Electronic cigarettes (ECs) are battery-powered devices that generate an aerosol of propylene glycol and/or glycerol, usually with nicotine and flavours, from a cartridge or reservoir of solution (‘e-liquid’), for inhalation (vaping). Unlike cigarettes, ECs do not combust tobacco—no smoke is involved.
Most ECs are cigarette lookalikes (‘cigalikes’), some are disposables (lacking re-chargeability), and some are ‘second-generation’ models containing a larger tank that permits the user to refill with e-liquid, and a larger battery, with ability to alter power or voltage.
The original EC from which all subsequent ECs have evolved was invented in 2003 by a North Chinese pharmacist, Hon Lik, and developed into a marketable product by the Beijing-based company, Ruyan. Early research on this product conducted by the University of Auckland found that among smokers without prior EC use, the Ruyan EC produced reductions in cigarette craving and low levels of nicotine delivery into the bloodstream, comparable with the pharmaceutical nicotine inhaler.1 Several laboratory studies of early ECs found toxic aldehydes, at levels far lower than in cigarette smole.2,3
In 2013, Bullen et al published a randomised controlled trial (RCT) comparing the cessation efficacy of Elusion brand EC popular in New Zealand (NZ) with nicotine and zero-nicotine cartridges, versus nicotine patches. This study suggested the EC at 6 months after quitting was at least as effective for sustained cessation as patches.4 To date, one other cessation RCT has confirmed this result.5 However, both trials were underpowered.
A recent Cochrane review included a meta-analysis of these studies, and concluded that the evidence for a cessation benefit compared with nicotine replacement therapy (NRT) was not sufficiently strong to change current regulations. ECs with nicotine, however, were more effective for cessation than ECs without nicotine.6
ECs have been available for sale in NZ since 2007 and have grown in popularity since, despite a regulatory regimen that treats nicotine as a medicine. Under the Medicines Act individuals may import ECs and e-liquid with nicotine for personal use only. If the EC or e-liquid contains nicotine or if therapeutic (i.e. cessation) claims are made then they cannot be sold. Nevertheless, ECs are widely available, although few retailers openly sell ECs. E-liquid with nicotine is thus generally purchased online from a range of overseas sources.
Remarkably, very little is known about the chemical composition of ECs available in NZ. In this paper I present findings from an analysis of 14 leading EC brands available in NZ in 2013.
Method
Selection of products—We selected 14 ECs based on probable origin—8 popular brands sold by importers direct from China, and 6 from the UK and USA based on popular brands promoted in e-cigarette forums. Nine were cigarette lookalikes with refill capacity, 3 were disposables (K, L, M in Table 1) which cannot be refilled, and two contained cartomisers (mouthpiece and nicotine reservoir) with a larger tank and battery (such as A and C in Table 1). “Mods” (modified by individual users) were not included.
We purchased products via the Internet from the distributors in 2013. Sales data for individual brands was not known due to the illegality of sales. All ECs were labelled as having high nicotine content (16–18 mg or higher) except for one with 14.5 mg, one with 11 mg and one with zero nicotine. Only tobacco flavour variants were tested. Brands were excluded if they lacked manufacturer information, if they failed to generate 150 puffs, or were expensive with no future access to refills.
Comparators—We compared the results from 2013 models of the products with those of the Ruyan classic V8 EC, tested in 2008 by Health New Zealand Ltd,3 and with those from testing in 2005 of the Marlboro king size filter cigarette, a globally known brand, by Labstat under Health Canada Intensive mode (one 55 mL puff every 30 seconds.7) To compare EC vapour with volume of puff from cigarettes we set mean daily cigarette consumption at 12 per day based on findings from a New Zealand study of manufactured cigarettes.8 We derived puffing parameters from Polish research9 but set puff duration longer at 3 seconds (not 1.8 seconds) to ensure ECs with heating coils slower to heat were included.
Selection of toxicants in vapour—Toxicants tested in the vapour were the volatile aldehydes: formaldehyde, acetaldehyde and acrolein; and the glycols (diethylene glycol [DEG] and monoethylene glycol [MEG]). We did not test tobacco-specific nitrosamines, as Goniewicz and other researchers who did so found nitrosamines NNN and NNK present in only trace quantities in 12 EC tested,9 similar to findings for nicotine gum and patches. We did not test for particulates as these have been found not to include the carcinogenic particulates found in diesel, cigarette or coal exhaust; nor for diacetyl.
Procedures—Labstat International ULC, Ontario, Canada, tested 9 of the EC brands for toxic aldehydes and glycols. The puffing parameters were derived from methods developed with Health Canada: 70 mL puff volume, inter-puff interval 10 seconds, puff duration 3 seconds, modified slightly from the Canadian Tobacco Reporting Regulations.10 Test ECs were vaped on a linear smoking machine. For nicotine and humectants, 60 puffs per brand were collected, and for testing of carbonyls, 150 puffs per brand were collected. Each EC was vaped in series of 15 puffs.
The first series of puffs, a priming series intended to ‘stabilise’ the EC deliveries, were vaped onto a pad that was subsequently discarded. After 5 minutes, the second series of 15 puffs was initiated, collecting the solids on a pre-weighed and conditioned pad, then repeated until a total of 60–150 puffs were collected on to the pad. Toxic aldehydes in vapourwere analysed by passing the vapour through two impingers containing acidified 2,4-dinitrophenylhydrazine in acetonitrile. Impinger contents were filtered and diluted with trizma base in aqueous acetonitrile.
High-performance liquid chromatography with ultraviolet detection (365 nm) was then used to achieve separation using a reverse phase C18 column (250 × 4 mm, 100, RP 18e) with a mobile phase gradient consisting of water, acetonitrile, tetrahydrofuran and isopropyl alcohol. To measure nicotine and its alkaloids in liquid, an entire EC cartomiser was transferred to a 15 mL glass culture tube, 10 mL of alkaloids extraction fluid added, the tube capped, then after 3 hours in a ultrasonic bath shaken by wrist action of 0.5 hours, analysis of the extract by gas chromatography with a thermionic specific detector equivalent to a nitrogen-phosphorus detector was undertaken. Separation was achieved using a fused silica coated column with base deactivated polyethylene glycol (PEG) stationary phase 30 m × 0.25 mm × 0.25 micrometres.
At Health New Zealand Ltd (HNZ) total vapour volumes were estimated by suctioning standard puffs of 70 mL from the ECs, using fully re-charged batteries, syringe and leak-free three-way tap until no more visible mist was obtained.
Canterbury Health Laboratories, Christchurch, New Zealand (CHL) measured the nicotine content in each EC before and after exhaustion of the nicotine by suction. In cartomiser ECs, nicotine content was determined by dismantling the cartomisers and dissolving the nicotine in ethanol. Nicotine delivery per cartomiser was calculated as the product of nicotine per puff and the number of standard puffs.
Results
In Table 1 considering those labelled 14 mg or more, the mean nicotine value was 18.1 mg (range 5 mg–46 mg) per cartomiser, and after average 199 (range 100–307) puffs per cartomiser a mean 8.7 mg (range 3 mg–16 mg) was available to be used by the vaper before exhaustion. ECs had a nicotine mean value of 43 mcg per puff (range 18 mcg–93 mcg per puff). Puff volumes were highest for clearomisers and lowest for cigalike brands. Nicotine content per puff of Elusion Ego (80 mcg per puff) and Innokin (93 mcg per puff) was about one-half to two-thirds that of the 147 mcg of nicotine per puff from a Marlboro cigarette.
Table 2. Aldehyde yields from nicotine ECs in 2013, compared with Ruyan and Marlboro yields in previous years
|
|
Laboratory: Labstat Canada |
Formaldehyde, (F) Acetaldehyde (Aa), Acrolein (Acr) |
||||||
|
E-cigarette brand name |
As micrograms per litre (mcg/L) of vapour or smoke |
As percentage of Marlboro toxicants yields |
||||||
|
|
|
F |
Aa |
Acr |
F |
Aa |
Acr |
Mean |
|
H |
Greensmoke |
2.50 |
1.52 |
1.90 |
2.1 |
0.1 |
0.9 |
1.0 |
|
E |
Easy Puff |
0.51 |
0.58 |
3.58 |
0.4 |
0.0 |
1.8 |
0.7 |
|
I |
Elusion 16 mg |
0.48 |
0.64 |
0.13 |
0.4 |
0.0 |
0.1 |
0.3 |
|
A |
Elusion Ego |
0.82 |
0.58 |
0.13 |
0.7 |
0.0 |
0.1 |
0.4 |
|
B |
Republic |
1.32 |
0.63 |
0.42 |
1.1 |
0.0 |
0.2 |
0.5 |
|
L |
Republic Liberty disposable |
1.46 |
0.58 |
0.42 |
1.2 |
0.0 |
0.2 |
0.8 |
|
F |
Blu |
0.56 |
0.58 |
2.39 |
0.5 |
0.0 |
1.2 |
0.2 |
|
G |
Mirage Goldstar |
0.70 |
0.58 |
0.13 |
0.4 |
0.0 |
0.1 |
0.2 |
|
D |
Liberro Purity |
0.48 |
0.64 |
0.13 |
0.6 |
0.0 |
0.1 |
0.2 |
|
|
Average 2013 |
1.07 |
0.81 |
1.06 |
0.93 |
0.04 |
0.43 |
0.48 |
|
|
Ruyan classic |
1.47 |
5.52 |
3.77 |
1.3 |
0.2 |
1.6 |
1.05 |
|
|
Marlboro KSF |
116 |
2282 |
231 |
100 |
100 |
100 |
100 |
Table 2 shows mean yields in the vapour for the toxicants formaldehyde, acetaldehyde and acrolein of around 1 mcg per litre of liquid. Mean aldehydes in the ECs were 73% lower on average than the same aldehydes tested in Ruyan EC vapour in 2008. A litre of Marlboro cigarette smoke in 2005 yielded over 100 times more formaldehyde, 2800 times more acetaldehyde and over 200 times more acrolein than the study EC brands. Propylene glycol (103 mg, range 63–149 mg per cigarette) exceeded glycerol (41 mg, range 23–103 mg per cigarette) in seven brands tested. DEG and MEG were below the level of detection (0.12% for DEG, 0.18% for MEG).
Discussion
Our analyses indicate that since 2008 the amount of nicotine in EC vapour has increased but is still lower per puff than that of a Marlboro cigarette. The ASCEND trial used a 2011 Elusion 16 mg cartomiser model,4 but by 2013 Table 1 shows eight brands had a higher nicotine content than the 2011 Elusion product. It is possible that if the ASCEND trial was repeated using current products the results for cessation might have been more impressive. We found differences between labelled and actual nicotine content. These highlight a lack of quality control that should be attended to through monitoring as part of a regulatory regimen.
The level of aldehydes in EC vapour has reduced over time and is 200 times lower than for the Marlboro cigarette. Formaldehyde concentrations for most brands were below the level at which mild sensory irritation in humans occurs (≥ 1 ppm) and at which respiratory tract cancer risks are considered very low.11 The level of non-nicotine alkaloids is also low, making up 0.49% of the nicotine content of the liquid in the refills or bottles. This is similar to the findings of Etter et al in 2013.12
The levels of propylene glycol and glycerol vapour are of no great concern. Propylene glycol has been tested long-term in rats, primates and children with no marked adverse effect;3 glycerol is non-toxic. Importantly, no DEG was detected in any of the brands.
Diacetyl may be toxic but was not tested for. Metals were found to be under the limit found acceptable for use12 but were not tested for. We did not test for particulates as these have been found not to include the carcinogenic particulates found in diesel, cigarette or coal exhaust.13
ECs are being used by many New Zealanders. A recent NZ Health Promotion Authority survey showed that 23% to 39% of respondents had used ECs (with the highest level among those who had quit or tried to quit recently), and 8–16% had used them in the past 2 weeks.14 These data and NZ research.1,4,13 suggest that ECs have potential to encourage smokers to switch from smoking cigarettes to using ECs, which the current study indicates are likely to be far safer.
