Investigating e-cigarette puffing patterns and user behaviour associated with high and low strength nicotine e-liquids is one of the objectives Lynne Dawkins wants to achieve with this study  that will be carried out at London South Bank University. The researcher expects to get insights in how this affects toxicant and carcinogen exposure.
Implications for public health messaging and for regulations on nicotine concentrations in e-liquids will be addressed by this study that aims at understanding the risks compensatory puffing will have. The researchers will not only take into consideration the relative risks but also subjective effects associated with using high and low strength nicotine e-liquid.
Lowering nicotine strength, a choice or a necessity dictated by regulations
The first reason evoked by the researchers was the belief that it is healthier. Other reasons were the desire to wean off nicotine or, due to the EU Tobacco Products Directive, the necessity to downgrade their nicotine strength to remain compliant with the 20 mg/ml nicotine concentrations in e-liquids introduced in May 2016.
“[…] contrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs.”
Lowering nicotine strength, what do we know about it?
Tobacco smokers, when switching to lower nicotine yield cigarettes, increase puff frequency, duration and volume when switching. Blood nicotine levels are maintained at high levels.
After switching to vaping, smokers typically take shorter puffs and it may take them a week or so to adjust their puffing patterns by a process called “self-titration” of nicotine, a subject that the principal researcher of this study knows very well.
“Self-titration” of nicotine, an inconspicuous mechanism
In a previous article , the Dr Dawkins explored the effects of high (24 mg/ml) and low (6 mg/ml) nicotine strength liquid on puffing topography (puff number, puff duration, volume of e-liquid consumed). She found that e-liquid consumption, puff number were higher and puff duration longer in the low nicotine strength condition, a nicotine compensation mechanism that is known as “Self-titration” in tobacco literature but poorly described in e-cigarette studies. No statistically significant differences were observed between conditions in self-reported craving, withdrawal symptoms, satisfaction, hit or adverse effects, which means that compensatory puffing was sufficient to reduce craving and withdrawal discomfort.
She reports doubled the amount of e-liquid consumed during a one-hour ad lib puffing period. However, self-titration was incomplete with significantly higher blood nicotine levels in the high condition.
Changes in puffing patterns and in e-cigarette use
According to her experience, much more than puffing patterns may be affected when switching to lower nicotine strength:
- Flavoring quality, intensity,
- PG/VG ratio,
- Wattage (or voltage),
- Resistance value.
Second and third generation devices offer multiple setting adjustments that may be interesting to survey along with e-liquid consumption.
“Exposure to toxicants and carcinogens from e-cigarettes is 9–450 times lower than from tobacco cigarettes, however, vaping is not risk-free and toxicant exposure will be related to the amount of e-liquid consumed.”
With longer, more frequent puffs and higher power to allow higher temperatures, the researchers anticipates vegetal glycerine (VG) and propylene glycol (PG) to undergo decomposition to carbonyl compounds including harmful aldehydes.
When switching to lower nicotine strength, compensatory puffing patterns and changes to device settings may therefore lead to increased toxicant/carcinogen exposure due either to increased liquid consumption, increased temperature or both.
It is therefore questionable whether switching to lower strength nicotine e-liquid mayor may not be the lower risk option vapers are seeking?
What’s new in the experimental settings?
The originality of the experimental setting is its design in two different times: Phase I will serve to record puffing patterns to be as close as possible from reality. Phase II will be dedicated to reproduce those patterns and address toxicological issues.
Participants must be vapers for more than 3 months, at least, and should be using a nicotine strength e-liquid ≥12 mg/ml (1.2 %) with a second or third generation device (open-systems with re-fillable tanks). Current tobacco cigarette users (or a CO reading > 10 ppm) will be discarded from the study.
Phase I will survey biological parameters (saliva and urine samples, exhaled breath for CO) and also record subjective craving (urge to vape), withdrawal symptoms through the use of a specific scale as well as direct (e.g. hit, satisfaction) and adverse (headache, nausea) effects relating to nicotine/e-cigarette use.
The study will be conducted with a third generation device (Joyetech eVic Supreme), Aspire nautilus tank and e-liquid (either 6 mg/ml or 18 mg/ml) and one of four flavours of e-liquid to choose from, based on one popular flavour from different flavour categories (fruit, bakery, menthol, tobacco). They are required to use the same e-liquid throughout the 4 week period of Phase I.
The e-cigarette will record puff number, puff duration, voltage, wattage and resistance. Self-reporting will be asked to participants for puff velocity or volume. They will also be asked to refrain from using any other e-cigarette device, e-liquid or nicotine containing products like tobacco cigarettes. Weekly appointments with the research team are programmed during which puffing data will be downloaded from the device, the atomizer replaced and ancillary data collected.
Formaldehyde, acetaldehyde, acrolein, acetone, propionic aldehyde, crotonaldehyde, butanal, benzaldehyde, isovaleric aldehyde, valeric aldehyde, m-methylbenzaldehyde, o-methylbenzaldehyde, p-methylbenzaldehyde, hexanal, 2,5-dimethylbenzaldehyde and nicotine levels will be determined in aerosol emissions during Phase II.
A good choice of material
Compared to number of studies on e-cigarettes the choice of the the device, a Nautilus screwed on an eVic Supreme, seems, from experimented vapers’ experience, adequate to cover the most current wattage including those leading to the emission of toxic aldehydes. Its compliance with regular and subohm resistive wires may also provide a larger spectrum to investigate power effects.
A recent study published by British American Tobacco in Scientific Reports describes the technical advance the UK-based Big Tobacco company is taking on e-cigarette puff topography, based on their experience with smoking tobacco. Their machine is capable of recording puff volumes, for example, a value that will be missing in the set of data gathered by the authors.
With their study, the British researchers want to pave the way for future research in this domain. Their target is to ground science on the “safest” way to vape and to identify behaviors that constitute a risk, ultimately to quantify this risk. As a member of the research team for this study M. Goniewicz will certain provide his expertise in aerosol and e-liquid analysis.
In New Zealand, Janet Hoek from the University of Otago has received a 150,000 AUD grant, this year, to initiate a research program and collect behavioural data from e-cigarette users. The convergence between the two programs is the use of High-Tech e-cigarettes to record individual vaping data.
Dr Lynne E. Dawkins’ research funded by Cancer Research UK will be presented at the E-cigarette Summit to be held in London on November 17, 2016.
Additional information on new vaping patterns and risk exposure:
 Cox S., Kośmider L., McRobbie H., Goniewicz M., Kimber CF., Doig M., Dawkins LE., 2016. E-cigarette puffing patterns associated with high and low nicotine e-liquid strength: effects on toxicant and carcinogen exposure. BMC Public Health, 16(1), 999.
 Dawkins LE., Kimber, CF., Doig, M., Feyerabend, C. Corcoran O., 2016. Self-titration by experienced e-cigarette users: blood nicotine delivery and subjective effects. Psychopharmacology, 1-9.