substances and Direc-
tive 1999/45/EC for preparations) on the
Classification, Labelling and Packaging
of substances and mixtures (CLP).
In the liquid some “dangerous”
substances (according to EC Regula-
tion 1272/2008) were also present:
methyl pyrazine, 2,3-dimethylpyrazine,
β-damascon, 1-hydroxy-2-propanone,
2,5-dimethyl pyrazine, 2,3,5,6-tetram-
ethyl pyrazine, 3-hydroxy-2-methyl-4-
pyranone, 5-methyl-2-furaldehyde, but
their concentrations were less than 0.1%,
the maximum limit allowed by law. This
statement, however, does not guarantee
the safety of e-cigarettes for smokers, but
it is related to just the production proc-
ess, the manipulation and holding of the
aromatic mixture.
The same substances recovered in
liquid were also present in the steam.
Their safety for users’ health strictly
depends on dosage (number of smoked
cartridges) and duration of active and/or
passive exposure, as well as on several
other variables related to the user (age,
gender, etc). Thus, it is difficult to trace
a universal risk profile since the danger
is related to personal habits. Moreover,
the difficulty in outlining the personal
risk profile is not only in evaluating the
quantities of airborne chemicals to which
one is exposed, but also the actual amount
that enters into the body. For this purpose,
it will be useful to study, in depth, users’
behaviour and to perform quantitative
risk assessment.
In the present study, both electronic
and conventional cigarettes caused an
increase of PM levels in indoor air. To
our knowledge, this is the first empirical
research on PM emissions of e-cigarettes;
thus it is not possible to compare our
data with other results. At the end of the
experiment with a conventional cigarette
PM emission was hundreds of times
higher than before smoking, in the same
order of magnitude as the results from
previous studies (21, 26, 31).
In both cases, the levels of PM10 and
PM2.5 exceeded the WHO air quality

285
Qualitative evaluation of exposure to an Italian electronic cigarette
guideline values (50 and 25 µg/m3 for
PM10 and PM2.5 respectively) (43). Nev-
ertheless, the guideline values refer to a
daily mean exposure, while PM concen-
trations of electronic and conventional
cigarettes were measured only during
and immediately after the experiment.
Notice that the increase of PM slightly
exceeds the WHO values in the case of
e-cigarettes, but is particularly conspicu-
ous in the case of a conventional cigarette.
Thus, data presented in this study should
not be considered a model of exposure
to PM emission for electronic or con-
ventional cigarettes, but they could be
the rational starting point for studies to
evaluate actual scenarios to compare daily
PM emission derived from the smoking
of electronic and conventional cigarettes.
Besides, since PM is a mixture of sub-
stances, it would be interesting to assess
not only the quantity of particles but also
their chemical composition (e.g. metals
or organic compounds).
However, it is important to highlight
that e-cigarettes may be less harmful
than tobacco given the lack of tar, carbon
monoxide, combustion products and all
the other chemicals (more than 4000 sub-
stances, some of them proven toxic and
carcinogenic) released from a “tobacco”
cigarette (23), and the lower production
of PM.
An important “human health” question
related to cigarette smoking is passive
smoking, better defined as environmental
tobacco smoke (ETS), that is the mix-
ture of the chemicals released from the
smouldering tobacco product. It is well
known that ETS is a threat to the health of
the non-smokers (36). In particular, ETS
exposure in the first years of life may re-
sult in irreversible damages in adult age:
together with the expected effects, such
as leukaemia, other kinds of cancer and
chronic respiratory diseases (28), recent
research evidenced long-term cardiovas-
cular effects in children exposed to ETS
(22, 33).
ETS results in a combination of sec-
ond- and third-hand smoke, where sec-
ondhand smoke is the mixture of chemi-
cals derived from the smoke exhaled by
a smoker together with the smoke from a
burning cigarette, while thirdhand smoke
is the combination of tobacco smoke pol-
lutants that adhere to the clothing and
hair of smokers and to surfaces, furnish-
ings, and dust in indoor environments,
persisting long after the clearing of sec-
ondhand smoke. Thus, secondhand smoke
exposure consists of an unintentional
inhalation of smoke that occurs close to
people smoking during the period of ac-
tive smoking. Thirdhand smoke exposure
consists of unintentional intake of smoke
that occurs in the absence of concurrent
smoking - even long after smoking has
ceased - through close contact with smok-
ers and in indoor environments in which
tobacco is regularly smoked (29).
In our opinion, this question should be
evaluated for e-cigarette too.
Conclusions
Overall, the e-cigarette seems to give
some advantages when used instead of
the conventional cigarette:
the users’ exposure to chemicals is
limited to few compounds included in the
aromatic mixture, while the combustion
of tobacco and paper of a conventional
cigarette produces more than 4000 sub-
stances;
PM emissions are significantly lower
for the e-cigarette for all the investigated
dimensional fractions;
given the above, the e-cigarette should
be less dangerous for second- and third-
hand smoke.
Due to the lack of specific research,
the e-cigarette should only be considered

286 R.M. Pellegrino et al.
a promising option to tobacco cigarettes.
First, toxicological studies should be con-
ducted on the whole chemical mixture, in
order to asses possible risks and, conse-
quently, to substitute the dangerous com-
ponents. Furthermore, there is a strong
need for studies on both users’ risks and
effectiveness in smoking cessation.
Abstract
The “electronic (e-)cigarette” generates intense
scientific debate about its use. Its popularity is increas-
ing worldwide as a method to reduce/quit smoking,
and to smoke indoors when restrictions on smoking
tobacco are present. WHO recommends caution, until
its effectiveness in helping smokers is clarified, and
the possible harm evaluated. The aim of this study was
to assess the content of the aromatic liquid mixture and
its vapour and the Particulate Matter (PM) emissions
of an Italian brand of e-cigarette and to compare its
PM emissions with a conventional cigarette.
Propylene glycol (66%) and glycerine (24%) were
main components in the liquid, while the flavouring
substances were less than 0.1%. The same substances
were detected in the vapour in similar proportions.
Fine and ultrafine PM emissions were higher for the
conventional versus the e-cigarette (e.g.: PM10=922
vs 52 µg/m3; PM1=80 vs 14 µg/m3).
The e-cigarette seems to give some advantages
when used instead of the conventional cigarette, but
studies are still scanty: it could help smokers to cope
with some of the rituals associated with smoking ges-
tures and to reduce or eliminate tobacco consumption
avoiding passive smoking. However, the e-cigarette
causes exposure to different chemicals compared with
conventional cigarettes and thus there is a need for
risk evaluation for both e-cigarettes and passive steam
exposure in smokers and non smokers.
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Corresponding author: Prof. Maria Sofia Cattaruzza, Department of Public Health and Infectious Diseases, Sapienza
University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
e-mail: mariasofia.cattaruzza@uniroma1.it