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Abstract

Objective: To evaluate performance of the I quit original smoking (iQOS) heat-not-burn system as a function of cleaning and puffing topography, investigate the validity of manufacturer's claims that this device does not burn tobacco and determine if the polymer-film filter is potentially harmful. Methods: iQOS performance was evaluated using five running conditions incorporating two different cleaning protocols. Heatsticks were visually and stereomicroscopically inspected preuse and postuse to determine the extent of tobacco plug charring (from pyrolysis) and polymer-film filter melting, and to elucidate the effects of cleaning on charring. Gas chromatography-mass spectrometry headspace analysis was conducted on unused polymer-film filters to determine if potentially toxic chemicals are emitted from the filter during heating. Results: For all testing protocols, pressure drop decreased as puff number increased. Changes in testing protocols did not affect aerosol density. Charring due to pyrolysis (a form of organic matter thermochemical decomposition) was observed in the tobacco plug after use. When the manufacturer's cleaning instructions were followed, both charring of the tobacco plug and melting of the polymer-film filter increased. Headspace analysis of the polymer-film filter revealed the release of formaldehyde cyanohydrin at 90°C, which is well below the maximum temperature reached during normal usage. Discussion: Device usage limitations may contribute to decreases in interpuff intervals, potentially increasing user's intake of nicotine and other harmful chemicals. This study found that the tobacco plug does char and that charring increases when the device is not cleaned between heatsticks. Release of formaldehyde cyanohydrin is a concern as it is highly toxic at very low concentrations.
34 DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
iQOS: evidence of pyrolysis and release of a toxicant
fromplastic
Barbara Davis, Monique Williams, Prue Talbot
Research paper
To cite: DavisB, WilliamsM,
TalbotP. Tob Control
2019;28:34–41.
Department of Molecular, Cell
and Systems Biology, University
of California, Riverside,
California, USA
Correspondence to
DrPrue Talbot, Department of
Molecular, Cell and Systems
Biology, University of California,
Riverside, CA 92521, USA;
talbot@ ucr. edu
Received 17 October 2017
Revised 12 January 2018
Accepted 26 January 2018
Published Online First
13March2018
ABSTRACT
Objective To evaluate performance of the I quit original
smoking (iQOS) heat-not-burn system as a function of
cleaning and puffing topography, investigate the validity
of manufacturer’s claims that this device does not
burn tobacco and determine if the polymer-film filter is
potentially harmful.
Methods iQOS performance was evaluated using
five running conditions incorporating two different
cleaning protocols. Heatsticks were visually and
stereomicroscopically inspected preuse and postuse
to determine the extent of tobacco plug charring
(from pyrolysis) and polymer-film filter melting, and
to elucidate the effects of cleaning on charring. Gas
chromatography–mass spectrometry headspace analysis
was conducted on unused polymer-film filters to
determine if potentially toxic chemicals are emitted from
the filter during heating.
Results For all testing protocols, pressure drop
decreased as puff number increased. Changes in testing
protocols did not affect aerosol density. Charring due
to pyrolysis (a form of organic matter thermochemical
decomposition) was observed in the tobacco plug after
use. When the manufacturer’s cleaning instructions
were followed, both charring of the tobacco plug and
melting of the polymer-film filter increased. Headspace
analysis of the polymer-film filter revealed the release of
formaldehyde cyanohydrin at 90°C, which is well below
the maximum temperature reached during normal usage.
Discussion Device usage limitations may contribute
to decreases in interpuff intervals, potentially increasing
user’s intake of nicotine and other harmful chemicals.
This study found that the tobacco plug does char
and that charring increases when the device is not
cleaned between heatsticks. Release of formaldehyde
cyanohydrin is a concern as it is highly toxic at very low
concentrations.
INTRODUCTION
With the rise of smoking alternatives, the electronic
nicotine delivery systems market has boomed, with
electronic cigarettes (EC) being among the most
popular worldwide.1 2 However, there are still a
number of conventional (combustible) cigarette
smokers who would welcome a cigarette-like tobac-
co-containing/nicotine-containing product that is
devoid of or has a significantly reduced toxicity
compared with conventional cigarettes.1 To appeal
to this demographic, Philip Morris International
(PMI) has released a new product called the iQOS
(I quit original smoking), which is a ‘heat-not-burn’
system,3 as an alternative to conventional cigarettes
and EC. The iQOS system uses a flange, called
the ‘heater’, which is composed of a silver, gold,
platinum, ceramic coating,4 to heat a rolled, cast-
leaf sheet of tobacco impregnated with glycerin,
thereby creating an aerosol without combustion.3
This aerosolisation process is proposed to reduce the
user’s exposure to toxic and carcinogenic chemicals
produced by the combustion of tobacco.5 6 Thus,
the consumer gets the ‘harm reduction’ component
of EC along with the mouth/throat feel of a conven-
tional cigarette. The iQOS system has been well
received in Japan and Italy. The iQOS is currently
sold in 26 markets by PMI with plans to expand to
over 30 countries, including the USA.7
Although this product has been extensively eval-
uated by the manufacturer,3 5 6 8–13 these studies
appeared in a journal that may have a deficient
review process,14 emphasising the need for inde-
pendent evaluation of the iQOS. As our initial
study, we have evaluated the performance of the
iQOS system under various conditions, tested the
effects of cleaning on performance and pyrolysis
and determined the composition of and potential
health risk from the polymer-film filter.
MATERIALS AND METHODS
iQOS product acquisition and storage
Four iQOS tobacco heating system kits, manufac-
tured by Philip Morris Products S.A. (Switzerland),
were purchased online at eBay (https://www. ebay.
com/) from sellers with a 98% or higher satisfac-
tion rating. Kits arrived sealed and in excellent
condition. Kits were inventoried, and the compo-
nents of each kit were placed into individual plastic
containers and stored in a dry area at 22°C when
not in use.
Cartons of Marlboro (blue box) heatsticks, manu-
factured by Philip Morris Brands Sàrl (Italy), were
purchased in Japan and shipped to us via a personal
shopper. Each carton was individually sealed and
in excellent condition. Heatsticks were stored,
unopened, in a dry, dark area at 22°C in their
cartons until used. Unused heatsticks from opened
packs were stored in an airtight bag in their carton.
Cleaning the iQOS
iQOS holders were tested using two cleaning regi-
mens: (1) the ‘per-use’ cleaning protocol in which
the device was thoroughly cleaned after each heat-
stick using the cleaning sticks to remove residual
fluid and tobacco plug debris from the heater and
surrounding base and to clean out the cap and (2)
the manufacturer’s recommended cleaning instruc-
tions in which the cleaning cycle was used after
every 20 heatsticks before using the brush cleaners.
When heatstick fragments were left behind, the
cleaning hook was used to remove these pieces, as
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DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
Research paper
Table 1 Performance of iQOS heat-not-burn holders
Holder Puff duration Puff interval Airflow rate (mL/s) Puff volume (mL)
Total number of
puffs
Average pressure
drop (mmH2O)
Average
absorbance
Low airflow rate 2 sprotocol*
A 2 25 7 14 14 13±5 0.42±0.08
B 2 25 7 14 14 13±4 0.45±0.08
C 2 25 7 14 14 18±7 0.46±0.06
Low airflow rate 4 sprotocol†
A 4 25 7 28 14 9±4 0.41±0.05
B 4 25 7 28 14 11±4 0.46±0.09
C 4 25 7 28 14 10±4 0.49±0.04
ISO standard‡
A 2 60 17.5 35 6 62±5 0.49±0.10
B 2 60 17.5 35 6 65±8 0.54±0.09
C 2 60 17.5 35 6 57±5 0.49±0.04
HCI standard§
A 2 30 27.5 55 12 103±9 0.26±0.03
B 2 30 27.5 55 12 100±9 0.41±0.05
C 2 30 27.5 55 12 105±13 0.42±0.05
Manufacturer’s recommended cleaning (HCI)¶
E 2 30 27.5 55 12 103±12 0.46±0.06
*Per-use cleaning protocol, standard pump head with Tygon 15 tubing.
†Per-use cleaning protocol, standard pump head with Tygon 15 tubing.
‡Per-use cleaning protocol, high-performance pump head with Tygon 15 tubing.
§Per-use cleaning protocol, high-performance pump head with Tygon 36 tubing.
¶Manufacturer’s recommended cleaning, HCI,high-performance pump head with Tygon 36 tubing.
HCI, Health Canada Standard ; ISO, International Organization for Standardization; iQOS, I quit original smoking.
necessary, and the holder cap was cleaned by a 5 min warm water
immersion. The instructions clearly state that the holder itself is
not to be wetted.
Performance evaluation
Pressure drop, which measures the draw resistance of the heat-
stick, aerosol absorbance (density), a measure of particulate
matter trapped within the aerosol, and puff number were evalu-
ated for iQOS products using equipment and protocols described
previously.15–17 Pressure drop across heatsticks was evaluated
using a Cole-Parmer Masterflex L/S peristaltic pump (Vernon
Hills, Illinois, USA) connected to a U-tube water manometer to
detect the change in differential pressure for each puff. Airflow
rates were precalculated/precalibrated to the appropriate
pump speed using a conversion factor provided by the pump
head manufacturer, and flow rate was verified using a Brooks
Instruments Sho-Rate flow meter (Hatfield, Pennsylvania, USA).
Aerosol density was evaluated by capturing aerosols in a tubular
cuvette, and absorbance was measured immediately at 420 nm
using a Bausch & Lomb spectrophotometer (120 V, 0.9 A, Roch-
ester, New York, USA).
iQOS devices were evaluated with five operating conditions;
four (conditions 1–4) used the per-use cleaning protocol and one
(condition 5) used the manufacturer’s recommended cleaning
instructions. The pump head, tubing set-up and running condi-
tions were as follows: (1) low airflow rate 2 s protocol—the peri-
staltic pump was outfitted with a Cole-Parmer Masterflex Model
7015-21 pump head (standard pump head) using Masterflex Tygon
E-LFL (tubing size 15) tubing to generate a flow rate of 7 mL/s with
a 2 s puff duration for a total puff volume of 14 mL, 14 puffs were
taken at 25 s intervals; (2) low airflow rate 4 s protocol—the same
pump set-up and running conditions as for condition 1 with a 4 s
puff duration generating a 28 mL puff volume; (3) International
Organization for Standardization (ISO)—the pump was outfitted
with a Cole-Parmer Masterflex L/S Easy-Load II Model 77200-52
high-performance pump head with Masterflex Tygon E-LFL
(tubing size 15) producing a 17.5 mL/s flow rate with a 2 s puff
duration, generating a total puff volume of 35 mL, with a total of
six puffs taken, one puff every minute; (4) the Health Canada stan-
dard (HCI)—a Cole-Parmer Masterflex L/S Easy-Load II Model
77200-52 high-performance pump head was used with Masterflex
Tygon E3603 (tubing size 36) tubing for a flow rate of 27.5 mL/s,
with a 2 s puff for a total puff volume of 55 mL, 12 puffs were taken
at 30 s intervals; (5) manufacturer’s recommended cleaning (HCI),
the same pump set-up and running conditions as described for
condition 4 but in the absence of per-use cleaning; for this protocol
the manufacturer’s recommended cleaning instructions were
followed (table 1). For conditions 1–4, three different iQOS devices
were evaluated with each device being tested in triplicate, that is, a
new heatstick was used for each experiment; condition 5 employed
a single device in which 10 heatsticks were tested without cleaning
between each stick.
Effect of use on the tobacco plug and polymer-film filter
The condition of the tobacco plugs was evaluated by visual
and microscopic inspection and imaged using a Nikon C-LEDS
stereomicroscope equipped with a Nikon Digital Sight DS-Vi1
camera head (Nikon, Minato, Tokyo, Japan) before and after
use. Some heatsticks were dissected before and after use to
further evaluate residual char (referred to as ‘char’ only) of the
tobacco plugs and the condition of the polymer-film filter.
Gas chromatography–mass spectrometry analysis of iQOS
heatstick polymer-film filters
Gas chromatography–mass spectrometry (GC–MS) using a qual-
itative wide-scope screening method was performed using an
Agilent 7890B GC coupled with a 5977A MSD equipped with a
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36 DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
Research paper
Figure 1 The I quit original smoking (iQOS) heat-not-burn system. (A) An iQOS starter kit. (B) The kit consists of an instruction manual, iQOSpocket
charger, iQOSholder, USB cable, iQOScleaning sticks, wall charging adapter and iQOS cleaner. (C) Profile view of iQOS holder inside a pocket charger.
(D) Individual pack of iQOScleaning sticks with an example of an unused stick and a stick after a single use per end. (E) A closed and opened
iQOScleaner; the larger end contains the long brush and protruding cleaning hook, and the shorter end contains the short brush. (F) Internal view of
the iQOS cleaner showing the two brushes (long brush on the left, short brush on the right). (G) The cleaning hook removed from the iQOScleaner. (H)
Marlboro iQOS Heat Stick carton (containing 10 individual packs), sealed individual pack and opened pack exposing heatsticks.
7698A Headspace Sampler (Santa Clara, California, USA). Eval-
uation of iQOS aerosols was performed using headspace analysis.
Chromatographic separation was accomplished using an Agilent
J&W HP-5ms Ultra Inert GC Column (30 mx0.25 mmx0.25 µm)
and ultra-pure helium (>99.999% purity) as the carrier gas at a
flow rate of 1.5 mL/min. For headspace analysis, three unused
heatsticks were dissected, polymer-film filters were removed,
and a 3 mm portion (16.7%) closest to the tobacco plug were
excised and placed into 20 mL headspace vials. All samples were
analysed with a split ratio of 50:1, a solvent delay of 2 min,
with blank analysis between each sample. GC ramp conditions
were as follows: 40°C for 5 min, 45°C for 5 min, 90°C for 5 min,
130°C for 5 min, 135°C for 5 min, 165°C for 5 min, 190°C for
2 min, all temperature ramps were at 10°C/min. Ionisation of
compounds was performed using electron impact ionisation at
70 eV in positive mode, the ion source maintained at 250°C
and chemicals were identified using the National Institue of
Standards and Technology mass spectral library (Gaithersburg,
Maryland, USA), only chemicals with an 85% or higher probably
match were listed as identifiable.
RESULTS
Components in the iQOS heat-not-burn system
The iQOS kit (figure 1A–G) consists of an instruction manual
written in German, English, Portuguese and Italian, a pocket
charger, the holder (device), a Universal Serial Bus (USB) cable
and a European wall adapter plug for charging, moist cleaning
sticks to clean the holder and cap, and the cleaner, which
contains a long brush for cleaning the inside of the holder,
where the heater is housed, a short brush for cleaning the cap
and a hook for removing pieces of tobacco plug left in the
holder/cap. A universal power adapter was purchased from
Amazon (https://www. amazon. com/) and used to charge the
pocket charger unit. Each carton of iQOS heatsticks contained
10 individually wrapped packs, and each pack had 20 heat-
sticks (figure 1H).
The iQOS kit components had an overall feel of good
craftsmanship. The fabrication of the tobacco plug cast-leaf
demonstrates a waste not want not strategy in that the plug is
fabricated from pulverised tobacco remnants/waste materials,
including tobacco stems, torn leaf material and leaf dust.18
These items are reconstituted with natural adhesives and glyc-
erin (a solvent that is used in EC fluids to produce aerosol) and
processed into sheets forming cast-leaf, which is rolled and
used as the tobacco plug.3
Cleaning of iQOS device
The interior chamber of the holder contained a heating element,
referred to in the iQOS instruction manual as the silver, gold,
platinum, ceramic-coated heater (figure 2). Unused holders
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Research paper
Figure 2 Internal view of the I quit original smokingholder. (A–C) Clean, unused holder showing heater (blue arrows). (D–F) Used holder that was
cleaned after every use; black residue remains on heater (red arrows). (G–I) Used holder that was not cleaned between uses (10 uses).
were clean and debris-free with a white base and white heater
with a metallic coil in its centre (figure 2A–C). Used holders
that were thoroughly cleaned with the cleaning sticks between
each heatstick were generally similar to the unused holder,
except that the heating element had deposits of hardened dark
debris that was not removed by the cleaning stick, cleaning
cycle of the pocket charger or long brush (figure 2D–F). In the
used holder that was not cleaned between heatsticks (manu-
facturer’s recommended cleaning), brown liquid and partic-
ulates covered the base, walls and heater (figure 2G–I). With
continued use in the absence of cleaning, the volume of liquid
and debris increased, and the pieces of debris became darker
and appeared more charred (figure 2D–I were taken after the
10th heatstick was used).
iQOS performance
The iQOS gives users a maximum of 14 puffs during a 6 min
window per heatstick, after which it must be recharged before
it can be used again. Performance of the iQOS was evaluated
using five puffing protocols (figure 3, table 1). For protocols
1–4, three different iQOS devices (holders A, B and C) were
tested in triplicate, that is, a new heatstick was used for each
experiment, and each device underwent an intensive cleaning
between each heatstick. For protocol 5, a single device (holder
E) was used, and it was not cleaned between 10 heatsticks
(average of the first three heatsticks is shown in figure 3I,J).
For all testing protocols, pressure drop decreased as puff
number increased. Aerosol density readings increased with
use, peaking around puffs 7–9 and then begin to decrease.
Although pump set-up affected pressure drop, it did not affect
aerosol absorbance which remained similar under all running
conditions, However, differences in testing conditions may
lead to alterations in the chemical constituents present within
the aerosol without altering aerosol density. Not cleaning did
not affect performance except that pressure drop was more
variable during the first four puffs in the uncleaned trials.
Tobacco plug charring
Dissection of unused and used heatsticks showed tobacco
plug charring (figure 4A). Stereomicroscopic comparison
of unused (figure 4B) and used (figure 4C) tobacco plugs
confirmed charring or blackening of the cast-leaf. Visual
and stereomicroscopic inspection of used heatsticks show
the effects cleaning had on device heat production. Compar-
ison of the first and 10th used heatstick from holder A (per-
use cleaning) shows that with regular cleaning the charred
area surrounding the heater, referred to as the zone of char-
ring, does not increase with use (figure 4D,E). The effects
of cleaning on heating were most evident during the course
of the manufacturer’s recommended cleaning (HCI) testing.
Comparison of these heatsticks to unused and per-use cleaned
heatsticks showed that in the absence of regular cleaning, the
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38 DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
Research paper
Figure 3 Performance characteristics of the I quit original smokingheat-not-burn system. (A, C, E, G and I) Pressure drop is plotted versus the puff
number for five puffing protocols. (B, D, F, H and J) Absorbance is plotted versus puff number for the five puffing protocols. Each line of the graph
represents the average of three heatsticks for an individual holder (holder A=red, holder B=green, holder C=blue and holder E=purple).HCI, Health
Canada Standard ; ISO, International Organization for Standardization.
zone of charring increased as the number of heatsticks tested
increased (figure 4H–L).
Polymer-film melting
Effects of cleaning on heating were not exclusive to the tobacco
plug; figure 4A shows that the polymer-film filter (labeled 2), which
is separated from the tobacco plug (condition 4) by the hollow
acetate filter (condition 3), was adversely effected. The aerosol
produced by the iQOS was hot enough to melt the polymer-film
filter, which could allow release of potentially hazardous chemicals.
Melting of the polymer-film filter was evident by slight yellowing of
the filter, as well as by narrowing of the end closest to the tobacco
plug (figure 4A indicated by black arrow). This melting and subse-
quent cooling of the filter caused it to harden, preventing it from
being longitudinally dissected. Comparison of unused and used
polymer-film filters from both per-use and manufacturer’s recom-
mended cleaning experiments showed the relationship between
cleaning and increased heat generation. First (figure 4F) and 10th
(figure 4G) filters from cleaned devices showed similar discol-
oration and melting to that of the first filter from the uncleaned
device (figure 4N). Comparison of these heatsticks to subsequent
manufacturer’s recommended cleaning used heatsticks showed
discoloration and melting of the polymer-film filter increased with
increased use (figure 4M–Q).
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Research paper
Figure 4 Charring of tobacco plug and melting of polymer-film filter. (A) Dissected heatsticks, each heatstick is composed of: (1) the low-density
cellulose mouthpiece filter, (2) polymer-film filter, (3) hollow acetate tube and (4) tobacco plug. Heatsticks from left to right are unused stick with
the paper overwrap peeled away, and used stick with the paper overwrap removed with the mouthpiece filter and hollow acetate tube sliced open;
black arrow indicates melted region of the polymer-film filter, black asterisk denotes tobacco plug fragments that have been drawn into the hollow
acetate tube. (B) An unused tobacco plug. (C) Used tobacco plug showing charring/darkening with use. (D,E) Cross sections of tobacco plugs from the
first (D) and 10th (E) heatstick of holder A of the cleaned experiment. Yellow outlined area indicates a void in the cast-leaf left by the heater, the area
between the yellow and green outlines are the charred portions of the tobacco plug. (F,G) Cross sections of polymer-film filter from the first (F) and
10th (G) heat stick. Polymer-film filter images shown coincide with tobacco plug images (D) and (E). (For D–G, CHS=cleaned device heatstick.) (H–L)
Cross sections of tobacco plugs before use (H) and after use from the first, fourth, sixth and 10th heatstick of the uncleaned experiment (I–L). Yellow
outlined area indicates a void in the cast-leaf left by the heater, area between the yellow and green outlines are the charred portions of the tobacco
plug. (M–Q) Cross sections of polymer-film filter before (M) and after use (N–Q). Polymer-film filter images shown coincide with tobacco plug images
(H–L). Blue arrowheads show charred pieces of cast-leaf that are affixed to the tobacco plug (K) and polymer-film filter (Q). (For (I–L) and (N–Q),
UHS=uncleaned device heatstick). (R) Unused and used whole polymer-film filters showing discoloration and film melting, as demonstrated by the
narrowing of the used filter. (S) Gas chromatography–mass spectrometry headspace analysis of unused polymer-film filter. Chromatogram shows an
overlay of three runs, relative abundance was plotted versus retention time in minutes, unidentifiable peaks were unlabelled. Inset shows a magnified
view of peaks with close retention times.
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40 DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
Research paper
What this paper adds
Performance characteristics were generally uniform between
devices and heatsticks.
I quit original smoking (iQOS) device usage limitations make
modifications to some current smoking standards necessary
for proper evaluation of products.
Device limitations may decrease users’ interpuff intervals,
increasing possible toxic exposures.
iQOS holders heat hot enough to cause charring of the
tobacco plug via pyrolysis and melting of the polymer-film
filter.
iQOS holder cleanliness affects and contributes to increased
charring of the tobacco plug and melting of the polymer-film
filter.
Formaldehyde cyanohydrin, a toxicant, was released from the
polymer-film filter at 90°C.
Headspace analysis of unused polymer-film filters
GC–MS headspace analysis of unused polymer-film filters
showed the presence of ε-caprolactone and lactide, common
components in plastics, as well as 1,2-diacetin, a plasticiser
(figure 4S). However, of most concern was the presence of form-
aldehyde cyanohydrin (glycolonitrile), an acute toxicant often
used in the production of synthetic resins and used as a solvent.19
Formaldehyde cyanohydrin was eluted at 17.97 min, when the
column reached 90°C.
DISCUSSION
Unlike some EC, which often show significant variation in crafts-
manship and performance within and between brands,15 20 the
iQOS appearance, design and performance data are consistent
with a product that is well manufactured. However, some design
features of the iQOS, such the limited time allowed per heatstick
and the need to consume the entire heatstick within this time or
alternatively waste part of it, will affect user’s topography and
may lead to unwanted exposure to potentially toxic chemicals
emitted from melting plastic and from pyrolysis of tobacco.
In contrast to tobacco and EC, which usually have no
constraints on puffing, the iQOS only operates for 6 min, at
which time it automatically shuts off and requires charging before
it can be used again. Since a maximum of 14 puffs can be taken
from each iQOS heatstick, puffing needs to be done at about
25 s intervals to take full advantage of each heatstick; used heat-
sticks that have not been fully exhausted cannot be used again
as reinsertion would cause the delicate cast-leaf tobacco plug to
crumble. This may not appeal to all users, and users who puff
less frequently would have a lower number of puffs/heatstick.
For users wishing to maximise each heatstick, this limitation will
force them to alter their smoking topography by decreasing the
interpuff interval and/or accelerating the rate at which they puff,
leading to larger volumes of aerosol inhalation.
The manufacturer’s cleaning instructions were not fully devel-
oped in the instruction manual. The cleaning protocol recom-
mended using the cleaning function of the charger followed by
cleaning with the brushes after 20 heatsticks and removing any
large fragments of tobacco plug with the hook if necessary. The
iQOS kit was equipped with cleaning sticks (figure 1B,D), yet
their use was not mentioned in the instruction manual. Our data
show that use of one heatstick left a significant amount of debris,
fluid and fragments of cast-leaf in the holder (figure 2).
While iQOS heatsticks do not produce a flame, they were
always charred after use, which we interpret to be a result of
pyrolysis. The zone of charring was greater when cleaning was
not performed between heatsticks, suggesting that build-up
of fluid and debris in the holder increases pyrolytic tempera-
tures. These data are consistent with the idea that despite simi-
larities in performance characteristics, the cleanliness of the
device plays a critical role in thermal regulation. Pyrolysis of
tobacco is an endothermic reaction which occurs at tempera-
tures between 200°C and 600°C, during which the majority of
volatile and semivolatile components of cigarette smoke are
formed.21 22 Although the Philip Morris study indicated that the
aerosol produced by iQOS devices reduce the amount of chemi-
cals found on the Food and Drug Administration's Harmful and
Potentially Harmful Constituents list by limiting tobacco pyrol-
ysis,5 our study, showing charring, in conjunction with a study
by Auer et al, which confirmed the presence of volatile organic
compounds, polycyclic aromatic hydrocarbons, carbon dioxide
and nitric oxide,23 contradict the claim that tobacco pyrolysis
is minimised in iQOS. Although iQOS operates at temperatures
less than 350°C, this does not negate the formation of volatile
and semivolatile harmful constituents of tobacco smoke, which
tend to have boiling points that range from 70°C to 300°C.21 22
Heatsticks used in this experiment were dissected and the
severity of polymer-film filter melting was examined. The func-
tion of the polymer-film filter is to cool the aerosol,3 thus, it
would seem that the polymer composing the film should be heat
resistant, although, ε-caprolactone, also known as polycaprolac-
tone, tends to have a low-melting point which is thickness depen-
dent.24 The intensity of the heat produced by the iQOS, under
both cleaned and uncleaned conditions, was sufficient to melt
the polymer-film filter, even though it was not in direct contact
with the heater. The amount of damage to the film (increase in
melt and alteration of coloration) increased with each heatstick
when cleaning was done per the manufacturer’s recommended
procedure (after 20 heatsticks). Discoloration may be a product
of heating and/or staining from the brown fluid that is expelled
from the tobacco plug during use.
Our GC–MS data indicate that components of the poly-
mer-film filter are aerosolised at relatively low temperatures.
GC–MS headspace analysis of unused filters suggests the poly-
mer-film filter is a combination of ε-caprolactone, lactide,
1,2-diacetin and other unidentified chemicals. The chemicals
released from the film filter during heating may not be suitable
for inhalation. Thus, it is unknown if the film filter material is
safe for use in products where it would undergo intense cycles
of heating and cooling. Of greatest concern was the release from
the polymer filter of formaldehyde cyanohydrin, a highly toxic
chemical that is metabolised in the liver and broken down into
formaldehyde and cyanide.19 Formaldehyde cyanohydrin can be
fatal to humans,19 25 26 with studies showing mouse inhalation
LDLo, the lowest dose of a toxicant that causes the death of an
animal,27 values as 27 ppm/8 hour.28 29 iQOS holders operate
at temperatures between 330°C and 349°C,3 23 and as a safety
feature, the device shuts off when temperatures reach 350°C.
The release of formaldehyde cyanohydrin from unused filters
during GC–MS analysis occurred at 90°C, a temperature that all
users will exceed.
In conclusion, the iQOS appears to be well manufactured, and
performance data were consistent between heatsticks. However,
the product has limitations that will affect user topography and
the application of standard smoking protocols, such as the ISO
3308, which could not be used for more than six puffs with this
product. Users may be forced to smoke at a rapid pace in order
copyright. on 17 December 2018 by guest. Protected byhttp://tobaccocontrol.bmj.com/Tob Control: first published as 10.1136/tobaccocontrol-2017-054104 on 13 March 2018. Downloaded from
41
DavisB, etal. Tob Control 2019;28:34–41. doi:10.1136/tobaccocontrol-2017-054104
Research paper
to fully maximise heatsticks. Decreasing the interpuff interval
could lead to an increase in intake of nicotine30 and carbonyls.31
This study also showed that the iQOS is not strictly a ‘heat-not-
burn’ tobacco product. The iQOS tobacco appeared to char
without ignition, and charring increased when cleaning was not
done after each use. This study also showed the potential dangers
that the polymer-film filter poses. This thin plastic sheet, readily
melts during iQOS use and releases formaldehyde cyanohy-
drin, a dangerous toxicant. This study has shown that the iQOS
system may not be as harm-free as claimed and also emphasises
the urgent need for further safety testing as the popularity and
user base of this product is growing rapidly.
Acknowledgements We thank Careen Khachatoorian for her help setting up the
GC-MS analysis and Vivian To for her help with GC-MS analysis.
Contributors BD: conceiving and designing experiments, performing experiments,
writing and editing manuscript. MW: performing performance experiments and
writing part of the Materials and methods section. PT: conceiving and designing
experiments, editing manuscript, obtaining funds and overseeing the project.
Funding This work was supported by a grant (number 25ST30041) from the
Tobacco-Related Disease Research Program (TRDRP) of California.
Disclaimer The content is solely the responsibility of the authors and does not
necessarily represent the official views of the TRDRP.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
© Article author(s) (or their employer(s) unless otherwise stated in the text of the
article) 2019. All rights reserved. No commercial use is permitted unless otherwise
expressly granted.
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As part of current harm reduction strategies, candidate modified risk tobacco products (MRTP) are developed to offer adult smokers who want to continue using tobacco product an alternative to cigarettes while potentially reducing individual risk and population harm compared to smoking cigarettes. One of these candidate MRTPs is the Tobacco Heating System (THS) 2.2 which does not burn tobacco, but instead heats it, thus producing significantly reduced levels of harmful and potentially harmful constituents (HPHC) compared with combustible cigarettes (CC). A controlled, parallel group, open-label clinical study was conducted with subjects randomized to three monitored groups: (1) switching from CCs to THS2.2; (2) continuous use of non-menthol CC brand (CC arm); or (3) smoking abstinence (SA arm) for five days. Exposure response was assessed by measuring biomarkers of exposure to selected HPHCs. To complement the classical exposure response measurements, we have used the previously reported whole blood derived gene signature that can distinguish current smokers from either non-smokers or former smokers with high specificity and sensitivity. We tested the small signature consisting of only 11 genes on the blood transcriptome of subjects enrolled in the clinical study and showed a reduced exposure response in subjects that either stopped smoking or switched to a candidate MRTP, the THS2.2, compared with subjects who continued smoking their regular tobacco product.