Introduction

Electronic cigarettes (e-Cigs) are battery operated devices that vaporize a

solution of inert compounds, nicotine and food flavorings. When e-Cigs were

first introduced into the American market in the early 2000s they designed look

and operate similarly to tobacco cigarettes (TC). Lately e-Cigs have evolved

drastically towards high output , long lasting devices with many design

innovations coming from vaping enthusiasts not manufacturers.

This trend towards more powerful devices has led to more effective nicotine

delivery which has (anecdotally) helped many smokers switch to vaping.

Unfortunately, evidence is growing that high energy vaping produces more

unintended contaminants such as formaldehyde, acetaldehyde, propanal,

acrolein, acetone and hemi-acetals (formaldehyde releasing compounds).

Delivery of nicotine depends mostly on two factors; aerosol concentration and

size of nicotine containing aerosols. In this study we show that both

concentration and size increase with vaping power. This supports the

anecdotal accounts that smokers are able to switch to vaping with 2nd and 3rd

generation e-cigs compared to 1st generation e-cigs. This also indicates greater

risk of exposure to unintended chemicals (formaldehyde, acetaldehyde,

propanal, acetone, acrolein and hemi-acetals) at potentially alarming levels

Methods and Materials E-juice vaporization was measured at 9 powers spanning 3.0 - 11.9 Wats (3.0 - 6.0 V)

using a lab power supply in place of the battery. Three trials were conducted with 5 or

10 puffs were administered at each power setting with 30 sec between puffs. Puffs

were 60 mL (20 mL/sec, 3 sec) (Fig 2 a).

Vaping aerosol size and concentration was measured using real-time equipment (SMPS

and APS) set-up to scan 16-20,000 nm . A typical 2nd generation e-cig (Figure 2b) was

used to generate puffs at maximum and minimum voltage settings. The puff was

diluted and injected into a sampling bag. The bag sample was further diluted just

before analysis to bring the count concentrations within optimal range of each

instrument (Figure 3). Count concentration was measured across 151 size bins.

Cigarette smoke was produced in similar manner and evaluated for comparison

purposes.

• Voltage delivered by e-cig battery was linear, but differed

substantially from the labeled voltage (figure 4, left)

Vdelivered = 1.89 Vlabeled - 3.28, R2 = 0.9999

• 86 times more e-juice was vaporized at 11.9 W than at 3.0 W (2X

voltage = 4X power = 86X e-juice)

• Nano-sized aerosols are more abundant at lower voltages (figs 5 & 8)

• Particle Size Distributions are right shifted (larger) as vaping power

increases (figs 5 & 8)

• A substantial peak was discovered around 900 nm, this mode

(previously un-reported in the literature) is believed to be growing

due to coagulation of the nano-sized vapor (figs 5 & 8)

e-Cigarette Power Influences Concentration

and Particle Size of Vaping Aerosol Evan Floyd, Subekchhya Aryal, Jun Wang, James Regens, David Johnson

Department of Occupational and Environmental Health, College of Public Health,

The University of Oklahoma Health Sciences Center

Figure 1

1st generation e-Cig, aka cig-a-like (top) 2nd generation e-Cig, aka tank style (above) 3rd generation e-Cig compared to a 2nd gen e-Cig (right), these were initially used with rebuildable atomizers and drip vaping, but can be used with tank style atomizers too.

Battery USB

Charger

Tank /

Atomizer

3rd gen

2nd gen

Fig. 3 - Schematic of experimental set up used to measure aerosol concentration and size

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Mass Distribution - Vapor at Several Powers

(Lab Power Supply)

3.0 V

3.4 V

3.8 V

4.2 V

4.4 V

4.8 V

5.2 V

5.6 V

6.0 V

Fig. 9 - Mass Distribution of vaping aerosol produced with a lab power supply. As power increases the mass of e-cig aerosol around 900 nm increases dramatically. Results are similar to those obtained with e-cig battery at lower power, but seem to deviate at higher powers, likely due to power limits of the e-cig

Fig. 10 - Cumulative Mass Fraction of vaping aerosol produced by lab power supply. As power vaping increases, median aerosol mass shift smaller. A greater fraction of aerosol is respirable (≤ 2.5 µm) i.e. 72% at 6.0V, 60% 4.4V, 46% at 3.0V. This coupled with large increase in e-juice vaporized at higher power and the respirable mass will be much larger.

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3.0 V

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5.2 V

5.6 V

6.0 V

Results

Fig. 2 a) Lab power supply used as e-cig “battery”, e-cig connected to puffing syringe. This was used to conduct vaporization trials (figure 4) and detailed study of power effect on vaping aerosol (figures 8-10). b) Typical 2nd generation e-cig set-up used to generate vaping aerosol at maximum (3.15 V) and minimum (5.81 V) battery settings (figures 5-7). Vision Spinner variable voltage battery (labeled as 1300 mAh, 3.3 - 4.8 V) with Kanger Tech ProTank II e-juice reservoir and 3.0Ω atomizer.

a b

Conclusions

In this study we demonstrated that the mass of e-juice vaporized increases

dramatically with increased vaping power. We demonstrated that aerosol

concentration and respirable fraction increase with vaping power. Since

more e-juice is vaporized and a greater fraction is respirable we expect

high-powered vaping be more effective in satisfying nicotine cravings.

This supports the myriad anecdotal evidence that 2nd and 3rd generation e-

cigs are more effective in assisting smokers switch to vaping exclusively.

Vaping aerosol has extremely high concentration and must be diluted

several orders of magnitude to measure accurately. Dilution accelerates

evaporation and leads to underestimation of particle size and count.

Further work is needed (and underway) to characterize the relationship of

unintended emissions with vaping power.

Acknowledgments Funding for this project was provided by Oklahoma Tobacco

Settlement Endowment Trust (TSET) through a pilot grant

awarded by Oklahoma Tobacco Research Center (OTRC, grant#

C1082808)

For further information Please contact Evan-Floyd@ouhsc.edu for more information on

this and related projects.

SmartPoster© Feedback Please send comments, criticisms and suggestions about this

SmartPoster© format to Evan-Floyd@ouhsc.edu or Jun-

Wang@ouhsc.edu

Fig. 6 - Mass Distribution of vaping aerosol produced with the e-cig battery and cigarette smoke. This shows much greater mass is found in the larger aerosols. The slight difference in particle count at the 900 nm peak is actually a substantial difference in mass and far out weighs the higher concentration of nano-sized aerosol found at the lower power setting.

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Mass Distribution - Vapor and Smoke

(e-Cig Battery)

Cigarette Smoke

e-cig 3.15 V

e-cig 5.81 V

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Size Distribution - Vapor at Several Powers

(Lab Power Supply)

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6.0 V

Fig. 8 - Size Distribution of vaping aerosol produced at several powers ranging from 3-11.9 W using a lab power supply. A clear trend of greater nano-sized aerosol at lower power and greater fine aerosol at higher power is observed, which confirms results obtained with e-cig battery.

Fig. 5 - Size Distribution of vaping aerosol produced with the e-cig battery and cigarette smoke. The lower power setting clearly produced more nano-sized aerosol while higher power setting produced more fine aerosol at a previously un-reported peak near 900 nm. Cigarette aerosol haas a main mode near 300 nm also with a smaller peak near 900 nm.

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Particle Size (nm)

Size Distribution - Vapor at Two Powers

(e-Cig Battery)

Cigarette Smoke

e-cig 3.15 V

e-cig 5.81 V

Fig. 4 - Mass of e-juice vaporized from 3.0 - 11.9 W (3 - 6 V) using a laboratory power supply. An 86-fold increase is observed from 3 - 11.9 W with an apparent energy threshold necessary to produce measurable vapor (x-intercept = 2.9W). Average of three trials are shown with standard errors.

y = 0.8786x - 2.5436

R² = 0.9484

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Power to Atomizer (W)

e-Juice Vaporized at Varied Power • Mass Distribution plots show much greater mass in the 900 nm peak

than in the nano-sized peaks, and an increasing dominance of this

peak as vaping power increases (figs 6 & 9)

• Cumulative Mass Fraction plots show a smaller mass median

diameter. While there are fewer nano-sized aerosols, there are more

fine particles (~1,000 nm); i.e. a greater mass of particles have a

smaller diameter at higher power (figs 7 & 10, dotted line at 0.5

cumulative mass and circles on plots)

• Low power e-cig vapor is more similar to cigarette smoke than high

power vapor, but not the same (figs 6 & 7)

• The respirable fraction (< 2,500 nm) increases with vaping power

with large differences between max and min settings on the real e-cig.

Low power = 39.3%, cigarette smoke = 43.3%, high power = 57.2%

Size Distributions Mass Distributions Cumulative Mass Distributions

Fig. 7 - Cumulative Mass Fraction of vaping aerosol and cigarette smoke shows that a greater fraction of the e-Cig vapor is respirable at high power compared to low power and cigarette smoke. Median diameter is 1.4 µm for high power vapor compared to 11.1 µm and 9.7 µm for low power vapor and cigarette smoke, respectively. Alternatively, the respirable mass fraction (≤ 2.5 µm) is 57%, 43% and 39% for high power, low power and cigarette smoke, respectively

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Cigarette Smoke

e-cig 5.81 V

e-cig 3.15 V1.6 µm 9.8 µm

11.1 µm

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Results Summary